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, Available online ,
doi: 10.11883/bzycj-2024-0457
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To study the loading characteristics of shock wave along the water surface in near-surface explosion scenarios, explosion tests were carried out with three typical scaled height of burst . The explosion tests were contact burst (H_ = 0), near-surface blast (H_ ≈ 0.2m /kg1/3) and air blast (H_ ≈ 0.6m /kg1/3). In the experiment, 100 g, 200 g and 400 g TNT/RDX(40/60) explosives were used, and the shock wave overpressure and high-speed photographic images of the explosion were measured. Meanwhile, numerical simulation method is used to simulate the experiment. Based on the experimental and numerical simulation results, the explosion phenomena and the characteristics of shock wave loading on water surface were studied. The results show that there are significant differences in the explosion phenomena of contact burst, near-surface blast, and air blast. In contact burst, the detonation products directly drive the water surface to form a hemispherical cavity, and the water on the edge of the cavity is squeezed upwards to form a hollow water column. In near-surface blast, the collision of the detonation products with the water surface is relatively weak, and the shock wave on the water surface mainly propagates outwards as Mach waves along the water surface. In air blast, there are obvious regular and irregular reflection zones of the shock wave on the water surface. The shock wave overpressure on water surface of contact burst is lower than that of near-surface blast, therefore, the water surface cannot be considered as a rigid plane in contact burst. The underwater shock wave pressure of contact burst is higher than that of near-surface blast. The formulas of overpressure and positive pressure duration of shock wave on water surface within the range of 0.5~4.0 m/kg1/3 in contact burst and near-surface blast were obtained through data fitting, which can provide reference for shock wave loading calculation and analysis.
To study the loading characteristics of shock wave along the water surface in near-surface explosion scenarios, explosion tests were carried out with three typical scaled height of burst . The explosion tests were contact burst (H_ = 0), near-surface blast (H_ ≈ 0.2m /kg1/3) and air blast (H_ ≈ 0.6m /kg1/3). In the experiment, 100 g, 200 g and 400 g TNT/RDX(40/60) explosives were used, and the shock wave overpressure and high-speed photographic images of the explosion were measured. Meanwhile, numerical simulation method is used to simulate the experiment. Based on the experimental and numerical simulation results, the explosion phenomena and the characteristics of shock wave loading on water surface were studied. The results show that there are significant differences in the explosion phenomena of contact burst, near-surface blast, and air blast. In contact burst, the detonation products directly drive the water surface to form a hemispherical cavity, and the water on the edge of the cavity is squeezed upwards to form a hollow water column. In near-surface blast, the collision of the detonation products with the water surface is relatively weak, and the shock wave on the water surface mainly propagates outwards as Mach waves along the water surface. In air blast, there are obvious regular and irregular reflection zones of the shock wave on the water surface. The shock wave overpressure on water surface of contact burst is lower than that of near-surface blast, therefore, the water surface cannot be considered as a rigid plane in contact burst. The underwater shock wave pressure of contact burst is higher than that of near-surface blast. The formulas of overpressure and positive pressure duration of shock wave on water surface within the range of 0.5~4.0 m/kg1/3 in contact burst and near-surface blast were obtained through data fitting, which can provide reference for shock wave loading calculation and analysis.
Preparation of NiP@Fe-SBA-15 Suppressant and Its Inhibition Mechanism on PP Dust Deflagration Flames
, Available online ,
doi: 10.11883/bzycj-2024-0434
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Polypropylene (PP) is a widely utilized plastic material in industrial production. However, during its production and transportation, it is highly prone to dust explosion accidents, posing significant threats to personnel and equipment safety. In this study, a novel explosion suppressant NiP@Fe-SBA-15 was synthesized to suppress the propagation of PP dust combustion flames. The synthesis method employed was in situ, whereby SBA-15 mesoporous silica was modified with metal ions, followed by the loading of active components NiP to prepare NiP@Fe-SBA-15.The results of SEM-Mapping test indicated that the active elements were uniformly distributed without significant aggregation, ensuring good dispersibility of the suppressant. In this paper, Hartman explosive device was used to evaluate the effect of NiP@Fe-SBA-15 explosion suppressor on PP dust deflation. The experimental results show that with the increase of NiP@Fe-SBA-15 additive, the flame propagation rate of PP dust deflagrator decreases significantly, and the flame propagation is almost completely inhibited when 70wt% inhibitor is added. The double explosion suppression mechanism of NiP@Fe-SBA-15 inhibiting the deflagging of PP dust is analyzed. On the physical level, NiP@Fe-SBA-15 inhibitor occupies the reaction space and reduces the concentration of oxygen and combustible volatiles, thus limiting the combustion reaction. At the same time, the SBA-15 molecular sieve exposed by thermal decomposition of the suppressor absorbs heat by forming a physical barrier, thus reducing the intensity of the combustion reaction. At the chemical level, the active ingredients NiP and Fe groups capture the living free radicals (H·, O·, OH·) produced during combustion, effectively interrupting the chain reaction and reducing the intensity of the explosion. In summary, this study proves that NiP@Fe-SBA-15 is an effective explosion suppressor for PP dust explosion, and reduces the combustion intensity of PP dust by combining physicochemical synergies. The research results of this paper can provide a new idea and method for improving the safety of polypropylene industry. Future research will focus on optimizing the application of NiP@Fe-SBA-15 explosion suppressors in industry, while solving the problems of cost, environmental sustainability and stability, so as to further promote the dust explosion prevention technology.
Polypropylene (PP) is a widely utilized plastic material in industrial production. However, during its production and transportation, it is highly prone to dust explosion accidents, posing significant threats to personnel and equipment safety. In this study, a novel explosion suppressant NiP@Fe-SBA-15 was synthesized to suppress the propagation of PP dust combustion flames. The synthesis method employed was in situ, whereby SBA-15 mesoporous silica was modified with metal ions, followed by the loading of active components NiP to prepare NiP@Fe-SBA-15.The results of SEM-Mapping test indicated that the active elements were uniformly distributed without significant aggregation, ensuring good dispersibility of the suppressant. In this paper, Hartman explosive device was used to evaluate the effect of NiP@Fe-SBA-15 explosion suppressor on PP dust deflation. The experimental results show that with the increase of NiP@Fe-SBA-15 additive, the flame propagation rate of PP dust deflagrator decreases significantly, and the flame propagation is almost completely inhibited when 70wt% inhibitor is added. The double explosion suppression mechanism of NiP@Fe-SBA-15 inhibiting the deflagging of PP dust is analyzed. On the physical level, NiP@Fe-SBA-15 inhibitor occupies the reaction space and reduces the concentration of oxygen and combustible volatiles, thus limiting the combustion reaction. At the same time, the SBA-15 molecular sieve exposed by thermal decomposition of the suppressor absorbs heat by forming a physical barrier, thus reducing the intensity of the combustion reaction. At the chemical level, the active ingredients NiP and Fe groups capture the living free radicals (H·, O·, OH·) produced during combustion, effectively interrupting the chain reaction and reducing the intensity of the explosion. In summary, this study proves that NiP@Fe-SBA-15 is an effective explosion suppressor for PP dust explosion, and reduces the combustion intensity of PP dust by combining physicochemical synergies. The research results of this paper can provide a new idea and method for improving the safety of polypropylene industry. Future research will focus on optimizing the application of NiP@Fe-SBA-15 explosion suppressors in industry, while solving the problems of cost, environmental sustainability and stability, so as to further promote the dust explosion prevention technology.
, Available online ,
doi: 10.11883/bzycj-2024-0388
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Abstract:
In reinforced concrete (RC) box structures, the blast wave is difficult to dissipate freely outwards, and the structure's damage degree can be intensified after multiple reflections. To thoroughly investigate the load characteristics and dynamic behavior of internal explosions in RC box structures, the internal explosion tests of fully enclosed and partially enclosed (with explosion venting) box structures were replicated. This process verified the applicability of the simulation material models and parameters, MAPPING method, and fluid-structure coupling algorithms. On this basis, for the prototypical RC box structures and the types of terrorist bombing attacks specified by the Federal Emergency Management Agency (FEMA), numerical simulations of internal explosions were conducted under three explosion threat scenarios and four venting areas. Furthermore, the load characteristic and its distribution at the structural inner surface centers and corners, as well as the structure's dynamic behavior, were analyzed. The results show that the venting area has a negligible effect on the overpressure, while the impulse decreases exponentially with the increase of venting area; the load distribution characteristics on the structure's inner surfaces are significantly influenced by the structural dimensions, exhibiting an 'indented' or 'W' pattern; the maximum displacement at the center of walls and slabs can be reduced by more than 50% for the venting coefficient increases from 0.457 to 1.220; the impulse criterion can more accurately assess the damage degree of components than overpressure. Finally, a calculation method for the impulse and damage enhancement coefficient considering the venting area was proposed, which could effectively predict the internal explosion load and structure's dynamic behavior at various venting coefficients.
In reinforced concrete (RC) box structures, the blast wave is difficult to dissipate freely outwards, and the structure's damage degree can be intensified after multiple reflections. To thoroughly investigate the load characteristics and dynamic behavior of internal explosions in RC box structures, the internal explosion tests of fully enclosed and partially enclosed (with explosion venting) box structures were replicated. This process verified the applicability of the simulation material models and parameters, MAPPING method, and fluid-structure coupling algorithms. On this basis, for the prototypical RC box structures and the types of terrorist bombing attacks specified by the Federal Emergency Management Agency (FEMA), numerical simulations of internal explosions were conducted under three explosion threat scenarios and four venting areas. Furthermore, the load characteristic and its distribution at the structural inner surface centers and corners, as well as the structure's dynamic behavior, were analyzed. The results show that the venting area has a negligible effect on the overpressure, while the impulse decreases exponentially with the increase of venting area; the load distribution characteristics on the structure's inner surfaces are significantly influenced by the structural dimensions, exhibiting an 'indented' or 'W' pattern; the maximum displacement at the center of walls and slabs can be reduced by more than 50% for the venting coefficient increases from 0.457 to 1.220; the impulse criterion can more accurately assess the damage degree of components than overpressure. Finally, a calculation method for the impulse and damage enhancement coefficient considering the venting area was proposed, which could effectively predict the internal explosion load and structure's dynamic behavior at various venting coefficients.
, Available online ,
doi: 10.11883/bzycj-2024-0431
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Compared to concrete and steel structures, research on the blast resistance of timber structures is relatively scarce. Although there have been experimental studies on the blast performance of light-frame wood walls, relevant numerical studies remain limited. This paper addresses the numerical modeling of light-frame wood walls under blast loads, with a focus on the determination of the dynamic increasing factor (DIF) for nail connections and the failure criteria for wood studs. Based on the partial composite theory, this study provides a reasonable value for the DIF of nail connections by introducing experimentally measured DIFs for wood studs and wood-frame walls. On this basis, a finite element (FE) model for blast resistance analysis of light-frame wood walls is developed. This model considers the orthotropic characteristics of wood-based structural panels, the nonlinear dynamic behavior of nail connections, and the dynamic elastic-plastic features of wood studs. Verification of the developed model against the experimental data indicates that it can accurately predict the dynamic response of light-frame wood walls under blast loads, as well as the time and corresponding peak displacement when wood studs fracture. FE analyses also show that if the variation of the studs’ material properties is reasonably accounted for, the predictions of the dynamic response and failure mode after the fracture of studs are also in good agreement with the experimental results. The developed model paves the way for assessing the blast vulnerability of light-frame wood structures in future research.
Compared to concrete and steel structures, research on the blast resistance of timber structures is relatively scarce. Although there have been experimental studies on the blast performance of light-frame wood walls, relevant numerical studies remain limited. This paper addresses the numerical modeling of light-frame wood walls under blast loads, with a focus on the determination of the dynamic increasing factor (DIF) for nail connections and the failure criteria for wood studs. Based on the partial composite theory, this study provides a reasonable value for the DIF of nail connections by introducing experimentally measured DIFs for wood studs and wood-frame walls. On this basis, a finite element (FE) model for blast resistance analysis of light-frame wood walls is developed. This model considers the orthotropic characteristics of wood-based structural panels, the nonlinear dynamic behavior of nail connections, and the dynamic elastic-plastic features of wood studs. Verification of the developed model against the experimental data indicates that it can accurately predict the dynamic response of light-frame wood walls under blast loads, as well as the time and corresponding peak displacement when wood studs fracture. FE analyses also show that if the variation of the studs’ material properties is reasonably accounted for, the predictions of the dynamic response and failure mode after the fracture of studs are also in good agreement with the experimental results. The developed model paves the way for assessing the blast vulnerability of light-frame wood structures in future research.
, Available online ,
doi: 10.11883/bzycj-2024-0227
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The scaled test method has the advantages of low testing cost, short testing time and low risk, and has been widely used in aerospace and other fields. Taking the lower structure of a typical civil aircraft fuselage as the research object, this study conducted theoretical analysis and experimental method research on the impact scaling of civil aircraft structures. Using dimensional analysis, the complex dynamics of the fuselage crash were simplified to identify key physical quantities and processes. The main research objects, critical physical parameters, and physical processes involved in the aircraft crash were clarified, leading to the extraction of key basic physical quantities and the derivation of primary dimensionless numbers that control the crash response of the fuselage structure. Based on the Buckingham π theorem, the scaling factor for civil aircraft crashes was derived, establishing the scaled experimental methodology. A 1/4 scale model was designed and fabricated, and an impact test at a speed of 6 m/s was performed. The velocity, acceleration, ground impact load, deformation, and failure modes of key components in both full-scale and scaled crash tests were obtained and compared. The applicability and accuracy of the scaled-down theory in the crash experiment of the civil aircraft fuselage frame section were verified. The results show that the deformation and failure modes of the 1/4 scaled test piece and the full-scale test piece are consistent at the frame and column. Structural response prediction deviation analysis shows that the prediction deviation of the maximum crash load is 14.4%, the prediction deviation of the maximum seat acceleration is 14.8%, and the prediction deviation of the maximum acceleration at the beam is 13.1%. Scaled tests can effectively predict the deformation, failure process and dynamic response of key parts of the prototype structure. The scaled test could be used to verify and evaluate the crash performance of civil aircraft structures.
The scaled test method has the advantages of low testing cost, short testing time and low risk, and has been widely used in aerospace and other fields. Taking the lower structure of a typical civil aircraft fuselage as the research object, this study conducted theoretical analysis and experimental method research on the impact scaling of civil aircraft structures. Using dimensional analysis, the complex dynamics of the fuselage crash were simplified to identify key physical quantities and processes. The main research objects, critical physical parameters, and physical processes involved in the aircraft crash were clarified, leading to the extraction of key basic physical quantities and the derivation of primary dimensionless numbers that control the crash response of the fuselage structure. Based on the Buckingham π theorem, the scaling factor for civil aircraft crashes was derived, establishing the scaled experimental methodology. A 1/4 scale model was designed and fabricated, and an impact test at a speed of 6 m/s was performed. The velocity, acceleration, ground impact load, deformation, and failure modes of key components in both full-scale and scaled crash tests were obtained and compared. The applicability and accuracy of the scaled-down theory in the crash experiment of the civil aircraft fuselage frame section were verified. The results show that the deformation and failure modes of the 1/4 scaled test piece and the full-scale test piece are consistent at the frame and column. Structural response prediction deviation analysis shows that the prediction deviation of the maximum crash load is 14.4%, the prediction deviation of the maximum seat acceleration is 14.8%, and the prediction deviation of the maximum acceleration at the beam is 13.1%. Scaled tests can effectively predict the deformation, failure process and dynamic response of key parts of the prototype structure. The scaled test could be used to verify and evaluate the crash performance of civil aircraft structures.
, Available online ,
doi: 10.11883/bzycj-2024-0261
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Abstract:
Tolerances in machining and assembly often result in gaps in engineering structures. Under strong dynamic loading, gap jets may form within these gaps, posing a threat to the reliability and safety of the structure. However, the formation mechanism of gap jets differs from that of traditional high-speed metal jets, and its formation process still requires systematic research. Based on a two-stage light gas gun, hypervelocity impact loading experiments were conducted on tungsten samples with gaps. The formation and evolution of the gap jet were recorded using a high-speed framing camera. A numerical model for predicting the formation of gap jets was established using ANSYS Autodyn. The applicability of the numerical simulation method was validated by comparing the numerical results with the jet morphology and head velocity history data obtained from a representative experiment. By adjusting the flyer velocity, gap width, and gap half-angle in the numerical model, the effects of these three factors on the formation of the gap jet were studied. The variations in the gap jet head velocity and mass with respect to these factors were obtained, and the limitations of the steady-state jet model were analyzed. Based on the findings from numerical simulations, an empirical model was developed to predict the jet head velocity and mass. The results show that the numerical model based on the Eulerian method can accurately predict the formation of the gap jet under strong dynamic loading. Loading pressure is the main factor controlling the jet head velocity and mass; as the loading pressure increases, both the jet head velocity and mass increase accordingly. The gap width and half-angle have little effect on the jet head velocity, but the mass increases linearly with the gap width and half-angle. Due to significant errors in estimating the gap closing velocity, the steady jet model fails to accurately predict the formation of the gap jet. In contrast, the developed empirical model shows good agreement with the numerical results.
Tolerances in machining and assembly often result in gaps in engineering structures. Under strong dynamic loading, gap jets may form within these gaps, posing a threat to the reliability and safety of the structure. However, the formation mechanism of gap jets differs from that of traditional high-speed metal jets, and its formation process still requires systematic research. Based on a two-stage light gas gun, hypervelocity impact loading experiments were conducted on tungsten samples with gaps. The formation and evolution of the gap jet were recorded using a high-speed framing camera. A numerical model for predicting the formation of gap jets was established using ANSYS Autodyn. The applicability of the numerical simulation method was validated by comparing the numerical results with the jet morphology and head velocity history data obtained from a representative experiment. By adjusting the flyer velocity, gap width, and gap half-angle in the numerical model, the effects of these three factors on the formation of the gap jet were studied. The variations in the gap jet head velocity and mass with respect to these factors were obtained, and the limitations of the steady-state jet model were analyzed. Based on the findings from numerical simulations, an empirical model was developed to predict the jet head velocity and mass. The results show that the numerical model based on the Eulerian method can accurately predict the formation of the gap jet under strong dynamic loading. Loading pressure is the main factor controlling the jet head velocity and mass; as the loading pressure increases, both the jet head velocity and mass increase accordingly. The gap width and half-angle have little effect on the jet head velocity, but the mass increases linearly with the gap width and half-angle. Due to significant errors in estimating the gap closing velocity, the steady jet model fails to accurately predict the formation of the gap jet. In contrast, the developed empirical model shows good agreement with the numerical results.
, Available online ,
doi: 10.11883/bzycj-2024-0268
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Abstract:
In order to investigate the coated aluminum powder explosion flame development and propagation mechanism, a shell and core structure of stearic acid coated aluminum powder(SA@Al) was prepared by solvent evaporation method; the improved Hartmann tube was applied to experimentally study the influence of dust cloud concentration on the explosion flame propagation characteristics of SA@Al dust with 5%, 10%, and 15% coating concentration, observing the flame propagation behavior through high-speed photography and calculate flame propagation speed; and the CHEMKIN-PRO software was applied to analyze the kinetic characteristics of gas-phase explosion reaction, thereby revealing the mechanism of SA@Al dust explosion flame propagation. The results indicated that with the increase of dust cloud concentration, the fullness and continuity of 5%, 10%, and 15% SA@Al dust explosion flames were enhanced firstly and then weakened, and the average flame propagation speed showed a trend of first increasing and then decreasing. The flame propagation speed reached its maximum when the dust cloud concentration was 500 g/m3. In comparison, the pure aluminum powder explosion flame propagation velocity reached a maximum at 750 g/m3, indicating that the stearic acid coating layer promotes the propagation of the aluminum powder explosion flame. In addition, under each dust cloud concentration, 10% coating concentration SA@Al explosion flame were the most intense, and the average flame propagation velocity was maximized. The temperature rise of the SA@Al explosion flame with different dust cloud concentrations mainly consisted of two stages: rapid heating stage and slow heating stage. The rapid heating stage had higher temperature sensitivity for R2, R11, and R10, while the slow heating stage had higher temperature sensitivity for R5 and R11. The dust cloud concentration has a significant effect on the rate of temperature rise in the slow heating stage, resulting in the highest explosion equilibrium temperature for SA@Al at 500 g/m3. The combustion of stearic acid coating promotes the oxidation of the aluminum core, which strengthens the explosion reaction, but high dust cloud concentration leads to the limitation of O radicals, which weakens the reaction intensity to some extent.
In order to investigate the coated aluminum powder explosion flame development and propagation mechanism, a shell and core structure of stearic acid coated aluminum powder(SA@Al) was prepared by solvent evaporation method; the improved Hartmann tube was applied to experimentally study the influence of dust cloud concentration on the explosion flame propagation characteristics of SA@Al dust with 5%, 10%, and 15% coating concentration, observing the flame propagation behavior through high-speed photography and calculate flame propagation speed; and the CHEMKIN-PRO software was applied to analyze the kinetic characteristics of gas-phase explosion reaction, thereby revealing the mechanism of SA@Al dust explosion flame propagation. The results indicated that with the increase of dust cloud concentration, the fullness and continuity of 5%, 10%, and 15% SA@Al dust explosion flames were enhanced firstly and then weakened, and the average flame propagation speed showed a trend of first increasing and then decreasing. The flame propagation speed reached its maximum when the dust cloud concentration was 500 g/m3. In comparison, the pure aluminum powder explosion flame propagation velocity reached a maximum at 750 g/m3, indicating that the stearic acid coating layer promotes the propagation of the aluminum powder explosion flame. In addition, under each dust cloud concentration, 10% coating concentration SA@Al explosion flame were the most intense, and the average flame propagation velocity was maximized. The temperature rise of the SA@Al explosion flame with different dust cloud concentrations mainly consisted of two stages: rapid heating stage and slow heating stage. The rapid heating stage had higher temperature sensitivity for R2, R11, and R10, while the slow heating stage had higher temperature sensitivity for R5 and R11. The dust cloud concentration has a significant effect on the rate of temperature rise in the slow heating stage, resulting in the highest explosion equilibrium temperature for SA@Al at 500 g/m3. The combustion of stearic acid coating promotes the oxidation of the aluminum core, which strengthens the explosion reaction, but high dust cloud concentration leads to the limitation of O radicals, which weakens the reaction intensity to some extent.
, Available online ,
doi: 10.11883/bzycj-2024-0315
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Abstract:
Based on the synchrotron radiation X-ray computed tomography technology and the in-situ mechanical loading test system, the macro-meso structures of Nitrate Ester Plasticized Polyether (NEPE) solid propellant at compression rates of 0.1 mm/s, 1 mm/s and 5 mm/s were in-situ observed. Meanwhile, typical damages and its evolutionary behaviors were analyzed. The macroscopic deformation of solid propellant as well as the distribution and propagation patterns of internal micro-cracks were explored. Results show that most of the micro-cracks nucleate and grow at the interface between filled particles and the matrix of solid propellant, and the evolution of meso-pores is rate-dependent. In contrast to the continuous growth of damage under tensile loading, the nucleation, growth and closure of pores occur simultaneously during compression. Under high-rate uniaxial compressive loading, solid propellant generates the characteristic trumpet-shaped deformation. The spatially distributed cracks mostly located around solid propellant. Macroscopic damage of sur-faces is caused by the propagation of micro-cracks between the near-surface particles and the matrix. The propagation of micro-cracks is related to the spatial location of filled particles in solid propellant. There are transversal and axial propagation modes of cracks under dynamic compressive loading. The transition from the vertically oriented crack to the horizontally oriented crack in matrix leads to closure of the crack.
Based on the synchrotron radiation X-ray computed tomography technology and the in-situ mechanical loading test system, the macro-meso structures of Nitrate Ester Plasticized Polyether (NEPE) solid propellant at compression rates of 0.1 mm/s, 1 mm/s and 5 mm/s were in-situ observed. Meanwhile, typical damages and its evolutionary behaviors were analyzed. The macroscopic deformation of solid propellant as well as the distribution and propagation patterns of internal micro-cracks were explored. Results show that most of the micro-cracks nucleate and grow at the interface between filled particles and the matrix of solid propellant, and the evolution of meso-pores is rate-dependent. In contrast to the continuous growth of damage under tensile loading, the nucleation, growth and closure of pores occur simultaneously during compression. Under high-rate uniaxial compressive loading, solid propellant generates the characteristic trumpet-shaped deformation. The spatially distributed cracks mostly located around solid propellant. Macroscopic damage of sur-faces is caused by the propagation of micro-cracks between the near-surface particles and the matrix. The propagation of micro-cracks is related to the spatial location of filled particles in solid propellant. There are transversal and axial propagation modes of cracks under dynamic compressive loading. The transition from the vertically oriented crack to the horizontally oriented crack in matrix leads to closure of the crack.
, Available online ,
doi: 10.11883/bzycj-2024-0395
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The viscous characteristics of fault granular interlayers have a significant impact on the dynamic mechanical behavior of faults. The problem of determining the viscosity of fault granular interlayers at different slip velocities has not yet been solved. This article conducts theoretical research on this issue. Firstly, the Maxwell relaxation model was used to study the evolution of force chains for slow shearing of granular gouge, and the dependence of force chain length on shear strain rate, effective extension speed of shear bands, and strength of granular medium was derived. Further the relaxation time of the shear band, the expression of the viscosity coefficient of the granular medium, the conditions for the transformation of solid-liquid mechanical behavior of the granular medium were established. The comparison with existing experimental data has verified the validity of this model. For high-speed slip shear, the motion of granular medium exhibits turbulent characteristics. Statistical physics was used to describe the interaction between granular particles, and it is obtained that the viscosity coefficient is inversely proportional to the shear rate at high slip rate. The research results have fundamental significance for understanding the viscous and other physico-mechanical properties of granular gouge in faults.
The viscous characteristics of fault granular interlayers have a significant impact on the dynamic mechanical behavior of faults. The problem of determining the viscosity of fault granular interlayers at different slip velocities has not yet been solved. This article conducts theoretical research on this issue. Firstly, the Maxwell relaxation model was used to study the evolution of force chains for slow shearing of granular gouge, and the dependence of force chain length on shear strain rate, effective extension speed of shear bands, and strength of granular medium was derived. Further the relaxation time of the shear band, the expression of the viscosity coefficient of the granular medium, the conditions for the transformation of solid-liquid mechanical behavior of the granular medium were established. The comparison with existing experimental data has verified the validity of this model. For high-speed slip shear, the motion of granular medium exhibits turbulent characteristics. Statistical physics was used to describe the interaction between granular particles, and it is obtained that the viscosity coefficient is inversely proportional to the shear rate at high slip rate. The research results have fundamental significance for understanding the viscous and other physico-mechanical properties of granular gouge in faults.
, Available online ,
doi: 10.11883/bzycj-2024-0403
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Abstract:
Through experimental and numerical simulation analyses, the shear mechanical properties and deformation damage mechanism of the double structural planes of traditional anchor cables and new anchor cable with C-shaped tube structures (abbreviated as ACC) under different loading rate conditions were investigated. Dual structural face shear tests were conducted at shear displacement loading rates of 2, 10, 20, 30, and 40 mm/min under 55 MPa concrete specimen strength and 200 kN preload. The tests were conducted with shear deformation curves, peak structural shear loads, steel wire damage patterns and structural plane shear strength contributions as the main parameters to be considered. The results show that the loading rate has a significant effect on the shear performance of the structure, and within a certain loading rate interval, affected by the damage accumulation rate and the strain rate strengthening effect, the structure will show the characteristics of strength weakening and strength strengthening respectively, and the shear load carrying capacity will show a large variation interval. In the vicinity of the structural plane, the support structure will show a combination of tensile and shear damage, but the ACC structure, due to the presence of the C-shaped tube, makes the stress concentration effect lower, the fluctuation of the test curve is weakened, and the damage of the internal steel wires by the shear action is significantly weakened compared with the traditional anchor cable. Meanwhile, the numerical model of double shear test of ACC structure constructed on the basis of the test results has high accuracy, and the numerical simulation of dynamic loading test shows that the anchoring system formed by ACC structure has good energy absorption effect, and the larger the impact energy, the more obvious the energy absorption effect; and the ACC structure under the action of high-speed impact is affected by the strain rate reinforcement effect significantly, and the larger the impact speed, the higher the shear bearing capacity.
Through experimental and numerical simulation analyses, the shear mechanical properties and deformation damage mechanism of the double structural planes of traditional anchor cables and new anchor cable with C-shaped tube structures (abbreviated as ACC) under different loading rate conditions were investigated. Dual structural face shear tests were conducted at shear displacement loading rates of 2, 10, 20, 30, and 40 mm/min under 55 MPa concrete specimen strength and 200 kN preload. The tests were conducted with shear deformation curves, peak structural shear loads, steel wire damage patterns and structural plane shear strength contributions as the main parameters to be considered. The results show that the loading rate has a significant effect on the shear performance of the structure, and within a certain loading rate interval, affected by the damage accumulation rate and the strain rate strengthening effect, the structure will show the characteristics of strength weakening and strength strengthening respectively, and the shear load carrying capacity will show a large variation interval. In the vicinity of the structural plane, the support structure will show a combination of tensile and shear damage, but the ACC structure, due to the presence of the C-shaped tube, makes the stress concentration effect lower, the fluctuation of the test curve is weakened, and the damage of the internal steel wires by the shear action is significantly weakened compared with the traditional anchor cable. Meanwhile, the numerical model of double shear test of ACC structure constructed on the basis of the test results has high accuracy, and the numerical simulation of dynamic loading test shows that the anchoring system formed by ACC structure has good energy absorption effect, and the larger the impact energy, the more obvious the energy absorption effect; and the ACC structure under the action of high-speed impact is affected by the strain rate reinforcement effect significantly, and the larger the impact speed, the higher the shear bearing capacity.
, Available online ,
doi: 10.11883/bzycj-2024-0361
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Abstract:
Calcium conglomerate is the second largest type of uranium deposits in Namibia. Calcium conglomerate is extremely difficult to be broken due to its special structure, and even if the unit consumption of explosives reaches 1.0kg/m3, a large number of large and super-large blocks will be produced, which not only restricts the shoveling operation and seriously affects the production of the mines, but also greatly increases the costs and dangers of the secondary crushing, and it is the biggest problem encountered in the process of mining. In order to study the damage law of calcium conglomerate under the action of blasting, based on the theory of damage fracture mechanics and wave dynamics, the blasting damage fracture process and mechanism of calcium conglomerate were revealed, and the fine numerical model including filler, conglomerate and interface transition zone was established by combining LS-DYNA and Fortran programming, and the blasting stress wave propagation law and damage characteristics of calcium conglomerate were analyzed. The fracture process of the blasting damage of calcium-caking conglomerate can be divided into four stages, namely: compression damage occurs in both conglomerate and filler; tensile damage occurs in conglomerate and compression damage occurs in filler; tensile damage occurs in both conglomerate and filler; and tensile damage occurs in the interfacial interface of conglomerate and filler. Numerical results show that: gravel in the blasting load characterizes a higher equivalent force, the filler equivalent force is the smallest, the interface transition zone at the obvious stress concentration phenomenon, with the increase of the distance between the gravel and the filler to withstand the stress gap decreases. Conglomerate damage is small, there is damage “around the stone” phenomenon, filler damage is larger. Calcium-caking conglomerate blasting crack expansion form is mainly along the direction of propagation of the stress wave to preferentially select the lower mechanical properties of the filler and the development of the intersection surface, the damage to the gravel is weaker. Blasting blockiness is mainly manifested as the gravel wrapped by the filler, and the distribution of blasting blockiness is affected by the bonding force of the intersection surface and the distribution of the gravel.
Calcium conglomerate is the second largest type of uranium deposits in Namibia. Calcium conglomerate is extremely difficult to be broken due to its special structure, and even if the unit consumption of explosives reaches 1.0kg/m3, a large number of large and super-large blocks will be produced, which not only restricts the shoveling operation and seriously affects the production of the mines, but also greatly increases the costs and dangers of the secondary crushing, and it is the biggest problem encountered in the process of mining. In order to study the damage law of calcium conglomerate under the action of blasting, based on the theory of damage fracture mechanics and wave dynamics, the blasting damage fracture process and mechanism of calcium conglomerate were revealed, and the fine numerical model including filler, conglomerate and interface transition zone was established by combining LS-DYNA and Fortran programming, and the blasting stress wave propagation law and damage characteristics of calcium conglomerate were analyzed. The fracture process of the blasting damage of calcium-caking conglomerate can be divided into four stages, namely: compression damage occurs in both conglomerate and filler; tensile damage occurs in conglomerate and compression damage occurs in filler; tensile damage occurs in both conglomerate and filler; and tensile damage occurs in the interfacial interface of conglomerate and filler. Numerical results show that: gravel in the blasting load characterizes a higher equivalent force, the filler equivalent force is the smallest, the interface transition zone at the obvious stress concentration phenomenon, with the increase of the distance between the gravel and the filler to withstand the stress gap decreases. Conglomerate damage is small, there is damage “around the stone” phenomenon, filler damage is larger. Calcium-caking conglomerate blasting crack expansion form is mainly along the direction of propagation of the stress wave to preferentially select the lower mechanical properties of the filler and the development of the intersection surface, the damage to the gravel is weaker. Blasting blockiness is mainly manifested as the gravel wrapped by the filler, and the distribution of blasting blockiness is affected by the bonding force of the intersection surface and the distribution of the gravel.
, Available online ,
doi: 10.11883/bzycj-2024-0399
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Abstract:
As global resource demand continues to rise, the scale of deep underground engineering development is expanding, facing increasingly complex geological conditions and high stress environments. This transition has made the study of the dynamic characteristics of deep rock masses with structural planes a hot and challenging research topic in recent years. This paper systematically summarizes the dynamic shear and dynamic tensile characteristics of structural planes and provides an in-depth analysis of various factors affecting their dynamic behavior. Additionally, it explores the impact of structural plane effects on the dynamic properties of rock masses, particularly regarding dynamic strength and deformation. For common deep dynamic disasters, such as rock bursts, large deformations, and dynamic pressure, this paper reviews their triggering mechanisms and prevention technologies, emphasizing the importance of establishing an effective theoretical and technical system. Finally, this paper offers a forward-looking perspective on future research directions for the dynamic characteristics of deep rock masses with structural planes and disaster prevention technologies, calling for the integration of emerging technologies and theoretical methods to enhance the depth and breadth of research, thereby promoting safety and effectiveness in engineering practice.
As global resource demand continues to rise, the scale of deep underground engineering development is expanding, facing increasingly complex geological conditions and high stress environments. This transition has made the study of the dynamic characteristics of deep rock masses with structural planes a hot and challenging research topic in recent years. This paper systematically summarizes the dynamic shear and dynamic tensile characteristics of structural planes and provides an in-depth analysis of various factors affecting their dynamic behavior. Additionally, it explores the impact of structural plane effects on the dynamic properties of rock masses, particularly regarding dynamic strength and deformation. For common deep dynamic disasters, such as rock bursts, large deformations, and dynamic pressure, this paper reviews their triggering mechanisms and prevention technologies, emphasizing the importance of establishing an effective theoretical and technical system. Finally, this paper offers a forward-looking perspective on future research directions for the dynamic characteristics of deep rock masses with structural planes and disaster prevention technologies, calling for the integration of emerging technologies and theoretical methods to enhance the depth and breadth of research, thereby promoting safety and effectiveness in engineering practice.
, Available online ,
doi: 10.11883/bzycj-2024-0225
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Abstract:
Additive manufacturing (AM) possesses significant advantages in processing critical components in aerospace and defense fields that feature intricate and geometrically complex designs, thanks to its high design freedom and rapid prototyping capabilities. Ti-6Al-4V titanium alloy, renowned for its low density, high specific strength, and creep resistance, is widely utilized in crucial parts of spacecraft and weaponry that frequently endure impact loads. A thorough understanding of the mechanical properties and underlying mechanisms of AM Ti-6Al-4V alloy under static and dynamic loads is crucial for enhancing the service performance of these components. This paper systematically reviews and summarizes the latest advancements in the mechanical response of AM Ti-6Al-4V titanium alloy, aiming at offering a scientific foundation and technical approach to promote the application of key load-bearing components fabricated by additive manufacturing process under extreme conditions. It begins with a brief overview of the classification and working principles of typical metal additive manufacturing technologies including laser direct energy deposition (LDED), laser powder bed fusion (LPBF) and electron beam melting (EBM). Typical microstructure of different metal additive manufacturing technologies is compared according to their thermal history characteristics, such as preheating treatment and cooling rate. Subsequently, it outlines the research efforts on the quasi-static tensile and dynamic compressive properties of AM Ti-6Al-4V alloy, comparing them with the mechanical properties of cast and forged Ti-6Al-4V components. Both quasi-static tensile and dynamic compressive properties of AM Ti-6Al-4V alloy are dependent on deposition direction, and its fundamental physical mechanisms are only partially understood. Furthermore, the paper delves into the correlation mechanisms between the microstructure and mechanical behavior of typical metal additive manufacturing titanium alloys. Additionally, it summarizes commonly used post-processing techniques, to mitigate the anisotropic mechanical response of AM Ti-6Al-4V alloy under static loads. The prospects are provided for AM titanium alloy research directions including mechanical response of at extreme environmental load, relationship between deposition direction and dynamic mechanical properties, correlation mechanisms between the microstructure and dynamic mechanical behavior, and dynamic constitutive model.
Additive manufacturing (AM) possesses significant advantages in processing critical components in aerospace and defense fields that feature intricate and geometrically complex designs, thanks to its high design freedom and rapid prototyping capabilities. Ti-6Al-4V titanium alloy, renowned for its low density, high specific strength, and creep resistance, is widely utilized in crucial parts of spacecraft and weaponry that frequently endure impact loads. A thorough understanding of the mechanical properties and underlying mechanisms of AM Ti-6Al-4V alloy under static and dynamic loads is crucial for enhancing the service performance of these components. This paper systematically reviews and summarizes the latest advancements in the mechanical response of AM Ti-6Al-4V titanium alloy, aiming at offering a scientific foundation and technical approach to promote the application of key load-bearing components fabricated by additive manufacturing process under extreme conditions. It begins with a brief overview of the classification and working principles of typical metal additive manufacturing technologies including laser direct energy deposition (LDED), laser powder bed fusion (LPBF) and electron beam melting (EBM). Typical microstructure of different metal additive manufacturing technologies is compared according to their thermal history characteristics, such as preheating treatment and cooling rate. Subsequently, it outlines the research efforts on the quasi-static tensile and dynamic compressive properties of AM Ti-6Al-4V alloy, comparing them with the mechanical properties of cast and forged Ti-6Al-4V components. Both quasi-static tensile and dynamic compressive properties of AM Ti-6Al-4V alloy are dependent on deposition direction, and its fundamental physical mechanisms are only partially understood. Furthermore, the paper delves into the correlation mechanisms between the microstructure and mechanical behavior of typical metal additive manufacturing titanium alloys. Additionally, it summarizes commonly used post-processing techniques, to mitigate the anisotropic mechanical response of AM Ti-6Al-4V alloy under static loads. The prospects are provided for AM titanium alloy research directions including mechanical response of at extreme environmental load, relationship between deposition direction and dynamic mechanical properties, correlation mechanisms between the microstructure and dynamic mechanical behavior, and dynamic constitutive model.
, Available online ,
doi: 10.11883/bzycj-2024-0282
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Abstract:
Abstract: Please compose your abstract in English here. Natural gas hydrogenation technology has been gradually used in pipeline transportation, but hydrogen/methane is prone to leakage and explosion accidents. This works uses a 20 L spherical device to study the effects of hydrogen ratio and adding CO2 on the explosion characteristics of methane. The results show that the hydrogen ratio has a promoting effect on the explosion pressure and flame propagation speed of methane, among which the maximum explosion pressure rise rate is the most significant. Carbon dioxide has an inhibitory effect on the explosion pressure and flame propagation speed of the mixed gas, but the suppression effect on pressure parameters with high hydrogen doping ratio is weak. As the hydrogen ratio increases, the hydrodynamic instability and thermal mass diffusion instability of the flame first increase and then weaken. Carbon dioxide has an inhibitory effect on hydrodynamic instability and a promotion effect on thermal mass diffusion instability. It can be seen from the reaction kinetics analysis that as the hydrogen doping ratio increases, the flame laminar burning velocity and adiabatic flame temperature gradually increase, the concentration of active free radicals and the product generation rate increase significantly, and the mixing of hydrogen changes the reaction path of methane. When XH2>0.5, the most sensitive reaction step in the forward direction changes from R38 to R84. Carbon dioxide can reduce the laminar burnin.
Abstract: Please compose your abstract in English here. Natural gas hydrogenation technology has been gradually used in pipeline transportation, but hydrogen/methane is prone to leakage and explosion accidents. This works uses a 20 L spherical device to study the effects of hydrogen ratio and adding CO2 on the explosion characteristics of methane. The results show that the hydrogen ratio has a promoting effect on the explosion pressure and flame propagation speed of methane, among which the maximum explosion pressure rise rate is the most significant. Carbon dioxide has an inhibitory effect on the explosion pressure and flame propagation speed of the mixed gas, but the suppression effect on pressure parameters with high hydrogen doping ratio is weak. As the hydrogen ratio increases, the hydrodynamic instability and thermal mass diffusion instability of the flame first increase and then weaken. Carbon dioxide has an inhibitory effect on hydrodynamic instability and a promotion effect on thermal mass diffusion instability. It can be seen from the reaction kinetics analysis that as the hydrogen doping ratio increases, the flame laminar burning velocity and adiabatic flame temperature gradually increase, the concentration of active free radicals and the product generation rate increase significantly, and the mixing of hydrogen changes the reaction path of methane. When XH2>0.5, the most sensitive reaction step in the forward direction changes from R38 to R84. Carbon dioxide can reduce the laminar burnin.
, Available online ,
doi: 10.11883/bzycj-2024-0353
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Abstract:
In practical engineering, rock masses frequently suffer from recurrent dynamic disturbances, posing serious threats to engineering safety. To investigate the dynamic mechanical behavior of jointed rock masses under cyclic dynamic disturbances, cyclic impact tests were conducted on single-jointed gabbro (SJG) using a split Hopkinson pressure bar test system. The stress equilibrium during the tests was verified using the three-wave method and the force balance coefficient method. The dynamic mechanical behavior of the specimens was comprehensively analyzed in terms of impact resistance, stress-strain relationships, energy and damage evolution, as well as dynamic failure mechanisms. The results show that single-jointed rock specimens can achieve stress equilibrium under cyclic impact conditions. The failure mode of the specimens under cyclic impacts is splitting, and the joint inclination angle significantly influences the impact resistance of the specimens. As the joint inclination angle increases, the impact resistance of the specimens also increases. During the cyclic impact process, strain rebound occurs in all specimens, and their mechanical properties do not monotonically degrade with an increasing number of impacts. The peak stress of the specimens generally exhibits a decreasing trend with the number of impacts. The cumulative damage coefficient, represented by dissipated energy, increases approximately linearly with the number of impacts, while the rate of increase decreases with larger joint inclination angles. Under low-stress impacts, the compressive-shear stress inside the specimens is insufficient to produce shear cracks, and tensile stress causes tensile cracks at the initiation points, which propagate along the loading direction and ultimately lead to splitting failure of the specimens.
In practical engineering, rock masses frequently suffer from recurrent dynamic disturbances, posing serious threats to engineering safety. To investigate the dynamic mechanical behavior of jointed rock masses under cyclic dynamic disturbances, cyclic impact tests were conducted on single-jointed gabbro (SJG) using a split Hopkinson pressure bar test system. The stress equilibrium during the tests was verified using the three-wave method and the force balance coefficient method. The dynamic mechanical behavior of the specimens was comprehensively analyzed in terms of impact resistance, stress-strain relationships, energy and damage evolution, as well as dynamic failure mechanisms. The results show that single-jointed rock specimens can achieve stress equilibrium under cyclic impact conditions. The failure mode of the specimens under cyclic impacts is splitting, and the joint inclination angle significantly influences the impact resistance of the specimens. As the joint inclination angle increases, the impact resistance of the specimens also increases. During the cyclic impact process, strain rebound occurs in all specimens, and their mechanical properties do not monotonically degrade with an increasing number of impacts. The peak stress of the specimens generally exhibits a decreasing trend with the number of impacts. The cumulative damage coefficient, represented by dissipated energy, increases approximately linearly with the number of impacts, while the rate of increase decreases with larger joint inclination angles. Under low-stress impacts, the compressive-shear stress inside the specimens is insufficient to produce shear cracks, and tensile stress causes tensile cracks at the initiation points, which propagate along the loading direction and ultimately lead to splitting failure of the specimens.
, Available online ,
doi: 10.11883/bzycj-2024-0062
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Abstract:
To delve into the nuanced understanding of the deformation characteristics of thin-walled ellipsoidal shells under localized impact loads, a systematic and comprehensive research approach was employed, integrating both experimental exploration and simulation analysis. The experimental setup featured a lightweight pneumatic gun for conducting projectile impact experiments, with the deformation process meticulously recorded using advanced three-dimensional Digital Image Correlation (DIC) technology. This extensive study necessitated a detailed examination of the overall deformation morphologies of ellipsoidal shells, particularly under varying initial impact velocities induced by cylindrical projectiles. The outcomes of the study provided crucial insights into determining the central depression depth and the corresponding boundary positions of the long and short axes. In the simulation analysis of ellipsoidal shell impacts by projectiles, the primary focus was directed towards elucidating the intricate interplay of alterations in three curvature radii on the complex interactions affecting the ellipsoidal shell's depression depth and the long and short axes. Employing dimensional analysis, essential dimensionless independent variables governing deformation characteristics were identified, refined through parameter sensitivity analysis to eliminate less influential parameters. The resulting specific response surface function elucidates the nuanced relationships among dimensionless deformation characteristics, the three curvature radii, and velocity. Under the condition of consistent material properties and the maintenance of equivalent shrinkage ratios for projectile body size and shell thickness, a predictive formula for global deformation based on depression depth and boundary conditions was derived. This formula demonstrates commendable dimensional consistency and affords high prediction accuracy. The potential application extends to informing the engineering design of impact load protection for large-sized curved shells, holding considerable promise in enhancing structural resilience and mitigating potential risks in engineering applications. The comprehensiveness and depth of this study provide a robust foundation for future research in related fields.
To delve into the nuanced understanding of the deformation characteristics of thin-walled ellipsoidal shells under localized impact loads, a systematic and comprehensive research approach was employed, integrating both experimental exploration and simulation analysis. The experimental setup featured a lightweight pneumatic gun for conducting projectile impact experiments, with the deformation process meticulously recorded using advanced three-dimensional Digital Image Correlation (DIC) technology. This extensive study necessitated a detailed examination of the overall deformation morphologies of ellipsoidal shells, particularly under varying initial impact velocities induced by cylindrical projectiles. The outcomes of the study provided crucial insights into determining the central depression depth and the corresponding boundary positions of the long and short axes. In the simulation analysis of ellipsoidal shell impacts by projectiles, the primary focus was directed towards elucidating the intricate interplay of alterations in three curvature radii on the complex interactions affecting the ellipsoidal shell's depression depth and the long and short axes. Employing dimensional analysis, essential dimensionless independent variables governing deformation characteristics were identified, refined through parameter sensitivity analysis to eliminate less influential parameters. The resulting specific response surface function elucidates the nuanced relationships among dimensionless deformation characteristics, the three curvature radii, and velocity. Under the condition of consistent material properties and the maintenance of equivalent shrinkage ratios for projectile body size and shell thickness, a predictive formula for global deformation based on depression depth and boundary conditions was derived. This formula demonstrates commendable dimensional consistency and affords high prediction accuracy. The potential application extends to informing the engineering design of impact load protection for large-sized curved shells, holding considerable promise in enhancing structural resilience and mitigating potential risks in engineering applications. The comprehensiveness and depth of this study provide a robust foundation for future research in related fields.
, Available online ,
doi: 10.11883/bzycj-2024-0350
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Abstract:
In the past, the design of structures resistant to conventional weapons has largely focused on the study of explosion stress waves in solid media, particularly in soil and rock media (i.e., ground shock issues), while the research on the propagation and attenuation of explosion stress waves in concrete remains relatively scarce. To investigate the propagation behavior of stress waves in the near-field of cylindrical charge explosions in concrete, this paper conducts a numerical simulation study based on the KCC constitutive model and the MM-ALE algorithm. Firstly, the applicability of the constitutive model parameters and numerical algorithm is validated by comparing the results with existing experimental data. Subsequently, the impact of charge shape on the explosion failure zone and the propagation behavior of explosion-induced stress waves is analyzed, and a formula for calculating the peak stress of stress waves generated by cylindrical charge explosions is established. Finally, a stress peak coupling coefficient is introduced to quantitatively analyze the impact of burial depth on the distribution of normal peak stress in explosion-induced stress waves. It was found that the attenuation patterns of explosion-induced stress waves differ significantly across various explosion failure zones. In comparison to the mid-field zone (transition and fracture zones), the near-field zone (quasi-fluid and crushing zones) exhibits faster attenuation. Additionally, an increase in the length-to-diameter ratio of the cylindrical charge accelerates the attenuation of normal peak stress. Moreover, the established formula for calculating the peak stress of explosion-induced stress waves enables accurate and rapid calculate of the normal peak stress for cylindrical charges with different length-to-diameter ratios and burial depths. This empirical formula can serve as a valuable reference for blast-resistant design of concrete structures.
In the past, the design of structures resistant to conventional weapons has largely focused on the study of explosion stress waves in solid media, particularly in soil and rock media (i.e., ground shock issues), while the research on the propagation and attenuation of explosion stress waves in concrete remains relatively scarce. To investigate the propagation behavior of stress waves in the near-field of cylindrical charge explosions in concrete, this paper conducts a numerical simulation study based on the KCC constitutive model and the MM-ALE algorithm. Firstly, the applicability of the constitutive model parameters and numerical algorithm is validated by comparing the results with existing experimental data. Subsequently, the impact of charge shape on the explosion failure zone and the propagation behavior of explosion-induced stress waves is analyzed, and a formula for calculating the peak stress of stress waves generated by cylindrical charge explosions is established. Finally, a stress peak coupling coefficient is introduced to quantitatively analyze the impact of burial depth on the distribution of normal peak stress in explosion-induced stress waves. It was found that the attenuation patterns of explosion-induced stress waves differ significantly across various explosion failure zones. In comparison to the mid-field zone (transition and fracture zones), the near-field zone (quasi-fluid and crushing zones) exhibits faster attenuation. Additionally, an increase in the length-to-diameter ratio of the cylindrical charge accelerates the attenuation of normal peak stress. Moreover, the established formula for calculating the peak stress of explosion-induced stress waves enables accurate and rapid calculate of the normal peak stress for cylindrical charges with different length-to-diameter ratios and burial depths. This empirical formula can serve as a valuable reference for blast-resistant design of concrete structures.
, Available online ,
doi: 10.11883/bzycj-2024-0269
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Abstract:
In order to obtain the ignition behavior of PBX molding powder under gap extrusion loading, an experimental device for gap extrusion of molding powder was designed based on projectile impact. In order to ensure that there is no other flow space except the designed gap, the surface of the sample was covered with cushion and coated with grease for sealing, and the movement and reaction of molding powder squeezing into the gap were recorded by high-speed photography. By changing the ratio of gap area to sample cross-sectional area, the influence of compaction on ignition was studied. The results show that in the absence of grease seal, PBX molding powder undergoes particle crushing and compaction, and then the compacted molding powder is extruded from the clearance near the cushion, and ignition occurs in the extrusion process. The ignition position is at the interface between explosive and cushion. In the case of grease seal, PBX molding powder does not ignite for a period of time after compaction. When the indenter moves halfway, a “wedge-shaped” slip zone is formed, and a slip-dead zone interface could be seen in high-speed camera photos. Then the deformation mode evolves from “single wedge” slip zone to “double wedge” slip zone, and the shear effect of slip-dead zone interface does not cause ignition. At the later stage of loading, the indenter travels close to the gap surface, and the “wedge-shaped” slip zone disappears. Before and after the collision between the indenter and the gap, the explosive ignites once, respectively. The first ignition occurs at the entrance of the gap, and the second ignition occurs at the corner of the indenter. Compaction effect has an important influence on ignition behavior. After compaction, the threshold value of ignition speed is obviously reduced, and the impact speed causing ignition is only 4.5 m/s.
In order to obtain the ignition behavior of PBX molding powder under gap extrusion loading, an experimental device for gap extrusion of molding powder was designed based on projectile impact. In order to ensure that there is no other flow space except the designed gap, the surface of the sample was covered with cushion and coated with grease for sealing, and the movement and reaction of molding powder squeezing into the gap were recorded by high-speed photography. By changing the ratio of gap area to sample cross-sectional area, the influence of compaction on ignition was studied. The results show that in the absence of grease seal, PBX molding powder undergoes particle crushing and compaction, and then the compacted molding powder is extruded from the clearance near the cushion, and ignition occurs in the extrusion process. The ignition position is at the interface between explosive and cushion. In the case of grease seal, PBX molding powder does not ignite for a period of time after compaction. When the indenter moves halfway, a “wedge-shaped” slip zone is formed, and a slip-dead zone interface could be seen in high-speed camera photos. Then the deformation mode evolves from “single wedge” slip zone to “double wedge” slip zone, and the shear effect of slip-dead zone interface does not cause ignition. At the later stage of loading, the indenter travels close to the gap surface, and the “wedge-shaped” slip zone disappears. Before and after the collision between the indenter and the gap, the explosive ignites once, respectively. The first ignition occurs at the entrance of the gap, and the second ignition occurs at the corner of the indenter. Compaction effect has an important influence on ignition behavior. After compaction, the threshold value of ignition speed is obviously reduced, and the impact speed causing ignition is only 4.5 m/s.
, Available online ,
doi: 10.11883/bzycj-2024-0147
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Abstract:
In order to achieve accurate characterization of the process of tungsten alloy projectile penetrating the target, Finite Element Method (FEM), Smoothed Particle Galerkin (SPG), Smoothed Particle Hydrodynamics (SPH) and FE-SPH adaptive numerical simulation methods were used respectively to carry out numerical simulation calculation of tungsten alloy projectile penetrating Q235A steel target. The advantages and disadvantages of four numerical simulation methods in describing the residual velocity of the projectile, the perforation diameter of the target plate and the formation of secondary fragments after the projectile penetrates the target are compared. The results show that in terms of describing the residual velocity of the projectile, FEM method and FE-SPH adaptive method are strictly dependent on the selection of failure criteria and failure parameters because FEM method is based on the element erosion algorithm when dealing with the material failure problem. The SPG method is based on the bond fracture model when simulating material failure. The bond can be broken to simulate material failure without deleting SPG particles, and it is insensitive to failure parameters, so relatively accurate results can be obtained without adjusting failure parameters. In terms of describing the perforation diameter of the target plate, FEM and FE-SPH adaptive methods have accurate material boundaries and can accurately characterize the perforation morphology of the target plate, but the perforation diameter of the target plate varies greatly under different failure criteria. The SPH method is inferior to the SPG method in characterizing the perforation diameter of the target plate, and because the SPG method is not sensitive to the failure parameters, it can also accurately characterize the perforation diameter of the target plate. In terms of secondary fragment generation, FEM method can only generate large fragments, but not small fragments. The SPG method can characterize large and small fragments, but cannot output SPG particles as fragment information. Both FE-SPH adaptive method and SPH method can characterize large and small fragments, and the FE-SPH adaptive method can directly obtain the information of large fragments, but compared with the SPH method, the calculation efficiency is low.
In order to achieve accurate characterization of the process of tungsten alloy projectile penetrating the target, Finite Element Method (FEM), Smoothed Particle Galerkin (SPG), Smoothed Particle Hydrodynamics (SPH) and FE-SPH adaptive numerical simulation methods were used respectively to carry out numerical simulation calculation of tungsten alloy projectile penetrating Q235A steel target. The advantages and disadvantages of four numerical simulation methods in describing the residual velocity of the projectile, the perforation diameter of the target plate and the formation of secondary fragments after the projectile penetrates the target are compared. The results show that in terms of describing the residual velocity of the projectile, FEM method and FE-SPH adaptive method are strictly dependent on the selection of failure criteria and failure parameters because FEM method is based on the element erosion algorithm when dealing with the material failure problem. The SPG method is based on the bond fracture model when simulating material failure. The bond can be broken to simulate material failure without deleting SPG particles, and it is insensitive to failure parameters, so relatively accurate results can be obtained without adjusting failure parameters. In terms of describing the perforation diameter of the target plate, FEM and FE-SPH adaptive methods have accurate material boundaries and can accurately characterize the perforation morphology of the target plate, but the perforation diameter of the target plate varies greatly under different failure criteria. The SPH method is inferior to the SPG method in characterizing the perforation diameter of the target plate, and because the SPG method is not sensitive to the failure parameters, it can also accurately characterize the perforation diameter of the target plate. In terms of secondary fragment generation, FEM method can only generate large fragments, but not small fragments. The SPG method can characterize large and small fragments, but cannot output SPG particles as fragment information. Both FE-SPH adaptive method and SPH method can characterize large and small fragments, and the FE-SPH adaptive method can directly obtain the information of large fragments, but compared with the SPH method, the calculation efficiency is low.
, Available online ,
doi: 10.11883/bzycj-2024-0245
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Abstract:
The defective cracks were prefabricated on the wall of the notch holes by using PMMA material，which were parallel or vertical to the notch, and the distance from the defective cracks to the centre of the holes was 2mm, 3mm and 4mm. The influence of notch hole wall defects on the expansion of notch blast cracks was investigated by using a digital dynamic caustic experimental system with numerical simulation. At the same time, TATP explosives were employed as a charge, which served to mitigate the effect of gun smoke on the dynamic caustic experimental system and to improve the experimental design. The results demonstrate that the reflection of the stress wave at parallel defects results in a downward shift in the direction of crack initiation at the notch, but the refraction of the stress wave at vertical defects don't affect the direction of crack initiation. The presence of wall defects in the hole impedes the impact of stress waves and blast gases on the cracks at the notch, resulting in a reduction in the length, expansion rate, and strength factor values of the cracks, and the degree of inhibition is contingent upon the distance of the defects from the centre of the borehole. As the distance between the parallel defects and the centre of the borehole increases, the inhibition effect of the parallel defects on both sides of the notch cracks gradually decreases; the inhibition effect of vertical defects on the far side of the notch cracks gradually decreases, while the inhibition effect on the proximal side of the notch cracks gradually enhances. The left and right notch cracks of vertical defects are more significantly affected by the boundary reflected stress wave than those of parallel defects. The left side notch cracks don't show an obvious pattern due to the pre-existing reflected stress wave at the defects; however, the right side notch cracks are significantly reduced by the boundary reflected stress wave with the vertical defects moving away from the centre of the notch holes.
The defective cracks were prefabricated on the wall of the notch holes by using PMMA material，which were parallel or vertical to the notch, and the distance from the defective cracks to the centre of the holes was 2mm, 3mm and 4mm. The influence of notch hole wall defects on the expansion of notch blast cracks was investigated by using a digital dynamic caustic experimental system with numerical simulation. At the same time, TATP explosives were employed as a charge, which served to mitigate the effect of gun smoke on the dynamic caustic experimental system and to improve the experimental design. The results demonstrate that the reflection of the stress wave at parallel defects results in a downward shift in the direction of crack initiation at the notch, but the refraction of the stress wave at vertical defects don't affect the direction of crack initiation. The presence of wall defects in the hole impedes the impact of stress waves and blast gases on the cracks at the notch, resulting in a reduction in the length, expansion rate, and strength factor values of the cracks, and the degree of inhibition is contingent upon the distance of the defects from the centre of the borehole. As the distance between the parallel defects and the centre of the borehole increases, the inhibition effect of the parallel defects on both sides of the notch cracks gradually decreases; the inhibition effect of vertical defects on the far side of the notch cracks gradually decreases, while the inhibition effect on the proximal side of the notch cracks gradually enhances. The left and right notch cracks of vertical defects are more significantly affected by the boundary reflected stress wave than those of parallel defects. The left side notch cracks don't show an obvious pattern due to the pre-existing reflected stress wave at the defects; however, the right side notch cracks are significantly reduced by the boundary reflected stress wave with the vertical defects moving away from the centre of the notch holes.
, Available online ,
doi: 10.11883/bzycj-2024-0381
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Abstract:
In order to study the propagation process of shock wave in the tunnel under different explosion yields and different charge positions, a test tunnel was established to meet the needs of personnel and equipment. The effects of charge amount and charge position on the overpressure time history curve and shock wave parameter distribution were compared by experiments. The same simulation calculations were carried out under the same experimental conditions, and combined with the simulated pressure contour diagram and overpressure time history curve, it was found that the wavefront motion was the main reason for the evolution of the overpressure time history curve and the change of parameter distribution. Based on the experimental and numerical simulation results, a prediction model of shock wave overpressure in the tunnel considering the aspect ratio of the tunnel cross-section size and width is obtained.
In order to study the propagation process of shock wave in the tunnel under different explosion yields and different charge positions, a test tunnel was established to meet the needs of personnel and equipment. The effects of charge amount and charge position on the overpressure time history curve and shock wave parameter distribution were compared by experiments. The same simulation calculations were carried out under the same experimental conditions, and combined with the simulated pressure contour diagram and overpressure time history curve, it was found that the wavefront motion was the main reason for the evolution of the overpressure time history curve and the change of parameter distribution. Based on the experimental and numerical simulation results, a prediction model of shock wave overpressure in the tunnel considering the aspect ratio of the tunnel cross-section size and width is obtained.
, Available online ,
doi: 10.11883/bzycj-2024-0371
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Abstract:
The containment process of aero-engine casing is very complex, which involves large deformation, material viscoplasticity and nonlinear dynamic response of structural elements. In this paper, a new method combining ballistic impact test and finite element analysis is proposed to evaluate the containment capability of real aero-engine fan casing. A blade-liked projectile was used to impact the half ring simulator to obtain the impact resistance of the titanium alloy casing. The high-speed cameras were aimed perpendicular to the path to measure pre- and post-impact velocities of the projectile. Using the DIC (Digital Image Correlation) technology to determine the deformation field of the half ring simulator. Based on the commercial finite element software LS-DYNA, a corresponding numerical simulation model was established. The predicted results of the residual velocity of the projectile, radial deformation of the target, and the morphology of structural damage are compared with experimental results. The good agreement between the two indicated the accuracy of the numerical method. Under the low energy impact, the projectile was rebound, and the half ring absorbed energy with bulge. Whereas in the high energy impact, the projectile penetrated the half ring target and result in tear in the rear surface. Finally, the validated numerical simulation method was employed to simulate the real fan blade/casing containment process, and the influence of the blade rotate speed and the blade size on casing containment are studied. The results show that, there were two major impacts between the fan blade and the casing, one is the leading edge of the blade impacts on the casing to form small tear marks, the other is the blade body subjected to the casing causing tear band and bend outward. Obviously, the second impact was the most destructive to the casing. With the increase of the blade rotate speed, the damage area of the casing enlarges, and the plastic deformation energy increases rapidly, thereby diminishing the containment capability. The size of the released blade mainly affects the second impact phase on the casing, with larger sizes resulting in higher levels of interaction forces.
The containment process of aero-engine casing is very complex, which involves large deformation, material viscoplasticity and nonlinear dynamic response of structural elements. In this paper, a new method combining ballistic impact test and finite element analysis is proposed to evaluate the containment capability of real aero-engine fan casing. A blade-liked projectile was used to impact the half ring simulator to obtain the impact resistance of the titanium alloy casing. The high-speed cameras were aimed perpendicular to the path to measure pre- and post-impact velocities of the projectile. Using the DIC (Digital Image Correlation) technology to determine the deformation field of the half ring simulator. Based on the commercial finite element software LS-DYNA, a corresponding numerical simulation model was established. The predicted results of the residual velocity of the projectile, radial deformation of the target, and the morphology of structural damage are compared with experimental results. The good agreement between the two indicated the accuracy of the numerical method. Under the low energy impact, the projectile was rebound, and the half ring absorbed energy with bulge. Whereas in the high energy impact, the projectile penetrated the half ring target and result in tear in the rear surface. Finally, the validated numerical simulation method was employed to simulate the real fan blade/casing containment process, and the influence of the blade rotate speed and the blade size on casing containment are studied. The results show that, there were two major impacts between the fan blade and the casing, one is the leading edge of the blade impacts on the casing to form small tear marks, the other is the blade body subjected to the casing causing tear band and bend outward. Obviously, the second impact was the most destructive to the casing. With the increase of the blade rotate speed, the damage area of the casing enlarges, and the plastic deformation energy increases rapidly, thereby diminishing the containment capability. The size of the released blade mainly affects the second impact phase on the casing, with larger sizes resulting in higher levels of interaction forces.
, Available online ,
doi: 10.11883/bzycj-2024-0414
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Abstract:
The presence of joints significantly influences the performance of rock blasting. The impact of different joint inclination on blasting fragmentation was studied through a combination of experiments and numerical simulations. In this study, a group of concrete model specimens containing joints with different angles was used to carry out blasting experiments to investigate the effect of joint inclination on blast fragmentation. During experiments, detonators were placed in vertical boreholes in the specimens and detonated, while high-speed camera was used to capture the fragmentation process. The dynamic responses of joint surfaces at different time intervals after detonation was observed, and blasting fragmentation distribution was extracted using image processing techniques. The effect of joint inclination on blasting fragmentation was analyzed. Then LS-DYNA finite element numerical simulations were developed to obtain the propagation of stress waves and the evolution of strain fields within the specimens. Experimental and numerical results indicated that the joints have a significant influence on the distribution of blasting fragmentation and the propagation of stress waves, and the impact of the joints on the blasting performance was mainly attributed to the reflection of blasting waves from the joints, which was related to the deformation characteristics of the joints. With the increase of joint inclination, the blasting fragmentation initially decreased followed by an increase. The effective stress and peak particle velocity (PPV) transmission in the joints decreased overall with the increase of joint inclination but showed a rebound between 45° and 60°, which identified approximately 45° as the most favorable condition for rock fragmentation under blasting. Moreover, the results obtained from numerical crack network reconstruction and image processing revealed that there was an upsurge in the occurrence of vertical cracks in the specimen as the joint inclination increased, while a decline was observed in the presence of horizontal cracks. These study results help in understanding the interaction between joints and blasting stresses and optimizing blasting parameters in jointed rock.
The presence of joints significantly influences the performance of rock blasting. The impact of different joint inclination on blasting fragmentation was studied through a combination of experiments and numerical simulations. In this study, a group of concrete model specimens containing joints with different angles was used to carry out blasting experiments to investigate the effect of joint inclination on blast fragmentation. During experiments, detonators were placed in vertical boreholes in the specimens and detonated, while high-speed camera was used to capture the fragmentation process. The dynamic responses of joint surfaces at different time intervals after detonation was observed, and blasting fragmentation distribution was extracted using image processing techniques. The effect of joint inclination on blasting fragmentation was analyzed. Then LS-DYNA finite element numerical simulations were developed to obtain the propagation of stress waves and the evolution of strain fields within the specimens. Experimental and numerical results indicated that the joints have a significant influence on the distribution of blasting fragmentation and the propagation of stress waves, and the impact of the joints on the blasting performance was mainly attributed to the reflection of blasting waves from the joints, which was related to the deformation characteristics of the joints. With the increase of joint inclination, the blasting fragmentation initially decreased followed by an increase. The effective stress and peak particle velocity (PPV) transmission in the joints decreased overall with the increase of joint inclination but showed a rebound between 45° and 60°, which identified approximately 45° as the most favorable condition for rock fragmentation under blasting. Moreover, the results obtained from numerical crack network reconstruction and image processing revealed that there was an upsurge in the occurrence of vertical cracks in the specimen as the joint inclination increased, while a decline was observed in the presence of horizontal cracks. These study results help in understanding the interaction between joints and blasting stresses and optimizing blasting parameters in jointed rock.
Study on dynamic energy dissipation mechanism and damage characteristics of high-temperature marbles
, Available online ,
doi: 10.11883/bzycj-2024-0405
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Abstract:
For the sake of investigate the effect of high temperature on the energy characteristics of marble， ANSYS/LS-DYNA was used to carry out dynamic compression tests on marble with six temperature gradients and five impact velocities，to analyse the mechanical properties of marble under high-temperature dynamic loading，the temperature effect of energy evolution，and ultimately，to explore the energy criterion of high-temperature marble strength failure from the perspective of energy dissipation. The results show that: (1) the Holmquist-Johnson-Cook（HJC）intrinsic model can reasonably and effectively simulate the dynamic change of marble damage process under different temperatures; (2) with the increase of temperature，the dynamic peak strength and dynamic elastic modulus of marble are quadratically negatively correlated with the temperature，and the dynamic peak strain is quadratically positively correlated with the temperature，and the damage morphology is changed from X-type to Conjugate shear damage. (3) The increase in temperature reduces the energy storage capacity of the marble specimen to a certain extent，while the effect of high temperature on the energy dissipation capacity of marble is transformed from a facilitating effect to an inhibiting effect with 600℃ as the cut-off point. When the temperature reaches 600℃，the peak strength is greatly reduced，the ductility of the marble increases，crushing damage is presented，and the dissipated strain energy reaches the maximum value. 600℃ can be used as the threshold temperature for the brittle-delayed transformation of the marble; (4) According to the characteristics of the energy evolution process，the point of steep increase of the dissipated strain energy will be (4) Based on the characteristics of energy evolution process，from the perspective of energy accumulation and dissipation，combined with the internal energy and kinetic energy evolution laws obtained by ANSYS/LS-DYNA，the point of steep increase of dissipated strain energy is regarded as the information point of the precursor of overall instability and damage of marble，and the inflection point of the first appearance of the growth rate of elastic energy consumption ratio is defined according to the curve of the stress-elastic energy consumption ratio-strain relationship as the criterion of the strength failure energy of the marble.
For the sake of investigate the effect of high temperature on the energy characteristics of marble， ANSYS/LS-DYNA was used to carry out dynamic compression tests on marble with six temperature gradients and five impact velocities，to analyse the mechanical properties of marble under high-temperature dynamic loading，the temperature effect of energy evolution，and ultimately，to explore the energy criterion of high-temperature marble strength failure from the perspective of energy dissipation. The results show that: (1) the Holmquist-Johnson-Cook（HJC）intrinsic model can reasonably and effectively simulate the dynamic change of marble damage process under different temperatures; (2) with the increase of temperature，the dynamic peak strength and dynamic elastic modulus of marble are quadratically negatively correlated with the temperature，and the dynamic peak strain is quadratically positively correlated with the temperature，and the damage morphology is changed from X-type to Conjugate shear damage. (3) The increase in temperature reduces the energy storage capacity of the marble specimen to a certain extent，while the effect of high temperature on the energy dissipation capacity of marble is transformed from a facilitating effect to an inhibiting effect with 600℃ as the cut-off point. When the temperature reaches 600℃，the peak strength is greatly reduced，the ductility of the marble increases，crushing damage is presented，and the dissipated strain energy reaches the maximum value. 600℃ can be used as the threshold temperature for the brittle-delayed transformation of the marble; (4) According to the characteristics of the energy evolution process，the point of steep increase of the dissipated strain energy will be (4) Based on the characteristics of energy evolution process，from the perspective of energy accumulation and dissipation，combined with the internal energy and kinetic energy evolution laws obtained by ANSYS/LS-DYNA，the point of steep increase of dissipated strain energy is regarded as the information point of the precursor of overall instability and damage of marble，and the inflection point of the first appearance of the growth rate of elastic energy consumption ratio is defined according to the curve of the stress-elastic energy consumption ratio-strain relationship as the criterion of the strength failure energy of the marble.
, Available online ,
doi: 10.11883/bzycj-2024-0404
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Abstract:
It is of great significance to develop an engineering model based on the physical mechanism of non-shock initiation reaction of structural charge, which can be used to describe the reaction evolution process and quantify the reaction intensity for evaluating the weapons and ammunition safety. Currently, some models describing the charge reaction evolution were one-dimensional pressurization of burning crack and charge burning crack network, but these models had many assumptions, and some restrictive problems, such as non-considering of the cavity expansion volume, and the unclear burning crack propagation coefficient. Therefore, a constrained charge combustion reaction evolution model was established with fracture toughness and reaction pressure as the main parameters based on the main control mechanism of charge reaction crack propagation in this study, which can describe the combustion gaseous product pressurization and shell constraint strength during combustion evolution. Relevant details for the control model establishment process were given. The model reliability of confined charge reaction combustion evolution was verified via the experiments of PBX-3 (87% HMX) explosive combustion reaction evolution under mass inertial confinement. The mass velocity-time was recorded by PDV (Photonic Doppler Velocimetry) transducers, the pressure-time profiles was recorded via pressure transducers and the experimental process was captured via high-speed camera. Above experimental results were compared with calculated results from the control model proposed in this work. The results show that the reaction pressurization process calculated via the model is roughly consistent with the pressure increasing trend in the experiment (calculated by the mass velocity), and the control model considering the structural venting effect can reflect the competition mechanism between combustion gas pressurization and venting in the pressure increasing process, and the relationship between the pressure increasing trend and the vent coefficient is in line with the mechanism analysis expectation. The results can provide support for deepening the understanding of accidental explosives combustion reaction evolution mechanism.
It is of great significance to develop an engineering model based on the physical mechanism of non-shock initiation reaction of structural charge, which can be used to describe the reaction evolution process and quantify the reaction intensity for evaluating the weapons and ammunition safety. Currently, some models describing the charge reaction evolution were one-dimensional pressurization of burning crack and charge burning crack network, but these models had many assumptions, and some restrictive problems, such as non-considering of the cavity expansion volume, and the unclear burning crack propagation coefficient. Therefore, a constrained charge combustion reaction evolution model was established with fracture toughness and reaction pressure as the main parameters based on the main control mechanism of charge reaction crack propagation in this study, which can describe the combustion gaseous product pressurization and shell constraint strength during combustion evolution. Relevant details for the control model establishment process were given. The model reliability of confined charge reaction combustion evolution was verified via the experiments of PBX-3 (87% HMX) explosive combustion reaction evolution under mass inertial confinement. The mass velocity-time was recorded by PDV (Photonic Doppler Velocimetry) transducers, the pressure-time profiles was recorded via pressure transducers and the experimental process was captured via high-speed camera. Above experimental results were compared with calculated results from the control model proposed in this work. The results show that the reaction pressurization process calculated via the model is roughly consistent with the pressure increasing trend in the experiment (calculated by the mass velocity), and the control model considering the structural venting effect can reflect the competition mechanism between combustion gas pressurization and venting in the pressure increasing process, and the relationship between the pressure increasing trend and the vent coefficient is in line with the mechanism analysis expectation. The results can provide support for deepening the understanding of accidental explosives combustion reaction evolution mechanism.
, Available online ,
doi: 10.11883/bzycj-2024-0366
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Abstract:
In order to effectively predict and control the consequences of fuel-air mixtures explosions in enclosed spaces, and thereby reduce the casualties and property losses caused by accidents, this study had investigated the relationship between the explosive overpressure characteristics of fuel-air mixtures and the spatial scale of explosions. The experiment carried out closed square pipes with varying length-to-diameter ratios, volumes and lengths to examine the impact of fuel-air mixtures explosive overpressure characteristics by keeping the initial oil and gas concentration, ignition position, and ignition energy constant. The experimental results showed that the rate of overpressure rise goes through three stages, a rapid increase period, a continuous oscillation period and an attenuation termination period, which reveals the dynamic relationship between reaction rate and heat loss. Under the same volume (21.2L), with the increase of length-diameter ratio (from 7.1 to 35.7), the maximum overpressure decreased by 47.5% (from 472.9kPa to 248.5kPa), and the average overpressure rise rate decreased by 73.5% (from 1359kPa·s-1 to 360kPa·s-1), and the maximum overpressure rise rate reduced by 66.4% (from 3204kPa·s-1 to 1078kPa·s-1), and the explosion power lessened by 86.2% (from 643 (kPa)2/ms to 89 (kPa)2/ms), which is attributed to the change in the nozzle area (from 207cm2 to 71cm2) affecting the reaction rate and the change in the internal surface area of the pipeline (from 629cm2 to 1022cm2) affecting the heat loss. Further analysis of the experimental results reveals that the changes in the nozzle area affecting the flame front area and reaction rate directly, impacts on the maximum overpressure more directly and significantly. While, the changes in the inner surface area has a relatively indirect effect on the maximum overpressure by regulating energy transfer and heat loss. Additionally, pipeline length is a crucial factor affecting the time to reach maximum overpressure. The increase of the pipeline not only increases the heat loss, but also delays the superposition time point of the reflected wave and the incident wave, with the energy of the reflected wave undergoing relatively attenuation.
In order to effectively predict and control the consequences of fuel-air mixtures explosions in enclosed spaces, and thereby reduce the casualties and property losses caused by accidents, this study had investigated the relationship between the explosive overpressure characteristics of fuel-air mixtures and the spatial scale of explosions. The experiment carried out closed square pipes with varying length-to-diameter ratios, volumes and lengths to examine the impact of fuel-air mixtures explosive overpressure characteristics by keeping the initial oil and gas concentration, ignition position, and ignition energy constant. The experimental results showed that the rate of overpressure rise goes through three stages, a rapid increase period, a continuous oscillation period and an attenuation termination period, which reveals the dynamic relationship between reaction rate and heat loss. Under the same volume (21.2L), with the increase of length-diameter ratio (from 7.1 to 35.7), the maximum overpressure decreased by 47.5% (from 472.9kPa to 248.5kPa), and the average overpressure rise rate decreased by 73.5% (from 1359kPa·s-1 to 360kPa·s-1), and the maximum overpressure rise rate reduced by 66.4% (from 3204kPa·s-1 to 1078kPa·s-1), and the explosion power lessened by 86.2% (from 643 (kPa)2/ms to 89 (kPa)2/ms), which is attributed to the change in the nozzle area (from 207cm2 to 71cm2) affecting the reaction rate and the change in the internal surface area of the pipeline (from 629cm2 to 1022cm2) affecting the heat loss. Further analysis of the experimental results reveals that the changes in the nozzle area affecting the flame front area and reaction rate directly, impacts on the maximum overpressure more directly and significantly. While, the changes in the inner surface area has a relatively indirect effect on the maximum overpressure by regulating energy transfer and heat loss. Additionally, pipeline length is a crucial factor affecting the time to reach maximum overpressure. The increase of the pipeline not only increases the heat loss, but also delays the superposition time point of the reflected wave and the incident wave, with the energy of the reflected wave undergoing relatively attenuation.
, Available online ,
doi: 10.11883/bzycj-2024-0274
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Abstract:
The purpose of this paper is to study the pressure characteristics and structural deformation mechanism of aluminum honeycomb sandwich plates (AHSPs) under water impact through experimental methods. The self-designed drop test platform was established in the water tank, and the water impact tests on AHSPs were carried out, then the repeatability of the experiment has been verified. On this basis, the water impact load characteristics, deformation mode, permanent deflection characteristics of AHSPs during the process of water entry were studied. Results show that, due to the influence of air cushion effect has a great influence on the pressure, the water impact pressure on the surface of AHSPs is unevenly distributed. Meanwhile, the peak value of water impact pressure at the middle gauging point is larger than that of the 1/4 gauging point, when the drop height is larger than 0.5m. In addition, the elastic-plastic deformation of AHSPs during the water entry process will affect value of the water impact pressure. Namely, compared with the water entry of rigid plate, the peak value of the water impact pressure of AHSPs is smaller. What’s more, compared with the equivalent aluminum plate with the same mass, the value of the peak water impact pressure of AHSPs is smaller, while the pressure duration is longer. For the water impact pressure obtained by different methods in references, the peak values of the water impact pressure approximately increase linearly with the drop height. The deformation modes of the face sheet of AHSPs at different drop heights are almost the same, meanwhile, the rectangular deformation zone composed of four plastic hinge lines is generated in the middle area, and the surrounding area is a trapezoidal deformation zone. What’s more, with the increase of the drop height, the rectangular deformation zone expands around. Besides, with the increase of the drop height, the permanent deflections of front and back faces of AHSPs increase approximately in form of quadratic parabola with decreasing slope. Suffering from water entry impact loadings, the AHSPs will experience large deformation and absorb energy, and the permanent deflections of the back sheet are obviously smaller than those of the equivalent aluminum plate, indicating that the AHSPs have better impact resistance compared with the equivalent aluminum plate.
The purpose of this paper is to study the pressure characteristics and structural deformation mechanism of aluminum honeycomb sandwich plates (AHSPs) under water impact through experimental methods. The self-designed drop test platform was established in the water tank, and the water impact tests on AHSPs were carried out, then the repeatability of the experiment has been verified. On this basis, the water impact load characteristics, deformation mode, permanent deflection characteristics of AHSPs during the process of water entry were studied. Results show that, due to the influence of air cushion effect has a great influence on the pressure, the water impact pressure on the surface of AHSPs is unevenly distributed. Meanwhile, the peak value of water impact pressure at the middle gauging point is larger than that of the 1/4 gauging point, when the drop height is larger than 0.5m. In addition, the elastic-plastic deformation of AHSPs during the water entry process will affect value of the water impact pressure. Namely, compared with the water entry of rigid plate, the peak value of the water impact pressure of AHSPs is smaller. What’s more, compared with the equivalent aluminum plate with the same mass, the value of the peak water impact pressure of AHSPs is smaller, while the pressure duration is longer. For the water impact pressure obtained by different methods in references, the peak values of the water impact pressure approximately increase linearly with the drop height. The deformation modes of the face sheet of AHSPs at different drop heights are almost the same, meanwhile, the rectangular deformation zone composed of four plastic hinge lines is generated in the middle area, and the surrounding area is a trapezoidal deformation zone. What’s more, with the increase of the drop height, the rectangular deformation zone expands around. Besides, with the increase of the drop height, the permanent deflections of front and back faces of AHSPs increase approximately in form of quadratic parabola with decreasing slope. Suffering from water entry impact loadings, the AHSPs will experience large deformation and absorb energy, and the permanent deflections of the back sheet are obviously smaller than those of the equivalent aluminum plate, indicating that the AHSPs have better impact resistance compared with the equivalent aluminum plate.
, Available online ,
doi: 10.11883/bzycj-2024-0250
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Abstract:
In the process of deep penetration of the earth penetration weapon (EPW) attacking the underground target, the non-ideal penetration attitude with initial attack angle is inevitable, which will introduce transverse overload with large peak value for the earth penetrator. However, the excessive overload peak value could damage some important components of the earth-penetrating projectile and reduce the penetration efficiency of the projectile. Therefore, it is necessary to study the methodology of reducing the transverse overload peak value of the earth-penetrating projectile. However, the previous research on the earth-penetrating projectile seldom takes into account the influence of transverse overload and it is difficult to effectively reduce the transverse overload. In order to overcome this problem, a new type of the earth-penetrating projectile with serrated configuration and the special shedding effect and mechanism of transverse overload were studied by numerical simulation method when penetrating the concrete target at the non-zero attack angle. The influences of the initial attack angle and the coefficient of the center of mass of projectile were studied, and the motion, contact force, contact moment and contact area of the projectile were analyzed by using conventional smooth projectile as comparison. The results show that for small initial attack angles of 1°, 2° and 3°, the peak value of transverse overload of the serrated projectile is reduced by about 30.6%, 5.2% and 11.3% compared to the smooth projectile, but the peak value of contact moment, pulse width and deflection angle are increased. The research reveals the mechanical mechanism to reduce transverse overload: the serrated body of the projectile reduces the contact area between the projectile and the target, and the transverse contact force is mainly concentrated on the upper surface of the right serrated parts of the first two serrated grooves near the head of the projectile; the transverse contact force between the serrated body and the target decreases, while the transverse contact force between the non-serrated parts (mainly the head of the projectile) and the target increases. Therefore, these two parts of the projectile are competed and control the reduction effects of the transverse overload of the whole projectile in the process of deep penetration with initial attack angle. When the ballistic deflection of the serrated projectile is suppressed by means of certain optimization of structural design, the transverse overload shedding efficiency of the serrated projectile can be effectively improved.
In the process of deep penetration of the earth penetration weapon (EPW) attacking the underground target, the non-ideal penetration attitude with initial attack angle is inevitable, which will introduce transverse overload with large peak value for the earth penetrator. However, the excessive overload peak value could damage some important components of the earth-penetrating projectile and reduce the penetration efficiency of the projectile. Therefore, it is necessary to study the methodology of reducing the transverse overload peak value of the earth-penetrating projectile. However, the previous research on the earth-penetrating projectile seldom takes into account the influence of transverse overload and it is difficult to effectively reduce the transverse overload. In order to overcome this problem, a new type of the earth-penetrating projectile with serrated configuration and the special shedding effect and mechanism of transverse overload were studied by numerical simulation method when penetrating the concrete target at the non-zero attack angle. The influences of the initial attack angle and the coefficient of the center of mass of projectile were studied, and the motion, contact force, contact moment and contact area of the projectile were analyzed by using conventional smooth projectile as comparison. The results show that for small initial attack angles of 1°, 2° and 3°, the peak value of transverse overload of the serrated projectile is reduced by about 30.6%, 5.2% and 11.3% compared to the smooth projectile, but the peak value of contact moment, pulse width and deflection angle are increased. The research reveals the mechanical mechanism to reduce transverse overload: the serrated body of the projectile reduces the contact area between the projectile and the target, and the transverse contact force is mainly concentrated on the upper surface of the right serrated parts of the first two serrated grooves near the head of the projectile; the transverse contact force between the serrated body and the target decreases, while the transverse contact force between the non-serrated parts (mainly the head of the projectile) and the target increases. Therefore, these two parts of the projectile are competed and control the reduction effects of the transverse overload of the whole projectile in the process of deep penetration with initial attack angle. When the ballistic deflection of the serrated projectile is suppressed by means of certain optimization of structural design, the transverse overload shedding efficiency of the serrated projectile can be effectively improved.
, Available online ,
doi: 10.11883/bzycj-2024-0252
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Abstract:
In order to explore the explosion reaction effect of zirconium-based reactive material casing and the ignition effect of fragments on fuel fuel driven by explosion, the reactive material casings containing Zr, Cu, Ni, Al and Y as the main elements was prepared by alloy melting and casting, and the outer diameter of the casing was 40mm, the height was 80mm, and the wall thickness was 5mm. In order to compare the aftereffect damage effect, the 45 steel casing of the same mass was prepared, and the internal charge of the two casings was JH-2 column. Through the explosion drive test and high-speed photography technology, the duration of the explosion fireball, the wave velocity of the shock wave, and the ignition of the impact of the fragments on the fuel box were studied. The results of the test showed that, compared with the steel shell of equal mass, the flame duration and shock wave speed of the Zr-based active material shell are longer and faster under the explosion drive, and the Zr-based active material shell has a strengthening effect on the air shock wave under the explosion drive. The fragments of the two materials were driven by the explosion to scatter and hit the oil tank, and both materials caused structural damage to the oil tank, and the 45 steel material did not ignite the internal fuel. The chemical energy released by the impact of the Zr-based active material on the fuel tank can ignite the fuel, and it has the performance of igniting the fuel.
In order to explore the explosion reaction effect of zirconium-based reactive material casing and the ignition effect of fragments on fuel fuel driven by explosion, the reactive material casings containing Zr, Cu, Ni, Al and Y as the main elements was prepared by alloy melting and casting, and the outer diameter of the casing was 40mm, the height was 80mm, and the wall thickness was 5mm. In order to compare the aftereffect damage effect, the 45 steel casing of the same mass was prepared, and the internal charge of the two casings was JH-2 column. Through the explosion drive test and high-speed photography technology, the duration of the explosion fireball, the wave velocity of the shock wave, and the ignition of the impact of the fragments on the fuel box were studied. The results of the test showed that, compared with the steel shell of equal mass, the flame duration and shock wave speed of the Zr-based active material shell are longer and faster under the explosion drive, and the Zr-based active material shell has a strengthening effect on the air shock wave under the explosion drive. The fragments of the two materials were driven by the explosion to scatter and hit the oil tank, and both materials caused structural damage to the oil tank, and the 45 steel material did not ignite the internal fuel. The chemical energy released by the impact of the Zr-based active material on the fuel tank can ignite the fuel, and it has the performance of igniting the fuel.
, Available online ,
doi: 10.11883/bzycj-2024-0278
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Abstract:
In order to study the damage mechanism of Zr-based amorphous alloy fragments penetrating CFRP and the destructive ability of the target material, a ballistic gun test was carried out to examine the ballistic performance of spherical Zr-based amorphous alloy. The area of the post-effect target of LY12 was analyzed using image recognition technology, with the aim of determining the extent of damage caused by the penetration of Zr-based amorphous alloy fragments through the laminated target and interstitial target, which was composed of 6mm-thick CFRP and 2mm-thick LY12. The results demonstrate that the damage area of the CFRP target is proportional to the fragmentation speed. There is no discernible reaction on the remaining portion of the target, with damage observed on the facing side, characterized by fiber shear and compression deformation, and on the backside, exhibiting tensile tearing and inter laminar failure. As the speed increases, the proportion of shear damage to the CFRP gradually increases. When a fragment impacts a target plate of the same setup, the damaged area of the LY12 target increases with the speed. When the speed is below 954.7 m·s-1, the damaged area of the interstitial target post-effect LY12 target is smaller than that of the laminated target post-effect LY12 target. With the increase of speed, the damaged area of the interstitial target post-effect LY12 target improves rapidly, while the damaged area of the laminated target post-effect LY12 target increases rapidly. The growth of the damaged area of the interstitial target post-effect LY12 target tends to slow down, and the former is much larger than the latter. Therefore, it is more favorable to set up interstitial targets for post-effect damage in high-speed impacts.
In order to study the damage mechanism of Zr-based amorphous alloy fragments penetrating CFRP and the destructive ability of the target material, a ballistic gun test was carried out to examine the ballistic performance of spherical Zr-based amorphous alloy. The area of the post-effect target of LY12 was analyzed using image recognition technology, with the aim of determining the extent of damage caused by the penetration of Zr-based amorphous alloy fragments through the laminated target and interstitial target, which was composed of 6mm-thick CFRP and 2mm-thick LY12. The results demonstrate that the damage area of the CFRP target is proportional to the fragmentation speed. There is no discernible reaction on the remaining portion of the target, with damage observed on the facing side, characterized by fiber shear and compression deformation, and on the backside, exhibiting tensile tearing and inter laminar failure. As the speed increases, the proportion of shear damage to the CFRP gradually increases. When a fragment impacts a target plate of the same setup, the damaged area of the LY12 target increases with the speed. When the speed is below 954.7 m·s-1, the damaged area of the interstitial target post-effect LY12 target is smaller than that of the laminated target post-effect LY12 target. With the increase of speed, the damaged area of the interstitial target post-effect LY12 target improves rapidly, while the damaged area of the laminated target post-effect LY12 target increases rapidly. The growth of the damaged area of the interstitial target post-effect LY12 target tends to slow down, and the former is much larger than the latter. Therefore, it is more favorable to set up interstitial targets for post-effect damage in high-speed impacts.
, Available online ,
doi: 10.11883/bzycj-2024-0280
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Abstract:
Aiming to investigate the performance and design approach of the carbon fiber reinforced polymer (CFRP) sheet strengthened masonry infilled walls subjected to blast loads, the commercial finite element program LS-DYNA is firstly used to develop the simplified micro-finite element model of masonry infilled walls and the corresponding blast-resistant analysis model of CFRP sheet strengthened walls. By comparing with the nine groups field explosion test results of unstrengthening and CFRP sheet strengthened masonry infilled walls, the applicability of the present simplified micro-modeling approach, as well as the material models and parameters of masonry and CFRP sheet, is verified. Furthermore, referring to the CFRP seismic strengthening methods recommended by Chinese standard GB 50608-2020, the dynamic behaviors of the prototype masonry infilled walls strengthened with CFRP sheets under blast loads are analyzed and compared. It is recommended to prioritize the diagonal two-way strengthening method, followed by vertical two-way and horizontal full-cover strengthening methods, and vertical full-cover and mixed three-way strengthening methods are not recommended. Finally, to simultaneously satisfy the CFRP is basically intact, no scattering debris and the peak central deflection less than wall thickness as the blast-resistant design goal, the ranges of scaled distance of prototype masonry infilled walls with different arrangements of tie bar (non-/cut-off/full-length tie bar) that need to be strengthened under typical sedan (227 kg equivalent TNT) and briefcase bombs (23 kg equivalent TNT) explode at different scaled distances are determined as 0.8-2 m/kg1/3 and 0.2-1.2 m/kg1/3, respectively. The suggestions for the optimal number of CFRP sheet layers for blast-resistant design are further given.
Aiming to investigate the performance and design approach of the carbon fiber reinforced polymer (CFRP) sheet strengthened masonry infilled walls subjected to blast loads, the commercial finite element program LS-DYNA is firstly used to develop the simplified micro-finite element model of masonry infilled walls and the corresponding blast-resistant analysis model of CFRP sheet strengthened walls. By comparing with the nine groups field explosion test results of unstrengthening and CFRP sheet strengthened masonry infilled walls, the applicability of the present simplified micro-modeling approach, as well as the material models and parameters of masonry and CFRP sheet, is verified. Furthermore, referring to the CFRP seismic strengthening methods recommended by Chinese standard GB 50608-2020, the dynamic behaviors of the prototype masonry infilled walls strengthened with CFRP sheets under blast loads are analyzed and compared. It is recommended to prioritize the diagonal two-way strengthening method, followed by vertical two-way and horizontal full-cover strengthening methods, and vertical full-cover and mixed three-way strengthening methods are not recommended. Finally, to simultaneously satisfy the CFRP is basically intact, no scattering debris and the peak central deflection less than wall thickness as the blast-resistant design goal, the ranges of scaled distance of prototype masonry infilled walls with different arrangements of tie bar (non-/cut-off/full-length tie bar) that need to be strengthened under typical sedan (227 kg equivalent TNT) and briefcase bombs (23 kg equivalent TNT) explode at different scaled distances are determined as 0.8-2 m/kg1/3 and 0.2-1.2 m/kg1/3, respectively. The suggestions for the optimal number of CFRP sheet layers for blast-resistant design are further given.
, Available online ,
doi: 10.11883/bzycj-2024-0335
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Abstract:
The influence mechanism the crack on the dynamic mechanical property of the rockmass is always an important and difficult problem in the field of rock mechanics. However, the establishment of the dynamic damage model for the fractured rockmass is the key to solve this problem, which has attracted much attention. At present, most of the dynamic damage models for the fractured rockmass are aimed at the flat cracks, which cannot take into account the influence of the crack roughness. To address this shortcoming, on basis of the calculation model for the rockmass macroscopic damage variable which can take into account the crack geometry parameter, strength parameter and deformation parameter, a calculation model for the rockmass macroscopic damage variable is proposed by introducing the JRC-JCS shear strength model for the rough crack established by Barton, which can consider the crack roughness. Secondly, the proposed calculation model is introduced into the uniaxial compressive dynamic damage model for the rock mass with the non-persistent crack, which both considers the coupling of the macroscopic and microscopic defects, and then a uniaxial compressive dynamic damage model for the rock mass with the non-persistent crack is established which can consider the crack roughness at the same time. Finally, the effect of crack roughness JRC and crack basic friction angle φb and crack length 2a on rockmass dynamic mechanical property is studied with the parametric sensitivity analysis. Taking the rockmass dynamic climax strength as an example, the calculation example shows that the rockmass dynamic climax strength increases from 26.42MPa to 27.28MPa and 28.37MPa with JRC increasing from 0 to 10 and 20 respectively. The rockmass dynamic climax strength increases from 26.42MPa to 27.28MPa and 28.80MPa with φb increasing from 0º to 15º and 30º respectively. The rockmass dynamic climax strength decreases from 31.37MPa to 27.28MPa and 23.90MPa with 2a increasing from 1cm to 2cm and 3cm respectively. At the same time, in order to describe the influence of the crack roughness more accurately, the crack fractal dimension is introduced into the dynamic damage model for the rock mass, which not only improves the calculation accuracy of the model, but also broadens its application range, which is more convenient for practical engineering application.
The influence mechanism the crack on the dynamic mechanical property of the rockmass is always an important and difficult problem in the field of rock mechanics. However, the establishment of the dynamic damage model for the fractured rockmass is the key to solve this problem, which has attracted much attention. At present, most of the dynamic damage models for the fractured rockmass are aimed at the flat cracks, which cannot take into account the influence of the crack roughness. To address this shortcoming, on basis of the calculation model for the rockmass macroscopic damage variable which can take into account the crack geometry parameter, strength parameter and deformation parameter, a calculation model for the rockmass macroscopic damage variable is proposed by introducing the JRC-JCS shear strength model for the rough crack established by Barton, which can consider the crack roughness. Secondly, the proposed calculation model is introduced into the uniaxial compressive dynamic damage model for the rock mass with the non-persistent crack, which both considers the coupling of the macroscopic and microscopic defects, and then a uniaxial compressive dynamic damage model for the rock mass with the non-persistent crack is established which can consider the crack roughness at the same time. Finally, the effect of crack roughness JRC and crack basic friction angle φb and crack length 2a on rockmass dynamic mechanical property is studied with the parametric sensitivity analysis. Taking the rockmass dynamic climax strength as an example, the calculation example shows that the rockmass dynamic climax strength increases from 26.42MPa to 27.28MPa and 28.37MPa with JRC increasing from 0 to 10 and 20 respectively. The rockmass dynamic climax strength increases from 26.42MPa to 27.28MPa and 28.80MPa with φb increasing from 0º to 15º and 30º respectively. The rockmass dynamic climax strength decreases from 31.37MPa to 27.28MPa and 23.90MPa with 2a increasing from 1cm to 2cm and 3cm respectively. At the same time, in order to describe the influence of the crack roughness more accurately, the crack fractal dimension is introduced into the dynamic damage model for the rock mass, which not only improves the calculation accuracy of the model, but also broadens its application range, which is more convenient for practical engineering application.
, Available online ,
doi: 10.11883/bzycj-2024-0336
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Abstract:
The dynamic constitutive model of rocks plays an important role in understanding the mechanical behavior of rocks under dynamic loads and solving rock dynamics problems. A dynamic constitutive model of rock with elastoplastic damage coupling based on continuum damage mechanics was established. This model uses the unified strength theory as the yield criterion and introduces a dynamic ratio of tension to compression to fully reflect the strain rate effect. The compressive damage variable is expressed with effective plastic strain and volumetric plastic strain, and the tensile damage variable with effective plastic strain to reflect the different damage evolution laws of rocks under tensile and compressive conditions. Using piecewise functions to characterize different plastic hardening behaviors of rocks under tensile and compressive conditions. The established constitutive model is numerically implemented of based on Fortran language and LS-DYNA user material customization interface (Umat). The established constitutive model is validated through three classic examples, namely, uniaxial and triaxial compression tests, uniaxial tensile tests, and ballistic tests on rocks. The results indicate that the constitutive model can comprehensively characterize the dynamic and static mechanical behavior of rocks.
The dynamic constitutive model of rocks plays an important role in understanding the mechanical behavior of rocks under dynamic loads and solving rock dynamics problems. A dynamic constitutive model of rock with elastoplastic damage coupling based on continuum damage mechanics was established. This model uses the unified strength theory as the yield criterion and introduces a dynamic ratio of tension to compression to fully reflect the strain rate effect. The compressive damage variable is expressed with effective plastic strain and volumetric plastic strain, and the tensile damage variable with effective plastic strain to reflect the different damage evolution laws of rocks under tensile and compressive conditions. Using piecewise functions to characterize different plastic hardening behaviors of rocks under tensile and compressive conditions. The established constitutive model is numerically implemented of based on Fortran language and LS-DYNA user material customization interface (Umat). The established constitutive model is validated through three classic examples, namely, uniaxial and triaxial compression tests, uniaxial tensile tests, and ballistic tests on rocks. The results indicate that the constitutive model can comprehensively characterize the dynamic and static mechanical behavior of rocks.
, Available online ,
doi: 10.11883/bzycj-2024-0309
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Abstract:
Abstract: This study investigates the dynamic response characteristics of silica sand under dynamic loading using the modified Split Hopkinson pressure bar (SHPB) to understand its crushing characteristics and energy-absorbing effects. Four different grain groups were examined, and the results demonstrate that the dynamic stress-strain behavior of the sand is influenced by grain size and strain rate. The deformation process of the sand can be categorized into three stages: elastic, yielding, and plastic. Plastic compaction dominates during the yielding stage, while crushing compaction is significant in the plastic stage. The relative crushing index of particles shows a direct relationship with both strain rate and effective particle size, while it is inversely related to the fractal dimension. The impact of particle size on energy absorption efficiency varies based on particle characteristics such as mineral composition, particle size, and degree of differentiation. At the same stress level, larger particle sizes exhibit higher energy absorption efficiency, and under the same loading strain rate conditions, larger particles experience lower peak stress. To enhance the energy absorption efficiency of sand and decrease the required loading level, it is advisable to utilize sand with larger particle sizes.
Abstract: This study investigates the dynamic response characteristics of silica sand under dynamic loading using the modified Split Hopkinson pressure bar (SHPB) to understand its crushing characteristics and energy-absorbing effects. Four different grain groups were examined, and the results demonstrate that the dynamic stress-strain behavior of the sand is influenced by grain size and strain rate. The deformation process of the sand can be categorized into three stages: elastic, yielding, and plastic. Plastic compaction dominates during the yielding stage, while crushing compaction is significant in the plastic stage. The relative crushing index of particles shows a direct relationship with both strain rate and effective particle size, while it is inversely related to the fractal dimension. The impact of particle size on energy absorption efficiency varies based on particle characteristics such as mineral composition, particle size, and degree of differentiation. At the same stress level, larger particle sizes exhibit higher energy absorption efficiency, and under the same loading strain rate conditions, larger particles experience lower peak stress. To enhance the energy absorption efficiency of sand and decrease the required loading level, it is advisable to utilize sand with larger particle sizes.
, Available online ,
doi: 10.11883/bzycj-2024-0294
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Abstract:
Cylindrical casing filled with charge under central point detonation at one end is the frequently-used structure for fragment weapons, whose fragment initial velocity produced by its fracture serves as an important parameter for evaluating the lethal power and the protective structures. To accurately predict the initial velocity distribution of cylindrical casing with different length-diameter ratios (L/D), it studied the impact of L/D ratios on the initial velocity of fragments and the applicability of existing empirical models for the initial velocity of fragments founded on the numerical model of experimental verification. On this basis, a correction term related to L/D ratio, which was often influenced by the axial rarefaction waves, was added to the fragment initial velocity index model. By fitting the data obtained from numerical simulations, the function expression of the correction term was derived and the calculation model for the initial velocity distribution of cylindrical casing with L/D ratio≥1 was obtained. Finally, the applicability of the established fragment initial velocity calculation model was validated through experimental data and numerical simulations. The research results indicate that the initial velocity distribution of fragments under different L/D ratios exhibits a trend where the initial velocities are lower at both ends and higher in the middle. Additionally, as the L/D ratio raises, the initial velocity of the fragment also increases. When the L/D ratio reaches 5, the relative error between the maximum initial velocity of the fragments and the calculated result using the Gurney formula is only 1.99%. However, the existing models for calculating initial velocities of fragment display significant errors when predicting smaller L/D ratios in cylindrical casing. The average error between the formula calculation results and the experimental and numerical simulation results does not exceed 6%, indicating that the proposed model is reliable for predicting the initial velocity distribution of fragments under different L/D ratios. The research work provides valuable insights for assessing the lethal power of fragment weapons and the structural design of protective devices in anti-terrorism projects.
Cylindrical casing filled with charge under central point detonation at one end is the frequently-used structure for fragment weapons, whose fragment initial velocity produced by its fracture serves as an important parameter for evaluating the lethal power and the protective structures. To accurately predict the initial velocity distribution of cylindrical casing with different length-diameter ratios (L/D), it studied the impact of L/D ratios on the initial velocity of fragments and the applicability of existing empirical models for the initial velocity of fragments founded on the numerical model of experimental verification. On this basis, a correction term related to L/D ratio, which was often influenced by the axial rarefaction waves, was added to the fragment initial velocity index model. By fitting the data obtained from numerical simulations, the function expression of the correction term was derived and the calculation model for the initial velocity distribution of cylindrical casing with L/D ratio≥1 was obtained. Finally, the applicability of the established fragment initial velocity calculation model was validated through experimental data and numerical simulations. The research results indicate that the initial velocity distribution of fragments under different L/D ratios exhibits a trend where the initial velocities are lower at both ends and higher in the middle. Additionally, as the L/D ratio raises, the initial velocity of the fragment also increases. When the L/D ratio reaches 5, the relative error between the maximum initial velocity of the fragments and the calculated result using the Gurney formula is only 1.99%. However, the existing models for calculating initial velocities of fragment display significant errors when predicting smaller L/D ratios in cylindrical casing. The average error between the formula calculation results and the experimental and numerical simulation results does not exceed 6%, indicating that the proposed model is reliable for predicting the initial velocity distribution of fragments under different L/D ratios. The research work provides valuable insights for assessing the lethal power of fragment weapons and the structural design of protective devices in anti-terrorism projects.
, Available online ,
doi: 10.11883/bzycj-2024-0272
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Abstract:
In order to study the dynamic mechanical properties of concrete and the dynamic temperature at the crack under impact, steel-polypropylene fiber reinforced concrete ( SPFRC ) was taken as the research object, and a self-built high-speed infrared temperature measurement system was used. The response rate of the system reached the microsecond level, and the concrete temperature curve was fitted by static calibration test. Combined with the Hopkinson pressure bar test device, the dynamic properties of SPFRC specimens with different steel fiber contents and the dynamic temperature change at the crack were studied. The results indicate a significant coupling effect between the temperature evolution and mechanical properties of the concrete specimens, with the steel fiber content substantially influencing both dynamic performance and temperature. Specifically, as the steel fiber content increases, the compressive strength of the concrete improves, reaching optimal mechanical performance at a 1.5% steel fiber content. However, at a 2% steel fiber content, the mechanical performance slightly decreases due to an increase in internal voids within the concrete. During impact, the dynamic temperature effect at the crack location exhibits a "stepped" pattern, with temperature change occurring in two distinct stages: an initial slow rise during early crack formation, followed by a sharp increase as friction and shear effects intensify with crack propagation. The influence of varying steel fiber content on temperature change is limited, with peak temperature and peak stress showing similar trends. The primary temperature variations are driven by crack propagation and frictional effects. After impact, the overall temperature in SPFRC specimens continues to rise within the first 300 μs. Due to thermal lag, the temperature does not decrease immediately after unloading. The high-speed infrared temperature measurement system provides a new method for real-time monitoring of temperature changes at concrete crack locations, offering a basis for assessing temperature evolution at cracks and aiding in the evaluation of crack propagation behavior.
In order to study the dynamic mechanical properties of concrete and the dynamic temperature at the crack under impact, steel-polypropylene fiber reinforced concrete ( SPFRC ) was taken as the research object, and a self-built high-speed infrared temperature measurement system was used. The response rate of the system reached the microsecond level, and the concrete temperature curve was fitted by static calibration test. Combined with the Hopkinson pressure bar test device, the dynamic properties of SPFRC specimens with different steel fiber contents and the dynamic temperature change at the crack were studied. The results indicate a significant coupling effect between the temperature evolution and mechanical properties of the concrete specimens, with the steel fiber content substantially influencing both dynamic performance and temperature. Specifically, as the steel fiber content increases, the compressive strength of the concrete improves, reaching optimal mechanical performance at a 1.5% steel fiber content. However, at a 2% steel fiber content, the mechanical performance slightly decreases due to an increase in internal voids within the concrete. During impact, the dynamic temperature effect at the crack location exhibits a "stepped" pattern, with temperature change occurring in two distinct stages: an initial slow rise during early crack formation, followed by a sharp increase as friction and shear effects intensify with crack propagation. The influence of varying steel fiber content on temperature change is limited, with peak temperature and peak stress showing similar trends. The primary temperature variations are driven by crack propagation and frictional effects. After impact, the overall temperature in SPFRC specimens continues to rise within the first 300 μs. Due to thermal lag, the temperature does not decrease immediately after unloading. The high-speed infrared temperature measurement system provides a new method for real-time monitoring of temperature changes at concrete crack locations, offering a basis for assessing temperature evolution at cracks and aiding in the evaluation of crack propagation behavior.
, Available online ,
doi: 10.11883/bzycj-2024-0142
Abstract:
Numerical simulation was carried out by using the Fluent simulation software and combining it with the situation of the working face3906 in a mine to investigate the propagation law of gas explosion in a U-shaped ventilation coal mining face and to explore the sensitivities of the overpressure attenuation of a gas explosion to different influencing factors. The relative errors between the numerically-simulated results and experimental ones are less than 15%, which verifies the reliability of the mathematical model developed in this paper. Then, the key parameters, namely, grid size, iteration time step, and ignition temperature are optimized to 0.2 m, 0.05 ms, and 1900 K, respectively. Numerical simulation indicates that the relationship between the peak of the explosion overpressure and the distance away from the explosion center of the coal face meets an exponential function relationship. The relationship between the arrival time of the peak explosion overpressure and the distance away from the explosion center meets a linear function. By designing an orthogonal array, 16 sets of data were obtained through simulation, and the following analyses were conducted based on this data. The extreme difference values of the three main control factors were obtained by using extreme difference analysis. The extreme difference value of the temperature is the greatest, the one of the gas concentration take the second, and the one of the gas accumulation area pressure is the least. The most significant impact of the temperature on the explosion overpressure attenuation in the numerical simulation, in which the R-value reaches 5.928. ANOVA analysis was carried out to study the significances of the main control factors affecting the explosion overpressure attenuation rate. In the three main control factors, the significance of the temperature is the most, the one of the gas accumulation zone pressure comes second, and the one of the gas concentration is the weakest. And the temperature shows a significance level of 31.835, while the other two factors are not significant.
Numerical simulation was carried out by using the Fluent simulation software and combining it with the situation of the working face
, Available online ,
doi: 10.11883/bzycj-2024-0128
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Abstract:
In the near-field explosion of improvised explosive device, the protective structure is often subjected to the combined action of blast wave and fragments. To improve the protection performance of the structure, a composite structural material containing foamed aluminum/fiber sandwich was designed and prepared. The "explosion + penetration" experiment was carried out to study the failure mode of the composite structure under the combined action of explosion shock wave and high-speed fragments. The influence of the two loading’s timing sequence of explosion shock wave and fragment on the failure mode was discussed, and the energy absorption mechanism of different materials was analyzed. The results show that the change of detonation distance directly affects the timing sequence of the action of explosion shock wave and fragment. In the conditions discussed in this paper, when the detonation distance is greater than 600mm, the fragment acts before the shock wave. Under the combined action of shock wave and fragment, the aluminum plate is accompanied by local sag deformation in addition to the penetration failure of fragments. The cellular structure of foamed aluminum was crushed and deformed under the impact load. The fibers at the bullet hole are stretched and fractured under the penetration of fragments, and are accompanied by high temperature failure. Under the two sequential effects, the existence of bullet holes weakens the effect of shock wave on the front aluminum plate, and the deformation and damage degree of the later sandwich structural material and the rear aluminum plate are more serious than that of the previous material. This research provides a technical basis for the application and functional design of lightweight composite structural materials in the field of near-burst protection in limited space.
In the near-field explosion of improvised explosive device, the protective structure is often subjected to the combined action of blast wave and fragments. To improve the protection performance of the structure, a composite structural material containing foamed aluminum/fiber sandwich was designed and prepared. The "explosion + penetration" experiment was carried out to study the failure mode of the composite structure under the combined action of explosion shock wave and high-speed fragments. The influence of the two loading’s timing sequence of explosion shock wave and fragment on the failure mode was discussed, and the energy absorption mechanism of different materials was analyzed. The results show that the change of detonation distance directly affects the timing sequence of the action of explosion shock wave and fragment. In the conditions discussed in this paper, when the detonation distance is greater than 600mm, the fragment acts before the shock wave. Under the combined action of shock wave and fragment, the aluminum plate is accompanied by local sag deformation in addition to the penetration failure of fragments. The cellular structure of foamed aluminum was crushed and deformed under the impact load. The fibers at the bullet hole are stretched and fractured under the penetration of fragments, and are accompanied by high temperature failure. Under the two sequential effects, the existence of bullet holes weakens the effect of shock wave on the front aluminum plate, and the deformation and damage degree of the later sandwich structural material and the rear aluminum plate are more serious than that of the previous material. This research provides a technical basis for the application and functional design of lightweight composite structural materials in the field of near-burst protection in limited space.
, Available online ,
doi: 10.11883/bzycj-2024-0119
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Abstract:
H-section steel columns have been widely employed in industrial buildings and parking lots, etc., which are vulnerable to crane-loading or vehicle collisions. Based on above background, the lateral impact model and residual load-carrying capacity model were established using Abaqus finite element software to analyze the performance of H-section steel columns during and after impact loading, following previous experimental studies. Firstly, the working mechanism, including the deformation characteristics, stress evolution and energy dissipation, was analyzed. Results indicated that under impact loading, the deformation pattern is mainly dominated by the global deformation, with the local deformation of the upper flange and out-of-plane buckling of web. The time history curve of impact force presents an obvious plateau phase, and the existence of the pre-axial loading obviously reduces the impact resistance of the specimens. In general, H-section steel columns exhibited favorable ductility performance during impact loading. Subsequently, a total of 108 parametric models were developed, and the influences of load parameters (impact mass, impact velocity and axial load ratio), material parameter (steel yield strength) and geometric parameters (sectional area and specimen length) on the impact force, deformation, and residual load-carrying capacity were emphatically studied. The results showed that as the impact mass, impact velocity, and pre-axial loading ratio increased, both the global and local deformations of H-section steel column increased, while the residual bearing capacity decreased. Finally, by considering the multi-factor interactions, the formulas for predicting global deformation and local deformation during impact and the residual load performance after impact were presented by using response surface method. Results showed that pre-axial loading was a key factor affecting global deformation, while the impact velocity affected local deformation. In addition, both the pre-axial loading and impact velocity significantly interact with other parameters. The proposed formulas can be employed for the damage evaluation and design of H-section steel columns during the whole impact process.
H-section steel columns have been widely employed in industrial buildings and parking lots, etc., which are vulnerable to crane-loading or vehicle collisions. Based on above background, the lateral impact model and residual load-carrying capacity model were established using Abaqus finite element software to analyze the performance of H-section steel columns during and after impact loading, following previous experimental studies. Firstly, the working mechanism, including the deformation characteristics, stress evolution and energy dissipation, was analyzed. Results indicated that under impact loading, the deformation pattern is mainly dominated by the global deformation, with the local deformation of the upper flange and out-of-plane buckling of web. The time history curve of impact force presents an obvious plateau phase, and the existence of the pre-axial loading obviously reduces the impact resistance of the specimens. In general, H-section steel columns exhibited favorable ductility performance during impact loading. Subsequently, a total of 108 parametric models were developed, and the influences of load parameters (impact mass, impact velocity and axial load ratio), material parameter (steel yield strength) and geometric parameters (sectional area and specimen length) on the impact force, deformation, and residual load-carrying capacity were emphatically studied. The results showed that as the impact mass, impact velocity, and pre-axial loading ratio increased, both the global and local deformations of H-section steel column increased, while the residual bearing capacity decreased. Finally, by considering the multi-factor interactions, the formulas for predicting global deformation and local deformation during impact and the residual load performance after impact were presented by using response surface method. Results showed that pre-axial loading was a key factor affecting global deformation, while the impact velocity affected local deformation. In addition, both the pre-axial loading and impact velocity significantly interact with other parameters. The proposed formulas can be employed for the damage evaluation and design of H-section steel columns during the whole impact process.
, Available online ,
doi: 10.11883/bzycj-2024-0102
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Abstract:
In order to reduce the great threat of gas explosion to coal mine operators and coal safety mining, the law of explosion overpressure and impact gas velocity attenuation with the propagation distance of different volumes of gas-air mixed gas in roadway was deeply studied. Firstly, based on dimensional analysis and energy similarity law, a dimensionless formula for the attenuation of gas explosion overpressure and impact gas velocity with propagation distance is established, considering the factors affecting the attenuation of gas explosion overpressure and impact gas velocity with propagation distance. Secondly, by regression analysis of the experimental data in large roadway, the attenuation models of overpressure and impact airflow velocity and their relations are obtained. Finally, the attenuation model and relation are verified. The results show that the energy of gas mixture, the amount of gas accumulation, the distance of measuring point, the hydraulic diameter and the cross-sectional area of roadway are the main factors affecting the attenuation of overpressure and impact gas velocity. Both overpressure and impact gas velocity are positively correlated with the accumulation of mixed gas. The greater the initial overpressure and impact gas velocity, the faster the attenuation. The relative errors between the theoretical value and the test value of the attenuation model and the relative errors between the theoretical value and the test value of the relation are controlled at about 10%, and the overall consistency of the data is high, which verifies the reliability of the data, and can describe the law of gas explosion propagation more simply and intuitively, and realize the rapid calculation of overpressure and gas velocity.
In order to reduce the great threat of gas explosion to coal mine operators and coal safety mining, the law of explosion overpressure and impact gas velocity attenuation with the propagation distance of different volumes of gas-air mixed gas in roadway was deeply studied. Firstly, based on dimensional analysis and energy similarity law, a dimensionless formula for the attenuation of gas explosion overpressure and impact gas velocity with propagation distance is established, considering the factors affecting the attenuation of gas explosion overpressure and impact gas velocity with propagation distance. Secondly, by regression analysis of the experimental data in large roadway, the attenuation models of overpressure and impact airflow velocity and their relations are obtained. Finally, the attenuation model and relation are verified. The results show that the energy of gas mixture, the amount of gas accumulation, the distance of measuring point, the hydraulic diameter and the cross-sectional area of roadway are the main factors affecting the attenuation of overpressure and impact gas velocity. Both overpressure and impact gas velocity are positively correlated with the accumulation of mixed gas. The greater the initial overpressure and impact gas velocity, the faster the attenuation. The relative errors between the theoretical value and the test value of the attenuation model and the relative errors between the theoretical value and the test value of the relation are controlled at about 10%, and the overall consistency of the data is high, which verifies the reliability of the data, and can describe the law of gas explosion propagation more simply and intuitively, and realize the rapid calculation of overpressure and gas velocity.
, Available online ,
doi: 10.11883/bzycj-2024-0071
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Abstract:
There are many microcracks and micropores in the rock, which will initiate, propagate, and coalescence under dynamic loading, leading to rock instability and failure. When blasting excavation is carried out, the retained rock mass will be subjected to the dynamic loading generated by cyclic blasting, resulting in cumulative damage, which will lead to the reduction of the rock mass strength, and even failure. In order to simulate this physical process, this study embeds the existing rock dynamic damage constitutive model, which can perfectly describe the rock dynamic damage induced by blasting, into FLAC through secondary development to analyze the cumulative damage of rock mass under cyclic blasting. And then it is adopted to simulate the dynamic response of the rock slope with the locked segment under cyclic blasting. The results show that the slope stability gradually decreases with increasing the number of cyclic blasting after considering the cumulative damage effect of the rock slope. For the rock slope with the locked segment, the damage of the locked segment firstly occurs at both ends, and then propagates to the middle, in which the rock mass shows a progressive failure mode. Because the cumulative damage of the rock slope is considered, the stability factor of the slope will decrease after each blasting. When the cumulative damage is not considered, the stability factor of the slope is basically unchanged. The failure mode of the rock slope with a locked segment under cyclic blasting is the combination of dynamic tensile failure and shear failure caused by rock mass slip. The location of the locked segment in the weak interlayer affects the failure mode and stability of the slope. Therefore, when carrying out similar engineering activities, the cumulative damage effect of rock mass should be considered to avoid engineering accidents.
There are many microcracks and micropores in the rock, which will initiate, propagate, and coalescence under dynamic loading, leading to rock instability and failure. When blasting excavation is carried out, the retained rock mass will be subjected to the dynamic loading generated by cyclic blasting, resulting in cumulative damage, which will lead to the reduction of the rock mass strength, and even failure. In order to simulate this physical process, this study embeds the existing rock dynamic damage constitutive model, which can perfectly describe the rock dynamic damage induced by blasting, into FLAC through secondary development to analyze the cumulative damage of rock mass under cyclic blasting. And then it is adopted to simulate the dynamic response of the rock slope with the locked segment under cyclic blasting. The results show that the slope stability gradually decreases with increasing the number of cyclic blasting after considering the cumulative damage effect of the rock slope. For the rock slope with the locked segment, the damage of the locked segment firstly occurs at both ends, and then propagates to the middle, in which the rock mass shows a progressive failure mode. Because the cumulative damage of the rock slope is considered, the stability factor of the slope will decrease after each blasting. When the cumulative damage is not considered, the stability factor of the slope is basically unchanged. The failure mode of the rock slope with a locked segment under cyclic blasting is the combination of dynamic tensile failure and shear failure caused by rock mass slip. The location of the locked segment in the weak interlayer affects the failure mode and stability of the slope. Therefore, when carrying out similar engineering activities, the cumulative damage effect of rock mass should be considered to avoid engineering accidents.
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Abstract:
To enhance the service safety of nodular cast iron structures such as the spent nuclear fuel storage and transportation vessel under low temperature and dynamic loads, the mode I dynamic fracture toughness of nodular cast iron was experimentally investigated at ambient and cryogenic temperatures (20℃, -40℃, -60℃ and -80℃) using an improved split Hopkinson pressure bar technique. The ductile-brittle transition behavior of the material was specially investigated. The crack initiation time of the specimen was determined by the strain gauge method. The dynamic stress intensity factor (DSIF) at the crack tip and the mode I dynamic fracture toughness (DFT) of the material were determined by the experimental-numerical method. The results show that under the same impact velocity, the DFT and fracture initiation time of nodular cast iron decrease significantly with the decrease in temperature. Through quantitative analysis of the microscopic fracture morphologies, it is revealed that there is a failure mechanism transition at different temperatures. As the temperature decreases, the number of dimples on the fracture surface decreases, while the river patterns as well as cleavage steps increase, which indicates that the ductility of the material is weakened but the brittleness is enhanced at low temperatures. This ductile-brittle transition phenomenon is consistent with the tendency of the measured toughness of the material.
To enhance the service safety of nodular cast iron structures such as the spent nuclear fuel storage and transportation vessel under low temperature and dynamic loads, the mode I dynamic fracture toughness of nodular cast iron was experimentally investigated at ambient and cryogenic temperatures (20℃, -40℃, -60℃ and -80℃) using an improved split Hopkinson pressure bar technique. The ductile-brittle transition behavior of the material was specially investigated. The crack initiation time of the specimen was determined by the strain gauge method. The dynamic stress intensity factor (DSIF) at the crack tip and the mode I dynamic fracture toughness (DFT) of the material were determined by the experimental-numerical method. The results show that under the same impact velocity, the DFT and fracture initiation time of nodular cast iron decrease significantly with the decrease in temperature. Through quantitative analysis of the microscopic fracture morphologies, it is revealed that there is a failure mechanism transition at different temperatures. As the temperature decreases, the number of dimples on the fracture surface decreases, while the river patterns as well as cleavage steps increase, which indicates that the ductility of the material is weakened but the brittleness is enhanced at low temperatures. This ductile-brittle transition phenomenon is consistent with the tendency of the measured toughness of the material.
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doi: 10.11883/bzycj-2024-0165
Abstract:
To investigate the effect of the longitudinal air gap on the detonation performance of HMX-based explosive, direct observation of steel plate deformation and damage under forward and slipping detonation of HMX based explosive was conducted based on the laser illumination combined with the ultra-high speed framing imaging technology. The multi-position optical speed measurement technology was also introduced to continuously measure the speed of steel plate, which enables a multidimensional characterization and quantitative research on steel plate damage under the influence of air gaps. It is found that when the air gap width is 0.05, 0.10 and 0.20 mm, the motion mode of the steel plate changes obviously under the forward detonation. The trend of the center point movement changes from step rising to oblique wave rising, indicating a notable elongation of the lead time of detonation wave. And the steel plate also has an obvious deformation and breakdown. Driven by slipping detonation, the motion patterns across various points of the steel plate are largely uniform, with only marginal variations in the lead time of detonation wave. No significant deformation or rupture of the steel plate is observed. It is considered that the wedge-shaped wave formed by the precursor shock wave and detonation waves is the key to the breakdown of the bottom of steel plate in the case of forward detonation. However, the momentum component of the precursor shock wave and detonation wave acting on the side of steel plate in the case of slipping detonation is small, so that no obvious damage occurs. This article also provides a lot of quantitative data on the deformation of steel plates subjected to longitudinal air gaps, which can provide high-precision experimental data for the related numerical simulations and theoretical analysis work.
To investigate the effect of the longitudinal air gap on the detonation performance of HMX-based explosive, direct observation of steel plate deformation and damage under forward and slipping detonation of HMX based explosive was conducted based on the laser illumination combined with the ultra-high speed framing imaging technology. The multi-position optical speed measurement technology was also introduced to continuously measure the speed of steel plate, which enables a multidimensional characterization and quantitative research on steel plate damage under the influence of air gaps. It is found that when the air gap width is 0.05, 0.10 and 0.20 mm, the motion mode of the steel plate changes obviously under the forward detonation. The trend of the center point movement changes from step rising to oblique wave rising, indicating a notable elongation of the lead time of detonation wave. And the steel plate also has an obvious deformation and breakdown. Driven by slipping detonation, the motion patterns across various points of the steel plate are largely uniform, with only marginal variations in the lead time of detonation wave. No significant deformation or rupture of the steel plate is observed. It is considered that the wedge-shaped wave formed by the precursor shock wave and detonation waves is the key to the breakdown of the bottom of steel plate in the case of forward detonation. However, the momentum component of the precursor shock wave and detonation wave acting on the side of steel plate in the case of slipping detonation is small, so that no obvious damage occurs. This article also provides a lot of quantitative data on the deformation of steel plates subjected to longitudinal air gaps, which can provide high-precision experimental data for the related numerical simulations and theoretical analysis work.
, Available online ,
doi: 10.11883/bzycj-2024-0192
Abstract:
The evaluation of protective performance and optimization of the design of building structures under impact loading is a key issue of concern in the fields of national defense, civil engineering, and other military and civilian use. Lattice columns are often used as the main load-bearing components in engineering structures and are inevitably impacted by other unintentional loads under engineering service environments. In this paper, 1∶2 scaled-down secondary impact tests were carried out on lattice columns along different impact directions with the same impact energy each time and compared with single-impact lattice columns under the same total energy to analyze the force and deformation characteristics of the lattice columns under the impact loads. Then, based on the experimentally verified finite element model, a continuous secondary impact simulation was carried out on the foot-foot lattice column. The dynamic response of the lattice column subjected to two consecutive impacts with the same total energy was obtained, and the effects of different energy distributions on the impact force, residual displacement, and residual kinetic energy were analyzed. The results show that under the same total energy, the displacement of lattice columns under a single impact is greater than that of a secondary impact. The optimal energy distribution obtained by numerical simulation can reduce the residual displacement of members impacted along different directions by about 12%. When the lattice column is subjected to a larger proportion of energy for the first time or a smaller proportion of impact energy for the second time, the total energy absorbed by the column is smaller. Finally, based on the results of tests and numerical simulations, the maximum impact velocity at which the damaged column can withstand a second impact is proposed. The results of the study can provide a reference for the design method of lattice steel columns under such loading conditions.
The evaluation of protective performance and optimization of the design of building structures under impact loading is a key issue of concern in the fields of national defense, civil engineering, and other military and civilian use. Lattice columns are often used as the main load-bearing components in engineering structures and are inevitably impacted by other unintentional loads under engineering service environments. In this paper, 1∶2 scaled-down secondary impact tests were carried out on lattice columns along different impact directions with the same impact energy each time and compared with single-impact lattice columns under the same total energy to analyze the force and deformation characteristics of the lattice columns under the impact loads. Then, based on the experimentally verified finite element model, a continuous secondary impact simulation was carried out on the foot-foot lattice column. The dynamic response of the lattice column subjected to two consecutive impacts with the same total energy was obtained, and the effects of different energy distributions on the impact force, residual displacement, and residual kinetic energy were analyzed. The results show that under the same total energy, the displacement of lattice columns under a single impact is greater than that of a secondary impact. The optimal energy distribution obtained by numerical simulation can reduce the residual displacement of members impacted along different directions by about 12%. When the lattice column is subjected to a larger proportion of energy for the first time or a smaller proportion of impact energy for the second time, the total energy absorbed by the column is smaller. Finally, based on the results of tests and numerical simulations, the maximum impact velocity at which the damaged column can withstand a second impact is proposed. The results of the study can provide a reference for the design method of lattice steel columns under such loading conditions.
, Available online ,
doi: 10.11883/bzycj-2024-0232
Abstract:
Applicable buffer-head covers and various open-cell foam buffer configurations were designed to meet the buffering and load reduction challenges during high-speed water entry vehicles. In the arbitrary Lagrangian-Euler method, the grid can move as the material flows within the spatial grid. This unique feature allows the arbitrary Lagrangian-Euler method to harness the advantages of both the Lagrangian and Euler methods. It not only overcomes numerical calculation challenges stemming from element distortion but also facilitates accurate computation of large deformations and displacements in solids and fluids. This makes it particularly well-suited for addressing high-speed water buffer load reduction problems. Based on the arbitrary Lagrangian-Eulerian method and considering the large deformation of the buffer foam and the hood, a numerical calculation model for buffering and load reduction during high-speed water entry of navigational bodies was established. Through numerical simulations, an in-depth study was conducted on the load reduction performance of buffer foams with different open-cell patterns. The results indicate that open-cell buffer foam exhibits significant advantages in dispersing the impact force and absorbing impact energy during water entry of navigational bodies, offering better buffering effects. Simultaneously, the buffer head cover experiences local progressive fragmentation upon water entry. The deformation and rupture of the outer wall surface of the buffer head cover at the connector between the buffer shell and the navigational body are caused by the stress concentration distribution generated during water impact. When the open-cell foam contacts the water surface, the front part enters the collapse stage, absorbing a large amount of energy and undergoing plastic deformation, resulting in a reduction of pores. This stage is the primary energy absorption phase for the buffer foam. In comparison, closed-cell foam exhibits poorer load reduction performance. Therefore, the adoption of open-cell foam represents a superior solution for buffering and load reduction during high-speed water entry of navigational bodies.
Applicable buffer-head covers and various open-cell foam buffer configurations were designed to meet the buffering and load reduction challenges during high-speed water entry vehicles. In the arbitrary Lagrangian-Euler method, the grid can move as the material flows within the spatial grid. This unique feature allows the arbitrary Lagrangian-Euler method to harness the advantages of both the Lagrangian and Euler methods. It not only overcomes numerical calculation challenges stemming from element distortion but also facilitates accurate computation of large deformations and displacements in solids and fluids. This makes it particularly well-suited for addressing high-speed water buffer load reduction problems. Based on the arbitrary Lagrangian-Eulerian method and considering the large deformation of the buffer foam and the hood, a numerical calculation model for buffering and load reduction during high-speed water entry of navigational bodies was established. Through numerical simulations, an in-depth study was conducted on the load reduction performance of buffer foams with different open-cell patterns. The results indicate that open-cell buffer foam exhibits significant advantages in dispersing the impact force and absorbing impact energy during water entry of navigational bodies, offering better buffering effects. Simultaneously, the buffer head cover experiences local progressive fragmentation upon water entry. The deformation and rupture of the outer wall surface of the buffer head cover at the connector between the buffer shell and the navigational body are caused by the stress concentration distribution generated during water impact. When the open-cell foam contacts the water surface, the front part enters the collapse stage, absorbing a large amount of energy and undergoing plastic deformation, resulting in a reduction of pores. This stage is the primary energy absorption phase for the buffer foam. In comparison, closed-cell foam exhibits poorer load reduction performance. Therefore, the adoption of open-cell foam represents a superior solution for buffering and load reduction during high-speed water entry of navigational bodies.
, Available online ,
doi: 10.11883/bzycj-2023-0343
Abstract:
Facing the challenges of accurate and effective prediction under extreme loads, machine learning has gradually demonstrated its potential to replace traditional methods. Existing approaches primarily focus on predicting the peak overpressure or impulse of explosive shock waves, with limited research on predicting the reflected overpressure time history. Load-time history prediction encompasses not only the peak overpressure but also embraces various multi-dimensional information including duration, waveform, and impulse, thereby offering a more comprehensive depiction of the dynamic temporal and spatial characteristics of shock waves. To address this issue, a prediction model for bridge surface reflected overpressure time history is proposed, targeting a planar shock wave diffracting around a bridge section. This model is based on Principal Component Analysis (PCA) and Backpropagation Neural Network (BPNN) algorithm with multi-task learning. A loss function considering the impact of peak overpressure and maximum impulse is introduced to fully consider the potential correlations between different modes after PCA dimension reduction. This enables the model to effectively predict bridge shock wave load time histories under varying incident overpressure. Through the analysis of three types of BPNN models - multitask learning model, multi-input single-output model, and multi-input multi-output model - it was found that the multitask learning model has the highest prediction accuracy, while the multi-input multi-output model struggles to effectively adapt to the current predictive task requirements. The multitask learning model, used for predicting, achieves high precision in forecasting the time history of reflected overpressure at various measurement points on the bridge surface and the peak overpressure values, with R2 values of 0.792 and 0.987. It also closely matches the simulation values in predicting the time history of combined forces and torque acting on the box girder. Additionally, this model performs better in interpolative value prediction than in extrapolative value prediction, but it also demonstrates a certain capability in predicting extrapolative values.
Facing the challenges of accurate and effective prediction under extreme loads, machine learning has gradually demonstrated its potential to replace traditional methods. Existing approaches primarily focus on predicting the peak overpressure or impulse of explosive shock waves, with limited research on predicting the reflected overpressure time history. Load-time history prediction encompasses not only the peak overpressure but also embraces various multi-dimensional information including duration, waveform, and impulse, thereby offering a more comprehensive depiction of the dynamic temporal and spatial characteristics of shock waves. To address this issue, a prediction model for bridge surface reflected overpressure time history is proposed, targeting a planar shock wave diffracting around a bridge section. This model is based on Principal Component Analysis (PCA) and Backpropagation Neural Network (BPNN) algorithm with multi-task learning. A loss function considering the impact of peak overpressure and maximum impulse is introduced to fully consider the potential correlations between different modes after PCA dimension reduction. This enables the model to effectively predict bridge shock wave load time histories under varying incident overpressure. Through the analysis of three types of BPNN models - multitask learning model, multi-input single-output model, and multi-input multi-output model - it was found that the multitask learning model has the highest prediction accuracy, while the multi-input multi-output model struggles to effectively adapt to the current predictive task requirements. The multitask learning model, used for predicting, achieves high precision in forecasting the time history of reflected overpressure at various measurement points on the bridge surface and the peak overpressure values, with R2 values of 0.792 and 0.987. It also closely matches the simulation values in predicting the time history of combined forces and torque acting on the box girder. Additionally, this model performs better in interpolative value prediction than in extrapolative value prediction, but it also demonstrates a certain capability in predicting extrapolative values.
, Available online ,
doi: 10.11883/bzycj-2025-0021
Abstract:
, Available online ,
doi: 10.11883/bzycj-2024-0368
Abstract:
Unavoidable electric vehicle collisions can cause defects in lithium-ion batteries (LIBs), and whether defective batteries after minor collisions can continue to be used is still unknown. In this work, we focus on the mechanical performance and electrochemical performance of defective batteries, safety boundaries, and its failure mechanism. Firstly, three typical defective cells , namely indentation, 50% offset compression and plate compression defect cells, are prepared by quasi-static loading and drop hammer impact with different indenters. These defective batteries did not exhibit voltage drops or temperature increases, indicating that no internal short circuits occurred. Subsequently, their mechanical and electrochemical responses were evaluated through quasi-static plate compression at a loading rate of 1 mm/min and 1C charge/discharge cycling, respectively. It was found that defective batteries exhibited significant deterioration in mechanical performance, including earlier onset of internal short circuit, reduced short circuit force, and decreased energy absorption capacity. Defective batteries also exhibited significant electrochemical performance degradation, with greater capacity loss during cycling compared to new batteries. Further, its degradation mechanism is explained through disassembling the cells. The separator of defective batteries exhibited significant thinning, making it more prone to rupture under secondary loading. Therefore, the mechanical failure criterion of the battery was proposed based on the separator thickness. After 500 cycles, graphite delamination was observed in the defective batteries, whereas the defective batteries without cycling only exhibited cracking. Therefore, the degradation of electrochemical performance in defective batteries is caused by the combined effects of initial defects and cyclic aging stress. The effects of loading speed and defect type on the performance of defective cells are also discussed. Defective batteries subjected to higher loading rates exhibit greater performance degradation, which is related to inertia effects. Different types of defects lead to variations in separator thickness and graphite delamination, resulting in different levels of degradation. Results are instructive for the study of safety identification and treatment of defective lithium-ion batteries.
Unavoidable electric vehicle collisions can cause defects in lithium-ion batteries (LIBs), and whether defective batteries after minor collisions can continue to be used is still unknown. In this work, we focus on the mechanical performance and electrochemical performance of defective batteries, safety boundaries, and its failure mechanism. Firstly, three typical defective cells , namely indentation, 50% offset compression and plate compression defect cells, are prepared by quasi-static loading and drop hammer impact with different indenters. These defective batteries did not exhibit voltage drops or temperature increases, indicating that no internal short circuits occurred. Subsequently, their mechanical and electrochemical responses were evaluated through quasi-static plate compression at a loading rate of 1 mm/min and 1C charge/discharge cycling, respectively. It was found that defective batteries exhibited significant deterioration in mechanical performance, including earlier onset of internal short circuit, reduced short circuit force, and decreased energy absorption capacity. Defective batteries also exhibited significant electrochemical performance degradation, with greater capacity loss during cycling compared to new batteries. Further, its degradation mechanism is explained through disassembling the cells. The separator of defective batteries exhibited significant thinning, making it more prone to rupture under secondary loading. Therefore, the mechanical failure criterion of the battery was proposed based on the separator thickness. After 500 cycles, graphite delamination was observed in the defective batteries, whereas the defective batteries without cycling only exhibited cracking. Therefore, the degradation of electrochemical performance in defective batteries is caused by the combined effects of initial defects and cyclic aging stress. The effects of loading speed and defect type on the performance of defective cells are also discussed. Defective batteries subjected to higher loading rates exhibit greater performance degradation, which is related to inertia effects. Different types of defects lead to variations in separator thickness and graphite delamination, resulting in different levels of degradation. Results are instructive for the study of safety identification and treatment of defective lithium-ion batteries.
, Available online ,
doi: 10.11883/bzycj-2024-0316
Abstract:
Electric vehicles are prone to collision accidents during operation, and power lithium-ion batteries are inevitably subjected to impact, which leads to varying degrees of damage to the battery, and assessing the extent of this damage is crucial for the safe use of the battery. Based on the above background, the study was conducted on the influence of different impact masses on the dynamic impact response and failure behavior of square lithium-ion batteries. Firstly, in the quasi-static compression test, six different feed rates were used to test the extrusion of lithium-ion batteries. The test results show that the peak load required for lithium-ion batteries to reach hard short-circuit failure continues to decrease with the increment of feed rate. This indicates that the short-circuit failure load of lithium-ion batteries under quasi-static conditions is mainly determined by the feed rate. Then the hammer impact test, through the regulation of the quality of the punch and impact speed, the system simulates the lithium-ion battery may encounter a variety of impact conditions. Impact quality is an important factor in determining the degree of damage to lithium-ion batteries. Under the same impact energy, the damage of low-speed large mass impact on lithium-ion battery is significantly higher than that of high-speed low mass impact. At a constant impact energy, mass is the dominant factor in determining the degree of battery damage. If the impact mass is heavier, it will produce a larger impact load, which will cause more serious damage to the internal structure of the lithium-ion battery, leading to its functional damage or even failure. Conversely, if the impact mass is lighter, the impact force generated is relatively small, and the damage to the battery structure is correspondingly reduced. Therefore, the size of the impact mass directly affects the degree of damage to the lithium-ion battery, which is a key indicator for evaluating its safety performance and durability. The impact speed has a significant impact on the voltage drop of lithium-ion batteries after damage. Especially accelerating the occurrence of hard short circuits, further exacerbating the sharp drop in voltage. This characteristic makes the impact velocity as an important consideration for evaluating the voltage stability and overall safety performance of lithium-ion batteries after damage.
Electric vehicles are prone to collision accidents during operation, and power lithium-ion batteries are inevitably subjected to impact, which leads to varying degrees of damage to the battery, and assessing the extent of this damage is crucial for the safe use of the battery. Based on the above background, the study was conducted on the influence of different impact masses on the dynamic impact response and failure behavior of square lithium-ion batteries. Firstly, in the quasi-static compression test, six different feed rates were used to test the extrusion of lithium-ion batteries. The test results show that the peak load required for lithium-ion batteries to reach hard short-circuit failure continues to decrease with the increment of feed rate. This indicates that the short-circuit failure load of lithium-ion batteries under quasi-static conditions is mainly determined by the feed rate. Then the hammer impact test, through the regulation of the quality of the punch and impact speed, the system simulates the lithium-ion battery may encounter a variety of impact conditions. Impact quality is an important factor in determining the degree of damage to lithium-ion batteries. Under the same impact energy, the damage of low-speed large mass impact on lithium-ion battery is significantly higher than that of high-speed low mass impact. At a constant impact energy, mass is the dominant factor in determining the degree of battery damage. If the impact mass is heavier, it will produce a larger impact load, which will cause more serious damage to the internal structure of the lithium-ion battery, leading to its functional damage or even failure. Conversely, if the impact mass is lighter, the impact force generated is relatively small, and the damage to the battery structure is correspondingly reduced. Therefore, the size of the impact mass directly affects the degree of damage to the lithium-ion battery, which is a key indicator for evaluating its safety performance and durability. The impact speed has a significant impact on the voltage drop of lithium-ion batteries after damage. Especially accelerating the occurrence of hard short circuits, further exacerbating the sharp drop in voltage. This characteristic makes the impact velocity as an important consideration for evaluating the voltage stability and overall safety performance of lithium-ion batteries after damage.
, Available online ,
doi: 10.11883/bzycj-2024-0318
Abstract:
The battery pack of electric vehicles is highly susceptible to failure and may catch fire under side pole collision. To accurately and rapidly evaluate the safety of battery packs under such conditions, this paper introduces a local region refined battery pack model that can effectively characterize the deformation and mechanical response of the jellyroll of battery. Simulation analyses were conducted under varying impact velocity, angles, positions, and vehicle loading configuration, with the latter achieved by uniformly applying mass compensation to the side wall of the battery pack. A simulation matrix was designed using an optimized Latin hypercube sampling strategy, and a dataset was generated through image recognition methods. This dataset includes parameters such as the maximum intrusion depth, intrusion location, intrusion width of the battery pack side wall, and the deformation of the jellyroll of battery. New features, including collision energy and velocity components in x and y directions, were derived and selected as input features for model training through correlation analysis. Support vector machine (SVM), random forest (RF) method, and error back propagation neural network (BPNN) machine learning method were employed to build a data-driven predictive model. The SVM model demonstrated superior performance, achieving an average determination coefficient R2 of 0.96 across prediction parameters. The prediction of the maximum intrusion depth of the battery pack side wall was particularly accurate, with an R2 exceeding 0.95 for all three models. Additionally, the robustness of the models was tested by Gaussian noise, where the BPNN exhibited better robustness. The BP model maintained an average R2 of 0.91 for the prediction parameters when Gaussian noise with a standard deviation of 0.5. The established data-driven model can effectively predict the mechanical response of battery packs under side pole collisions and provide a reliable tool for evaluating the battery pack safety.
The battery pack of electric vehicles is highly susceptible to failure and may catch fire under side pole collision. To accurately and rapidly evaluate the safety of battery packs under such conditions, this paper introduces a local region refined battery pack model that can effectively characterize the deformation and mechanical response of the jellyroll of battery. Simulation analyses were conducted under varying impact velocity, angles, positions, and vehicle loading configuration, with the latter achieved by uniformly applying mass compensation to the side wall of the battery pack. A simulation matrix was designed using an optimized Latin hypercube sampling strategy, and a dataset was generated through image recognition methods. This dataset includes parameters such as the maximum intrusion depth, intrusion location, intrusion width of the battery pack side wall, and the deformation of the jellyroll of battery. New features, including collision energy and velocity components in x and y directions, were derived and selected as input features for model training through correlation analysis. Support vector machine (SVM), random forest (RF) method, and error back propagation neural network (BPNN) machine learning method were employed to build a data-driven predictive model. The SVM model demonstrated superior performance, achieving an average determination coefficient R2 of 0.96 across prediction parameters. The prediction of the maximum intrusion depth of the battery pack side wall was particularly accurate, with an R2 exceeding 0.95 for all three models. Additionally, the robustness of the models was tested by Gaussian noise, where the BPNN exhibited better robustness. The BP model maintained an average R2 of 0.91 for the prediction parameters when Gaussian noise with a standard deviation of 0.5. The established data-driven model can effectively predict the mechanical response of battery packs under side pole collisions and provide a reliable tool for evaluating the battery pack safety.
, Available online ,
doi: 10.11883/bzycj-2024-0218
Abstract:
In order to predict the quasi-static pressure of internal explosion in a closed environment composed of aluminum containing active materials and explosive rings, this paper summarizes the existing quasi-static pressure calculation models for hydrogen, oxygen, and nitrogen explosives considering post ignition effects, and proposes an optimization method for the quasi-static pressure calculation mode applicable to internal explosion of aluminum containing composite charges. After obtaining the ideal maximum reaction heat using the Geiss theorem, this method uses a parameter correction related to the aluminum containing composite explosive itself. Taking Herzog as an example, a specific prediction formula is provided. Then, composite charges of active materials and explosives, as well as aluminum containing explosives, were tested for implosion. Typical overpressure curves were provided, and the method for obtaining quasi-static pressure in the tests and related sources were explained. The experimental data was compared and analyzed with the quasi-static pressure results calculated by the established optimization model, demonstrating the reliability of the modified model. At the same time, the internal explosion results of two types of explosives were compared, and the calculation model was extended to general aluminum containing explosives. The accuracy of the model was verified using quasi-static pressure data from relevant literature, and the reasons for errors and possible improvement methods were analyzed. The research results show that the established quasi-static pressure correction model for post combustion of composite explosives is in good agreement with experimental and literature data, with an average error of 9.1% and a maximum error of 15.8%; The average error of the calculation results for aluminum containing explosives is 12.1%, with a maximum error of 20.6%.
In order to predict the quasi-static pressure of internal explosion in a closed environment composed of aluminum containing active materials and explosive rings, this paper summarizes the existing quasi-static pressure calculation models for hydrogen, oxygen, and nitrogen explosives considering post ignition effects, and proposes an optimization method for the quasi-static pressure calculation mode applicable to internal explosion of aluminum containing composite charges. After obtaining the ideal maximum reaction heat using the Geiss theorem, this method uses a parameter correction related to the aluminum containing composite explosive itself. Taking Herzog as an example, a specific prediction formula is provided. Then, composite charges of active materials and explosives, as well as aluminum containing explosives, were tested for implosion. Typical overpressure curves were provided, and the method for obtaining quasi-static pressure in the tests and related sources were explained. The experimental data was compared and analyzed with the quasi-static pressure results calculated by the established optimization model, demonstrating the reliability of the modified model. At the same time, the internal explosion results of two types of explosives were compared, and the calculation model was extended to general aluminum containing explosives. The accuracy of the model was verified using quasi-static pressure data from relevant literature, and the reasons for errors and possible improvement methods were analyzed. The research results show that the established quasi-static pressure correction model for post combustion of composite explosives is in good agreement with experimental and literature data, with an average error of 9.1% and a maximum error of 15.8%; The average error of the calculation results for aluminum containing explosives is 12.1%, with a maximum error of 20.6%.
, Available online ,
doi: 10.11883/bzycj-2024-0132
Abstract:
The sheet explosive loading technology is a crucial method for evaluating the dynamic response of the space structure under the X-ray radiation in laboratory. To achieve the ultra-low specific impulse explosive loading required for the structural assessment of new space vehicles, a sheet explosive has been developed, primarily composed of PETN as the main explosive and polymer rubber as the binder. The mass fraction of PETN is 90%–92%, the thickness range is 0.15–0.20 mm, the density range is 1.63–1.68 g/cm3, and the explosive velocity range is 7.44–7.71 km/s. To verify the high-impact initiation sensitivity of the sheet explosive, three rounds of verification experiments were designed based on the blast marketing method. In the experiment, the sheet explosive was directly applied to the effect plate or a certain air gap reserved between the sheet explosive and the effect plate. The detonation of the explosive is confirmed by examining the explosive marks left on the effect plate post-explosion. The experimental results show that: the sheet explosive with a thickness of 0.15–0.50 mm can be reliably detonated by a mild detonating fuse with a charge line density of 0.2 g/m, and the explosive strips with a thickness of 0.20–0.50 mm can reliably transmit detonation. The specific impulse characteristic of the sheet explosive with different diameters and thicknesses was measured and studied by the impact pendulum measurement device. Combined with theoretical analysis, The specific impulse calculation model of sheet explosive was used to perform polynomial fitting on the specific impulse direct measurement data of sheet explosives with thicknesses of 0.20, 0.30, 0.40 and 0.50 mm, respectively. The specific impulse values of sheet explosives with four thicknesses were linearly fitted. The results show that the specific impulse of the sheet explosive is proportional to the thickness and the ratio coefficient is 3 418.56 Pa·s/mm. The development of ultra-thin sheet explosive with a thickness of 0.2 mm and a specific impulse of about 680 Pa·s has been successfully realized.
The sheet explosive loading technology is a crucial method for evaluating the dynamic response of the space structure under the X-ray radiation in laboratory. To achieve the ultra-low specific impulse explosive loading required for the structural assessment of new space vehicles, a sheet explosive has been developed, primarily composed of PETN as the main explosive and polymer rubber as the binder. The mass fraction of PETN is 90%–92%, the thickness range is 0.15–0.20 mm, the density range is 1.63–1.68 g/cm3, and the explosive velocity range is 7.44–7.71 km/s. To verify the high-impact initiation sensitivity of the sheet explosive, three rounds of verification experiments were designed based on the blast marketing method. In the experiment, the sheet explosive was directly applied to the effect plate or a certain air gap reserved between the sheet explosive and the effect plate. The detonation of the explosive is confirmed by examining the explosive marks left on the effect plate post-explosion. The experimental results show that: the sheet explosive with a thickness of 0.15–0.50 mm can be reliably detonated by a mild detonating fuse with a charge line density of 0.2 g/m, and the explosive strips with a thickness of 0.20–0.50 mm can reliably transmit detonation. The specific impulse characteristic of the sheet explosive with different diameters and thicknesses was measured and studied by the impact pendulum measurement device. Combined with theoretical analysis, The specific impulse calculation model of sheet explosive was used to perform polynomial fitting on the specific impulse direct measurement data of sheet explosives with thicknesses of 0.20, 0.30, 0.40 and 0.50 mm, respectively. The specific impulse values of sheet explosives with four thicknesses were linearly fitted. The results show that the specific impulse of the sheet explosive is proportional to the thickness and the ratio coefficient is 3 418.56 Pa·s/mm. The development of ultra-thin sheet explosive with a thickness of 0.2 mm and a specific impulse of about 680 Pa·s has been successfully realized.
, Available online ,
doi: 10.11883/bzycj-2024-0181
Abstract:
To investigate the stress wave characteristics within concrete targets under hypervelocity impact, a stress wave testing system based on PVDF piezoelectric stress gauges was established. A calibration method for PVDF piezoelectric stress gauges was proposed and conducted. The stress waveforms within concrete targets impacted by kilogram-scale cylindrical 93W tungsten alloy projectiles at hypervelocity were measured, and the generation and propagation mechanisms of stress waves were analyzed using numerical simulation methods. The following conclusions were drawn: (1) The dynamic characteristic parameters of the PVDF piezoelectric stress gauge were calibrated to yield a dynamic sensitivity coefficient of 17.5±0.5 pC/N for the PVDF piezoelectric stress gauge; (2) High signal-to-noise ratio stress waveforms within the concrete target under hypervelocity impact conditions were obtained using the PVDF piezoelectric stress gauge; (3) The stress waveforms obtained from numerical simulation were in good agreement with the experimentally measured waveforms where the maximum deviation of the stress wave peak values between simulation and experimental results is less than 20%, providing a useful tool for mechanism exploration; (4) The characteristics of stress waves within the concrete target and the mechanisms of generation and attenuation were further explored using numerical simulation methods.
To investigate the stress wave characteristics within concrete targets under hypervelocity impact, a stress wave testing system based on PVDF piezoelectric stress gauges was established. A calibration method for PVDF piezoelectric stress gauges was proposed and conducted. The stress waveforms within concrete targets impacted by kilogram-scale cylindrical 93W tungsten alloy projectiles at hypervelocity were measured, and the generation and propagation mechanisms of stress waves were analyzed using numerical simulation methods. The following conclusions were drawn: (1) The dynamic characteristic parameters of the PVDF piezoelectric stress gauge were calibrated to yield a dynamic sensitivity coefficient of 17.5±0.5 pC/N for the PVDF piezoelectric stress gauge; (2) High signal-to-noise ratio stress waveforms within the concrete target under hypervelocity impact conditions were obtained using the PVDF piezoelectric stress gauge; (3) The stress waveforms obtained from numerical simulation were in good agreement with the experimentally measured waveforms where the maximum deviation of the stress wave peak values between simulation and experimental results is less than 20%, providing a useful tool for mechanism exploration; (4) The characteristics of stress waves within the concrete target and the mechanisms of generation and attenuation were further explored using numerical simulation methods.
, Available online ,
doi: 10.11883/bzycj-2024-0121
Abstract:
The large-scale explosive dispersal and the unconfined detonation of particle-spray-air ternary mixtures are closely related to industrial accidents and military applications. However, most of the existing research focuses on the small-scale experiment in the laboratory. The large-scale explosive dispersal experiment is rare. According to most of the research findings, the explosive power was determined by the detonation state of aerosol. The charge and specific central explosive were the main factors affecting the shape of the aerosol. To study the damaging effect of aerosol, the large-scale dispersed experiment of 125 kg fuel was carried out. The process of aerosol development was observed by high-speed video recording. Variation characteristics of FAE cloud with different canisters and the specific central explosive were studied. The aerosol diameter and height were used to describing the aerosol shape, then they were analyzed under different initial experiment conditions. There were three types of designing canisters, including basic canister, compound canister and strengthen canister. And the main difference between those types of canisters was the radial restraint. The specific quantities of buster charge was adopted the T-shaped charge. The results show that the aerosol formation is reliable through the replication experiments. Because of its strong radial restraint, the compound canister has the advantage in the aerosol diameters. The aerosol diameters of compound canister can reach 25.5 m, compared to strong canister coverage area increased by 13%. Therefore, the compound canister with the specific quantities of buster charge of 0.8% has the best aerosol performance for 125 kg fuel. On this basis, characteristics of the aerosol were further analyzed. Thus the optimal secondary detonation delay time is 240 ms. The aerosol calculating concentration before burst is 64 g/m3 and the chemical equivalent ratio of fuel to oxygen in the air is 0.54.
The large-scale explosive dispersal and the unconfined detonation of particle-spray-air ternary mixtures are closely related to industrial accidents and military applications. However, most of the existing research focuses on the small-scale experiment in the laboratory. The large-scale explosive dispersal experiment is rare. According to most of the research findings, the explosive power was determined by the detonation state of aerosol. The charge and specific central explosive were the main factors affecting the shape of the aerosol. To study the damaging effect of aerosol, the large-scale dispersed experiment of 125 kg fuel was carried out. The process of aerosol development was observed by high-speed video recording. Variation characteristics of FAE cloud with different canisters and the specific central explosive were studied. The aerosol diameter and height were used to describing the aerosol shape, then they were analyzed under different initial experiment conditions. There were three types of designing canisters, including basic canister, compound canister and strengthen canister. And the main difference between those types of canisters was the radial restraint. The specific quantities of buster charge was adopted the T-shaped charge. The results show that the aerosol formation is reliable through the replication experiments. Because of its strong radial restraint, the compound canister has the advantage in the aerosol diameters. The aerosol diameters of compound canister can reach 25.5 m, compared to strong canister coverage area increased by 13%. Therefore, the compound canister with the specific quantities of buster charge of 0.8% has the best aerosol performance for 125 kg fuel. On this basis, characteristics of the aerosol were further analyzed. Thus the optimal secondary detonation delay time is 240 ms. The aerosol calculating concentration before burst is 64 g/m3 and the chemical equivalent ratio of fuel to oxygen in the air is 0.54.
, Available online ,
doi: 10.11883/bzycj-2024-0159
Abstract:
To exploring the dynamic response characteristics of the shed-tunnel structure under multiple rockfall impacts, an FEM-SPH coupled numerical model is established base on ANSYS/LS-DYNA and is also tested with the data before. Then, the model is combine with the full restart technique to study the effects of the shed-tunnel structure dynamic response under multiple rockfall impacts by considering four factors, e.g., rockfall impact velocity, rockfall mass, impact angle and rockfall shape. The results show that the impact force, buffer top impact displacement, roof displacement and plastic strain of the shed-tunnel are positively correlated with the rockfall mass, velocity and angle. The impact force, roof displacement and plastic strain of the shed-tunnel structure generated by the cuboid rockfall impact are all larger than those of the spherical rockfall, and the impact displacement generated by the spherical rockfall impact is larger than that of the cuboid. For the cuboid rockfall, the impact displacement, roof displacement and plastic strain are negatively correlated with the contact area. Under the multiple rockfall impacts, the peak impact force usually increases firstly and then tends to be stable.
To exploring the dynamic response characteristics of the shed-tunnel structure under multiple rockfall impacts, an FEM-SPH coupled numerical model is established base on ANSYS/LS-DYNA and is also tested with the data before. Then, the model is combine with the full restart technique to study the effects of the shed-tunnel structure dynamic response under multiple rockfall impacts by considering four factors, e.g., rockfall impact velocity, rockfall mass, impact angle and rockfall shape. The results show that the impact force, buffer top impact displacement, roof displacement and plastic strain of the shed-tunnel are positively correlated with the rockfall mass, velocity and angle. The impact force, roof displacement and plastic strain of the shed-tunnel structure generated by the cuboid rockfall impact are all larger than those of the spherical rockfall, and the impact displacement generated by the spherical rockfall impact is larger than that of the cuboid. For the cuboid rockfall, the impact displacement, roof displacement and plastic strain are negatively correlated with the contact area. Under the multiple rockfall impacts, the peak impact force usually increases firstly and then tends to be stable.
, Available online ,
doi: 10.11883/bzycj-2024-0359
Abstract:
Oxy-fuel combustion is one of the effective means to reduce greenhouse gases. In order to grasp the combustion characteristics of the clean fuel acetylene in O2/CO2 atmosphere and to investigate the effect of different concentrations of CO2 on the lower flammable limit of acetylene, the lower flammable limit of acetylene was experimentally measured in a 5L cylindrical explosive reaction device. With the increase of CO2 concentration from 14% to 85%, the experimental value of the lower flammable limit of acetylene increased from 2.64% to 3.93%, which was linearly increased in a small range. Compared with hydrocarbon fuels such as ethylene, ethane, and propylene, the lower flammability limit presents alkanes > olefins > alkynes, indicating that alkynes have a larger combustion range and a higher hazard factor. Based on the calculation model of limiting laminar flame velocity method, a prediction model applicable to the lower flammability limit of acetylene was established. Through the verification of experimental data, the average absolute error of this prediction model using the USC II combustion reaction mechanism is at 0.52%, and the model is accurate and reliable. In order to explain the reason for the existence of the lower flammability limit from the perspective of the competition between the temperature rise of the heat generation from fuel consumption and the temperature drop of the heat dissipation from the expansion of the fuel body, the thermodynamic, chemical, and transport effects of CO2 on the lower flammability limit are discussed by using the model and modifying the combustion reaction mechanism of USC II to introduce the virtual substances FCO2, TCO2, and MCO2, and comparing the flammability limits of the three virtual substances as well as those of the five atmospheres of N2 and CO2. The thermodynamic, chemical and transport effects of CO2 on the lower flammability limit were discussed. The results show that the average proportion of thermodynamic effect is 64%, chemical effect is 35% and transportation effect is 1%.
Oxy-fuel combustion is one of the effective means to reduce greenhouse gases. In order to grasp the combustion characteristics of the clean fuel acetylene in O2/CO2 atmosphere and to investigate the effect of different concentrations of CO2 on the lower flammable limit of acetylene, the lower flammable limit of acetylene was experimentally measured in a 5L cylindrical explosive reaction device. With the increase of CO2 concentration from 14% to 85%, the experimental value of the lower flammable limit of acetylene increased from 2.64% to 3.93%, which was linearly increased in a small range. Compared with hydrocarbon fuels such as ethylene, ethane, and propylene, the lower flammability limit presents alkanes > olefins > alkynes, indicating that alkynes have a larger combustion range and a higher hazard factor. Based on the calculation model of limiting laminar flame velocity method, a prediction model applicable to the lower flammability limit of acetylene was established. Through the verification of experimental data, the average absolute error of this prediction model using the USC II combustion reaction mechanism is at 0.52%, and the model is accurate and reliable. In order to explain the reason for the existence of the lower flammability limit from the perspective of the competition between the temperature rise of the heat generation from fuel consumption and the temperature drop of the heat dissipation from the expansion of the fuel body, the thermodynamic, chemical, and transport effects of CO2 on the lower flammability limit are discussed by using the model and modifying the combustion reaction mechanism of USC II to introduce the virtual substances FCO2, TCO2, and MCO2, and comparing the flammability limits of the three virtual substances as well as those of the five atmospheres of N2 and CO2. The thermodynamic, chemical and transport effects of CO2 on the lower flammability limit were discussed. The results show that the average proportion of thermodynamic effect is 64%, chemical effect is 35% and transportation effect is 1%.
, Available online ,
doi: 10.11883/bzycj-2024-0163
Abstract:
To discuss the flying gap effect of the metal flyer on the initiating behavior for TATB-based explosives, initiation experiments for PBX-6 and PBXL-7 were performed. The target velocity and shape of the flyer to explosives were obtained using a 1 550 nm photon Doppler velocimetry. The running distance to detonation (RDTD) of explosive samples was gained by a Terahertz-wave Doppler interferometric velocimetry at the center point. The relationship between the experiment data captured above was analyzed. It reveals that the running distance to detonation of the TATB-based explosive changes non-monotonously with the increase of gap. With the gap increasing from zero to 20 mm, there are five stages. The initial stage is named S0, the flyer velocity declining stage is named S1, the free running stage of spallation is named S2, the remerging stage when the main flyer catches up and remerging with its spallation layer is named S3, and the stage when the main flyer and spallation are united as one is named S4. The RDTD for the TATB-based explosive is the smallest when the flyer velocity comes to stage S4, the RDTD at stage S0 is the next, and the RDTD at the velocity declining stage S1 and remerging stage S3 are the worst together. These experiment results suggest that the initiating performance of TATB-based explosives impacted by the flyer is not always better than the gap layer results. The initiation mechanism of explosives by flyer under different gaps is probably related to the target velocity together with the structure of the flyer. The simplex target velocity rising of flyer can’t always make the running distance to detonation of TATB-based explosives shorter. The initiation mechanism of TATB-based explosives impacted by flyer is more complex than the gap layer, requiring much experiment data and numerical simulation for further discussion.
To discuss the flying gap effect of the metal flyer on the initiating behavior for TATB-based explosives, initiation experiments for PBX-6 and PBXL-7 were performed. The target velocity and shape of the flyer to explosives were obtained using a 1 550 nm photon Doppler velocimetry. The running distance to detonation (RDTD) of explosive samples was gained by a Terahertz-wave Doppler interferometric velocimetry at the center point. The relationship between the experiment data captured above was analyzed. It reveals that the running distance to detonation of the TATB-based explosive changes non-monotonously with the increase of gap. With the gap increasing from zero to 20 mm, there are five stages. The initial stage is named S0, the flyer velocity declining stage is named S1, the free running stage of spallation is named S2, the remerging stage when the main flyer catches up and remerging with its spallation layer is named S3, and the stage when the main flyer and spallation are united as one is named S4. The RDTD for the TATB-based explosive is the smallest when the flyer velocity comes to stage S4, the RDTD at stage S0 is the next, and the RDTD at the velocity declining stage S1 and remerging stage S3 are the worst together. These experiment results suggest that the initiating performance of TATB-based explosives impacted by the flyer is not always better than the gap layer results. The initiation mechanism of explosives by flyer under different gaps is probably related to the target velocity together with the structure of the flyer. The simplex target velocity rising of flyer can’t always make the running distance to detonation of TATB-based explosives shorter. The initiation mechanism of TATB-based explosives impacted by flyer is more complex than the gap layer, requiring much experiment data and numerical simulation for further discussion.
, Available online ,
doi: 10.11883/bzycj-2024-0112
Abstract:
Research on blasting craters is one of the most fundamental studies in blasting engineering. To elucidate the formation process and mechanisms of blasting craters and to investigate the roles of blasting stress waves and explosion gases in rock fragmentation during this process, a blasting load model was developed. This model is based on a double-exponential explosive load function and the equation of state for explosion gas pressure, incorporating the dynamic-static sequential effects of blasting. By combining the distinct loading characteristics of blasting stress waves and explosion gases, a discrete element numerical model of the blasting crater was established to simulate the development of fractures, rock fragmentation, and ejection of blasted rock. Simulations were performed both with and without the inclusion of explosion gas loading to explore the respective contributions of blasting stress waves and explosion gases to crater formation. The results show that the blasting crater dimensions simulated with the dynamic-static sequential loading model align closely with field test results, accurately capturing the formation and evolution of fractures in the blasting zone and the ejection behavior of fragmented rock. The high loading rate of blasting stress waves is the primary cause of ring-shaped microfractures in the near-field region of the explosion source, which can also induce reflective tensile damage, forming “slice drop” failure at free surfaces. Explosion gases, on the other hand, are the main drivers of radially extensive fractures in the far-field region of the explosion source and propel fragmented rock outward at a high velocity. Explosion gases exhibit not only quasi-static effects but also dynamic effects, extending the duration of blasting vibrations and amplifying the peak vibration velocity. The development of fractures during crater formation can be broadly categorized into three stages: stress wave-induced fracturing, explosion gas-induced fracturing, and deformation energy release-induced fracturing.
Research on blasting craters is one of the most fundamental studies in blasting engineering. To elucidate the formation process and mechanisms of blasting craters and to investigate the roles of blasting stress waves and explosion gases in rock fragmentation during this process, a blasting load model was developed. This model is based on a double-exponential explosive load function and the equation of state for explosion gas pressure, incorporating the dynamic-static sequential effects of blasting. By combining the distinct loading characteristics of blasting stress waves and explosion gases, a discrete element numerical model of the blasting crater was established to simulate the development of fractures, rock fragmentation, and ejection of blasted rock. Simulations were performed both with and without the inclusion of explosion gas loading to explore the respective contributions of blasting stress waves and explosion gases to crater formation. The results show that the blasting crater dimensions simulated with the dynamic-static sequential loading model align closely with field test results, accurately capturing the formation and evolution of fractures in the blasting zone and the ejection behavior of fragmented rock. The high loading rate of blasting stress waves is the primary cause of ring-shaped microfractures in the near-field region of the explosion source, which can also induce reflective tensile damage, forming “slice drop” failure at free surfaces. Explosion gases, on the other hand, are the main drivers of radially extensive fractures in the far-field region of the explosion source and propel fragmented rock outward at a high velocity. Explosion gases exhibit not only quasi-static effects but also dynamic effects, extending the duration of blasting vibrations and amplifying the peak vibration velocity. The development of fractures during crater formation can be broadly categorized into three stages: stress wave-induced fracturing, explosion gas-induced fracturing, and deformation energy release-induced fracturing.
, Available online ,
doi: 10.11883/bzycj-2024-0217
Abstract:
To study the penetration resistance to the projectile by the reinforced concrete, the mechanical response of reinforcing bars under the dynamic constraint of both the projectile and concrete was analysed and the limitation of existing finite-length rigid beam models have been obtained. Based on this foundation, a shear-plastic hinge model was used to analyze the case of a projectile directly hitting the reinforcing bars, and a plastic string model was used to analyze the case of a projectile colliding with the side of the reinforcing bars, resulting in a more accurate equation for penetration resistance. In the shear-plastic hinge model, stress analysis was performed based on the shear sliding of the reinforcing bar before fracture, and energy dissipation was calculated based on the deformation of the plastic hinge after the reinforcing bar fractures. In the plastic string model, the yield criterion of reinforcing bars under the combined action of bending moment and axial force was analyzed, and the plastic energy dissipation equations for reinforcing bar tension and bending were established. At the same time, the influence of changes in reinforcing bar kinetic energy was considered. Based on the theoretical model of cavity expansion and the empirical formula for the depth of projectile penetration, the concrete resistance equation under the indirect influence of steel reinforcement was obtained. By comparing with existing test data, the rationality of the theoretical models was verified. By analyzing the yield strength, diameter, mesh size of reinforcing bars, as well as the impact location of projectile, suggestions for the reinforcement design of the bulletproof layer were given. The adjacent two layers of reinforcing bars mesh should be staggered. The ratio of steel mesh to projectile diameter should be set between 0.5 and 0.8. It is not advisable to simply pursue high-strength reinforcing bars, and the ultimate plastic strain of reinforcing bars should also be considered as an important factor.
To study the penetration resistance to the projectile by the reinforced concrete, the mechanical response of reinforcing bars under the dynamic constraint of both the projectile and concrete was analysed and the limitation of existing finite-length rigid beam models have been obtained. Based on this foundation, a shear-plastic hinge model was used to analyze the case of a projectile directly hitting the reinforcing bars, and a plastic string model was used to analyze the case of a projectile colliding with the side of the reinforcing bars, resulting in a more accurate equation for penetration resistance. In the shear-plastic hinge model, stress analysis was performed based on the shear sliding of the reinforcing bar before fracture, and energy dissipation was calculated based on the deformation of the plastic hinge after the reinforcing bar fractures. In the plastic string model, the yield criterion of reinforcing bars under the combined action of bending moment and axial force was analyzed, and the plastic energy dissipation equations for reinforcing bar tension and bending were established. At the same time, the influence of changes in reinforcing bar kinetic energy was considered. Based on the theoretical model of cavity expansion and the empirical formula for the depth of projectile penetration, the concrete resistance equation under the indirect influence of steel reinforcement was obtained. By comparing with existing test data, the rationality of the theoretical models was verified. By analyzing the yield strength, diameter, mesh size of reinforcing bars, as well as the impact location of projectile, suggestions for the reinforcement design of the bulletproof layer were given. The adjacent two layers of reinforcing bars mesh should be staggered. The ratio of steel mesh to projectile diameter should be set between 0.5 and 0.8. It is not advisable to simply pursue high-strength reinforcing bars, and the ultimate plastic strain of reinforcing bars should also be considered as an important factor.
, Available online ,
doi: 10.11883/bzycj-2023-0395
Abstract:
The propeller is a critical component of a ship’s propulsion system that significantly influences the vessel’s performance through its stability and efficiency. Current research on the propulsion shaft system’s anti-shock properties often oversimplifies the propeller as a uniform circular disk, which disregards its structural intricacies and leads to inaccuracies in the transient damage characteristics during underwater explosions. This research focused on the propeller’s structural details and developed both an equivalent shell model and a more intricate solid model. Through structural wet modal numerical simulations, the study had determined that solid modeling outperforms shell modeling in accuracy. This finding is corroborated by coMParisons with empirical formulas, thereby validating the fluid-structure coupling analysis model.Building upon this foundation, the research examines the propeller’s transient Shock response and damage characteristics when subjected to far-field shockwaves. Utilizing the total wave algorithm in ABAQUS, the investigation extends to the cavitation and damage patterns of the propeller under such conditions, with confirmation provided by the one-dimensional Bleich-Sandler finite element model. To delve deeper into the phenomenon of hydrodynamic cavitation caused by the propeller’s high-speed rotation, the coupled Eulerian-Lagrangian (CEL) method was applied. Initially, a simplified propeller model was created to confirm the cavitation bubble layer’s fragmentation due to the flow field load resulting from explosive product expansion. Subsequent modifications to the propeller’s transient fluid-structure coupling calculation model allow for a more thorough analysis of its transient damage characteristics.The findings indicate that at attack angles of 0 and 90 degrees, the propeller surface experiences heightened shockwave loads, albeit with a threshold linked to the propeller’s structural properties. When hydrodynamic cavitation is factored in, the stress distribution on the propeller blade tends to be more uniform; the blade’s primary plastic damage is localized at the root, exhibiting both localized and complete plastic deformation patterns. This research elucidates the damage and cavitation effects on propellers due to far-field explosions, offering valuable insights for enhancing the anti-shock defenses of both the propulsion shaft system and the propeller itself.
The propeller is a critical component of a ship’s propulsion system that significantly influences the vessel’s performance through its stability and efficiency. Current research on the propulsion shaft system’s anti-shock properties often oversimplifies the propeller as a uniform circular disk, which disregards its structural intricacies and leads to inaccuracies in the transient damage characteristics during underwater explosions. This research focused on the propeller’s structural details and developed both an equivalent shell model and a more intricate solid model. Through structural wet modal numerical simulations, the study had determined that solid modeling outperforms shell modeling in accuracy. This finding is corroborated by coMParisons with empirical formulas, thereby validating the fluid-structure coupling analysis model.Building upon this foundation, the research examines the propeller’s transient Shock response and damage characteristics when subjected to far-field shockwaves. Utilizing the total wave algorithm in ABAQUS, the investigation extends to the cavitation and damage patterns of the propeller under such conditions, with confirmation provided by the one-dimensional Bleich-Sandler finite element model. To delve deeper into the phenomenon of hydrodynamic cavitation caused by the propeller’s high-speed rotation, the coupled Eulerian-Lagrangian (CEL) method was applied. Initially, a simplified propeller model was created to confirm the cavitation bubble layer’s fragmentation due to the flow field load resulting from explosive product expansion. Subsequent modifications to the propeller’s transient fluid-structure coupling calculation model allow for a more thorough analysis of its transient damage characteristics.The findings indicate that at attack angles of 0 and 90 degrees, the propeller surface experiences heightened shockwave loads, albeit with a threshold linked to the propeller’s structural properties. When hydrodynamic cavitation is factored in, the stress distribution on the propeller blade tends to be more uniform; the blade’s primary plastic damage is localized at the root, exhibiting both localized and complete plastic deformation patterns. This research elucidates the damage and cavitation effects on propellers due to far-field explosions, offering valuable insights for enhancing the anti-shock defenses of both the propulsion shaft system and the propeller itself.
, Available online ,
doi: 10.11883/bzycj-2024-0117
Abstract:
In this paper, the microspheres in flying-ash are used as sensitizer and inert additive to prepare the low detonation velocity emulsion explosives. The detonation velocity and the parameters of explosive shock wave in the air of emulsion explosives were measured by the probe method, the lead column compression method and the air explosion method, respectively. The safety of emulsion explosives was tested by the storage life experiment and thermal analysis experiment. The experimental results show that the detonation velocity, the brisance, the peak pressure, the positive impulse and the positive pressure action time of shock wave of emulsion explosives increased first and then decreased with the increase of the content of flying-ash microspheres. When the content of flying-ash microspheres was 15%, the detonation performance of emulsion explosive was the best, and when the content of flying-ash microspheres was 45% , the detonation velocity of the explosive decreased obviously. Meanwhile, the detonation velocity ranged from 2191 to 2312 m/s, which can satisfy the condition of using explosive for explosive welding. In addition, it is found that the detonation performance of emulsion explosives with D50=79 μm flying-ash microspheres was higher than those of flying-ash microspheres with D50=116 and 47 μm. The storage life and thermal analysis results indicate that the storage life of low detonation velocity emulsion explosives with flying-ash microspheres is significantly better than that of traditional low detonation velocity emulsion explosive with clay particles, the activation energy of thermal decomposition of the emulsion explosive with 15% flying-ash microspheres was only 0.3% higher than that of emulsion matrix. The results also show that the addition of flying-ash microspheres has no obvious effect on the thermal stability of the emulsion matrix. The research results have important reference value for green resource disposal of coal-based solid waste and formulation design of the low detonation velocity emulsion explosive.
In this paper, the microspheres in flying-ash are used as sensitizer and inert additive to prepare the low detonation velocity emulsion explosives. The detonation velocity and the parameters of explosive shock wave in the air of emulsion explosives were measured by the probe method, the lead column compression method and the air explosion method, respectively. The safety of emulsion explosives was tested by the storage life experiment and thermal analysis experiment. The experimental results show that the detonation velocity, the brisance, the peak pressure, the positive impulse and the positive pressure action time of shock wave of emulsion explosives increased first and then decreased with the increase of the content of flying-ash microspheres. When the content of flying-ash microspheres was 15%, the detonation performance of emulsion explosive was the best, and when the content of flying-ash microspheres was 45% , the detonation velocity of the explosive decreased obviously. Meanwhile, the detonation velocity ranged from 2191 to 2312 m/s, which can satisfy the condition of using explosive for explosive welding. In addition, it is found that the detonation performance of emulsion explosives with D50=79 μm flying-ash microspheres was higher than those of flying-ash microspheres with D50=116 and 47 μm. The storage life and thermal analysis results indicate that the storage life of low detonation velocity emulsion explosives with flying-ash microspheres is significantly better than that of traditional low detonation velocity emulsion explosive with clay particles, the activation energy of thermal decomposition of the emulsion explosive with 15% flying-ash microspheres was only 0.3% higher than that of emulsion matrix. The results also show that the addition of flying-ash microspheres has no obvious effect on the thermal stability of the emulsion matrix. The research results have important reference value for green resource disposal of coal-based solid waste and formulation design of the low detonation velocity emulsion explosive.
, Available online ,
doi: 10.11883/bzycj-2024-0175
Abstract:
The safety of propulsion lithium-ion batteries is a technical bottleneck to restrict the operation and airworthiness certification of electric aircraft and affects the development of electric aviation worldwide. Failure events such as combustion and explosion triggered by thermal runaway of lithium-ion batteries will cause catastrophic consequences of aircraft destruction and casualties. This paper aims to introduce the latest research status on the thermal runaway explosion characteristics of aircraft lithium-ion battery from three aspects, i.e., lithium-ion battery’s thermal runaway combustion and explosion behavior, the limit of thermal runaway gas explosion and the hazard assessment of thermal runaway and gas explosion. For lithium-ion battery thermal runaway and explosion behaviors, this paper introduced the lithium-ion battery thermal runaway development process, analyzed the determination of the characteristic parameters of the thermal runaway shock and summarized the evolution of the thermal jet mechanism as well as the associated simulation and experimental methods. For the limit of thermal runaway gas explosion, the national and international testing standards for the gas explosion limit were compared and the theoretical calculation of the explosion limit of thermal runaway gas are summarized together with the introduction of the in-situ detection method of the gas explosion limit. For the thermal runaway gas explosion risk assessment, a risk assessment method of ageing lithium-ion battery is introduced by innovatively combining CT non-destructive testing technology with explosion limit in-situ testing method, from which a severity factor of gas explosion hazard is obtained. Based on the characteristics of lithium-ion battery’s thermal runaway gas explosion limit and pressure rise rate, the factors of explosion risk and severity are obtained together with the formula for the calculation of explosion risk and severity. This study shows that future research will focus on areas such as advanced diagnostic techniques, enhanced electrolyte stability, multi-scale modelling, advanced inhibition techniques, and the establishment of standardized testing processes and safety regulations. It proposes that future research should focus on areas such as advanced diagnostic techniques, enhanced electrolyte stability, multi-scale modeling, advanced inhibition techniques and the establishment of standardized test procedures and technical regulations.
The safety of propulsion lithium-ion batteries is a technical bottleneck to restrict the operation and airworthiness certification of electric aircraft and affects the development of electric aviation worldwide. Failure events such as combustion and explosion triggered by thermal runaway of lithium-ion batteries will cause catastrophic consequences of aircraft destruction and casualties. This paper aims to introduce the latest research status on the thermal runaway explosion characteristics of aircraft lithium-ion battery from three aspects, i.e., lithium-ion battery’s thermal runaway combustion and explosion behavior, the limit of thermal runaway gas explosion and the hazard assessment of thermal runaway and gas explosion. For lithium-ion battery thermal runaway and explosion behaviors, this paper introduced the lithium-ion battery thermal runaway development process, analyzed the determination of the characteristic parameters of the thermal runaway shock and summarized the evolution of the thermal jet mechanism as well as the associated simulation and experimental methods. For the limit of thermal runaway gas explosion, the national and international testing standards for the gas explosion limit were compared and the theoretical calculation of the explosion limit of thermal runaway gas are summarized together with the introduction of the in-situ detection method of the gas explosion limit. For the thermal runaway gas explosion risk assessment, a risk assessment method of ageing lithium-ion battery is introduced by innovatively combining CT non-destructive testing technology with explosion limit in-situ testing method, from which a severity factor of gas explosion hazard is obtained. Based on the characteristics of lithium-ion battery’s thermal runaway gas explosion limit and pressure rise rate, the factors of explosion risk and severity are obtained together with the formula for the calculation of explosion risk and severity. This study shows that future research will focus on areas such as advanced diagnostic techniques, enhanced electrolyte stability, multi-scale modelling, advanced inhibition techniques, and the establishment of standardized testing processes and safety regulations. It proposes that future research should focus on areas such as advanced diagnostic techniques, enhanced electrolyte stability, multi-scale modeling, advanced inhibition techniques and the establishment of standardized test procedures and technical regulations.
, Available online ,
doi: 10.11883/bzycj-2024-0093
Abstract:
Explosion experiments utilizing a 20 L spherical explosion apparatus were conducted to investigate the explosion characteristics of aluminum and aluminum-silicon alloy powders, prevalent in additive manufacturing. The tested samples included Al, Al-12Si, and Al-20Si. Various parameters were measured under different influencing factors, including the lower explosion limit, maximum explosion pressure, maximum pressure rise rate, explosion temperature, and time to reach peak temperature. Thermogravimetric analysis-differential scanning calorimetry was employed to analyze the thermal oxidation properties of the samples. The results indicated that an increase in the silicon content within the alloy corresponded with a lower explosion limit. Conversely, the maximum explosion pressure and peak temperature showed a downward trend. Meanwhile. a reduction in the maximum pressure rise rate was observed. The exothermic amount of the oxidation process reduced, and the oxidation rate slowed down. The concentrations at which the three samples reached the maximum explosion pressure and peak temperature were 300 g/m3 for Al, 750 g/m3 for Al-12Si, and 900 g/m3 for Al-20Si, respectively. When the ignition energy increased, the rate of increase in maximum explosion pressure for the aluminum-silicon alloys was lower than that for aluminum powder. The effect of environmental temperature changes on the lower explosive limit was less significant compared to that of particle size variations. As the environmental temperature increased, the explosion pressure did not show a significant change, while the pressure rise rate increased slightly. X-ray diffraction analysis of the explosion products revealed that, in addition to Al2O3 and Al, the explosion products of the aluminum-silicon alloys also contained SiO2 and Si. This indicates that the Si element in the alloy participated in the explosion reaction. It confirms that the explosion of aluminum-silicon alloy powder is caused by the heating and vaporization of the particles, leading to the formation of a combustible gas composed of gaseous aluminum and silicon, which then combusts with oxygen.
Explosion experiments utilizing a 20 L spherical explosion apparatus were conducted to investigate the explosion characteristics of aluminum and aluminum-silicon alloy powders, prevalent in additive manufacturing. The tested samples included Al, Al-12Si, and Al-20Si. Various parameters were measured under different influencing factors, including the lower explosion limit, maximum explosion pressure, maximum pressure rise rate, explosion temperature, and time to reach peak temperature. Thermogravimetric analysis-differential scanning calorimetry was employed to analyze the thermal oxidation properties of the samples. The results indicated that an increase in the silicon content within the alloy corresponded with a lower explosion limit. Conversely, the maximum explosion pressure and peak temperature showed a downward trend. Meanwhile. a reduction in the maximum pressure rise rate was observed. The exothermic amount of the oxidation process reduced, and the oxidation rate slowed down. The concentrations at which the three samples reached the maximum explosion pressure and peak temperature were 300 g/m3 for Al, 750 g/m3 for Al-12Si, and 900 g/m3 for Al-20Si, respectively. When the ignition energy increased, the rate of increase in maximum explosion pressure for the aluminum-silicon alloys was lower than that for aluminum powder. The effect of environmental temperature changes on the lower explosive limit was less significant compared to that of particle size variations. As the environmental temperature increased, the explosion pressure did not show a significant change, while the pressure rise rate increased slightly. X-ray diffraction analysis of the explosion products revealed that, in addition to Al2O3 and Al, the explosion products of the aluminum-silicon alloys also contained SiO2 and Si. This indicates that the Si element in the alloy participated in the explosion reaction. It confirms that the explosion of aluminum-silicon alloy powder is caused by the heating and vaporization of the particles, leading to the formation of a combustible gas composed of gaseous aluminum and silicon, which then combusts with oxygen.
, Available online ,
doi: 10.11883/bzycj-2024-0244
Abstract:
Accurately evaluating the continuous effect of penetration and moving charge explosion of Earth Penetrating Weapons is the premise of reliable design of shield on the protective structure. Firstly, a three-stage integrated projectile penetration and moving charge explosion finite element analysis method was proposed based on the technologies of volume filling of explosive and the two-step coupling in penetration and explosion processes. By conducting the numerical simulations of the existing tests of moving charge explosion, penetration and static charge explosion of normal strength concrete (NSC) and ultra-high performance concrete (UHPC) targets, the accuracy of the proposed method in describing the propagation of explosive waves, peak stress, cracking behavior and damage evolution of target under the penetration and explosion was fully verified. Besides, for the scenario of an NSC target against a 105 mm-caliber scaled projectile, the differences of target damage predicted by the proposed finite element analysis method and traditional penetration and static charge explosion method were compared. Meanwhile, the superimposed effect of the penetration and explosion stress field and the influence of shell constraint and fracture fragment were analyzed. Based on the damage characteristics of targets at different detonation time instants of explosive, the most unfavorable detonation time instant of the warhead was determined. Finally, numerical simulations were conducted for the scenarios of three prototype warheads: SDB, WDU-43/B and BLU-109/B. The destructive depths of NSC and UHPC shields subjected to the penetration and moving charge explosion loadings are 1.33, 2.70, 2.35 m and 0.79, 1.76, 1.70 m, respectively. The corresponding scabbing and perforation limits of shields were further given. The results show that the destructive depths, scabbing limits and perforation limits calculated by the finite element analysis method with considering integrated penetration and moving charge explosion are about 5%–30% higher than those calculated by the traditional penetration and static charge explosion method.
Accurately evaluating the continuous effect of penetration and moving charge explosion of Earth Penetrating Weapons is the premise of reliable design of shield on the protective structure. Firstly, a three-stage integrated projectile penetration and moving charge explosion finite element analysis method was proposed based on the technologies of volume filling of explosive and the two-step coupling in penetration and explosion processes. By conducting the numerical simulations of the existing tests of moving charge explosion, penetration and static charge explosion of normal strength concrete (NSC) and ultra-high performance concrete (UHPC) targets, the accuracy of the proposed method in describing the propagation of explosive waves, peak stress, cracking behavior and damage evolution of target under the penetration and explosion was fully verified. Besides, for the scenario of an NSC target against a 105 mm-caliber scaled projectile, the differences of target damage predicted by the proposed finite element analysis method and traditional penetration and static charge explosion method were compared. Meanwhile, the superimposed effect of the penetration and explosion stress field and the influence of shell constraint and fracture fragment were analyzed. Based on the damage characteristics of targets at different detonation time instants of explosive, the most unfavorable detonation time instant of the warhead was determined. Finally, numerical simulations were conducted for the scenarios of three prototype warheads: SDB, WDU-43/B and BLU-109/B. The destructive depths of NSC and UHPC shields subjected to the penetration and moving charge explosion loadings are 1.33, 2.70, 2.35 m and 0.79, 1.76, 1.70 m, respectively. The corresponding scabbing and perforation limits of shields were further given. The results show that the destructive depths, scabbing limits and perforation limits calculated by the finite element analysis method with considering integrated penetration and moving charge explosion are about 5%–30% higher than those calculated by the traditional penetration and static charge explosion method.
, Available online ,
doi: 10.11883/bzycj-2024-0393
Abstract:
Traumatic brain injury (TBI) is the neurological disorder with the highest incidence and prevalence, and poses a huge public health burden for the whole society. An in-depth study of the biomechanics of TBI can help to improve the effectiveness of head protection, develop rapid assessment techniques and take timely interventions, thus reducing the risk of injury deterioration. As a numerical analysis tool, the finite element head model (FEHM) is able to simulate the dynamic response of the head during impact, including the spatial and temporal distribution of stress-strain in brain tissues, and the change of intracranial pressure, which provides an important basis for understanding the mechanical mechanism of traumatic brain injury (TBI). This paper summarizes in detail the current status and development of mainstream finite element models of the human head at home and abroad, traces the development of the models, summarises the characteristics of the models and introduces the research progress of TBI mechanisms based on finite element models. The summary and sorting out of related research will be helpful for the development of new FEHMs and provide theoretical guidance and technical support for the risk assessment of traumatic brain injury and the design of protective equipment.
Traumatic brain injury (TBI) is the neurological disorder with the highest incidence and prevalence, and poses a huge public health burden for the whole society. An in-depth study of the biomechanics of TBI can help to improve the effectiveness of head protection, develop rapid assessment techniques and take timely interventions, thus reducing the risk of injury deterioration. As a numerical analysis tool, the finite element head model (FEHM) is able to simulate the dynamic response of the head during impact, including the spatial and temporal distribution of stress-strain in brain tissues, and the change of intracranial pressure, which provides an important basis for understanding the mechanical mechanism of traumatic brain injury (TBI). This paper summarizes in detail the current status and development of mainstream finite element models of the human head at home and abroad, traces the development of the models, summarises the characteristics of the models and introduces the research progress of TBI mechanisms based on finite element models. The summary and sorting out of related research will be helpful for the development of new FEHMs and provide theoretical guidance and technical support for the risk assessment of traumatic brain injury and the design of protective equipment.
, Available online ,
doi: 10.11883/bzycj-2024-0307
Abstract:
Biological soft materials, often with high water content and ultra-softness, display mechanical properties that non-linearly enhance over a broad range of strain rates. However, existing experimental constraints make it challenging to perform large deformation tests on these materials at intermediate strain rates. This study introduces a 15-meter-long long split Hopkinson pressure bar (LSHPB) system, driven by a dual-bullet electromagnetic mechanism, designed for large deformation intermediate strain rate testing of ultra-soft materials. Comparative tests conducted using both the LSHPB and a high-speed SHPB system validated the reliability of the newly developed system. The LSHPB system was then applied to measure the dynamic mechanical performance of polyvinyl alcohol (PVA) hydrogel at intermediate strain rates. The results, combined with existing data from low and high strain rate analyses, underscore the necessity for intermediate strain rate dynamic performance testing. This work not only broadens our understanding of the mechanical behavior of ultra-soft materials like PVA hydrogel across various strain rates but also introduces an innovative experimental technique for studying materials under intermediate strain conditions, thereby advancing the field of soft material dynamics.
Biological soft materials, often with high water content and ultra-softness, display mechanical properties that non-linearly enhance over a broad range of strain rates. However, existing experimental constraints make it challenging to perform large deformation tests on these materials at intermediate strain rates. This study introduces a 15-meter-long long split Hopkinson pressure bar (LSHPB) system, driven by a dual-bullet electromagnetic mechanism, designed for large deformation intermediate strain rate testing of ultra-soft materials. Comparative tests conducted using both the LSHPB and a high-speed SHPB system validated the reliability of the newly developed system. The LSHPB system was then applied to measure the dynamic mechanical performance of polyvinyl alcohol (PVA) hydrogel at intermediate strain rates. The results, combined with existing data from low and high strain rate analyses, underscore the necessity for intermediate strain rate dynamic performance testing. This work not only broadens our understanding of the mechanical behavior of ultra-soft materials like PVA hydrogel across various strain rates but also introduces an innovative experimental technique for studying materials under intermediate strain conditions, thereby advancing the field of soft material dynamics.
, Available online ,
doi: 10.11883/bzycj-2024-0352
Abstract:
The thermal runaway reactions of lithium-ion batteries exhibit significant deviations following full life-cycle cycling aging when compared to their fresh-state counterparts, particularly under low-temperature conditions. These conditions more closely simulate the operational scenarios encountered in low-altitude aviation, where the risk of catastrophic failure in battery systems is heightened. This study, utilizing a custom-built platform designed for testing thermal runaway and gas explosion phenomena, systematically investigates the impact of low-temperature (−10 °C) cycling aging on the associated explosion hazards. Key parameters analyzed in this research include the initiation time of thermal runaway, the peak surface temperature of the battery, the overpressure generated during thermal runaway, the lower explosion limit (LEL) of the gases produced, and the explosion pressure and temperature—each serving as crucial indicators of the system’s safety performance. Experimental results demonstrate that, under ambient temperature conditions, aged batteries exhibit a marked increase in the thermal runaway initiation time, as well as a notable extension in the interval between the activation of the safety valve and the onset of complete thermal runaway (Δt), when compared to fresh batteries. Specifically, thermal runaway occurs at 559.86 s, while Δt increases to 122.56 s. Moreover, the LEL of hazardous gases rises by 30.95%, and the resulting explosion pressure diminishes to 258.6 kPa, suggesting a reduced likelihood of catastrophic failure. However, when subjected to low-temperature cycling aging, the explosion risk profile shifts dramatically. In this case, the thermal runaway initiation time is significantly reduced to 412.38 seconds, with Δt contracting sharply to 56.66 s. Furthermore, the LEL of the gases decreases by 20.49%, while the explosion pressure surges to 319.5 kPa, indicating an elevated risk of severe explosion. The multifaceted analysis of these hazard indicators reveals a complex interplay between aging processes and environmental conditions, profoundly influencing the explosion risks and thermal runaway behavior of lithium-ion batteries. These findings emphasize the critical necessity of developing advanced battery management systems that incorporate predictive early-warning mechanisms, strategic battery layout designs, and improved containment strategies, specifically tailored to the demands of electric aviation. By incorporating the effects of both cycling aging and low-temperature environments into risk assessments, this study provides vital insights for mitigating the elevated hazards associated with thermal runaway and the explosion of emitted gases in aviation applications. Ultimately, these findings contribute to the enhancement of safety protocols and risk mitigation strategies for the reliable and secure operation of lithium-ion battery systems throughout their entire operational lifecycle.
The thermal runaway reactions of lithium-ion batteries exhibit significant deviations following full life-cycle cycling aging when compared to their fresh-state counterparts, particularly under low-temperature conditions. These conditions more closely simulate the operational scenarios encountered in low-altitude aviation, where the risk of catastrophic failure in battery systems is heightened. This study, utilizing a custom-built platform designed for testing thermal runaway and gas explosion phenomena, systematically investigates the impact of low-temperature (−10 °C) cycling aging on the associated explosion hazards. Key parameters analyzed in this research include the initiation time of thermal runaway, the peak surface temperature of the battery, the overpressure generated during thermal runaway, the lower explosion limit (LEL) of the gases produced, and the explosion pressure and temperature—each serving as crucial indicators of the system’s safety performance. Experimental results demonstrate that, under ambient temperature conditions, aged batteries exhibit a marked increase in the thermal runaway initiation time, as well as a notable extension in the interval between the activation of the safety valve and the onset of complete thermal runaway (Δt), when compared to fresh batteries. Specifically, thermal runaway occurs at 559.86 s, while Δt increases to 122.56 s. Moreover, the LEL of hazardous gases rises by 30.95%, and the resulting explosion pressure diminishes to 258.6 kPa, suggesting a reduced likelihood of catastrophic failure. However, when subjected to low-temperature cycling aging, the explosion risk profile shifts dramatically. In this case, the thermal runaway initiation time is significantly reduced to 412.38 seconds, with Δt contracting sharply to 56.66 s. Furthermore, the LEL of the gases decreases by 20.49%, while the explosion pressure surges to 319.5 kPa, indicating an elevated risk of severe explosion. The multifaceted analysis of these hazard indicators reveals a complex interplay between aging processes and environmental conditions, profoundly influencing the explosion risks and thermal runaway behavior of lithium-ion batteries. These findings emphasize the critical necessity of developing advanced battery management systems that incorporate predictive early-warning mechanisms, strategic battery layout designs, and improved containment strategies, specifically tailored to the demands of electric aviation. By incorporating the effects of both cycling aging and low-temperature environments into risk assessments, this study provides vital insights for mitigating the elevated hazards associated with thermal runaway and the explosion of emitted gases in aviation applications. Ultimately, these findings contribute to the enhancement of safety protocols and risk mitigation strategies for the reliable and secure operation of lithium-ion battery systems throughout their entire operational lifecycle.
, Available online ,
doi: 10.11883/bzycj-2024-0191
Abstract:
For the estimation of blast loading in complex structures, traditional numerical simulation methods were computationally intensive whereas rapid estimation methods based on neural networks can only provide estimates at local points without providing confidence intervals for the predicted results. To achieve fast and reliable estimation of the blast loading in complex structures, Bayesian theory was combined with deep learning to develop a Bayesian deep learning approach for rapid estimation of blast loading in complex structures. The approach initially utilized open-source numerical simulation software to generate a dataset of blast loading in complex structures, encompassing a wide range of parameters such as explosion equivalents, locations, and velocities. During this process, mesh sizes that balanced computational accuracy and speed were determined through mesh sensitivity analysis and the verification of the numerical simulation accuracy. Then, the deep learning model was extended into a Bayesian deep learning model based on Bayesian theory. By introducing probability distributions over the weights of the neural network, the model parameters were treated as random variables. Variational Bayesian inference was then employed to efficiently train the model, ensuring the accuracy of rapid blast loading estimation while also equipping the model with the ability to quantify uncertainty. Finally, metrics such as mean absolute percentage error (MAPE), normalized mean prediction interval width (NMPIW) and prediction interval coverage probability (PICP) were adopted to quantitatively assess the model's estimated accuracy and the precision of the uncertainty quantification. Additionally, an error decomposition of the estimation results was conducted to analyze model’s performance based on target parameters and scaled distance. The results indicate that the proposed method achieved an estimation error of 12.2% on the test set, with a confidence interval covering over 81.6% of true values, and less than 20 milliseconds of the estimation time for a single sample point. This method provides a novel approach for fast and accurate estimation of blast loading in complex structures with sufficient confidence for the estimation results.
For the estimation of blast loading in complex structures, traditional numerical simulation methods were computationally intensive whereas rapid estimation methods based on neural networks can only provide estimates at local points without providing confidence intervals for the predicted results. To achieve fast and reliable estimation of the blast loading in complex structures, Bayesian theory was combined with deep learning to develop a Bayesian deep learning approach for rapid estimation of blast loading in complex structures. The approach initially utilized open-source numerical simulation software to generate a dataset of blast loading in complex structures, encompassing a wide range of parameters such as explosion equivalents, locations, and velocities. During this process, mesh sizes that balanced computational accuracy and speed were determined through mesh sensitivity analysis and the verification of the numerical simulation accuracy. Then, the deep learning model was extended into a Bayesian deep learning model based on Bayesian theory. By introducing probability distributions over the weights of the neural network, the model parameters were treated as random variables. Variational Bayesian inference was then employed to efficiently train the model, ensuring the accuracy of rapid blast loading estimation while also equipping the model with the ability to quantify uncertainty. Finally, metrics such as mean absolute percentage error (MAPE), normalized mean prediction interval width (NMPIW) and prediction interval coverage probability (PICP) were adopted to quantitatively assess the model's estimated accuracy and the precision of the uncertainty quantification. Additionally, an error decomposition of the estimation results was conducted to analyze model’s performance based on target parameters and scaled distance. The results indicate that the proposed method achieved an estimation error of 12.2% on the test set, with a confidence interval covering over 81.6% of true values, and less than 20 milliseconds of the estimation time for a single sample point. This method provides a novel approach for fast and accurate estimation of blast loading in complex structures with sufficient confidence for the estimation results.
, Available online ,
doi: 10.11883/bzycj-2024-0214
Abstract:
To understand the relationship between fragmentation and energy dissipation in copper-bearing ore rock subjected to impact loading, a split Hopkinson pressure bar (SHPB) testing apparatus was employed to study the mechanical properties and energy transfer mechanisms of copper-bearing tuff under varying impact loads. Additionally, fractal theory was used to establish the correlation between dissipated energy and rock fragmentation. Utilizing the finite discrete element method (FDEM), numerical simulations of crack propagation within the rock were conducted. The results indicate that as the incident energy increases, the distribution patterns of the transmission energy, absorbed energy and reflection energy remain consistent, which are characterized by transmission energy, absorbed energy and reflection energy decreased successively. Furthermore, significant variations in fragment size distribution are observed with changes in dissipated energy. Specifically, as dissipated energy increases from 19.52 J to 105.72 J, the average fragment size decreases from 27.98 mm to 16.94 mm, while the fractal dimension increases by 26.43%. This suggests that higher dissipated energy results in more extensive macroscopic fragmentation, an increase in the number of fragments, smaller particle sizes and enhanced uniformity. As the impact load intensifies, the time to crack initiation decreases, and the proportion of tensile cracks relative to total cracks increases. The application of the FDEM offers new insights into the fracture and failure characteristics of rocks.
To understand the relationship between fragmentation and energy dissipation in copper-bearing ore rock subjected to impact loading, a split Hopkinson pressure bar (SHPB) testing apparatus was employed to study the mechanical properties and energy transfer mechanisms of copper-bearing tuff under varying impact loads. Additionally, fractal theory was used to establish the correlation between dissipated energy and rock fragmentation. Utilizing the finite discrete element method (FDEM), numerical simulations of crack propagation within the rock were conducted. The results indicate that as the incident energy increases, the distribution patterns of the transmission energy, absorbed energy and reflection energy remain consistent, which are characterized by transmission energy, absorbed energy and reflection energy decreased successively. Furthermore, significant variations in fragment size distribution are observed with changes in dissipated energy. Specifically, as dissipated energy increases from 19.52 J to 105.72 J, the average fragment size decreases from 27.98 mm to 16.94 mm, while the fractal dimension increases by 26.43%. This suggests that higher dissipated energy results in more extensive macroscopic fragmentation, an increase in the number of fragments, smaller particle sizes and enhanced uniformity. As the impact load intensifies, the time to crack initiation decreases, and the proportion of tensile cracks relative to total cracks increases. The application of the FDEM offers new insights into the fracture and failure characteristics of rocks.
, Available online ,
doi: 10.11883/bzycj-2024-0248
Abstract:
The penetration depth of the earth-penetrating projectile is a basic problem in the design of protection engineering. Scaled testing is an important method to study the penetration law. The size effect between the model test results and the prototype is a problem that must be solved to establish the calculation method of penetration using scaled tests. In this study, the stress and strain state evolution of the rock-like target medium subjected to the penetration of earth-penetrating projectiles and the penetration resistance function of the projectiles were derived using cavity expansion theory. The formula for the caliber coefficient characterizing the size effect was obtained, and a simplified analysis of the nose shape coefficient and caliber coefficient was conducted using curve fitting and Taylor expansion within the penetration velocity range of the conventional earth-penetrating weapons. A practical calculation formula for the penetration depth of conventional earth-penetrating weapons into rock-like media was proposed, whose coefficients can be directly determined by parameters of target and projectiles. The results show that the main influencing factor of the projectile’s penetration resistance is the impedance of the target. The source of the size effect is originated from the fact that the ranges of the target damage zones do not satisfy the geometric similarity law. The nose shape coefficient can be simplified into a linear function of the projectile’s aspect ratio, and the nose shape coefficient of a flat-nosed projectile is 0.57. The caliber coefficient of the projectile is determined by the ratio of the cavity radius of the penetration to the radius of the fracture zone and can be taken as 1.2−1.4 for conventional earth-penetrating weapons. The theoretical calculation formula of penetration depth is in good agreement with experimental results, and thus, has high reliability.
The penetration depth of the earth-penetrating projectile is a basic problem in the design of protection engineering. Scaled testing is an important method to study the penetration law. The size effect between the model test results and the prototype is a problem that must be solved to establish the calculation method of penetration using scaled tests. In this study, the stress and strain state evolution of the rock-like target medium subjected to the penetration of earth-penetrating projectiles and the penetration resistance function of the projectiles were derived using cavity expansion theory. The formula for the caliber coefficient characterizing the size effect was obtained, and a simplified analysis of the nose shape coefficient and caliber coefficient was conducted using curve fitting and Taylor expansion within the penetration velocity range of the conventional earth-penetrating weapons. A practical calculation formula for the penetration depth of conventional earth-penetrating weapons into rock-like media was proposed, whose coefficients can be directly determined by parameters of target and projectiles. The results show that the main influencing factor of the projectile’s penetration resistance is the impedance of the target. The source of the size effect is originated from the fact that the ranges of the target damage zones do not satisfy the geometric similarity law. The nose shape coefficient can be simplified into a linear function of the projectile’s aspect ratio, and the nose shape coefficient of a flat-nosed projectile is 0.57. The caliber coefficient of the projectile is determined by the ratio of the cavity radius of the penetration to the radius of the fracture zone and can be taken as 1.2−1.4 for conventional earth-penetrating weapons. The theoretical calculation formula of penetration depth is in good agreement with experimental results, and thus, has high reliability.
, Available online ,
doi: 10.11883/bzycj-2024-0203
Abstract:
The equation of state for the detonation products of explosives is one of the foundations in explosion physics. JWL equation of state has been widely applied to study the properties of various explosives. In order to obtain the equation of state of the detonation products, an underwater explosion method was used to study JWL equation of state for the detonation of RDX. It considered the explosion bubble expansion process based on the conservation of energy including Es0 (initial shock wave energy), Ept (potential energy of water), Ec (kinetic energy of water) and Er (energy loss by bubble expansion), which are related to the underwater explosion bubble radius (R-t) and shock wave front (Rs-t) measured in the underwater explosion experiments as functions of time. Based on the experimental results and using the same method to process the experimental data in cylinder experiment, the time functions of explosion bubble expansion radius and variation of shock wave front position were fitted and the parameters of the JWL equation of state for RDX detonation products were obtained. In order to analyze the accuracy of the parameters of the JWL equation of state obtained by the underwater explosion method, the time history of the underwater explosions bubble pulsating pressure wave was calculated using the bubble dynamics equation. It shows that the calculation results agree well with the bubble expansion radius and bubble pulsation period determined using the underwater explosion experiments in a pool. The calculated bubble radius obtained by the proposed measurement method has a smaller deviation from that obtained by the cylinder experimental value, especially in the low-pressure stage compare with the JWL state parameters obtained from cylinder method. This method provides a testing approach for the equation of state of detonation products with low cost, reduced size limitations and a wide pressure range.
The equation of state for the detonation products of explosives is one of the foundations in explosion physics. JWL equation of state has been widely applied to study the properties of various explosives. In order to obtain the equation of state of the detonation products, an underwater explosion method was used to study JWL equation of state for the detonation of RDX. It considered the explosion bubble expansion process based on the conservation of energy including Es0 (initial shock wave energy), Ept (potential energy of water), Ec (kinetic energy of water) and Er (energy loss by bubble expansion), which are related to the underwater explosion bubble radius (R-t) and shock wave front (Rs-t) measured in the underwater explosion experiments as functions of time. Based on the experimental results and using the same method to process the experimental data in cylinder experiment, the time functions of explosion bubble expansion radius and variation of shock wave front position were fitted and the parameters of the JWL equation of state for RDX detonation products were obtained. In order to analyze the accuracy of the parameters of the JWL equation of state obtained by the underwater explosion method, the time history of the underwater explosions bubble pulsating pressure wave was calculated using the bubble dynamics equation. It shows that the calculation results agree well with the bubble expansion radius and bubble pulsation period determined using the underwater explosion experiments in a pool. The calculated bubble radius obtained by the proposed measurement method has a smaller deviation from that obtained by the cylinder experimental value, especially in the low-pressure stage compare with the JWL state parameters obtained from cylinder method. This method provides a testing approach for the equation of state of detonation products with low cost, reduced size limitations and a wide pressure range.
, Available online ,
doi: 10.11883/bzycj-2024-0136
Abstract:
Aiming at the resistance evaluation and engineering design of the rock-rubble concrete shield under the combination of penetration and explosion of Earth Penetrating Weapons, firstly, a finite element modeling method for rock-rubble concrete shields was proposed. By conducting numerical simulations of quasi-static and penetration tests on ultra-high performance concrete targets containing different coarse aggregate types (corundum and basalt), particle sizes (5–15 mm, 5–20 mm, 35–45 mm, and 65–75 mm), and volume fractions (15% and 30%), the reliability of the finite element analysis approach was thoroughly verified. Then, using the semi-infinite rock-rubble concrete shield penetrated by the SDB as a case study, the quantitative influence of type (corundum, basalt, and granite) and dimensionless particle size of rock-rubble (ranging from 0.3 to 2.2 times the projectile diameter) on the penetration depth was analyzed, and optimal design recommendations were determined. Furthermore, the penetration analyses of three typical prototype warheads, i.e., SDB, WDU-43/B, and BLU-109/B, were carried out, and the corresponding penetration resistances of normal strength concrete (NSC), ultra-high performance concrete (UHPC), and corundum rubble concrete (CRC) shields against the above three warheads were quantitatively compared. Finally, the engineering design method for the CRC shield under the combined effects of penetration and explosion of prototype warheads was proposed. The results indicate that the CRC shield containing the particle size of 1.3 to 1.7 times the projectile diameter exhibits the most excellent penetration resistance. Under the penetration of three types of warheads, the penetration depths in CRC shield were 0.29, 0.78, and 0.68 m, respectively, which are reduced by 61.8%–69.1% and 43.3%–58.0% compared to those in NSC and UHPC shields. Under the combined effects of penetration and explosion, the perforation limits of the CRC shield are 0.55, 1.41, and 1.48 m, while the scabbing limits are 1.11, 2.26, and 3.17 m. Compared with NSC and UHPC shields, the perforation limits are reduced by 58.5%–61.2% and 43.2%–58.1%, respectively, and the scabbing limits are reduced by 61.8%–69.2% and 34.7%–40.5%, respectively.
Aiming at the resistance evaluation and engineering design of the rock-rubble concrete shield under the combination of penetration and explosion of Earth Penetrating Weapons, firstly, a finite element modeling method for rock-rubble concrete shields was proposed. By conducting numerical simulations of quasi-static and penetration tests on ultra-high performance concrete targets containing different coarse aggregate types (corundum and basalt), particle sizes (5–15 mm, 5–20 mm, 35–45 mm, and 65–75 mm), and volume fractions (15% and 30%), the reliability of the finite element analysis approach was thoroughly verified. Then, using the semi-infinite rock-rubble concrete shield penetrated by the SDB as a case study, the quantitative influence of type (corundum, basalt, and granite) and dimensionless particle size of rock-rubble (ranging from 0.3 to 2.2 times the projectile diameter) on the penetration depth was analyzed, and optimal design recommendations were determined. Furthermore, the penetration analyses of three typical prototype warheads, i.e., SDB, WDU-43/B, and BLU-109/B, were carried out, and the corresponding penetration resistances of normal strength concrete (NSC), ultra-high performance concrete (UHPC), and corundum rubble concrete (CRC) shields against the above three warheads were quantitatively compared. Finally, the engineering design method for the CRC shield under the combined effects of penetration and explosion of prototype warheads was proposed. The results indicate that the CRC shield containing the particle size of 1.3 to 1.7 times the projectile diameter exhibits the most excellent penetration resistance. Under the penetration of three types of warheads, the penetration depths in CRC shield were 0.29, 0.78, and 0.68 m, respectively, which are reduced by 61.8%–69.1% and 43.3%–58.0% compared to those in NSC and UHPC shields. Under the combined effects of penetration and explosion, the perforation limits of the CRC shield are 0.55, 1.41, and 1.48 m, while the scabbing limits are 1.11, 2.26, and 3.17 m. Compared with NSC and UHPC shields, the perforation limits are reduced by 58.5%–61.2% and 43.2%–58.1%, respectively, and the scabbing limits are reduced by 61.8%–69.2% and 34.7%–40.5%, respectively.
, Available online ,
doi: 10.11883/bzycj-2024-0096
Abstract:
An experimental investigation of typical projectiles penetrating multi-layer spaced Q355B steel targets was conducted to study the trajectory characteristics of elliptical cross-section projectiles penetrating multi-layer spaced steel targets. Numerical simulations were performed on LS-DYNA finite element software and typical results obtained were validated by experimental results. The attitude and trajectory parameters in the penetration process and the deflection mechanism of the projectile were obtained. The influence of cross-section shape, the minor-to-major axis length ratio of the projectile cross-section, initial velocity, rotation angle, and incident angle on the penetration trajectories and attitude deflection was investigated. The research results show that the penetration trajectory stability of the circular cross-section projectile is better than the elliptical and asymmetric elliptical cross-section projectiles when the rotation angle is 0°. As the minor-to-major axis length ratio increases, the trajectory is more stable. The trajectory deflection reduces with a higher initial velocity. When the rotation angle is 90°, the penetration trajectory of both symmetric and asymmetric elliptical cross-section projectiles in the incident plane is the most stable, and the trajectory deflection of the two projectiles in the horizontal plane reaches its maximum at rotation angles of 45° and 90°, respectively. The trajectory stability of an asymmetric elliptical projectile, when the rotation angle is obtuse, is better than that at the acute angle. When the incident angle is in the range of [0°, 50°], the trajectory instability and attitude deflection of the projectile increase with the increase of incident angle and then decrease, and both reach the largest when the incident angle is about 30°. It is also found that the projectile will separate from the target during the penetration stage of the projectile nose when penetrating a thin steel target in a stable attitude. When the projectile penetrates a thin steel target at a large attack angle, the attachment of the projectile and target mainly occurs on the upper surface of the projectile.
An experimental investigation of typical projectiles penetrating multi-layer spaced Q355B steel targets was conducted to study the trajectory characteristics of elliptical cross-section projectiles penetrating multi-layer spaced steel targets. Numerical simulations were performed on LS-DYNA finite element software and typical results obtained were validated by experimental results. The attitude and trajectory parameters in the penetration process and the deflection mechanism of the projectile were obtained. The influence of cross-section shape, the minor-to-major axis length ratio of the projectile cross-section, initial velocity, rotation angle, and incident angle on the penetration trajectories and attitude deflection was investigated. The research results show that the penetration trajectory stability of the circular cross-section projectile is better than the elliptical and asymmetric elliptical cross-section projectiles when the rotation angle is 0°. As the minor-to-major axis length ratio increases, the trajectory is more stable. The trajectory deflection reduces with a higher initial velocity. When the rotation angle is 90°, the penetration trajectory of both symmetric and asymmetric elliptical cross-section projectiles in the incident plane is the most stable, and the trajectory deflection of the two projectiles in the horizontal plane reaches its maximum at rotation angles of 45° and 90°, respectively. The trajectory stability of an asymmetric elliptical projectile, when the rotation angle is obtuse, is better than that at the acute angle. When the incident angle is in the range of [0°, 50°], the trajectory instability and attitude deflection of the projectile increase with the increase of incident angle and then decrease, and both reach the largest when the incident angle is about 30°. It is also found that the projectile will separate from the target during the penetration stage of the projectile nose when penetrating a thin steel target in a stable attitude. When the projectile penetrates a thin steel target at a large attack angle, the attachment of the projectile and target mainly occurs on the upper surface of the projectile.
, Available online ,
doi: 10.11883/bzycj-2024-0320
Abstract:
In order to study the dynamic response mode and explosion ignition characteristics of lithium battery in light and small unmanned aerial vehicle (UAV) under high-energy impact, and evaluate the safety performance of lithium battery under dynamic impact, this paper takes the soft-package lithium battery as the research object, and have used the drop-hammer impact and gas gun impact test methods to carry out the drop hammer impact of the soft-package battery pack and the high-velocity impact of the battery on the aluminum plate. The deformation mode and ignition of the soft-package lithium battery under different battery power after impact were studied respectively. Combined with the mechanical deformation response and ignition characteristics of the battery, the impact safety of the small soft-package lithium battery was analyzed. The results show that the ignition risk of small soft-package lithium battery after being impacted by loads in the out-of-plane direction under the conditions of conventional battery shell protection is much higher than that under the condition of out-of-plane load impact. The ignition risk of lithium battery is obviously related to battery power and impact velocity. The thickness of the impacted aluminum plate has little effect on the ignition risk of lithium battery. Due to the buffering effect of the external battery shell, the lithium battery for light and small UAV has a relatively low risk of ignition after an unpredictable heading impact accident at low altitude in the urban environment.
In order to study the dynamic response mode and explosion ignition characteristics of lithium battery in light and small unmanned aerial vehicle (UAV) under high-energy impact, and evaluate the safety performance of lithium battery under dynamic impact, this paper takes the soft-package lithium battery as the research object, and have used the drop-hammer impact and gas gun impact test methods to carry out the drop hammer impact of the soft-package battery pack and the high-velocity impact of the battery on the aluminum plate. The deformation mode and ignition of the soft-package lithium battery under different battery power after impact were studied respectively. Combined with the mechanical deformation response and ignition characteristics of the battery, the impact safety of the small soft-package lithium battery was analyzed. The results show that the ignition risk of small soft-package lithium battery after being impacted by loads in the out-of-plane direction under the conditions of conventional battery shell protection is much higher than that under the condition of out-of-plane load impact. The ignition risk of lithium battery is obviously related to battery power and impact velocity. The thickness of the impacted aluminum plate has little effect on the ignition risk of lithium battery. Due to the buffering effect of the external battery shell, the lithium battery for light and small UAV has a relatively low risk of ignition after an unpredictable heading impact accident at low altitude in the urban environment.
, Available online ,
doi: 10.11883/bzycj-2024-0089
Abstract:
Plasma blasting rock breaking technology is characterized by green, high efficiency, controllability, and has a good application prospect in deep rock breaking. In order to provide a new rock-breaking method for the rock-breaking engineering under deep stress, four groups of plasma sandstone blasting tests under different peripheral pressures were carried out. The morphology, structure and distribution of three-dimensional cracks inside the rock were comparatively analyzed by CT scanning and three-dimensional reconstruction, so as to study the effects of the plasma rock-breaking technology in rock-breaking under different peripheral pressures. Meanwhile numerical simulation is conducted by using LS-DYNA, and a plasma equivalent explosive model in the coupled stress field is established to assist the verification of the coupled stress field, the plasma blasting mechanism as well as the rock-breaking process in the blasting process. Numerical simulation is conducted by using LS-DYNA to establish the plasma equivalent explosive model, supplementing the verification of the role of plasma blasting in the coupled stress field, and investigating the mechanism of plasma blasting under different pressures, as well as the rock body in the blasting process of the internal crack expansion, distribution and damage evolution laws. The results show that under the same voltage, with the increase of the 3D peripheral pressure, the number and distribution range of cracks on the surface of the rock exhibit a trend of gradual reduction, while the complexity of the cracks within the sandstone and the degree of penetration are significantly reduced. Due to the dynamic stress field generated by plasma blasting and the static stress coupling field generated by the surrounding pressure, the shock wave generated by the plasma blasting in the initial stage of the explosion plays a major role for the effect of different pressures under the action of the rock crack morphology and the center of the expansion of the region does not show obvious differences. With the attenuation of the shock wave, the 3D surrounding pressure in the middle and late stages of the plasma blasting process plays a decisive role in inhibiting the cracks of the rock mass expansion and damage evolution. At the same time, with the increase of the surrounding pressure, the more significant inhibition effect on the expansion of cracks in the rock body, resulting in the body fractal dimension and damage degree of 3D cracks in the rock body, while the role of the surrounding pressure approximately follows a linearly decreasing relationship.
Plasma blasting rock breaking technology is characterized by green, high efficiency, controllability, and has a good application prospect in deep rock breaking. In order to provide a new rock-breaking method for the rock-breaking engineering under deep stress, four groups of plasma sandstone blasting tests under different peripheral pressures were carried out. The morphology, structure and distribution of three-dimensional cracks inside the rock were comparatively analyzed by CT scanning and three-dimensional reconstruction, so as to study the effects of the plasma rock-breaking technology in rock-breaking under different peripheral pressures. Meanwhile numerical simulation is conducted by using LS-DYNA, and a plasma equivalent explosive model in the coupled stress field is established to assist the verification of the coupled stress field, the plasma blasting mechanism as well as the rock-breaking process in the blasting process. Numerical simulation is conducted by using LS-DYNA to establish the plasma equivalent explosive model, supplementing the verification of the role of plasma blasting in the coupled stress field, and investigating the mechanism of plasma blasting under different pressures, as well as the rock body in the blasting process of the internal crack expansion, distribution and damage evolution laws. The results show that under the same voltage, with the increase of the 3D peripheral pressure, the number and distribution range of cracks on the surface of the rock exhibit a trend of gradual reduction, while the complexity of the cracks within the sandstone and the degree of penetration are significantly reduced. Due to the dynamic stress field generated by plasma blasting and the static stress coupling field generated by the surrounding pressure, the shock wave generated by the plasma blasting in the initial stage of the explosion plays a major role for the effect of different pressures under the action of the rock crack morphology and the center of the expansion of the region does not show obvious differences. With the attenuation of the shock wave, the 3D surrounding pressure in the middle and late stages of the plasma blasting process plays a decisive role in inhibiting the cracks of the rock mass expansion and damage evolution. At the same time, with the increase of the surrounding pressure, the more significant inhibition effect on the expansion of cracks in the rock body, resulting in the body fractal dimension and damage degree of 3D cracks in the rock body, while the role of the surrounding pressure approximately follows a linearly decreasing relationship.
, Available online ,
doi: 10.11883/bzycj-2024-0150
Abstract:
The protection level and domestic standard test level of commonly used passive flexible barriers against rockfall impact are not higher than 5 000 kJ, while bridges in mountains and other important transportation infrastructures are facing rockfall disaster threats with higher impact energy levels. Considering that the design method for passive flexible barriers with higher impact energy levels is lacking, to provide a feasible and reliable tool for the infrastructure engineers, the analysis and design of 8 000 kJ-level passive flexible barrier against rockfall impact were carried out at present based on the numerical simulation method. Firstly, by adopting the explicit dynamic software ANSYS/LS-DYNA, quasi-static tests, including the tensile test on single wire ring and three-ring chain, net puncturing test, and the dynamic impact test, i.e., 2 000 kJ rockfall impacting the full-scale passive flexible barrier, were numerically reproduced, and the reliability of the numerical simulation method was fully verified by comparing with the test data, i.e., the maximum breaking force and breaking displacement of the wire ring and its failure characteristics, the whole impact process of rockfall, and the cable force-time history curves, the influencing factors, i.e., the inclining angle, span, and height of the steel post and different specifications of energy dissipating devices ranging from 50 kJ to 70 kJ, on the dynamic behavior of the passive flexible barrier were further analyzed. The results show that the specification of the energy dissipation device is the most critical parameter controlling the internal force and displacement of the passive flexible barrier. The inclining angle of the steel post is recommended to be 10°. An increase in the post spacing can reduce the in-plane stiffness of the structure while having less effect on the transverse anchorage. An increase in the post height will cause a significant increase in the support reaction force at the post bottom. A reasonable adjustment of the anchorage position of each wire rope is required when the post height and spacing are changed. Finally, based on the results of parameter analysis, two design schemes for a passive flexible barrier against 8 000 kJ rockfall impact were given by adjusting the geometry of the structure, the specification of the energy dissipating device, and the addition of transmission support ropes. Both of them passed the test of the European standard EAD 340059-00-0106.
The protection level and domestic standard test level of commonly used passive flexible barriers against rockfall impact are not higher than 5 000 kJ, while bridges in mountains and other important transportation infrastructures are facing rockfall disaster threats with higher impact energy levels. Considering that the design method for passive flexible barriers with higher impact energy levels is lacking, to provide a feasible and reliable tool for the infrastructure engineers, the analysis and design of 8 000 kJ-level passive flexible barrier against rockfall impact were carried out at present based on the numerical simulation method. Firstly, by adopting the explicit dynamic software ANSYS/LS-DYNA, quasi-static tests, including the tensile test on single wire ring and three-ring chain, net puncturing test, and the dynamic impact test, i.e., 2 000 kJ rockfall impacting the full-scale passive flexible barrier, were numerically reproduced, and the reliability of the numerical simulation method was fully verified by comparing with the test data, i.e., the maximum breaking force and breaking displacement of the wire ring and its failure characteristics, the whole impact process of rockfall, and the cable force-time history curves, the influencing factors, i.e., the inclining angle, span, and height of the steel post and different specifications of energy dissipating devices ranging from 50 kJ to 70 kJ, on the dynamic behavior of the passive flexible barrier were further analyzed. The results show that the specification of the energy dissipation device is the most critical parameter controlling the internal force and displacement of the passive flexible barrier. The inclining angle of the steel post is recommended to be 10°. An increase in the post spacing can reduce the in-plane stiffness of the structure while having less effect on the transverse anchorage. An increase in the post height will cause a significant increase in the support reaction force at the post bottom. A reasonable adjustment of the anchorage position of each wire rope is required when the post height and spacing are changed. Finally, based on the results of parameter analysis, two design schemes for a passive flexible barrier against 8 000 kJ rockfall impact were given by adjusting the geometry of the structure, the specification of the energy dissipating device, and the addition of transmission support ropes. Both of them passed the test of the European standard EAD 340059-00-0106.
, Available online ,
doi: 10.11883/bzycj-2024-0224
Abstract:
To reasonably describe the reaction evolution behavior of explosives after ignition under mechanical confinement, we conduct in-depth analysis of the deformation and movement characteristics of the shell, and divide the response process of the shell into three stages: elastoplastic stage, complete yield stage, and shell rupture stage with inertial motion constraint. The combustion rate theory and the combustion crack-network theory are employed as pivotal parameters for the reaction evolution of the explosives. In the initial stage, the mechanical properties of the shell are taken into consideration, with the material properties serving as the upper limit for structural constraint strength. During this stage, the deformation of the shell remains relatively small. In the second stage, a generalized equivalent stiffness concept is introduced in order to account for the inertial confinement effect of the shell movement. Furthermore, a mechanical deformation analysis of cylindrical shells and end caps is conducted, which takes into account the coupled effects of combustion crack network reaction evolution and shell deformation movement based on a kinematic theory. The third stage is building upon the foundation established in preceding stages, the impact of gas leakage following shell rupture on the progression of the explosive reaction process is considered, The integration of these three stages yields a formula for pressure, shell velocity, and time in the non-impact ignition reaction evolution process of solid explosives. A model for explosives reaction evolution is established to characterize the inertial confinement effects of the shell movement. This model and the related parameters are verified by comparing the calculating results with typical experimental data. It is found that the velocity of shell motion and the changes in internal pressure fundamentally characterize the relationship between the energy release of the explosives and the work done by the product gas. Considering the inertial confinement effects of shell motion is more indicative for the evolution process of explosives reaction, by using this model, the internal pressure of the shell, reaction rate and reaction degree of solid explosives can be calculated based on the historical changes in the velocity of the shell’s motion, thus providing a theoretical method for the explosive safety design and for evaluation under unexpected stimuli.
To reasonably describe the reaction evolution behavior of explosives after ignition under mechanical confinement, we conduct in-depth analysis of the deformation and movement characteristics of the shell, and divide the response process of the shell into three stages: elastoplastic stage, complete yield stage, and shell rupture stage with inertial motion constraint. The combustion rate theory and the combustion crack-network theory are employed as pivotal parameters for the reaction evolution of the explosives. In the initial stage, the mechanical properties of the shell are taken into consideration, with the material properties serving as the upper limit for structural constraint strength. During this stage, the deformation of the shell remains relatively small. In the second stage, a generalized equivalent stiffness concept is introduced in order to account for the inertial confinement effect of the shell movement. Furthermore, a mechanical deformation analysis of cylindrical shells and end caps is conducted, which takes into account the coupled effects of combustion crack network reaction evolution and shell deformation movement based on a kinematic theory. The third stage is building upon the foundation established in preceding stages, the impact of gas leakage following shell rupture on the progression of the explosive reaction process is considered, The integration of these three stages yields a formula for pressure, shell velocity, and time in the non-impact ignition reaction evolution process of solid explosives. A model for explosives reaction evolution is established to characterize the inertial confinement effects of the shell movement. This model and the related parameters are verified by comparing the calculating results with typical experimental data. It is found that the velocity of shell motion and the changes in internal pressure fundamentally characterize the relationship between the energy release of the explosives and the work done by the product gas. Considering the inertial confinement effects of shell motion is more indicative for the evolution process of explosives reaction, by using this model, the internal pressure of the shell, reaction rate and reaction degree of solid explosives can be calculated based on the historical changes in the velocity of the shell’s motion, thus providing a theoretical method for the explosive safety design and for evaluation under unexpected stimuli.
, Available online ,
doi: 10.11883/bzycj-2024-0138
Abstract:
In this study, AlSi10Mg alloy was prepared by selective laser melting (SLM) first, and then subjected to stress relieved annealing treatment. The microstructures of the alloy were analyzed by optical microscope (OM), scanning electron microscope (SEM) and electron backscatter diffraction (EBSD) technology. To understand the influence of coupling effects on the mechanical behavior of AlSi10Mg alloy under wide strain rates and wide temperatures, the mechanical behavior of the alloy under extreme conditions (high and low temperatures, high strain-rate) were analyzed by universal testing machine with an environmental chamber and split Hopkinson pressure bar. The results show that AlSi10Mg alloy possesses fine cellular dendritic microstructure, mainly including α-Al and Si phases, and annealing treatment can result in the discontinuous distribution of eutectic Si particles. The average grain size is 3.7 μm. AlSi10Mg alloy displays strain-rate strengthening effect under room temperature condition at 0.002–4 800 s−1, and has different strain-rate sensitivity in different strain-rate ranges. Under high strain-rate conditions, strain hardening effect still dominates. The material has higher yield strength and flow stress at 173 K. When the strain-rate is 0.002 s−1, the SLM AlSi10Mg alloy has different temperature sensitivities in different temperature ranges. The alloy does not have temperature sensitivity in the range of 173–243 K; the material exhibits temperature sensitivity ranging from 293 K to 573 K, and the softening effect due to temperature on the material intensifies with increasing temperature. Based on the J-C constitutive model, a modified J-C constitutive model expressed by piecewise functions is constructed and the experimental results are fitted. In addition, experimental verification was conducted on the modified J-C constitutive model, and the predicted results are basically consistent with the experimental results. Within the scope of the study, the modified J-C constitutive model effectively reflects the mechanical behavior of the alloy at high and low temperatures and under different strain-rate.
In this study, AlSi10Mg alloy was prepared by selective laser melting (SLM) first, and then subjected to stress relieved annealing treatment. The microstructures of the alloy were analyzed by optical microscope (OM), scanning electron microscope (SEM) and electron backscatter diffraction (EBSD) technology. To understand the influence of coupling effects on the mechanical behavior of AlSi10Mg alloy under wide strain rates and wide temperatures, the mechanical behavior of the alloy under extreme conditions (high and low temperatures, high strain-rate) were analyzed by universal testing machine with an environmental chamber and split Hopkinson pressure bar. The results show that AlSi10Mg alloy possesses fine cellular dendritic microstructure, mainly including α-Al and Si phases, and annealing treatment can result in the discontinuous distribution of eutectic Si particles. The average grain size is 3.7 μm. AlSi10Mg alloy displays strain-rate strengthening effect under room temperature condition at 0.002–4 800 s−1, and has different strain-rate sensitivity in different strain-rate ranges. Under high strain-rate conditions, strain hardening effect still dominates. The material has higher yield strength and flow stress at 173 K. When the strain-rate is 0.002 s−1, the SLM AlSi10Mg alloy has different temperature sensitivities in different temperature ranges. The alloy does not have temperature sensitivity in the range of 173–243 K; the material exhibits temperature sensitivity ranging from 293 K to 573 K, and the softening effect due to temperature on the material intensifies with increasing temperature. Based on the J-C constitutive model, a modified J-C constitutive model expressed by piecewise functions is constructed and the experimental results are fitted. In addition, experimental verification was conducted on the modified J-C constitutive model, and the predicted results are basically consistent with the experimental results. Within the scope of the study, the modified J-C constitutive model effectively reflects the mechanical behavior of the alloy at high and low temperatures and under different strain-rate.
, Available online ,
doi: 10.11883/bzycj-2024-0351
Abstract:
As lithium-ion batteries are widely used in the industry represented by electric vehicles, their collision-induced safety problems have aroused widespread concern in the industry and society. Under the collision condition of electric vehicles, on the one hand, the deformation of the battery will lead to direct fire and explosion, and on the other hand, the unknown deformation of the battery caused by the collision will bring safety risks to the subsequent use. For the unknown deformation of batteries after collision, abnormal batteries are only sensed by physical signals such as voltage, temperature and current, and there is no direct monitoring method for battery deformation. To bridge this gap, this paper uses small piezoelectric plates and realizes deformation and collision monitoring of lithium-ion batteries based on ultrasonic guided waves. Firstly, an experimental platform for different loads of lithium-ion batteries was built, and quasi-static and micro-collision experiments were carried out. Further, the experimental results were analyzed and discussed to clarify the change law of ultrasonic signal under different loads. The results showed that: in the quasi-static battery experiment, the ultrasonic amplitude signal was negatively correlated with the deformation degree of the battery. When the battery was subjected to gradually increasing load and the deformation became more serious, the amplitude would gradually decrease; when the battery was deformed to failure, the amplitude signal would also drop instantaneously. In ball-dropped experiment, the impact deformation will affect the change of amplitude and energy integration of the ultrasonic signal, which can be used as a basis to judge whether the battery collision occurs. Finally, the mapping relationship between ultrasonic and battery deformation failure monitoring under large deformation is established, and the criteria based on ultrasonic sensor under collision deformation is proposed. The results of this paper propose a new method for the safety monitoring of lithium-ion batteries, which is expected to be applied in electric vehicles and other fields.
As lithium-ion batteries are widely used in the industry represented by electric vehicles, their collision-induced safety problems have aroused widespread concern in the industry and society. Under the collision condition of electric vehicles, on the one hand, the deformation of the battery will lead to direct fire and explosion, and on the other hand, the unknown deformation of the battery caused by the collision will bring safety risks to the subsequent use. For the unknown deformation of batteries after collision, abnormal batteries are only sensed by physical signals such as voltage, temperature and current, and there is no direct monitoring method for battery deformation. To bridge this gap, this paper uses small piezoelectric plates and realizes deformation and collision monitoring of lithium-ion batteries based on ultrasonic guided waves. Firstly, an experimental platform for different loads of lithium-ion batteries was built, and quasi-static and micro-collision experiments were carried out. Further, the experimental results were analyzed and discussed to clarify the change law of ultrasonic signal under different loads. The results showed that: in the quasi-static battery experiment, the ultrasonic amplitude signal was negatively correlated with the deformation degree of the battery. When the battery was subjected to gradually increasing load and the deformation became more serious, the amplitude would gradually decrease; when the battery was deformed to failure, the amplitude signal would also drop instantaneously. In ball-dropped experiment, the impact deformation will affect the change of amplitude and energy integration of the ultrasonic signal, which can be used as a basis to judge whether the battery collision occurs. Finally, the mapping relationship between ultrasonic and battery deformation failure monitoring under large deformation is established, and the criteria based on ultrasonic sensor under collision deformation is proposed. The results of this paper propose a new method for the safety monitoring of lithium-ion batteries, which is expected to be applied in electric vehicles and other fields.
, Available online ,
doi: 10.11883/bzycj-2024-0239
Abstract:
In order to explore the underwater anti-explosion protection effect of steel fiber reinforced cellular concrete materials, the damage process of reinforced concrete slabs under underwater contact explosion was reproduced by the coupling method of smoothed particle hydrodynamics and finite element method (SPH-FEM). The validity of the simulation method was verified by comparing with the experimental results. On this basis, a three-dimensional refined simulation model of water-explosive-protective layer-reinforced concrete slab was established by the SPH-FEM coupling method. The damage evolution process, failure mode and failure mechanism of protective layer of steel fiber reinforced cellular concrete (SAP10S5, SAP10S10, SAP10S15 and SAP10S20) with different fiber ratios and explosive mass were studied, and the prediction curve of damage level of reinforced concrete slabs was constructed. The results show that the numerical simulation results are in good agreement with the experimental results, which verifies the effectiveness of the simulation method. Under the underwater contact explosion, the addition of protective layer of steel fiber reinforced cellular concrete can effectively reduce the damage degree of protected reinforced concrete (RC) slab, and its influence on the damage degree of RC slab decreases first and then increases with the increase of steel fiber volume fraction in the protective layer. Among them, the anti-explosion protection effect of protective layer of SAP10S15 ratio is the best. When the amount of explosive increases within a certain range, the protective layer of SAP10S15 ratio can still maintain a high proportion of energy consumption and effectively reduce the damage degree of the RC plate. When the amount of explosive is 0.25 kg, the damage index of RC slabs strengthened with protective layer of SAP10S15 has the most obvious attenuation compared with the unprotected scheme, which is 42.5%, and the damage level is reduced from serious damage to moderate damage. The prediction curve of constructed damage level can directly evaluate the influence of steel fiber volume fraction/explosive amount on the damage degree of RC panel. The above research results can provide reference for the anti-explosion protection design of wading concrete structures.
In order to explore the underwater anti-explosion protection effect of steel fiber reinforced cellular concrete materials, the damage process of reinforced concrete slabs under underwater contact explosion was reproduced by the coupling method of smoothed particle hydrodynamics and finite element method (SPH-FEM). The validity of the simulation method was verified by comparing with the experimental results. On this basis, a three-dimensional refined simulation model of water-explosive-protective layer-reinforced concrete slab was established by the SPH-FEM coupling method. The damage evolution process, failure mode and failure mechanism of protective layer of steel fiber reinforced cellular concrete (SAP10S5, SAP10S10, SAP10S15 and SAP10S20) with different fiber ratios and explosive mass were studied, and the prediction curve of damage level of reinforced concrete slabs was constructed. The results show that the numerical simulation results are in good agreement with the experimental results, which verifies the effectiveness of the simulation method. Under the underwater contact explosion, the addition of protective layer of steel fiber reinforced cellular concrete can effectively reduce the damage degree of protected reinforced concrete (RC) slab, and its influence on the damage degree of RC slab decreases first and then increases with the increase of steel fiber volume fraction in the protective layer. Among them, the anti-explosion protection effect of protective layer of SAP10S15 ratio is the best. When the amount of explosive increases within a certain range, the protective layer of SAP10S15 ratio can still maintain a high proportion of energy consumption and effectively reduce the damage degree of the RC plate. When the amount of explosive is 0.25 kg, the damage index of RC slabs strengthened with protective layer of SAP10S15 has the most obvious attenuation compared with the unprotected scheme, which is 42.5%, and the damage level is reduced from serious damage to moderate damage. The prediction curve of constructed damage level can directly evaluate the influence of steel fiber volume fraction/explosive amount on the damage degree of RC panel. The above research results can provide reference for the anti-explosion protection design of wading concrete structures.
, Available online ,
doi: 10.11883/bzycj-2024-0339
Abstract:
The deformation and failure of the internal separator in lithium-ion batteries under external impact are key factors in triggering internal short circuits. The surface of the battery electrodes is usually not smooth, which can cause stress concentration in the separator, affecting the mechanical stability of the battery. Therefore, this study, based on numerical simulation and theoretical analysis, deeply explores the mechanical behavior of the battery separator under compression on uneven surfaces and its short-circuit safety boundary. The model is established using the finite element software ABAQUS, selecting a section of a separator with a width of 50 μm and the nearby positive and negative electrode coatings as a representative unit cell for two-dimensional finite element modeling and numerical calculation. The study compares the surface morphology of three forms: (1) ideal plane; (2) densely packed granular surface; (3) single granular protrusion plane, as well as the effects of particle size, separator thickness, and loading rate. By analyzing the stress-strain curve of the separator, it is found that the separator compressed by uneven surfaces exhibits a "softening phenomenon" compared to compression on an ideal plane. For the ideal plane case, the strain distribution is very uniform, so the battery’s load-bearing capacity is larger. However, for densely packed granular and single granular protrusion cases, under the same loading displacement, the loaded area is smaller, and the generated reaction force is also smaller. As the loading progresses, the gaps are gradually filled, the loaded area increases, and gradually tends to be loaded on the entire surface, and the load difference gradually decreases. Through parametric analysis of the failure stress, it is found that as the particle diameter increases, the separator thickness decreases, or within a certain range of loading rates increases, the separator exhibits a softening behavior, that is, the average stress decreases, the yield point shifts backward, and the short-circuit failure stress also decreases. Furthermore, this study also establishes an equivalent compression constitutive model of the separator under compression on uneven surfaces, thereby theoretically explaining the effect of roughness on failure stress and deriving a quantitative relationship between the two.
The deformation and failure of the internal separator in lithium-ion batteries under external impact are key factors in triggering internal short circuits. The surface of the battery electrodes is usually not smooth, which can cause stress concentration in the separator, affecting the mechanical stability of the battery. Therefore, this study, based on numerical simulation and theoretical analysis, deeply explores the mechanical behavior of the battery separator under compression on uneven surfaces and its short-circuit safety boundary. The model is established using the finite element software ABAQUS, selecting a section of a separator with a width of 50 μm and the nearby positive and negative electrode coatings as a representative unit cell for two-dimensional finite element modeling and numerical calculation. The study compares the surface morphology of three forms: (1) ideal plane; (2) densely packed granular surface; (3) single granular protrusion plane, as well as the effects of particle size, separator thickness, and loading rate. By analyzing the stress-strain curve of the separator, it is found that the separator compressed by uneven surfaces exhibits a "softening phenomenon" compared to compression on an ideal plane. For the ideal plane case, the strain distribution is very uniform, so the battery’s load-bearing capacity is larger. However, for densely packed granular and single granular protrusion cases, under the same loading displacement, the loaded area is smaller, and the generated reaction force is also smaller. As the loading progresses, the gaps are gradually filled, the loaded area increases, and gradually tends to be loaded on the entire surface, and the load difference gradually decreases. Through parametric analysis of the failure stress, it is found that as the particle diameter increases, the separator thickness decreases, or within a certain range of loading rates increases, the separator exhibits a softening behavior, that is, the average stress decreases, the yield point shifts backward, and the short-circuit failure stress also decreases. Furthermore, this study also establishes an equivalent compression constitutive model of the separator under compression on uneven surfaces, thereby theoretically explaining the effect of roughness on failure stress and deriving a quantitative relationship between the two.
, Available online ,
doi: 10.11883/bzycj-2024-0329
Abstract:
As a crucial component to ensure the safety and reliability of lithium-ion batteries (LIBs), the polymer separator plays a significant role in ensuring the mechanical abuse safety of the battery, and its mechanical properties have become an important indicator of battery safety performance. This study focuses on the compressive mechanical behavior of separators in prismatic power batteries under coupled strain rate and temperature conditions. A comprehensive experiment has been conducted including quasi-static and dynamic compression tests across a wide range of strain rates and temperatures. These tests assessed the separator’s mechanical behavior under different strain rates and temperature conditions, with a specific focus on properties and damage mechanism at elevated temperatures and different strain rates. The mechanical response of the separator was meticulously explored, involving an in-depth analysis of strain rate-dependent and temperature-dependent mechanical properties. The results indicated that the separator's mechanical behavior is highly sensitive to both strain rate and temperature. As the strain rate increases, the yield point is reached earlier, causing the separator to yield sooner. Additionally, both the elastic modulus and the yield stress of the separator decrease as the temperature rises. At low strain rates, the yield point shifts forward, whereas at high strain rates, the yield strain increases with temperature. Additionally, the coupled effects of temperature and strain rate were found to alter the damage failure modes, subsequently affecting the separator’s mechanical properties and structural integrity. At low strain rates, the failure of the separator is primarily characterized by plastic deformation and local buckling, whereas complex dynamic failure modes may occur at high strain rates. Based on experimental data, a nonlinear viscoelastic constitutive model was developed, incorporating the effects of temperature-strain rate coupling. This model offers essential insights for the safe and optimized design of lithium-ion batteries. The comprehensive experimental analysis and model developed in this study provide critical references for advancing the design, manufacturing, and practical application of LIB separators, enhancing their reliability and safety across a diverse range of operational conditions.
As a crucial component to ensure the safety and reliability of lithium-ion batteries (LIBs), the polymer separator plays a significant role in ensuring the mechanical abuse safety of the battery, and its mechanical properties have become an important indicator of battery safety performance. This study focuses on the compressive mechanical behavior of separators in prismatic power batteries under coupled strain rate and temperature conditions. A comprehensive experiment has been conducted including quasi-static and dynamic compression tests across a wide range of strain rates and temperatures. These tests assessed the separator’s mechanical behavior under different strain rates and temperature conditions, with a specific focus on properties and damage mechanism at elevated temperatures and different strain rates. The mechanical response of the separator was meticulously explored, involving an in-depth analysis of strain rate-dependent and temperature-dependent mechanical properties. The results indicated that the separator's mechanical behavior is highly sensitive to both strain rate and temperature. As the strain rate increases, the yield point is reached earlier, causing the separator to yield sooner. Additionally, both the elastic modulus and the yield stress of the separator decrease as the temperature rises. At low strain rates, the yield point shifts forward, whereas at high strain rates, the yield strain increases with temperature. Additionally, the coupled effects of temperature and strain rate were found to alter the damage failure modes, subsequently affecting the separator’s mechanical properties and structural integrity. At low strain rates, the failure of the separator is primarily characterized by plastic deformation and local buckling, whereas complex dynamic failure modes may occur at high strain rates. Based on experimental data, a nonlinear viscoelastic constitutive model was developed, incorporating the effects of temperature-strain rate coupling. This model offers essential insights for the safe and optimized design of lithium-ion batteries. The comprehensive experimental analysis and model developed in this study provide critical references for advancing the design, manufacturing, and practical application of LIB separators, enhancing their reliability and safety across a diverse range of operational conditions.
, Available online ,
doi: 10.11883/bzycj-2024-0321
Abstract:
This investigation seeks to elucidate the impact of various discharge states on the dynamic mechanical responses and failure mechanisms of lithium-ion batteries through a comprehensive experimental study. Employing quasi-static compression tests, the research systematically analyzes the compression characteristics and safety performance of lithium-ion batteries preset to specific discharge levels. These tests were conducted at critical junctures: during discharge, following a 1-hour rest period, and after a 24-hour rest period. This methodology enabled a detailed examination of the force-displacement response characteristics, ultimate load-bearing capacity, and overall safety behaviors under varying electrochemical states. The experimental findings indicate that batteries in a discharged state exhibit lower force-displacement curves, suggesting a decrease in structural stiffness attributable to the electro-chemical reaction inside the battery during the discharge process. Notably, these batteries demonstrated a higher maximum load-bearing capacity compared to those tested after rest periods. Additionally, batteries undergoing compression tests in the midst of discharge were more susceptible to catastrophic failures, such as explosions, whereas those allowed to rest showed significantly enhanced safety characteristics. Further microscopic analysis using Scanning Electron Microscopy (SEM) provided insights into the internal structural changes, revealing extensive damage to electrode particles in batteries tested in the discharged state compared to those tested post-rest. The observed damage and increased risk of mechanical failure are primarily attributed to diffusive stresses generated during the discharge process, which accumulate and intensify the vulnerability of the battery structure under mechanical loads. This study contributes valuable experimental evidence and theoretical insights that are crucial for advancing the understanding of the mechanical integrity and safety of lithium-ion batteries under operational stresses. The findings underscore the importance of considering discharge states in the safety design and evaluation of lithium-ion batteries, potentially leading to enhanced durability and safer application in practical scenarios.
This investigation seeks to elucidate the impact of various discharge states on the dynamic mechanical responses and failure mechanisms of lithium-ion batteries through a comprehensive experimental study. Employing quasi-static compression tests, the research systematically analyzes the compression characteristics and safety performance of lithium-ion batteries preset to specific discharge levels. These tests were conducted at critical junctures: during discharge, following a 1-hour rest period, and after a 24-hour rest period. This methodology enabled a detailed examination of the force-displacement response characteristics, ultimate load-bearing capacity, and overall safety behaviors under varying electrochemical states. The experimental findings indicate that batteries in a discharged state exhibit lower force-displacement curves, suggesting a decrease in structural stiffness attributable to the electro-chemical reaction inside the battery during the discharge process. Notably, these batteries demonstrated a higher maximum load-bearing capacity compared to those tested after rest periods. Additionally, batteries undergoing compression tests in the midst of discharge were more susceptible to catastrophic failures, such as explosions, whereas those allowed to rest showed significantly enhanced safety characteristics. Further microscopic analysis using Scanning Electron Microscopy (SEM) provided insights into the internal structural changes, revealing extensive damage to electrode particles in batteries tested in the discharged state compared to those tested post-rest. The observed damage and increased risk of mechanical failure are primarily attributed to diffusive stresses generated during the discharge process, which accumulate and intensify the vulnerability of the battery structure under mechanical loads. This study contributes valuable experimental evidence and theoretical insights that are crucial for advancing the understanding of the mechanical integrity and safety of lithium-ion batteries under operational stresses. The findings underscore the importance of considering discharge states in the safety design and evaluation of lithium-ion batteries, potentially leading to enhanced durability and safer application in practical scenarios.
, Available online ,
doi: 10.11883/bzycj-2024-0279
Abstract:
Prefabricated concrete bursting layer has a very important application prospect in the field of protective engineering attributed to its technical advantages including high construction efficiency and construction quality. However, compared with the monolithic cast-in-situ concrete bursting layer, the impact resistance of the prefabricated concrete bursting layer may be significantly reduced because of the interfaces between the prefabricated blocks and the cast-in-situ part. Therefore, it is important for engineers to reasonably design the prefabricated concrete bursting layer to make its penetration resistance comparable to the monolithic one. To this end, a kind of prefabricated bursting layer connected by wet joints and rebars was proposed in our previous study. In order to apply the prefabricated bursting layer in protective engineering, a series of numerical models were developed to further study its penetration resistance. Firstly, based on the Kong-Fang model and smoothed particle Galerkin (SPG) method, the numerical models were developed and validated against the experimental data of projectile penetrating monolithic and prefabricated targets. Then, the validated numerical models were further used to investigate the influences of prefabricated block size, wet joint width and anchorage length, spacing and diameter of rebars on the penetration resistance of prefabricated targets. Numerical results indicate that increasing the width of wet joints, reducing the spacing between rebars, and extending the anchorage length of rebars can significantly enhance the penetration resistance of prefabricated targets. After clarifying the influences of these parameters, an engineering design method for a prefabricated concrete bursting layer was proposed. Finally, based on this method, two prefabricated high performance concrete targets subjected to two typical types of warhead penetration were designed. Numerical results show that the penetration resistances of two prefabricated targets were comparable to monolithic targets. The proposed engineering design method can provide a reference for engineering applications of prefabricated concrete bursting layers connected by the wet joints and rebars.
Prefabricated concrete bursting layer has a very important application prospect in the field of protective engineering attributed to its technical advantages including high construction efficiency and construction quality. However, compared with the monolithic cast-in-situ concrete bursting layer, the impact resistance of the prefabricated concrete bursting layer may be significantly reduced because of the interfaces between the prefabricated blocks and the cast-in-situ part. Therefore, it is important for engineers to reasonably design the prefabricated concrete bursting layer to make its penetration resistance comparable to the monolithic one. To this end, a kind of prefabricated bursting layer connected by wet joints and rebars was proposed in our previous study. In order to apply the prefabricated bursting layer in protective engineering, a series of numerical models were developed to further study its penetration resistance. Firstly, based on the Kong-Fang model and smoothed particle Galerkin (SPG) method, the numerical models were developed and validated against the experimental data of projectile penetrating monolithic and prefabricated targets. Then, the validated numerical models were further used to investigate the influences of prefabricated block size, wet joint width and anchorage length, spacing and diameter of rebars on the penetration resistance of prefabricated targets. Numerical results indicate that increasing the width of wet joints, reducing the spacing between rebars, and extending the anchorage length of rebars can significantly enhance the penetration resistance of prefabricated targets. After clarifying the influences of these parameters, an engineering design method for a prefabricated concrete bursting layer was proposed. Finally, based on this method, two prefabricated high performance concrete targets subjected to two typical types of warhead penetration were designed. Numerical results show that the penetration resistances of two prefabricated targets were comparable to monolithic targets. The proposed engineering design method can provide a reference for engineering applications of prefabricated concrete bursting layers connected by the wet joints and rebars.
, Available online ,
doi: 10.11883/bzycj-2024-0207
Abstract:
To investigate the dynamic mechanical characterization of non-pure and non-intact ice materials under impact loads, a modified split Hopkinson pressure bar (SHPB) was used. Rapid loading, rod end cooling and waveform shaping techniques were used to ensure the stability of the ice material and achieve dynamic stress balance during loading. The impact mechanical properties of complete ice (pure water, containing 2.5%, 3.5%, 4.5% salt, containing 2.0%, 4.5%, 8.5% coconut) and spliced ice (splicing interface inclination 30°, 60°) at freezing temperature of −10 ℃ were studied. The strain rate ranges from 150~250 s−1. The failure process was recorded by using the high-speed camera triggered simultaneously with the pressure rod. The correlation between the stress and strain of the sample, along with the failure process, was determined by analyzing the time history curve of sample. The failure mode of the spliced ice sample was analyzed by combining the Mohr-Coulomb strength criterion. The results show that the pure water ice exhibits the highest compressive strength, followed by the ice with coconut shreds, and both of them show a positive strain rate effect. However, the compressive strength of the ice with salt addition decreases significantly due to its loose structure and the strain rate effect is not obvious. The dynamic compressive strength of ice samples added with coconut fiber increases firstly and then decreases with the increase of coconut fiber content. Ice samples with high coconut fiber content are prone to "double peak" phenomenon due to the binding effect of coconut fiber on broken ice with small particle size. The splicing plane affects the crack growth, resulting in lower compressive strength than the intact ice sample, and affects the failure mode as well. The ice with small interface inclination is mainly damaged by interface slip, while the ice with large interface inclination is mainly damaged by whole ice, which is similar to the intact ice. The research results provide theoretical basis and method reference for the dynamic mechanical properties of non-pure and non-intact ice materials under impact loads.
To investigate the dynamic mechanical characterization of non-pure and non-intact ice materials under impact loads, a modified split Hopkinson pressure bar (SHPB) was used. Rapid loading, rod end cooling and waveform shaping techniques were used to ensure the stability of the ice material and achieve dynamic stress balance during loading. The impact mechanical properties of complete ice (pure water, containing 2.5%, 3.5%, 4.5% salt, containing 2.0%, 4.5%, 8.5% coconut) and spliced ice (splicing interface inclination 30°, 60°) at freezing temperature of −10 ℃ were studied. The strain rate ranges from 150~250 s−1. The failure process was recorded by using the high-speed camera triggered simultaneously with the pressure rod. The correlation between the stress and strain of the sample, along with the failure process, was determined by analyzing the time history curve of sample. The failure mode of the spliced ice sample was analyzed by combining the Mohr-Coulomb strength criterion. The results show that the pure water ice exhibits the highest compressive strength, followed by the ice with coconut shreds, and both of them show a positive strain rate effect. However, the compressive strength of the ice with salt addition decreases significantly due to its loose structure and the strain rate effect is not obvious. The dynamic compressive strength of ice samples added with coconut fiber increases firstly and then decreases with the increase of coconut fiber content. Ice samples with high coconut fiber content are prone to "double peak" phenomenon due to the binding effect of coconut fiber on broken ice with small particle size. The splicing plane affects the crack growth, resulting in lower compressive strength than the intact ice sample, and affects the failure mode as well. The ice with small interface inclination is mainly damaged by interface slip, while the ice with large interface inclination is mainly damaged by whole ice, which is similar to the intact ice. The research results provide theoretical basis and method reference for the dynamic mechanical properties of non-pure and non-intact ice materials under impact loads.
, Available online ,
doi: 10.11883/bzycj-2024-0229
Abstract:
To investigate the influence of the density of crushed ice region on the cavity evolution of a structure, an oblique water-entry experiment of the structure was conducted by high-speed photography technology under different crushed ice cover densities. Moreover, by comparing the water-entry process of the oblique structure in varying densities of crushed ice cover, the influence of crushed ice cover density on cavity evolution during the oblique water-entry process of the structure was obtained. Results indicate that during the cavity expansion, the presence of crushed ice reduces the cavity diameter by impeding the outward expansion of the fluid near the free surface, compared with the ice-free environment. When the cavity closes, crushed ice also impedes the inward contraction of the free surface fluid and prolongs the cavity expansion time. The augmentation in the total volume of air within the cavity results in a decrement of the pressure differential between the inside and outside of the cavity, ultimately leading to a retardation in the cavity closure time. As the coverage density of crushed ice gradually increases, the impedance exerted by the crushed ice on the inward contraction of fluid at the free surface progressively intensifies. This enhanced obstruction from the crushed ice further prolongs the cavity closure time and concurrently augments its length and maximum diameter. In conditions of lower crushed ice densities, jets point to the interior of the cavity when the cavity collapses. Besides, under conditions of higher crushed ice cover densities, the cavity wall is wrinkled by the irregular impact of the fluid. As the submerged depth of the structure increases, the cavity undergoes a deep necking under the influence of ambient pressure. As the coverage density of crushed ice gradually increases, the velocity of the underwater motion of the structure shows a trend of faster decay compared to ice-free environments.
To investigate the influence of the density of crushed ice region on the cavity evolution of a structure, an oblique water-entry experiment of the structure was conducted by high-speed photography technology under different crushed ice cover densities. Moreover, by comparing the water-entry process of the oblique structure in varying densities of crushed ice cover, the influence of crushed ice cover density on cavity evolution during the oblique water-entry process of the structure was obtained. Results indicate that during the cavity expansion, the presence of crushed ice reduces the cavity diameter by impeding the outward expansion of the fluid near the free surface, compared with the ice-free environment. When the cavity closes, crushed ice also impedes the inward contraction of the free surface fluid and prolongs the cavity expansion time. The augmentation in the total volume of air within the cavity results in a decrement of the pressure differential between the inside and outside of the cavity, ultimately leading to a retardation in the cavity closure time. As the coverage density of crushed ice gradually increases, the impedance exerted by the crushed ice on the inward contraction of fluid at the free surface progressively intensifies. This enhanced obstruction from the crushed ice further prolongs the cavity closure time and concurrently augments its length and maximum diameter. In conditions of lower crushed ice densities, jets point to the interior of the cavity when the cavity collapses. Besides, under conditions of higher crushed ice cover densities, the cavity wall is wrinkled by the irregular impact of the fluid. As the submerged depth of the structure increases, the cavity undergoes a deep necking under the influence of ambient pressure. As the coverage density of crushed ice gradually increases, the velocity of the underwater motion of the structure shows a trend of faster decay compared to ice-free environments.
, Available online ,
doi: 10.11883/bzycj-2024-0099
Abstract:
Artificial intelligence/machine learning methods can discover hidden physical patterns in data. By constructing an end-to-end surrogate model between state parameters and dynamic results, many complex engineering problems such as strong coupling, nonlinearity, and multiphysics can be efficiently solved. In the field of highly nonlinear explosion and shock dynamics, a classic detonation driving problem was chosen as the research object. Using numerical simulation results as training data for machine learning surrogate models, and combining forward simulation and reverse design organically. Based on deep neural network technology, an end-to-end surrogate model was constructed between feature position velocity profiles, material dynamic deformation, and engineering factors. And the calculation accuracy of the surrogate model was provided, verifying the ability to invert engineering factors from velocity profiles. The research results indicate that the end-to-end surrogate model has high predictive ability, with relative errors of less than 1% in both velocity profile prediction and engineering factor estimation. It can be applied to the rapid design, high-precision prediction, and agile iteration of highly nonlinear explosion and impact dynamics problems.
Artificial intelligence/machine learning methods can discover hidden physical patterns in data. By constructing an end-to-end surrogate model between state parameters and dynamic results, many complex engineering problems such as strong coupling, nonlinearity, and multiphysics can be efficiently solved. In the field of highly nonlinear explosion and shock dynamics, a classic detonation driving problem was chosen as the research object. Using numerical simulation results as training data for machine learning surrogate models, and combining forward simulation and reverse design organically. Based on deep neural network technology, an end-to-end surrogate model was constructed between feature position velocity profiles, material dynamic deformation, and engineering factors. And the calculation accuracy of the surrogate model was provided, verifying the ability to invert engineering factors from velocity profiles. The research results indicate that the end-to-end surrogate model has high predictive ability, with relative errors of less than 1% in both velocity profile prediction and engineering factor estimation. It can be applied to the rapid design, high-precision prediction, and agile iteration of highly nonlinear explosion and impact dynamics problems.
, Available online ,
doi: 10.11883/bzycj-2024-0118
Abstract:
With the wide application of new types of ammunition and large-caliber heavy artillery, the non-contact killing mode caused by explosive shock is rapidly replacing the original direct contact killing caused by bullets, fragments, etc., and its killing power, precision, etc., on the combat personnel and equipment is more threatening. This paper will start from the introduction of the typical test environment and methods of explosive shock wave, through an overview of the explosive impact monitoring and sensing technology and explosive impact flow field reconstruction technology analysis to summarize the development trend, and finally the application of portable explosive shock wave sensing system in the foreign military was briefly introduced for the research and development of China's related products to provide reference experience. At present, the most commonly used sensors in explosion impact tests are overpressure sensors and acceleration sensors. Among them, overpressure sensors can be divided into piezoresistive sensor, piezoelectric sensor and fiber-optic sensor; acceleration sensors cloud be divided into piezoresistive acceleration sensors, piezoelectric acceleration sensors, capacitive acceleration sensors, resonance acceleration sensors, electron tunneling acceleration sensors, thermal convection acceleration sensors and optical acceleration sensors (space light acceleration sensors, fiber-optic acceleration sensors). accelerometers, fiber optic accelerometers). The demanding testing environment requires all sensors to have high frequency response , good detection linear characteristics, high signal-to-noise ratio, high sensitivity, good anti-interference performance, and excellent characteristics such as small size and light weight. Shock wave over-pressure sensor toward miniaturization, standardization, integration and intelligent research direction, while vigorously developing new sensing technology research. Based on CFD data and experimental data, artificial intelligence technology is introduced into the explosion wave signal processing and flow field reconstruction; portable explosion impact detection and evaluation system with independent intellectual property rights in China is developed to provide rapid classification and rapid diagnosis and treatment basis for the protection and rescue of special industry practitioners in extreme environments.
With the wide application of new types of ammunition and large-caliber heavy artillery, the non-contact killing mode caused by explosive shock is rapidly replacing the original direct contact killing caused by bullets, fragments, etc., and its killing power, precision, etc., on the combat personnel and equipment is more threatening. This paper will start from the introduction of the typical test environment and methods of explosive shock wave, through an overview of the explosive impact monitoring and sensing technology and explosive impact flow field reconstruction technology analysis to summarize the development trend, and finally the application of portable explosive shock wave sensing system in the foreign military was briefly introduced for the research and development of China's related products to provide reference experience. At present, the most commonly used sensors in explosion impact tests are overpressure sensors and acceleration sensors. Among them, overpressure sensors can be divided into piezoresistive sensor, piezoelectric sensor and fiber-optic sensor; acceleration sensors cloud be divided into piezoresistive acceleration sensors, piezoelectric acceleration sensors, capacitive acceleration sensors, resonance acceleration sensors, electron tunneling acceleration sensors, thermal convection acceleration sensors and optical acceleration sensors (space light acceleration sensors, fiber-optic acceleration sensors). accelerometers, fiber optic accelerometers). The demanding testing environment requires all sensors to have high frequency response , good detection linear characteristics, high signal-to-noise ratio, high sensitivity, good anti-interference performance, and excellent characteristics such as small size and light weight. Shock wave over-pressure sensor toward miniaturization, standardization, integration and intelligent research direction, while vigorously developing new sensing technology research. Based on CFD data and experimental data, artificial intelligence technology is introduced into the explosion wave signal processing and flow field reconstruction; portable explosion impact detection and evaluation system with independent intellectual property rights in China is developed to provide rapid classification and rapid diagnosis and treatment basis for the protection and rescue of special industry practitioners in extreme environments.
, Available online ,
doi: 10.11883/bzycj-2024-0254
Abstract:
To address the issues of over-excavation at the tunnel arch foot due to the difficulty of forming the perimeter hole blasting and under-excavation at the tunnel face bottom, the damage characteristics of surrounding rock caused by perimeter hole blasting at the arch foot of a horseshoe-shaped tunnel were studied through a combination of theoretical calculations and numerical simulations. On the theoretical level, an in-depth analysis of the stress distribution and crack radius in the arch foot area was conducted based on the principles of blasting mechanics, and the theoretical charge length for the perimeter holes at the arch foot was derived. Building on this, a 3D numerical model of the perimeter holes at the arch foot was established through numerical simulation. During the modeling process, the damage evolution in the surrounding rock during blasting was simulated by introducing an appropriate damage model, and post-blast damage cloud maps were generated. By comparing the damage cloud maps under different conditions, the relationship between blasting effectiveness and parameters such as free surface shape, charge amount, and void deflection angle was analyzed, further revealing the mechanisms by which these parameters influence the blasting formation results, which were validated through field experiments. The research results indicate that the shape of the free surface significantly impacts the extent of surrounding rock damage and the energy utilization efficiency of explosives. A concave free surface results in a smaller damage range compared to a flat free surface, with greater rock confinement, making it difficult for the explosives to effectively fracture the surrounding rock, leading to an energy utilization rate of only 78%. The blasting effectiveness shows a trend of first increasing and then decreasing with the increase in charge amount, with the optimal blasting effectiveness achieved when the linear charge density of the perimeter holes at the arch foot is 0.624. Additionally, by setting voids and adjusting the void deflection angle, the blasting effectiveness of the perimeter holes at the arch foot can be improved. With the optimized blasting parameters, the maximum linear over-excavation at the arch foot was reduced by 53.1%, resulting in a smooth tunnel contour. The research outcomes are engineeringly feasible and provide valuable insights for similar projects.
To address the issues of over-excavation at the tunnel arch foot due to the difficulty of forming the perimeter hole blasting and under-excavation at the tunnel face bottom, the damage characteristics of surrounding rock caused by perimeter hole blasting at the arch foot of a horseshoe-shaped tunnel were studied through a combination of theoretical calculations and numerical simulations. On the theoretical level, an in-depth analysis of the stress distribution and crack radius in the arch foot area was conducted based on the principles of blasting mechanics, and the theoretical charge length for the perimeter holes at the arch foot was derived. Building on this, a 3D numerical model of the perimeter holes at the arch foot was established through numerical simulation. During the modeling process, the damage evolution in the surrounding rock during blasting was simulated by introducing an appropriate damage model, and post-blast damage cloud maps were generated. By comparing the damage cloud maps under different conditions, the relationship between blasting effectiveness and parameters such as free surface shape, charge amount, and void deflection angle was analyzed, further revealing the mechanisms by which these parameters influence the blasting formation results, which were validated through field experiments. The research results indicate that the shape of the free surface significantly impacts the extent of surrounding rock damage and the energy utilization efficiency of explosives. A concave free surface results in a smaller damage range compared to a flat free surface, with greater rock confinement, making it difficult for the explosives to effectively fracture the surrounding rock, leading to an energy utilization rate of only 78%. The blasting effectiveness shows a trend of first increasing and then decreasing with the increase in charge amount, with the optimal blasting effectiveness achieved when the linear charge density of the perimeter holes at the arch foot is 0.624. Additionally, by setting voids and adjusting the void deflection angle, the blasting effectiveness of the perimeter holes at the arch foot can be improved. With the optimized blasting parameters, the maximum linear over-excavation at the arch foot was reduced by 53.1%, resulting in a smooth tunnel contour. The research outcomes are engineeringly feasible and provide valuable insights for similar projects.
, Available online ,
doi: 10.11883/bzycj-2024-0069
Abstract:
In relation to the application of high-entropy alloy systems containing high-density and high-calorific value elements in the liner of shaped charge warheads, the Ta-Hf-Nb-Zr high-entropy alloy system is investigated. The study employed an INSTRON material testing machine and a split Hopkinson pressure bar testing platform to explore the mechanical response of this high-entropy alloy across a wide range of strain rates from 10−3 to 103 s−1, temperatures ranging from 25 to 900 °C, and stress triaxiality values ranging from 0.33 to 0.89. Yield strength and failure strain data were obtained from static round bar tensile tests and dynamic compression tests conducted under these varying conditions. By using least squares fitting, the parameters of the Johnson-Cook (J-C) constitutive equation as well as the damage failure model parameters, are derived. Subsequently, a simulation model for explosively formed projectile (EFP) made from high-entropy alloys under explosive loading conditions was developed. Pulse X-ray tests of the EFP formation were performed, and numerical simulations of the EFP formation process are conducted using LS-DYNA software. The results show that at 117 μs, the high-entropy alloy EFP remains largely intact, with a length of 51.1 mm and a diameter of 12.27 mm. At 187 μs, three fractures are observed at the tail of the EFP, with the head length measuring 24.3 mm, the diameter at 12.27 mm, and the EFP speed recorded at2496.3 m/s. The numerical simulations demonstrate that the EFP length, diameter, and velocity at these time instants match the test data with errors of less than 8.2%. Moreover, the fracture patterns observed experimentally align closely with those predicted by the simulations. This consistency indicates that the J-C model effectively predicts the formation characteristics of high-entropy alloy EFPs under explosive loading conditions, confirming its utility in accurately simulating the EFP formation process.
In relation to the application of high-entropy alloy systems containing high-density and high-calorific value elements in the liner of shaped charge warheads, the Ta-Hf-Nb-Zr high-entropy alloy system is investigated. The study employed an INSTRON material testing machine and a split Hopkinson pressure bar testing platform to explore the mechanical response of this high-entropy alloy across a wide range of strain rates from 10−3 to 103 s−1, temperatures ranging from 25 to 900 °C, and stress triaxiality values ranging from 0.33 to 0.89. Yield strength and failure strain data were obtained from static round bar tensile tests and dynamic compression tests conducted under these varying conditions. By using least squares fitting, the parameters of the Johnson-Cook (J-C) constitutive equation as well as the damage failure model parameters, are derived. Subsequently, a simulation model for explosively formed projectile (EFP) made from high-entropy alloys under explosive loading conditions was developed. Pulse X-ray tests of the EFP formation were performed, and numerical simulations of the EFP formation process are conducted using LS-DYNA software. The results show that at 117 μs, the high-entropy alloy EFP remains largely intact, with a length of 51.1 mm and a diameter of 12.27 mm. At 187 μs, three fractures are observed at the tail of the EFP, with the head length measuring 24.3 mm, the diameter at 12.27 mm, and the EFP speed recorded at
, Available online ,
doi: 10.11883/bzycj-2024-0312
Abstract:
Lithium-ion battery combustion accidents are known for their rapid onset and difficulty in extinguishment, raising significant safety concerns in environments with collision risks. These risks highlight the need for stringent damage assessment and failure prediction methods for power batteries. While severe collisions can cause immediate catastrophic damage and thermal runaway, most collisions occur at low speeds, where the impact may result in only minor external deformation without immediate failure. However, the potential safety risks associated with continued use of batteries after such minor collisions are not well understood. Current research and battery safety standards primarily focus on immediate or short-term failure after impact, leaving a gap in understanding the long-term effects of low-energy collisions on battery safety. This study addresses this gap by investigating the impact of low-energy collisions on the safety and reliability of lithium-ion batteries. A shock-compression sequential loading experiment was used to evaluate the mechanical response and failure behavior of pouch batteries under dynamic loading. The study also explored the deterioration of batteries subjected to weaker impact loads through electrochemical performance testing and internal structural damage analysis. The results reveal that even if a battery does not fail immediately under low-impact energy, its internal mechanical integrity may still be compromised, leading to a lower failure threshold under subsequent loads. Significant deterioration in capacity and internal resistance was observed, with the battery’s ability to withstand secondary loads and its electrochemical performance declining as impact energy increased. This indicates a clear correlation between impact-induced deformation and overall battery performance. The study also proposes a quantitative evaluation method for assessing the battery's condition after minor impacts, offering a valuable tool for predicting the risks associated with reusing impacted batteries. These insights are essential for understanding the response mechanisms of lithium-ion batteries under low-energy collision conditions and for optimizing safety standards for their continued use in collision-prone environments.
Lithium-ion battery combustion accidents are known for their rapid onset and difficulty in extinguishment, raising significant safety concerns in environments with collision risks. These risks highlight the need for stringent damage assessment and failure prediction methods for power batteries. While severe collisions can cause immediate catastrophic damage and thermal runaway, most collisions occur at low speeds, where the impact may result in only minor external deformation without immediate failure. However, the potential safety risks associated with continued use of batteries after such minor collisions are not well understood. Current research and battery safety standards primarily focus on immediate or short-term failure after impact, leaving a gap in understanding the long-term effects of low-energy collisions on battery safety. This study addresses this gap by investigating the impact of low-energy collisions on the safety and reliability of lithium-ion batteries. A shock-compression sequential loading experiment was used to evaluate the mechanical response and failure behavior of pouch batteries under dynamic loading. The study also explored the deterioration of batteries subjected to weaker impact loads through electrochemical performance testing and internal structural damage analysis. The results reveal that even if a battery does not fail immediately under low-impact energy, its internal mechanical integrity may still be compromised, leading to a lower failure threshold under subsequent loads. Significant deterioration in capacity and internal resistance was observed, with the battery’s ability to withstand secondary loads and its electrochemical performance declining as impact energy increased. This indicates a clear correlation between impact-induced deformation and overall battery performance. The study also proposes a quantitative evaluation method for assessing the battery's condition after minor impacts, offering a valuable tool for predicting the risks associated with reusing impacted batteries. These insights are essential for understanding the response mechanisms of lithium-ion batteries under low-energy collision conditions and for optimizing safety standards for their continued use in collision-prone environments.
, Available online ,
doi: 10.11883/bzycj-2024-0240
Abstract:
The thermal shock caused by thermal runaway of lithium batteries will damage the installation structure and pose a threat to the safety of surrounding personnel and equipment, which is a key issue limiting their aviation applications. Through a self-built high-temperature impact experimental platform for lithium battery thermal runaway, it was found that the impact pressure on the battery pack top plate from single-cell thermal shock can reach up to 13.23 kPa, causing the external surface temperature to exceed 274 ℃. The combined effect of high temperature and impact pressure increases the risk of the casing undergoing plastic deformation, buckling, or even failure. To effectively mitigate such risks, a passive protection method of coating the top plate of the battery pack with fireproof coating is proposed. Through large panel combustion experiments and cone calorimeter tests, it was found that the epoxy resin-based intumescent fireproof coatings can effectively block the impact pressure of lithium battery thermal runaway by expanding, and they absorb heat, reducing and delaying the temperature rise of the battery pack top plate, demonstrating excellent thermal shock resistance. By comparing the containment effects of fireproof coatings of different thicknesses, it was found that the 1mm coating is more suitable for practical application needs. Referring to relevant airworthiness regulations, verification tests were conducted on the containment of lithium battery thermal runaway. The analysis of the experiment results shows that the 1.0 mm thick E80S20 coating and E85S15B3 coating reduced the maximum temperature of the battery pack top plate by 52.16% and 55.80%, respectively. Additionally, the maximum structural deformation decreased by 72.2% and 44.4%, respectively. The study indicates that passive protection technology of fireproof coating can effectively enhance the containment of high temperatures and impact hazards caused by thermal runaway. This approach can serve as an effective measure in the safety design of aviation power lithium battery systems.
The thermal shock caused by thermal runaway of lithium batteries will damage the installation structure and pose a threat to the safety of surrounding personnel and equipment, which is a key issue limiting their aviation applications. Through a self-built high-temperature impact experimental platform for lithium battery thermal runaway, it was found that the impact pressure on the battery pack top plate from single-cell thermal shock can reach up to 13.23 kPa, causing the external surface temperature to exceed 274 ℃. The combined effect of high temperature and impact pressure increases the risk of the casing undergoing plastic deformation, buckling, or even failure. To effectively mitigate such risks, a passive protection method of coating the top plate of the battery pack with fireproof coating is proposed. Through large panel combustion experiments and cone calorimeter tests, it was found that the epoxy resin-based intumescent fireproof coatings can effectively block the impact pressure of lithium battery thermal runaway by expanding, and they absorb heat, reducing and delaying the temperature rise of the battery pack top plate, demonstrating excellent thermal shock resistance. By comparing the containment effects of fireproof coatings of different thicknesses, it was found that the 1mm coating is more suitable for practical application needs. Referring to relevant airworthiness regulations, verification tests were conducted on the containment of lithium battery thermal runaway. The analysis of the experiment results shows that the 1.0 mm thick E80S20 coating and E85S15B3 coating reduced the maximum temperature of the battery pack top plate by 52.16% and 55.80%, respectively. Additionally, the maximum structural deformation decreased by 72.2% and 44.4%, respectively. The study indicates that passive protection technology of fireproof coating can effectively enhance the containment of high temperatures and impact hazards caused by thermal runaway. This approach can serve as an effective measure in the safety design of aviation power lithium battery systems.
, Available online ,
doi: 10.11883/bzycj-2024-0188
Abstract:
To improve the safety performance of cylindrical lithium-ion batteries under radial dynamic impacting, the dynamic response characteristics of the batteries under large deformation were investigated based on the membrane factor method. Firstly, the battery was simplified to sandwich beam including the casing and inner core. The plastic yield criterion and membrane factor of the battery cross-section were established based on tensile yield strengths. The membrane factor was introduced into the motion equation to solve the dynamic response under large deformation. Furthermore, the mechanical properties of the battery components were determined based on tensile and compression tests. Then the finite element (FE) model of the battery was developed. It has been shown that the theoretical results and FE results of the displacement responses and velocity responses of the battery were in good agreement. The larger the initial velocity of the battery under impact loading, the larger the effect of axial force effect on the dynamic response. The maximum deflection of the battery increases approximately linearly with initial velocity, and the actual response time shows saturation. The maximum deflection of the battery increases with the decrease of the ratio of casing yield strength to core yield strength. The effect of yield strength is significant under thin battery casings. The maximum deflection of the battery decreases with the increase of the casing thickness. Under high yield strength ratio, the effect of casing thickness is significant. The research can provide technical support for the failure prediction and structural safety design of the battery.
To improve the safety performance of cylindrical lithium-ion batteries under radial dynamic impacting, the dynamic response characteristics of the batteries under large deformation were investigated based on the membrane factor method. Firstly, the battery was simplified to sandwich beam including the casing and inner core. The plastic yield criterion and membrane factor of the battery cross-section were established based on tensile yield strengths. The membrane factor was introduced into the motion equation to solve the dynamic response under large deformation. Furthermore, the mechanical properties of the battery components were determined based on tensile and compression tests. Then the finite element (FE) model of the battery was developed. It has been shown that the theoretical results and FE results of the displacement responses and velocity responses of the battery were in good agreement. The larger the initial velocity of the battery under impact loading, the larger the effect of axial force effect on the dynamic response. The maximum deflection of the battery increases approximately linearly with initial velocity, and the actual response time shows saturation. The maximum deflection of the battery increases with the decrease of the ratio of casing yield strength to core yield strength. The effect of yield strength is significant under thin battery casings. The maximum deflection of the battery decreases with the increase of the casing thickness. Under high yield strength ratio, the effect of casing thickness is significant. The research can provide technical support for the failure prediction and structural safety design of the battery.
, Available online ,
doi: 10.11883/bzycj-2024-0158
Abstract:
Combined with the actual distribution characteristics of tungsten fibers and metallic glass matrix, a three-dimensional (3D) mesoscale finite element (FE) geometric model of a long rod of tungsten fiber-reinforced metallic glass composite was established, and the coupled thermo-mechanical constitutive model was used to describe the high strength and high shear sensitivity of metallic glass matrix. FE simulations on the oblique penetration/perforation of composite and tungsten alloy long rods into steel targets were carried out combined with related oblique penetrating tests, and comparative analyses on the deformation and failure characteristics of projectiles and targets were conducted. Furthermore, the influences of oblique angle and impact velocity on the ‘self-sharpening’ behavior of composite long rods and the corresponding ballistic performance were investigated in detail. Related analysis shows that in the oblique impact condition, due to the asymmetrical characteristics of target resistance on the rod, the rod nose gradually sharpens into an asymmetrical pointed configuration, and certain deflection occurs in the trajectory. Consequently, the ‘self-sharpening’ behavior in the composite long rod is weakened to a certain extent, and thus a decay occurs in its penetrating property. Besides, the impact velocity also contributes to the ‘self-sharpening’ characteristics and the corresponding ballistic behavior in the oblique impact condition, and the decay of penetrating capability derived from the oblique angle is more remarkable at lower impact velocities. When the oblique angle increases to 50°, the composite long rod is hard to effectively penetrate the target at an impact velocity lower than 900 m/s, and ricochet becomes easy when it impacts under a higher oblique angle. The results are of good significance in predicting the penetrating ability of tungsten fiber-reinforced metallic glass matrix composite long rods and optimizing its impact attitude.
Combined with the actual distribution characteristics of tungsten fibers and metallic glass matrix, a three-dimensional (3D) mesoscale finite element (FE) geometric model of a long rod of tungsten fiber-reinforced metallic glass composite was established, and the coupled thermo-mechanical constitutive model was used to describe the high strength and high shear sensitivity of metallic glass matrix. FE simulations on the oblique penetration/perforation of composite and tungsten alloy long rods into steel targets were carried out combined with related oblique penetrating tests, and comparative analyses on the deformation and failure characteristics of projectiles and targets were conducted. Furthermore, the influences of oblique angle and impact velocity on the ‘self-sharpening’ behavior of composite long rods and the corresponding ballistic performance were investigated in detail. Related analysis shows that in the oblique impact condition, due to the asymmetrical characteristics of target resistance on the rod, the rod nose gradually sharpens into an asymmetrical pointed configuration, and certain deflection occurs in the trajectory. Consequently, the ‘self-sharpening’ behavior in the composite long rod is weakened to a certain extent, and thus a decay occurs in its penetrating property. Besides, the impact velocity also contributes to the ‘self-sharpening’ characteristics and the corresponding ballistic behavior in the oblique impact condition, and the decay of penetrating capability derived from the oblique angle is more remarkable at lower impact velocities. When the oblique angle increases to 50°, the composite long rod is hard to effectively penetrate the target at an impact velocity lower than 900 m/s, and ricochet becomes easy when it impacts under a higher oblique angle. The results are of good significance in predicting the penetrating ability of tungsten fiber-reinforced metallic glass matrix composite long rods and optimizing its impact attitude.
, Available online ,
doi: 10.11883/bzycj-2024-0073
Abstract:
To improve the accuracy and robustness of the explicit FEM algorithm based on penalty method for simulating large deformation contact-impact problem, a new large-deformation non-penetration contact algorithm based on forward incremental displacement central difference (FIDCD) was developed. On the one hand, according to FIDCD, the solving step of the dynamic equation was decomposed into an estimated step without considering contact and a correction step considering contact constraint. At the current moment, a contact force was applied thorough the penalty method to make the deformation of entities satisfy the non-penetration condition. The contact force was calculated by a soft constraint penalty stiffness, which helped to maintain stability of contact localization. It enhanced the numerical accuracy of the explicit contact computation. On the other hand, to accurately calculate the large-deformation internal force of the next moment while only obtaining the displacement, the internal force term of the dynamic equation was mapped to a known configuration for solution based on the arbitrary reference configurations (ARC) theory. It avoided using the values of variables at intermediate configuration to approximate them, thereby improving the numerical accuracy of the large deformation computation. More rigorous contact algorithms and geometric nonlinear solution strategy can effectively suppress mesh distortion and non-physical penetration between entities during large-deformation impact simulation. This thus improved the robustness of the new explicit algorithm. Finally, the computational program written according to the new developed algorithm was applied to simulate several impact and penetration examples with different impact velocities. By comparing the simulation results with those obtained from commercial software, the correctness of the developed algorithm and computational program was verified. At the same time, it can also be proven that the algorithm proposed is more robust in simulating high-speed and large-deformation impact problems than the classical explicit contact-impact algorithm based on the frog jump center difference scheme combining with penalty method.
To improve the accuracy and robustness of the explicit FEM algorithm based on penalty method for simulating large deformation contact-impact problem, a new large-deformation non-penetration contact algorithm based on forward incremental displacement central difference (FIDCD) was developed. On the one hand, according to FIDCD, the solving step of the dynamic equation was decomposed into an estimated step without considering contact and a correction step considering contact constraint. At the current moment, a contact force was applied thorough the penalty method to make the deformation of entities satisfy the non-penetration condition. The contact force was calculated by a soft constraint penalty stiffness, which helped to maintain stability of contact localization. It enhanced the numerical accuracy of the explicit contact computation. On the other hand, to accurately calculate the large-deformation internal force of the next moment while only obtaining the displacement, the internal force term of the dynamic equation was mapped to a known configuration for solution based on the arbitrary reference configurations (ARC) theory. It avoided using the values of variables at intermediate configuration to approximate them, thereby improving the numerical accuracy of the large deformation computation. More rigorous contact algorithms and geometric nonlinear solution strategy can effectively suppress mesh distortion and non-physical penetration between entities during large-deformation impact simulation. This thus improved the robustness of the new explicit algorithm. Finally, the computational program written according to the new developed algorithm was applied to simulate several impact and penetration examples with different impact velocities. By comparing the simulation results with those obtained from commercial software, the correctness of the developed algorithm and computational program was verified. At the same time, it can also be proven that the algorithm proposed is more robust in simulating high-speed and large-deformation impact problems than the classical explicit contact-impact algorithm based on the frog jump center difference scheme combining with penalty method.
, Available online ,
doi: 10.11883/bzycj-2023-0452
Abstract:
To predict precisely the lower explosion limit of thermal runaway products of lithium iron phosphate batteries, thermal runaway tests of lithium iron phosphate batteries were carried out in a closed pressure vessel. The experiments were carried out at 25 ℃ and 0.1 MPa, and the method was used to analyze the thermal runaway gas production. The vent gas species composition of lithium iron phosphate batteries was analyzed by gas chromatography and mass spectrometry. Combined with the thermal runaway characteristics of the battery and gas chromatography-mass spectrometry (GC-MS) technology, the gas composition of thermal runaway products of lithium iron phosphate batteries was calculated. It was assumed that the thermal runway products released from the relief valve to the first injection were all dimethyl carbonate (DMC), and the secondary injection gas was the mixed gas generated by the internal chemical reaction, which is mainly composed of H2, CO2, CO, CH4, and C2H4. A prediction model of the lower explosion limit of thermal runaway products was established based on the energy conservation equation and adiabatic flame temperature. The prediction methods of lower explosion limit of multicomponent gases based on adiabatic flame temperature, Le Chatelier law method, and Jones method were verified, and the influence of electrolyte vapor on the lower explosion limit of thermal runaway production was also investigated. The smallest deviation of the lower explosion limit calculated by the Le Chatelier law method at normal temperature and pressure was 1.14%, and the largest deviation of the lower explosion limit calculated by the adiabatic flame temperature method was 10.02%. Within the range from 60% SOC to 100% SOC, the lower explosion limit of the thermal runaway gases increases first and then decreases. When the electrolyte vapor is considered in the thermal runaway products, the lower explosion limit of thermal runaway products of lithium iron phosphate batteries with 60% SOC is only 3.93%, which is 22.49% lower than that of the thermal runaway gas without considering the electrolyte vapor. Actually, the electrolyte vapor is contained in the thermal runaway products of lithium iron phosphate batteries. These results indicate that the addition of electrolyte vapor increases the explosion risk of thermal runaway production of lithium iron phosphate batteries.
To predict precisely the lower explosion limit of thermal runaway products of lithium iron phosphate batteries, thermal runaway tests of lithium iron phosphate batteries were carried out in a closed pressure vessel. The experiments were carried out at 25 ℃ and 0.1 MPa, and the method was used to analyze the thermal runaway gas production. The vent gas species composition of lithium iron phosphate batteries was analyzed by gas chromatography and mass spectrometry. Combined with the thermal runaway characteristics of the battery and gas chromatography-mass spectrometry (GC-MS) technology, the gas composition of thermal runaway products of lithium iron phosphate batteries was calculated. It was assumed that the thermal runway products released from the relief valve to the first injection were all dimethyl carbonate (DMC), and the secondary injection gas was the mixed gas generated by the internal chemical reaction, which is mainly composed of H2, CO2, CO, CH4, and C2H4. A prediction model of the lower explosion limit of thermal runaway products was established based on the energy conservation equation and adiabatic flame temperature. The prediction methods of lower explosion limit of multicomponent gases based on adiabatic flame temperature, Le Chatelier law method, and Jones method were verified, and the influence of electrolyte vapor on the lower explosion limit of thermal runaway production was also investigated. The smallest deviation of the lower explosion limit calculated by the Le Chatelier law method at normal temperature and pressure was 1.14%, and the largest deviation of the lower explosion limit calculated by the adiabatic flame temperature method was 10.02%. Within the range from 60% SOC to 100% SOC, the lower explosion limit of the thermal runaway gases increases first and then decreases. When the electrolyte vapor is considered in the thermal runaway products, the lower explosion limit of thermal runaway products of lithium iron phosphate batteries with 60% SOC is only 3.93%, which is 22.49% lower than that of the thermal runaway gas without considering the electrolyte vapor. Actually, the electrolyte vapor is contained in the thermal runaway products of lithium iron phosphate batteries. These results indicate that the addition of electrolyte vapor increases the explosion risk of thermal runaway production of lithium iron phosphate batteries.
, Available online ,
doi: 10.11883/bzycj-2024-0152
Abstract:
To investigate the dynamic mechanical properties of sandstone in deep strata under impact loads, an improved Hopkinson pressure bar experimental system was established. The traditional Hopkinson pressure bar's transmission rod was replaced with a long rod specimen made of gray sandstone to better simulate deep geological conditions. Point spalling treatment was applied to the specimen, and strain gauges were meticulously affixed at critical measurement points.Dynamic compression experiments were meticulously conducted on the gray sandstone long rod specimen at various loading rates (9.57 m/s, 14.78 m/s, 19.32 m/s, and 27.60 m/s). Utilizing high-speed digital image correlation (DIC) technology, the evolution of displacement and strain fields on the surface of the specimen throughout each test was closely monitored. This advanced technique enabled a detailed exploration of how the gray sandstone responded to near-field impact loading, particularly focusing on its tensile failure characteristics.Employing the Lagrangian analysis method, displacement-time curves for different mass points derived from the DIC analysis of displacement fields were extracted. These curves provided critical data to compute the stress-strain behavior of the gray sandstone material under dynamic loading conditions. The study reveals several key findings: the gray sandstone long rod specimen predominantly exhibits tensile failure, with distinct patterns of fragmentation near the loading end and layer cracking away from it. Moreover, the dynamic compressive strength factor of the gray sandstone long rod specimen shows a notable increase with higher strain rates, indicating a significant strain rate effect. Correspondingly, both stress and strain peaks observe an upward trend at various measurement points with increasing loading rates.Remarkably, under identical loading rates, stress-strain curves of the gray sandstone long rod specimen exhibit a unique phenomenon where curves from measurement points closer to the loading end envelop those from points farther away. This observation underscores the complex nature of dynamic loading responses in geological materials.Overall, this comprehensive investigation provides essential theoretical insights and methodological references for understanding the dynamic behavior of sandstone within deep geological formations under impact loads. The findings offer valuable contributions to engineering practices concerned with the stability and resilience of underground structures subjected to dynamic loading conditions.
To investigate the dynamic mechanical properties of sandstone in deep strata under impact loads, an improved Hopkinson pressure bar experimental system was established. The traditional Hopkinson pressure bar's transmission rod was replaced with a long rod specimen made of gray sandstone to better simulate deep geological conditions. Point spalling treatment was applied to the specimen, and strain gauges were meticulously affixed at critical measurement points.Dynamic compression experiments were meticulously conducted on the gray sandstone long rod specimen at various loading rates (9.57 m/s, 14.78 m/s, 19.32 m/s, and 27.60 m/s). Utilizing high-speed digital image correlation (DIC) technology, the evolution of displacement and strain fields on the surface of the specimen throughout each test was closely monitored. This advanced technique enabled a detailed exploration of how the gray sandstone responded to near-field impact loading, particularly focusing on its tensile failure characteristics.Employing the Lagrangian analysis method, displacement-time curves for different mass points derived from the DIC analysis of displacement fields were extracted. These curves provided critical data to compute the stress-strain behavior of the gray sandstone material under dynamic loading conditions. The study reveals several key findings: the gray sandstone long rod specimen predominantly exhibits tensile failure, with distinct patterns of fragmentation near the loading end and layer cracking away from it. Moreover, the dynamic compressive strength factor of the gray sandstone long rod specimen shows a notable increase with higher strain rates, indicating a significant strain rate effect. Correspondingly, both stress and strain peaks observe an upward trend at various measurement points with increasing loading rates.Remarkably, under identical loading rates, stress-strain curves of the gray sandstone long rod specimen exhibit a unique phenomenon where curves from measurement points closer to the loading end envelop those from points farther away. This observation underscores the complex nature of dynamic loading responses in geological materials.Overall, this comprehensive investigation provides essential theoretical insights and methodological references for understanding the dynamic behavior of sandstone within deep geological formations under impact loads. The findings offer valuable contributions to engineering practices concerned with the stability and resilience of underground structures subjected to dynamic loading conditions.
, Available online ,
doi: 10.11883/bzycj-2024-0109
Abstract:
For the launch safety problem of the typical CL-20-based high detonation velocity pressed explosive (C-1, 94.5% CL-20+5.5% additive), the impact response characteristics of the explosive were studied by a large-scale hammer test with 400 kg, which has an impact loading curve similar to the loading characteristics of artillery chamber pressure. Meanwhile, the improved stress rate characterization method, the lower limit method, and the drop height method were used to characterize the drop hammer impact response characteristics of the explosive, and compared with the same kind of pressed explosives JO-8 and JH-2. The improved stress rate characterization method is obtained by improving the data processing process based on existing criteria and weakening the sensitivity of the original criterion formula to oscillatory waveforms. The measured stress curves and characterization parameters of the bottom of the three pressed explosives under different drop heights are obtained by tests, and the impact sensitivity differences of the explosives and influence factors of the impact sensitivity of C-1 are discussed. The results show that the improved stress rate characterization method has certain effectiveness and universality for characterizing the impact sensitivity of explosives. Meanwhile, the improved stress rate characterization method is consistent with other methods in reflecting the law. The drop height of C-1 (H50) is 1.0 m, which is 62.5% and 50.0% of JO-8 and JH-2, respectively; the peak stress of the backseat corresponding to non-detonation (σ0) is 748.90 MPa, which is 85.42% and 64.33% of JO-8 and JH-2, respectively; the safety stress rate parameter (C0) is 344 GPa2/s, which is 45.87% and 39.14% of JO-8 and JH-2, respectively. The molecular structure of CL-20, the mechanical properties, and the thermal-chemical characteristics of the C-1 explosive cylinder are the main factors that make its impact sensitivity higher than JO-8 and JH-2. The research results can provide a reference for the application and design calculation of CL-20-based high detonation velocity pressed explosives in a high overload environment.
For the launch safety problem of the typical CL-20-based high detonation velocity pressed explosive (C-1, 94.5% CL-20+5.5% additive), the impact response characteristics of the explosive were studied by a large-scale hammer test with 400 kg, which has an impact loading curve similar to the loading characteristics of artillery chamber pressure. Meanwhile, the improved stress rate characterization method, the lower limit method, and the drop height method were used to characterize the drop hammer impact response characteristics of the explosive, and compared with the same kind of pressed explosives JO-8 and JH-2. The improved stress rate characterization method is obtained by improving the data processing process based on existing criteria and weakening the sensitivity of the original criterion formula to oscillatory waveforms. The measured stress curves and characterization parameters of the bottom of the three pressed explosives under different drop heights are obtained by tests, and the impact sensitivity differences of the explosives and influence factors of the impact sensitivity of C-1 are discussed. The results show that the improved stress rate characterization method has certain effectiveness and universality for characterizing the impact sensitivity of explosives. Meanwhile, the improved stress rate characterization method is consistent with other methods in reflecting the law. The drop height of C-1 (H50) is 1.0 m, which is 62.5% and 50.0% of JO-8 and JH-2, respectively; the peak stress of the backseat corresponding to non-detonation (σ0) is 748.90 MPa, which is 85.42% and 64.33% of JO-8 and JH-2, respectively; the safety stress rate parameter (C0) is 344 GPa2/s, which is 45.87% and 39.14% of JO-8 and JH-2, respectively. The molecular structure of CL-20, the mechanical properties, and the thermal-chemical characteristics of the C-1 explosive cylinder are the main factors that make its impact sensitivity higher than JO-8 and JH-2. The research results can provide a reference for the application and design calculation of CL-20-based high detonation velocity pressed explosives in a high overload environment.
, Available online ,
doi: 10.11883/bzycj-2024-0083
Abstract:
Reinforced concrete slabs, as the main load-bearing components in the structure of construction projects, are very likely to suffer serious damage in explosive accidents, while polyurea elastomers, with their better anti-blast and anti-impact properties, have been widely used in the field of protective engineering. It is well known that the mechanical properties and deformation mechanisms of thin slabs in the range from 100 mm to 250 mm and thick concrete slabs above 250 mm are not the same, and the thickness of reinforced concrete substrates studied so far is generally concentrated in the range from 100 mm to 250 mm, and there are relatively few studies on thick slabs of polyurea-coated reinforced concrete with a slab thickness of 250 mm or more. In order to study the anti-blast performance of the polyurea/reinforced concrete thick slab composite structure, firstly, the contact explosion tests were carried out on the polyurea/reinforced concrete thick slab composite structure with different charges, while the overall and local damage characteristics were analyzed. Secondly, numerical simulations were carried out using LS-DYNA finite element simulation software to verify the correctness of the numerical model by comparing with the experimental results. Based on LS-DYNA finite element simulations, the damage process of polyurea/reinforced concrete thick plate composite structure and the evolution of shock wave inside the polyurea/reinforced concrete thick plate were investigated, which revealed the anti-blast mechanism of the polyurea coating, and further analyzed the damage mode and damage characteristics of the polyurea/reinforced concrete thick plate composite structure. The test and finite element results showed that the polyurea/steel-reinforced concrete composite structure exhibited six damage modes under the contact explosion load (i.e., crate; spall; spall and bulge; threshold spall, bulging deformation of the polyurea coating; severe spall, serious bulging deformation of the polyurea coating; perforation). The investigation also demonstrated that the backside polyurea-coated reinforced concrete thick slabs effectively improved the anti-blast performance of the composite structure. The results of the study can provide a basis and reference for the design of blast resistance of polyurea/reinforced concrete thick slab composite structures.
Reinforced concrete slabs, as the main load-bearing components in the structure of construction projects, are very likely to suffer serious damage in explosive accidents, while polyurea elastomers, with their better anti-blast and anti-impact properties, have been widely used in the field of protective engineering. It is well known that the mechanical properties and deformation mechanisms of thin slabs in the range from 100 mm to 250 mm and thick concrete slabs above 250 mm are not the same, and the thickness of reinforced concrete substrates studied so far is generally concentrated in the range from 100 mm to 250 mm, and there are relatively few studies on thick slabs of polyurea-coated reinforced concrete with a slab thickness of 250 mm or more. In order to study the anti-blast performance of the polyurea/reinforced concrete thick slab composite structure, firstly, the contact explosion tests were carried out on the polyurea/reinforced concrete thick slab composite structure with different charges, while the overall and local damage characteristics were analyzed. Secondly, numerical simulations were carried out using LS-DYNA finite element simulation software to verify the correctness of the numerical model by comparing with the experimental results. Based on LS-DYNA finite element simulations, the damage process of polyurea/reinforced concrete thick plate composite structure and the evolution of shock wave inside the polyurea/reinforced concrete thick plate were investigated, which revealed the anti-blast mechanism of the polyurea coating, and further analyzed the damage mode and damage characteristics of the polyurea/reinforced concrete thick plate composite structure. The test and finite element results showed that the polyurea/steel-reinforced concrete composite structure exhibited six damage modes under the contact explosion load (i.e., crate; spall; spall and bulge; threshold spall, bulging deformation of the polyurea coating; severe spall, serious bulging deformation of the polyurea coating; perforation). The investigation also demonstrated that the backside polyurea-coated reinforced concrete thick slabs effectively improved the anti-blast performance of the composite structure. The results of the study can provide a basis and reference for the design of blast resistance of polyurea/reinforced concrete thick slab composite structures.
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2025, 45(1): 011001.
doi: 10.11883/bzycj-2024-0097
Abstract:
Concrete materials are widely used in the construction of infrastructure and defense facilities. In order to study the dynamic mechanical properties of high-temperature concrete with different cooling methods, the dynamic mechanical properties of C30 cylindrical concrete samples at different temperatures with different cooling methods were tested by\begin{document}$\varnothing $\end{document} ![]()
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Concrete materials are widely used in the construction of infrastructure and defense facilities. In order to study the dynamic mechanical properties of high-temperature concrete with different cooling methods, the dynamic mechanical properties of C30 cylindrical concrete samples at different temperatures with different cooling methods were tested by
2025, 45(1): 011101.
doi: 10.11883/bzycj-2023-0463
Abstract:
Experimental and numerical investigations are carried out to clarify the influence of the thickness and strength of the foam concrete layer on the blast resistance of the new composite protective structure. The multilayer graded foam concrete is applied to adequately and rationally use the good wave dissipation performance of foam concrete. Then the advantage of the new composite protective structure is verified by comparison with the traditional layered structure with medium/coarse sand as the distribution layer. Finally, the design concept of composite protective structures based on the controllability of blast load on the structure layer is summarized. The foam concrete can be used as an energy control layer of the composite protective structure mainly due to its long yield plateau and low wave impedance. The blast load acting on the structure layer can be exactly equal to the yield strength of the foam concrete by choosing the appropriate thickness and strength (density) of the foam concrete layer, as well as the use of the multilayer graded foam concrete. Based on the controllable design concept of blast load on the structure layer in the new composite protective structure, the defects of traditional layered protective structure with medium/coarse sand as the distribution layer can be solved thoroughly. The results can provide an important reference for the design of protective structures against new earth penetration weapons.
Experimental and numerical investigations are carried out to clarify the influence of the thickness and strength of the foam concrete layer on the blast resistance of the new composite protective structure. The multilayer graded foam concrete is applied to adequately and rationally use the good wave dissipation performance of foam concrete. Then the advantage of the new composite protective structure is verified by comparison with the traditional layered structure with medium/coarse sand as the distribution layer. Finally, the design concept of composite protective structures based on the controllability of blast load on the structure layer is summarized. The foam concrete can be used as an energy control layer of the composite protective structure mainly due to its long yield plateau and low wave impedance. The blast load acting on the structure layer can be exactly equal to the yield strength of the foam concrete by choosing the appropriate thickness and strength (density) of the foam concrete layer, as well as the use of the multilayer graded foam concrete. Based on the controllable design concept of blast load on the structure layer in the new composite protective structure, the defects of traditional layered protective structure with medium/coarse sand as the distribution layer can be solved thoroughly. The results can provide an important reference for the design of protective structures against new earth penetration weapons.
2025, 45(1): 012101.
doi: 10.11883/bzycj-2024-0130
Abstract:
The high reactivity of hydrogen and oxygen poses a huge challenge to the stable propagation of rotating detonation waves. To study the propagation instability of hydrogen-oxygen rotating detonation waves, based on the RYrhoCentralFoam solver developed by OpenFOAM, numerical simulations were conducted on two-dimensional hydrogen-oxygen rotating detonation waves in small scale model by changing the equivalence ratio. The complex and variable propagation characteristics of hydrogen-oxygen rotating detonation waves were revealed, and the typical flow field was analyzed. The instability of propagation modes and the quenching and re-initiation mechanisms of detonation waves were explored. The results show that as the equivalence ratio increases, the flow field exhibits three propagation modes: extinction, single wave, and hybrid waves. The detonation wave velocity increases almost linearly with the increase of equivalence ratio, with a velocity deficit of 5% to 8%. The disturbance of shock waves causes significant distortion and wrinkling on the deflagration surface, while the high reactivity of hydrogen and oxygen results in obvious layering on the deflagration surface and different instability at the two interfaces. The upper interface exhibits Kelvin-Helmholtz (K-H) instability, while the lower interface exhibits Rayleigh-Taylor (R-T) instability. As for the hybrid waves, the detonation wave is extremely unstable, maintaining a cycle between three states: quenching, single wave, and double wave collision. There are two ways in which detonation waves can be extinguished: firstly, the collision of two waves leads to the quenching of the detonation wave, and secondly, the intensification of combustion on the deflagration surface leads to the downward movement of the deflagration surface, ultimately resulting in the quenching of the detonation wave. The main reason for re-initiation is that the R-T instability induces detonation products and fresh premixed gas squeezing each other on the deflagration surface. The interaction between fresh premixed gas and products produces spikes and bubbles, enhances the reaction heat release on the deflagration surface, and generates local hotspots. The hotspots gradually increase into detonation waves, achieving the transition from deflagration to detonation.
The high reactivity of hydrogen and oxygen poses a huge challenge to the stable propagation of rotating detonation waves. To study the propagation instability of hydrogen-oxygen rotating detonation waves, based on the RYrhoCentralFoam solver developed by OpenFOAM, numerical simulations were conducted on two-dimensional hydrogen-oxygen rotating detonation waves in small scale model by changing the equivalence ratio. The complex and variable propagation characteristics of hydrogen-oxygen rotating detonation waves were revealed, and the typical flow field was analyzed. The instability of propagation modes and the quenching and re-initiation mechanisms of detonation waves were explored. The results show that as the equivalence ratio increases, the flow field exhibits three propagation modes: extinction, single wave, and hybrid waves. The detonation wave velocity increases almost linearly with the increase of equivalence ratio, with a velocity deficit of 5% to 8%. The disturbance of shock waves causes significant distortion and wrinkling on the deflagration surface, while the high reactivity of hydrogen and oxygen results in obvious layering on the deflagration surface and different instability at the two interfaces. The upper interface exhibits Kelvin-Helmholtz (K-H) instability, while the lower interface exhibits Rayleigh-Taylor (R-T) instability. As for the hybrid waves, the detonation wave is extremely unstable, maintaining a cycle between three states: quenching, single wave, and double wave collision. There are two ways in which detonation waves can be extinguished: firstly, the collision of two waves leads to the quenching of the detonation wave, and secondly, the intensification of combustion on the deflagration surface leads to the downward movement of the deflagration surface, ultimately resulting in the quenching of the detonation wave. The main reason for re-initiation is that the R-T instability induces detonation products and fresh premixed gas squeezing each other on the deflagration surface. The interaction between fresh premixed gas and products produces spikes and bubbles, enhances the reaction heat release on the deflagration surface, and generates local hotspots. The hotspots gradually increase into detonation waves, achieving the transition from deflagration to detonation.
2025, 45(1): 012301.
doi: 10.11883/bzycj-2024-0074
Abstract:
The annular shaped charges serve as the precursor of a tandem warhead, prized for its ability to create large diameter perforation in targets. In an effort to enhance the penetration capacity of the annular shaped charge jet and mitigate the impact of the inner casing on subsequent sections induced by a reversed penetrator, a novel approach was taken to implement the investigation. Four different combinations of inner and outer casing materials based on steel and aluminum alloy were explored. It was found that when the inner casing was made of aluminum alloy, the average penetration depth in the rear target was 36.13% lower than that when the inner casing was made of steel. Selecting an inner casing of aluminum alloy and an outer casing of steel, the effects of tip offset, liner thickness, and standoff distance on the formation and penetration characteristics of the annular jet were further investigated. The results show that the jet formed by the non-eccentric liner exhibits radial offset, negatively influencing its penetration capability. However, by offsetting the liner tip to the outer side by 0.05d (where d represents the radial thickness of the annular shaped charge), both the forming and penetration performances of the jet are significantly improved. In addition, as the liner thickness increases, the velocity of the jet tip gradually decreases. Notably, the annular jet formed by an eccentric conical liner with a thickness of 0.045d exhibits superior penetration performance. Furthermore, the standoff distance emerges as a critical factor influencing the penetration capability of the annular jet. Optimal performance is achieved at a standoff distance of 1.12d. Under the same scenario, jet penetration tests were implemented. The difference between the radius of the penetration tunnel from numerical and experimental study lies within 12%. Subsequently, the reliability of the numerical simulation model and the conclusions are verified.
The annular shaped charges serve as the precursor of a tandem warhead, prized for its ability to create large diameter perforation in targets. In an effort to enhance the penetration capacity of the annular shaped charge jet and mitigate the impact of the inner casing on subsequent sections induced by a reversed penetrator, a novel approach was taken to implement the investigation. Four different combinations of inner and outer casing materials based on steel and aluminum alloy were explored. It was found that when the inner casing was made of aluminum alloy, the average penetration depth in the rear target was 36.13% lower than that when the inner casing was made of steel. Selecting an inner casing of aluminum alloy and an outer casing of steel, the effects of tip offset, liner thickness, and standoff distance on the formation and penetration characteristics of the annular jet were further investigated. The results show that the jet formed by the non-eccentric liner exhibits radial offset, negatively influencing its penetration capability. However, by offsetting the liner tip to the outer side by 0.05d (where d represents the radial thickness of the annular shaped charge), both the forming and penetration performances of the jet are significantly improved. In addition, as the liner thickness increases, the velocity of the jet tip gradually decreases. Notably, the annular jet formed by an eccentric conical liner with a thickness of 0.045d exhibits superior penetration performance. Furthermore, the standoff distance emerges as a critical factor influencing the penetration capability of the annular jet. Optimal performance is achieved at a standoff distance of 1.12d. Under the same scenario, jet penetration tests were implemented. The difference between the radius of the penetration tunnel from numerical and experimental study lies within 12%. Subsequently, the reliability of the numerical simulation model and the conclusions are verified.
2025, 45(1): 013101.
doi: 10.11883/bzycj-2024-0036
Abstract:
X-ray diffraction test was used to analyze the changes in the mineral composition of the granite before and after filling with water to study the effects of saturated water and initial damage degree on macroscopic and microscopic failure characteristics of granite under impact load. The Hopkinson device was used to carry out dynamic mechanical tests on the granite samples under different states to analyze the dynamic mechanical properties of the granite and the block size characteristics under different states. In addition, some of the granite fragments after impact were selected for electron microscope scanning test to analyze the fracture failure characteristics. The fractal dimension was used to analyze the fragmentation degree of the granite fragments after impact and the scanning images of the fracture under electron microscopy. The influence of the image magnification selected during electron microscope scanning on the fractal dimension is discussed. The micro-cracking mechanism of granite induced by saturated water under impact load is briefly analyzed. The results show that the mineral composition of the saturated granite changes compared with the natural granite. The proportions of hornblende, albite, microcline, and quartz in the saturated granite decrease, while the proportion of kaolinite increases significantly. With the increase of initial damage, the dynamic peak stress of granite gradually decreases while the fragmentation degree and the fractal dimension of the block increase gradually, and the influence of initial damage on the fractal dimension of the block is greater than that of saturated water. With the increase of initial damage, more micro-cracks and debris appear in the fracture image, and the fractal dimension of the fracture image increases gradually. In a certain range, the fractal dimension of electron microscope scanning images increases with the increase of image magnification, but when the image exceeds a certain multiple, the fractal dimension will decrease. The research results can provide some theoretical and engineering references for the failure and instability mechanism analysis of disturbed water-saturated granite with initial damage in geotechnical engineering.
X-ray diffraction test was used to analyze the changes in the mineral composition of the granite before and after filling with water to study the effects of saturated water and initial damage degree on macroscopic and microscopic failure characteristics of granite under impact load. The Hopkinson device was used to carry out dynamic mechanical tests on the granite samples under different states to analyze the dynamic mechanical properties of the granite and the block size characteristics under different states. In addition, some of the granite fragments after impact were selected for electron microscope scanning test to analyze the fracture failure characteristics. The fractal dimension was used to analyze the fragmentation degree of the granite fragments after impact and the scanning images of the fracture under electron microscopy. The influence of the image magnification selected during electron microscope scanning on the fractal dimension is discussed. The micro-cracking mechanism of granite induced by saturated water under impact load is briefly analyzed. The results show that the mineral composition of the saturated granite changes compared with the natural granite. The proportions of hornblende, albite, microcline, and quartz in the saturated granite decrease, while the proportion of kaolinite increases significantly. With the increase of initial damage, the dynamic peak stress of granite gradually decreases while the fragmentation degree and the fractal dimension of the block increase gradually, and the influence of initial damage on the fractal dimension of the block is greater than that of saturated water. With the increase of initial damage, more micro-cracks and debris appear in the fracture image, and the fractal dimension of the fracture image increases gradually. In a certain range, the fractal dimension of electron microscope scanning images increases with the increase of image magnification, but when the image exceeds a certain multiple, the fractal dimension will decrease. The research results can provide some theoretical and engineering references for the failure and instability mechanism analysis of disturbed water-saturated granite with initial damage in geotechnical engineering.
2025, 45(1): 013102.
doi: 10.11883/bzycj-2024-0082
Abstract:
When X-rays generated by high-altitude nuclear detonation irradiates on the shell structure of missile, blow-off impulse (BOI) and thermal shock waves generated may produce dynamic response and damage on it. The existing three one-dimensional theoretical models, Whitener, BBAY, and MBBAY, can only provide approximate BOI values and accurate results of peak pressure and other information are inaccessible. Solving this problem requires numerical calculations based on real physical laws. The numerical simulation program TSHOCK3D for X-ray thermal excitation wave is used to calculate the BOI and peak pressure to make a comparative analysis. An aluminum plate with a length and width of 4 mm and a thickness of 1 mm is set as the target for X-ray radiation. The range of the working conditions is 0.1−3.0 keV for the Planck’s blackbody temperatures and radiant energy flux are in the range of 220−400 J/cm2. The results indicate that the TSHOCK3D can give the results effectively and reliably. The simulation results are consistent with the theoretical models mentioned above. The BOI and peak pressure are approximately linear with the energy flux, while the maximum value exist for different blackbody temperatures.
When X-rays generated by high-altitude nuclear detonation irradiates on the shell structure of missile, blow-off impulse (BOI) and thermal shock waves generated may produce dynamic response and damage on it. The existing three one-dimensional theoretical models, Whitener, BBAY, and MBBAY, can only provide approximate BOI values and accurate results of peak pressure and other information are inaccessible. Solving this problem requires numerical calculations based on real physical laws. The numerical simulation program TSHOCK3D for X-ray thermal excitation wave is used to calculate the BOI and peak pressure to make a comparative analysis. An aluminum plate with a length and width of 4 mm and a thickness of 1 mm is set as the target for X-ray radiation. The range of the working conditions is 0.1−3.0 keV for the Planck’s blackbody temperatures and radiant energy flux are in the range of 220−400 J/cm2. The results indicate that the TSHOCK3D can give the results effectively and reliably. The simulation results are consistent with the theoretical models mentioned above. The BOI and peak pressure are approximately linear with the energy flux, while the maximum value exist for different blackbody temperatures.
2025, 45(1): 013103.
doi: 10.11883/bzycj-2024-0095
Abstract:
As an environmentally friendly energy-absorbing material, shear-thickening fluid (STF) can be applied to protective structures to improve impact resistance. STF was obtained by mixing fumed silica particles with polyethylene glycol solution. It was then filled into a honeycomb core layer to make STF-filled honeycomb sandwich panels. Finally, the effect of STF on the impact resistance of the structure was explored. The impact force-displacement curves were obtained by using the drop weight impact experiment, and the effects of impact velocity (1.0, 1.5, 2.0 m/s), honeycomb aperture diameter (2.0, 2.5, 3.0 mm), and wall thickness (0.04, 0.06, 0.08 mm) on the mechanical properties of the sandwich panel were studied. At the same time, digital image correlation technology was utilized, which is an optical method for measuring the deformation of the surface of an object. By comparing the pixel displacements in multiple images, the strain history and deflection field distribution of the back panel of the structure were obtained, and the low-velocity impact response process of the structure was discussed. The experimental results show that under low-velocity impact, there is bump deformation in the center area of the back panel of the STF-unfilled honeycomb sandwich panel, and there is obvious bulging deformation in the surrounding area. The central area of the back panel of the STF-filled honeycomb sandwich panels has a wider range of bump deformations and no bulging around it. The shear-thickening effect of STF can increase the honeycomb elements involved in energy absorption, expand the local deformation area of the structure, and reduce the deflection of the back panel of the structure. Increasing the impact velocity, increasing the honeycomb aperture diameter, or decreasing the wall thickness are all more conducive to the shear-thickening effect of STF. The results provide a reference for the application of STF in protective structures.
As an environmentally friendly energy-absorbing material, shear-thickening fluid (STF) can be applied to protective structures to improve impact resistance. STF was obtained by mixing fumed silica particles with polyethylene glycol solution. It was then filled into a honeycomb core layer to make STF-filled honeycomb sandwich panels. Finally, the effect of STF on the impact resistance of the structure was explored. The impact force-displacement curves were obtained by using the drop weight impact experiment, and the effects of impact velocity (1.0, 1.5, 2.0 m/s), honeycomb aperture diameter (2.0, 2.5, 3.0 mm), and wall thickness (0.04, 0.06, 0.08 mm) on the mechanical properties of the sandwich panel were studied. At the same time, digital image correlation technology was utilized, which is an optical method for measuring the deformation of the surface of an object. By comparing the pixel displacements in multiple images, the strain history and deflection field distribution of the back panel of the structure were obtained, and the low-velocity impact response process of the structure was discussed. The experimental results show that under low-velocity impact, there is bump deformation in the center area of the back panel of the STF-unfilled honeycomb sandwich panel, and there is obvious bulging deformation in the surrounding area. The central area of the back panel of the STF-filled honeycomb sandwich panels has a wider range of bump deformations and no bulging around it. The shear-thickening effect of STF can increase the honeycomb elements involved in energy absorption, expand the local deformation area of the structure, and reduce the deflection of the back panel of the structure. Increasing the impact velocity, increasing the honeycomb aperture diameter, or decreasing the wall thickness are all more conducive to the shear-thickening effect of STF. The results provide a reference for the application of STF in protective structures.
2025, 45(1): 013301.
doi: 10.11883/bzycj-2024-0061
Abstract:
Due to the high compressive/tensile strengths and fracture toughness, ultra-high performance concrete (UHPC) has great application potential in protective structures against the attack of earth penetrating weapons. Accurately evaluating the damage and failure and establishing reliable design methods of UHPC shields against the combination of penetration and explosion of warheads can provide a helpful reference for protective structure design and resistance improvement. In this study, combined tests of 105 mm-caliber projectile penetration test and 5 kg TNT explosion test on semi-infinite UHPC target were conducted first. The detailed test data of the projectile and target under penetration and the combined effect of penetration and explosion were recorded. Then, a finite element model of UHPC under penetration and explosion was established. By conducting the numerical simulations of the above conducted test and the existing prefabricated hole charge explosion test on the finite UHPC slab, as well as comprehensively comparing the destroy depth and cracking dimension of the target, the reliability of the established finite element model and the corresponding analysis approach in predicting the damage and failure of UHPC shield against the combination of penetration and explosion of warheads were validated. Finally, the perforation limit and scabbing limit of the UHPC shield under the combination of penetration and explosion of three typical prototype warheads, i.e., SDB, WDU-43/B, and BLU-109/B, were determined and compared with those of normal strength concrete shield. The results show that, the perforation limit and scabbing limit of the UHPC shield against the above three warheads are in ranges of 1.30−2.60 m and 1.70−5.00 m, respectively. The corresponding critical perforation and scabbing coefficients are in the ranges of 1.81−2.17 and 2.46−4.17, respectively. Compared with the normal strength concrete shield, the cracking diameter of the UHPC shield is reduced by 34.4%−42.4%. The perforation limit and scabbing limit are reduced by 7.1%−31.6% and 39.7%−52.8%, respectively. The present work can provide an analysis method and reference for the resistance evaluation and design of the UHPC shield.
Due to the high compressive/tensile strengths and fracture toughness, ultra-high performance concrete (UHPC) has great application potential in protective structures against the attack of earth penetrating weapons. Accurately evaluating the damage and failure and establishing reliable design methods of UHPC shields against the combination of penetration and explosion of warheads can provide a helpful reference for protective structure design and resistance improvement. In this study, combined tests of 105 mm-caliber projectile penetration test and 5 kg TNT explosion test on semi-infinite UHPC target were conducted first. The detailed test data of the projectile and target under penetration and the combined effect of penetration and explosion were recorded. Then, a finite element model of UHPC under penetration and explosion was established. By conducting the numerical simulations of the above conducted test and the existing prefabricated hole charge explosion test on the finite UHPC slab, as well as comprehensively comparing the destroy depth and cracking dimension of the target, the reliability of the established finite element model and the corresponding analysis approach in predicting the damage and failure of UHPC shield against the combination of penetration and explosion of warheads were validated. Finally, the perforation limit and scabbing limit of the UHPC shield under the combination of penetration and explosion of three typical prototype warheads, i.e., SDB, WDU-43/B, and BLU-109/B, were determined and compared with those of normal strength concrete shield. The results show that, the perforation limit and scabbing limit of the UHPC shield against the above three warheads are in ranges of 1.30−2.60 m and 1.70−5.00 m, respectively. The corresponding critical perforation and scabbing coefficients are in the ranges of 1.81−2.17 and 2.46−4.17, respectively. Compared with the normal strength concrete shield, the cracking diameter of the UHPC shield is reduced by 34.4%−42.4%. The perforation limit and scabbing limit are reduced by 7.1%−31.6% and 39.7%−52.8%, respectively. The present work can provide an analysis method and reference for the resistance evaluation and design of the UHPC shield.
2025, 45(1): 013302.
doi: 10.11883/bzycj-2024-0145
Abstract:
In order to explore the structural response characteristics of projectile obliquely penetrating granite target, based on a 30 mm ballistic gun platform, the tests of projectile obliquely penetrating granite target were carried out, and the damage parameters of projectile structure under non-normal penetration were obtained. On this basis, combined with the numerical simulation, the deformation and fracture mechanism of the projectile structure of the projectile obliquely penetrating the granite target are studied, and the influence of the initial conditions of penetration on the structural response of the projectile is analyzed. The results show that the projectile is prone to bending and fracture when it is not penetrating the granite target. The asymmetric force on the head and tail of the projectile is the main factor affecting the response characteristics of the projectile. The degree of deformation and failure of the projectile is determined by the peak value of the angular velocity difference between the head and tail of the projectile. As the yaw increases, the bending degree of the projectile increases linearly, and the projectile breaks when the yaw increases to 8°. With the increase of the impact angle, the bending degree of the projectile increases first, followed by decrease and then increase again. When the impact angle is 15°, the bending degree of the projectile is the smallest. When the impact angle reaches 30°, the projectile breaks. Compared with the impact angle, the yaw has a more significant effect on the response behavior of the projectile structure. When the yaw and impact angle are combined, the introduction of the impact angle will increase the critical fracture positive yaw of the projectile, and the negative yaw will weaken the ability of the projectile to resist bending deformation and fracture. When the impact velocity is greater than1600 m/s, the impact velocity of the projectile becomes the main controlling factor for the different response behaviors of the projectile.
In order to explore the structural response characteristics of projectile obliquely penetrating granite target, based on a 30 mm ballistic gun platform, the tests of projectile obliquely penetrating granite target were carried out, and the damage parameters of projectile structure under non-normal penetration were obtained. On this basis, combined with the numerical simulation, the deformation and fracture mechanism of the projectile structure of the projectile obliquely penetrating the granite target are studied, and the influence of the initial conditions of penetration on the structural response of the projectile is analyzed. The results show that the projectile is prone to bending and fracture when it is not penetrating the granite target. The asymmetric force on the head and tail of the projectile is the main factor affecting the response characteristics of the projectile. The degree of deformation and failure of the projectile is determined by the peak value of the angular velocity difference between the head and tail of the projectile. As the yaw increases, the bending degree of the projectile increases linearly, and the projectile breaks when the yaw increases to 8°. With the increase of the impact angle, the bending degree of the projectile increases first, followed by decrease and then increase again. When the impact angle is 15°, the bending degree of the projectile is the smallest. When the impact angle reaches 30°, the projectile breaks. Compared with the impact angle, the yaw has a more significant effect on the response behavior of the projectile structure. When the yaw and impact angle are combined, the introduction of the impact angle will increase the critical fracture positive yaw of the projectile, and the negative yaw will weaken the ability of the projectile to resist bending deformation and fracture. When the impact velocity is greater than
2025, 45(1): 014201.
doi: 10.11883/bzycj-2024-0070
Abstract:
Silicone rubber has been widely used as a typical sandwich-structure or cushion-structure material in various high pressure loading environments. Under pressure loading of up to tens of GPa, silicone rubber may undergo shock decomposition reaction, and the decomposition products contain gas-solid mixture. Numerical simulation without the shock decomposition of silicone rubber cannot interpret some complex physical phenomena observed in detonation driven experiment. In order to illustrate the shock decomposition effect of silicone rubber, a simple shock decomposition model for silicone rubber is proposed based on the existing physical knowledge. By using the simple shock decomposition model for silicone rubber, the simulations of the experiment setup of detonation driven silicone rubber foam are carried out, and the simulated free surface velocities are compared with the experiments. The results show that the shock decomposition of silicone rubber can reasonably interpret the two grotesque phenomena observed in the experiment. During the shock decomposition process, the first incident pressure of silicone rubber would relax around the critical shock decomposition pressure for a period of time. As a result, the free surface velocity of steel plate exhibits a platform as observed in the experiment during the first take-off process. The compressibility of gas phase products of silicone rubber after shock decomposition is much higher than the solid/fluid materials, so more energy in the first incident wave is consumed to compress gas products to do work, leading to energy attenuation and peak pressure reduction when the first incident wave propagates to the outer surface of steel plate. Consequently, the peak value of the first take-off free surface velocity of steel plate decreases. Insight into the dynamic behavior of silicone rubber at high pressures is particularly valuable for predicting their response to extreme conditions, and it contributes to a deeper understanding of such experimental phenomena and to the proposal of a more refined shock decomposition model for silicone rubber.
Silicone rubber has been widely used as a typical sandwich-structure or cushion-structure material in various high pressure loading environments. Under pressure loading of up to tens of GPa, silicone rubber may undergo shock decomposition reaction, and the decomposition products contain gas-solid mixture. Numerical simulation without the shock decomposition of silicone rubber cannot interpret some complex physical phenomena observed in detonation driven experiment. In order to illustrate the shock decomposition effect of silicone rubber, a simple shock decomposition model for silicone rubber is proposed based on the existing physical knowledge. By using the simple shock decomposition model for silicone rubber, the simulations of the experiment setup of detonation driven silicone rubber foam are carried out, and the simulated free surface velocities are compared with the experiments. The results show that the shock decomposition of silicone rubber can reasonably interpret the two grotesque phenomena observed in the experiment. During the shock decomposition process, the first incident pressure of silicone rubber would relax around the critical shock decomposition pressure for a period of time. As a result, the free surface velocity of steel plate exhibits a platform as observed in the experiment during the first take-off process. The compressibility of gas phase products of silicone rubber after shock decomposition is much higher than the solid/fluid materials, so more energy in the first incident wave is consumed to compress gas products to do work, leading to energy attenuation and peak pressure reduction when the first incident wave propagates to the outer surface of steel plate. Consequently, the peak value of the first take-off free surface velocity of steel plate decreases. Insight into the dynamic behavior of silicone rubber at high pressures is particularly valuable for predicting their response to extreme conditions, and it contributes to a deeper understanding of such experimental phenomena and to the proposal of a more refined shock decomposition model for silicone rubber.
2025, 45(1): 015101.
doi: 10.11883/bzycj-2024-0053
Abstract:
Damage assessment of building structures plays an important role in military operations and engineering protection design. However, there is a lack of high-efficiency and validated damage assessment methods due to the complexity, variety, and large size of building structures. Therefore, a structural damage assessment method was proposed based on the high-precision numerical simulation analysis, in which the blast loadings, as well as the damage degrees of members, rooms, and building structures, were comprehensively considered. Firstly, the typical explosion tests and collapse accidents of reinforced concrete (RC) structures and masonry walls were numerically reproduced to verify the reliability of the numerical simulation approach for masonry-infilled RC frame structures. Subsequently, the blast-resistant analysis of a typical three-story masonry-infilled RC frame structure was conducted under internal explosions of different charge weights (25−200 kg TNT), including the propagation of blast waves, structural damage, and scattering of infilled walls. Besides, the proposed high-efficiency assessment method exhibited four key characteristics: (1) the concept of mirror explosion source and the non-linear shock addition rules were combined to predict the internal blast loadings in central and adjacent rooms; (2) the damage degrees of structural and non-structural members, i.e., beams, slabs, columns, and infilled walls, were determined by the equivalent single degree of freedom method; (3) the importance factor of members was considered and weighted to evaluate the damage degree of the room; (4) the influence of usage and location of each room on the damage degree of the building structure was considered. Finally, the proposed assessment method was employed to predict the aforementioned explosion scenarios. It derives that the RC frame structures exhibit slight, moderate, and severe damage under the explosions of 25, 100, and 200 kg TNT, respectively. The predicted damage degrees are identical to the simulation results, while the calculation time is reduced by over 99%. Therefore, the proposed method possesses reliability and timeliness in damage assessment of building structures.
Damage assessment of building structures plays an important role in military operations and engineering protection design. However, there is a lack of high-efficiency and validated damage assessment methods due to the complexity, variety, and large size of building structures. Therefore, a structural damage assessment method was proposed based on the high-precision numerical simulation analysis, in which the blast loadings, as well as the damage degrees of members, rooms, and building structures, were comprehensively considered. Firstly, the typical explosion tests and collapse accidents of reinforced concrete (RC) structures and masonry walls were numerically reproduced to verify the reliability of the numerical simulation approach for masonry-infilled RC frame structures. Subsequently, the blast-resistant analysis of a typical three-story masonry-infilled RC frame structure was conducted under internal explosions of different charge weights (25−200 kg TNT), including the propagation of blast waves, structural damage, and scattering of infilled walls. Besides, the proposed high-efficiency assessment method exhibited four key characteristics: (1) the concept of mirror explosion source and the non-linear shock addition rules were combined to predict the internal blast loadings in central and adjacent rooms; (2) the damage degrees of structural and non-structural members, i.e., beams, slabs, columns, and infilled walls, were determined by the equivalent single degree of freedom method; (3) the importance factor of members was considered and weighted to evaluate the damage degree of the room; (4) the influence of usage and location of each room on the damage degree of the building structure was considered. Finally, the proposed assessment method was employed to predict the aforementioned explosion scenarios. It derives that the RC frame structures exhibit slight, moderate, and severe damage under the explosions of 25, 100, and 200 kg TNT, respectively. The predicted damage degrees are identical to the simulation results, while the calculation time is reduced by over 99%. Therefore, the proposed method possesses reliability and timeliness in damage assessment of building structures.
2025, 45(1): 015201.
doi: 10.11883/bzycj-2024-0023
Abstract:
Simultaneous or slightly different explosions at multiple points in concrete medium can generate a complex superposition and aggregation effect of ground shock waves, significantly enhancing the pressure of ground shock waves in a specific area and greatly improving the destructive power of the explosion. To obtain the explosion aggregation effect and ground shock propagation attenuation law under the different arrangement of multi-point explosive sources, field tests were first carried out on single and seven-point aggregated explosions in concrete. Then, the reliability of the RHT material model parameters and the SPH numerical algorithm are verified based on experimental data. On this basis the orthogonal design method and gray system theory on the multi-point detonation parameters are adopted for design optimization. Gray correlation coefficients and gray correlations between scaled charge spacing, scaled active charge height, scaled detonation time difference and peak pressure at different proportional bursting center distances are established. Finally, by carrying out single-objective factor optimization and multi-objective factor optimization, a set of preferred combinations of the factors is determined, and simulation tests are conducted to verify the results. The analysis results show that the RHT model of concrete material and the SPH algorithm can reasonably predict the shock wave propagation attenuation characteristics of multipoint charge explosions at different scaled bursting center distances as well as the induced damage and destruction of concrete. The main factors affecting the impact of the ground shock aggregation of explosive effect, in order of magnitude, are: scaled charge spacing, scaled detonation time difference and scaled active charge height. Under the conditions of the present test, the optimized detonation parameters are found as: the proportional charge spacing is 0.549 m/kg1/3, the proportional detonation time difference is 0.239 m/kg1/3, the proportional active charge height is 0. This set of parameters will result in the best ground shock aggregation effect, being up to 4.7 times the ground shock pressure produced by the same amount of single-point group charging.
Simultaneous or slightly different explosions at multiple points in concrete medium can generate a complex superposition and aggregation effect of ground shock waves, significantly enhancing the pressure of ground shock waves in a specific area and greatly improving the destructive power of the explosion. To obtain the explosion aggregation effect and ground shock propagation attenuation law under the different arrangement of multi-point explosive sources, field tests were first carried out on single and seven-point aggregated explosions in concrete. Then, the reliability of the RHT material model parameters and the SPH numerical algorithm are verified based on experimental data. On this basis the orthogonal design method and gray system theory on the multi-point detonation parameters are adopted for design optimization. Gray correlation coefficients and gray correlations between scaled charge spacing, scaled active charge height, scaled detonation time difference and peak pressure at different proportional bursting center distances are established. Finally, by carrying out single-objective factor optimization and multi-objective factor optimization, a set of preferred combinations of the factors is determined, and simulation tests are conducted to verify the results. The analysis results show that the RHT model of concrete material and the SPH algorithm can reasonably predict the shock wave propagation attenuation characteristics of multipoint charge explosions at different scaled bursting center distances as well as the induced damage and destruction of concrete. The main factors affecting the impact of the ground shock aggregation of explosive effect, in order of magnitude, are: scaled charge spacing, scaled detonation time difference and scaled active charge height. Under the conditions of the present test, the optimized detonation parameters are found as: the proportional charge spacing is 0.549 m/kg1/3, the proportional detonation time difference is 0.239 m/kg1/3, the proportional active charge height is 0. This set of parameters will result in the best ground shock aggregation effect, being up to 4.7 times the ground shock pressure produced by the same amount of single-point group charging.
2025, 45(1): 015202.
doi: 10.11883/bzycj-2024-0064
Abstract:
Sympathetic detonation is defined as the phenomenon where the detonation pressure in one borehole causes explosives in another adjacent borehole to be detonated through an inert medium. It can increase the stress wave and the value of peak particle velocity, even causing fly rock to be thrown far away. These effects can impact the safety of blasting operation, slope stability, and blasting effects. Sympathetic detonation was identified by comparing the fluctuation difference of recorded blast-induced vibration signals. To investigate the mechanism of sympathetic detonation and methods of preventing sympathetic detonation in water-rich fissure open-pit mines, numerical simulation and field tests were adopted to analyze the effects of parameters on the occurrence of sympathetic detonation, such as the quantity of donor charge, crack width, and distance between charges. These results indicated that the borehole pressure increased with the decrease in decoupled charge coefficient, the increase of the crack width between boreholes (0.25−1.00 cm), and the decrease in the distance between boreholes. By using a wave-blocking tube, filling rock power, or setting up an air gap, the impact pressure produced by the donor charge was transmitted to the acceptor charge through the water-rich cracks. These methods made impact pressure lower than the critical detonation pressure of the emulsion explosive, which could prevent the sympathetic detonation of the accepted charge. Based on the field tests and simulated results, rock power filling was the best method of preventing sympathetic detonation when there was a single crack between the boreholes. Meanwhile, using a wave-blocking tube with a thickness of 2.6 mm was the best method of preventing sympathetic detonation when there were multiple cracks between the boreholes. Above all, the proposed detection method and obtained technologies provide the theory and guidance for preventing sympathetic detonation, which leads to improved blasting effects and the safety of blasting operations.
Sympathetic detonation is defined as the phenomenon where the detonation pressure in one borehole causes explosives in another adjacent borehole to be detonated through an inert medium. It can increase the stress wave and the value of peak particle velocity, even causing fly rock to be thrown far away. These effects can impact the safety of blasting operation, slope stability, and blasting effects. Sympathetic detonation was identified by comparing the fluctuation difference of recorded blast-induced vibration signals. To investigate the mechanism of sympathetic detonation and methods of preventing sympathetic detonation in water-rich fissure open-pit mines, numerical simulation and field tests were adopted to analyze the effects of parameters on the occurrence of sympathetic detonation, such as the quantity of donor charge, crack width, and distance between charges. These results indicated that the borehole pressure increased with the decrease in decoupled charge coefficient, the increase of the crack width between boreholes (0.25−1.00 cm), and the decrease in the distance between boreholes. By using a wave-blocking tube, filling rock power, or setting up an air gap, the impact pressure produced by the donor charge was transmitted to the acceptor charge through the water-rich cracks. These methods made impact pressure lower than the critical detonation pressure of the emulsion explosive, which could prevent the sympathetic detonation of the accepted charge. Based on the field tests and simulated results, rock power filling was the best method of preventing sympathetic detonation when there was a single crack between the boreholes. Meanwhile, using a wave-blocking tube with a thickness of 2.6 mm was the best method of preventing sympathetic detonation when there were multiple cracks between the boreholes. Above all, the proposed detection method and obtained technologies provide the theory and guidance for preventing sympathetic detonation, which leads to improved blasting effects and the safety of blasting operations.
Founded in 1981 monthly
Sponsored byChinese Society of Theoretical and Applied Mechanics
Institude of Fluid Physics, CAEP
Editor-in-ChiefCangli Liu
