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, Available online , doi: 10.11883/bzycj-2025-0355
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The design of blast wave simulators for prototype or large-scale engineering structures and components must carefully balance safety, cost, and performance. To address this challenge, a blast wave simulator driven by methane–air deflagration was developed in this study. Numerical models of methane–air deflagration in large-scale tubes were established using the CFD software OpenFOAM and validated against experimental data. On the basis of the validated model, numerical simulations were performed to investigate the effects of gas cloud length, venting conditions, and obstacle configurations on overpressure loads, thereby revealing the mechanisms of blast wave and flame propagation in the methane–air deflagration-driven simulator. A testing scheme was subsequently proposed to generate different levels of blast loading. The results show that the developed numerical model can reasonably predict the overpressure time histories and spatial distributions of gas explosions in large-scale tubes. In the simulator, increasing the gas cloud volume and placing obstacles near the ignition zone of the driven section can significantly intensify the deflagration of methane–air mixtures. Moreover, side venting effectively separates the pressure wave from the flame, thereby preventing high-temperature effects in the loading area. An optimized loading configuration was proposed, in which four obstacles (1×50% blockage ratio and 3×25% blockage ratio, spaced at 3 m intervals) were arranged, and different blast load levels were achieved by varying the gas cloud length from 1.5 m to 6 m in the driven section. Trial tests of the developed simulator showed that the measured peak overpressures agree well with the numerical predictions, with deviations less than 12%, and the results exhibit good uniformity and high repeatability. These findings demonstrate that the proposed methane-air deflagration-driven blast wave simulator is suitable for blast testing of structural components such as reinforced concrete slabs.
The design of blast wave simulators for prototype or large-scale engineering structures and components must carefully balance safety, cost, and performance. To address this challenge, a blast wave simulator driven by methane–air deflagration was developed in this study. Numerical models of methane–air deflagration in large-scale tubes were established using the CFD software OpenFOAM and validated against experimental data. On the basis of the validated model, numerical simulations were performed to investigate the effects of gas cloud length, venting conditions, and obstacle configurations on overpressure loads, thereby revealing the mechanisms of blast wave and flame propagation in the methane–air deflagration-driven simulator. A testing scheme was subsequently proposed to generate different levels of blast loading. The results show that the developed numerical model can reasonably predict the overpressure time histories and spatial distributions of gas explosions in large-scale tubes. In the simulator, increasing the gas cloud volume and placing obstacles near the ignition zone of the driven section can significantly intensify the deflagration of methane–air mixtures. Moreover, side venting effectively separates the pressure wave from the flame, thereby preventing high-temperature effects in the loading area. An optimized loading configuration was proposed, in which four obstacles (1×50% blockage ratio and 3×25% blockage ratio, spaced at 3 m intervals) were arranged, and different blast load levels were achieved by varying the gas cloud length from 1.5 m to 6 m in the driven section. Trial tests of the developed simulator showed that the measured peak overpressures agree well with the numerical predictions, with deviations less than 12%, and the results exhibit good uniformity and high repeatability. These findings demonstrate that the proposed methane-air deflagration-driven blast wave simulator is suitable for blast testing of structural components such as reinforced concrete slabs.
, Available online , doi: 10.11883/bzycj-2025-0352
Abstract:
During service, numerous structural metals in nuclear reactors are subjected to high-energy particle irradiation under prestressed conditions and may also experience unpredictable impact loads. These conditions can lead to significant degradation of the mechanical properties of structural metals, including irradiation hardening, irradiation embrittlement, irradiation swelling, and irradiation creep, thereby reducing reactor safety and reliability. However, existing studies have predominantly focused on the effects of either irradiation or impact loading on the mechanical properties and deformation mechanisms of metals. A limited number of studies have investigated the degradation behavior of irradiated metals under dynamic loading, whereas the coupled effect of prestress, which is a typical reactor service condition, has been considered even less frequently. The current status of experimental research on the hardening and embrittlement behavior and underlying micromechanisms of metals subjected to the coupled effects of irradiation, prestress, and impact loading is reviewed and summarized. Shortcomings and major challenges in current research are identified, and perspectives and recommendations are proposed regarding the key scientific issues requiring further attention and the critical technological bottlenecks that must be overcome in future studies. Specifically, the following issues should be addressed: (1) the necessity and sufficiency of the causal relationship between dislocation channels and irradiation-induced hardening and embrittlement mechanisms require thorough investigation; (2) equivalent dose-rate assessment methods for metal hardening and embrittlement induced by different irradiation particle sources need to be strengthened; (3) the hardening and embrittlement mechanisms of structural metals in nuclear reactors under prestress and neutron irradiation conditions require further investigation; and (4) research on the impact behavior of prestressed and neutron-irradiated metals urgently needs to be initiated, while safe and efficient experimental techniques for characterizing the dynamic properties of neutron-irradiated metals must be developed immediately. This review is expected to provide a scientific basis and research methodology for future investigations into the hardening and embrittlement behavior and mechanisms of metals under irradiation-prestress conditions, as required in major national projects such as nuclear reactor life extension and the development of advanced reactors.
During service, numerous structural metals in nuclear reactors are subjected to high-energy particle irradiation under prestressed conditions and may also experience unpredictable impact loads. These conditions can lead to significant degradation of the mechanical properties of structural metals, including irradiation hardening, irradiation embrittlement, irradiation swelling, and irradiation creep, thereby reducing reactor safety and reliability. However, existing studies have predominantly focused on the effects of either irradiation or impact loading on the mechanical properties and deformation mechanisms of metals. A limited number of studies have investigated the degradation behavior of irradiated metals under dynamic loading, whereas the coupled effect of prestress, which is a typical reactor service condition, has been considered even less frequently. The current status of experimental research on the hardening and embrittlement behavior and underlying micromechanisms of metals subjected to the coupled effects of irradiation, prestress, and impact loading is reviewed and summarized. Shortcomings and major challenges in current research are identified, and perspectives and recommendations are proposed regarding the key scientific issues requiring further attention and the critical technological bottlenecks that must be overcome in future studies. Specifically, the following issues should be addressed: (1) the necessity and sufficiency of the causal relationship between dislocation channels and irradiation-induced hardening and embrittlement mechanisms require thorough investigation; (2) equivalent dose-rate assessment methods for metal hardening and embrittlement induced by different irradiation particle sources need to be strengthened; (3) the hardening and embrittlement mechanisms of structural metals in nuclear reactors under prestress and neutron irradiation conditions require further investigation; and (4) research on the impact behavior of prestressed and neutron-irradiated metals urgently needs to be initiated, while safe and efficient experimental techniques for characterizing the dynamic properties of neutron-irradiated metals must be developed immediately. This review is expected to provide a scientific basis and research methodology for future investigations into the hardening and embrittlement behavior and mechanisms of metals under irradiation-prestress conditions, as required in major national projects such as nuclear reactor life extension and the development of advanced reactors.
, Available online , doi: 10.11883/bzycj-2025-0419
Abstract:
Addressing the high probability of injury and fatality associated with traditionalanti-riot kinetic energy projectiles represented by rubber bullets, a novel low-kinetic-energy frangible projectile with the characteristics of reliable shell fragmentation and the energy release of powder dispersion was designed based on the existing launch platforms of non-lethal weapons, aimed to improve the application safety of anti-riot kinetic energy projectiles. Through shooting tests on anthropomorphic dummy targets and ballistic gelatin targets, the dynamic impact responses of the two targets under the blunt impacts of frangible projectiles were obtained. In the dummy target tests, the frangible projectile achieved reliable fragmentation and exhibited a significant kinetic energy slow-release effect; the calculated injury assessment indicators for different parts of the dummy were all within the safety threshold. Comparative analyses with the blunt impact test results of rubber bullets show that this type of frangible projectile has significantly higher safety than rubber bullets while maintaining effective pain-inducing performance. In the ballistic gelatin target shooting tests, under the same projectile mass and impact velocity, the peak pressure generated in the gelatin measured by the internal sensor differed by approximately one order of magnitude between the frangible projectile and the rubber bullet. The test results show that the novel low-kinetic-energy frangible projectile can effectively attenuate the peak impact pressure of the projectile and greatly reduce its injury potential through the fragmentation of the projectile shell and the dispersion of the powder filled inside the projectile, which provides technical support for improving the application safety of anti-riot kinetic energy ammunition.
Addressing the high probability of injury and fatality associated with traditionalanti-riot kinetic energy projectiles represented by rubber bullets, a novel low-kinetic-energy frangible projectile with the characteristics of reliable shell fragmentation and the energy release of powder dispersion was designed based on the existing launch platforms of non-lethal weapons, aimed to improve the application safety of anti-riot kinetic energy projectiles. Through shooting tests on anthropomorphic dummy targets and ballistic gelatin targets, the dynamic impact responses of the two targets under the blunt impacts of frangible projectiles were obtained. In the dummy target tests, the frangible projectile achieved reliable fragmentation and exhibited a significant kinetic energy slow-release effect; the calculated injury assessment indicators for different parts of the dummy were all within the safety threshold. Comparative analyses with the blunt impact test results of rubber bullets show that this type of frangible projectile has significantly higher safety than rubber bullets while maintaining effective pain-inducing performance. In the ballistic gelatin target shooting tests, under the same projectile mass and impact velocity, the peak pressure generated in the gelatin measured by the internal sensor differed by approximately one order of magnitude between the frangible projectile and the rubber bullet. The test results show that the novel low-kinetic-energy frangible projectile can effectively attenuate the peak impact pressure of the projectile and greatly reduce its injury potential through the fragmentation of the projectile shell and the dispersion of the powder filled inside the projectile, which provides technical support for improving the application safety of anti-riot kinetic energy ammunition.
, Available online , doi: 10.11883/bzycj-2026-0035
Abstract:
Aiming at the problems of complex characteristics of blast load induced by fuel-rich explosives in confined spaces, as well as the high cost of high-precision solution and engineering application, a numerical calculation method for confined blast loading considering the afterburning effect was established. The method was verified for its reliability by comparing the calculated quasi-static pressure, impulse within the saturation response time and residual deformation of the target with the experimental results, with all relative errors controlled within 10%. The spatiotemporal distribution law of confined blast loading in confined spaces was systematically analyzed, and a simplified equivalent loading method considering both the saturation response time and quasi-static pressure was proposed. The reliability of the simplification method was validated by comparing the calculated first peak deformation and residual deformation at the central point with the results from fully coupled calculation, with all errors within 10%. Through an investigation into the spatial distribution form of the equivalent load and the influence of quasi-static pressure on structural response, the results show that within the scope of the current research, the spatial distribution of the equivalent load has a relatively minor effect on structural response, while the contribution of quasi-static pressure cannot be neglected. On the basis of the above findings, a two-stage load simplification model based on the load characteristics at the central point of the target plate was proposed. The reliability of the simplified model was confirmed by comparing the residual deformation values obtained from 10 groups of simplified model calculations with the experimental data, with all errors within 15%. The research results indicate that the proposed model exhibits good applicability under different working conditions; it can significantly improve the calculation efficiency while ensuring the calculation accuracy, and thus provides a technical approach for the simplified analysis of engineering problems related to confined space explosions.
Aiming at the problems of complex characteristics of blast load induced by fuel-rich explosives in confined spaces, as well as the high cost of high-precision solution and engineering application, a numerical calculation method for confined blast loading considering the afterburning effect was established. The method was verified for its reliability by comparing the calculated quasi-static pressure, impulse within the saturation response time and residual deformation of the target with the experimental results, with all relative errors controlled within 10%. The spatiotemporal distribution law of confined blast loading in confined spaces was systematically analyzed, and a simplified equivalent loading method considering both the saturation response time and quasi-static pressure was proposed. The reliability of the simplification method was validated by comparing the calculated first peak deformation and residual deformation at the central point with the results from fully coupled calculation, with all errors within 10%. Through an investigation into the spatial distribution form of the equivalent load and the influence of quasi-static pressure on structural response, the results show that within the scope of the current research, the spatial distribution of the equivalent load has a relatively minor effect on structural response, while the contribution of quasi-static pressure cannot be neglected. On the basis of the above findings, a two-stage load simplification model based on the load characteristics at the central point of the target plate was proposed. The reliability of the simplified model was confirmed by comparing the residual deformation values obtained from 10 groups of simplified model calculations with the experimental data, with all errors within 15%. The research results indicate that the proposed model exhibits good applicability under different working conditions; it can significantly improve the calculation efficiency while ensuring the calculation accuracy, and thus provides a technical approach for the simplified analysis of engineering problems related to confined space explosions.
, Available online , doi: 10.11883/bzycj-2025-0386
Abstract:
To investigate the damage characteristics of concrete arch slabs subjected to underwater contact explosions, a series of underwater contact explosion tests was conducted on three concrete arch slabs. During the experiments, the spalled fragments generated by detonation were carefully collected and quantitatively analyzed using a mass-based partitioning statistical method, thereby enabling systematic characterization of the slabs’ fragmentation and spalling behavior. On this basis, a three-dimensional fluid–structure interaction numerical model was developed using the Coupled Eulerian-Lagrangian (CEL) method, which incorporates water, a concrete arch slab, and TNT. The reliability and effectiveness of the numerical model were validated by comparing the simulated macroscopic failure patterns and crack propagation paths with the experimental observations. Further analyses were conducted using the validated model to investigate the damage evolution process and the characteristics of stress wave propagation within the arch slabs under explosive loading, thereby systematically elucidating the damage mechanisms of concrete arch slabs subjected to underwater contact explosions. In addition, parametric studies were performed to examine the effects of explosive charge and span length on the damage characteristics of the arch slabs. The results indicate that, under underwater contact explosion, an annular damage zone composed of radial and circumferential cracks forms on the blast-facing surface of the arch slab. With increasing explosive charge, the number of spalled fragments increases, and their size becomes progressively finer. As the span length increases, the structure tends to generate larger fragments. When the TNT charge increases from 0.4 g to 1.6 g, the annular damage zone on the blast-facing surface expands from a localized region to the full width of the slab, and the failure mode transitions from localized damage to global failure. With increasing span length, the degree of damage at the arch ends decreases, while the damaged region near the mid-span expands. Compared with the slab with a span of 400 mm, the total energy dissipation of the slab with a span of 600 mm increases by 4.3%.
To investigate the damage characteristics of concrete arch slabs subjected to underwater contact explosions, a series of underwater contact explosion tests was conducted on three concrete arch slabs. During the experiments, the spalled fragments generated by detonation were carefully collected and quantitatively analyzed using a mass-based partitioning statistical method, thereby enabling systematic characterization of the slabs’ fragmentation and spalling behavior. On this basis, a three-dimensional fluid–structure interaction numerical model was developed using the Coupled Eulerian-Lagrangian (CEL) method, which incorporates water, a concrete arch slab, and TNT. The reliability and effectiveness of the numerical model were validated by comparing the simulated macroscopic failure patterns and crack propagation paths with the experimental observations. Further analyses were conducted using the validated model to investigate the damage evolution process and the characteristics of stress wave propagation within the arch slabs under explosive loading, thereby systematically elucidating the damage mechanisms of concrete arch slabs subjected to underwater contact explosions. In addition, parametric studies were performed to examine the effects of explosive charge and span length on the damage characteristics of the arch slabs. The results indicate that, under underwater contact explosion, an annular damage zone composed of radial and circumferential cracks forms on the blast-facing surface of the arch slab. With increasing explosive charge, the number of spalled fragments increases, and their size becomes progressively finer. As the span length increases, the structure tends to generate larger fragments. When the TNT charge increases from 0.4 g to 1.6 g, the annular damage zone on the blast-facing surface expands from a localized region to the full width of the slab, and the failure mode transitions from localized damage to global failure. With increasing span length, the degree of damage at the arch ends decreases, while the damaged region near the mid-span expands. Compared with the slab with a span of 400 mm, the total energy dissipation of the slab with a span of 600 mm increases by 4.3%.
, Available online , doi: 10.11883/bzycj-2026-0056
Abstract:
To clarify the ultimate load-bearing capacity characteristics of prestressed concrete T-girder bridges under typical blast loads and address the technical difficulties in the residual load-bearing capacity evaluation of blast-damaged bridge structures, a two-stage test method combining blast damage test and post-blast static loading test is adopted in this study. A full-scale (1:1) prestressed concrete T-girder bridge specimen consistent with practical engineering structural parameters is taken as the test object to carry out large-equivalent field blast tests. Multi-stage graded static loading tests are further implemented on the blast-damaged specimen to obtain structural damage evolution features and deflection response data under post-blast service conditions. Based on the measured damage morphologies, deformation data and mechanical response laws acquired from physical tests, a refined three-dimensional finite element (FE) numerical simulation model for prestressed concrete T-girder bridges is established. Key structural characteristics including concrete and reinforcement strain-rate effects, material nonlinearity, prestress loss and structural contact interaction are fully considered in model establishment. The accuracy and reliability of the numerical model are validated through comparative calibration with experimental results. The validated model is subsequently employed to quantitatively investigate the ultimate load-bearing performance of bridges under three typical blast working conditions, including deck central contact blast, combined blast of deck central explosion and inter-girder internal explosion, and bilateral inter-girder internal explosion. The research results demonstrate distinct structural damage and bearing degradation characteristics under different blast scenarios. Contact blast acting on the bridge deck mainly induces local slab perforation failure and concentrated plastic deformation of deck concrete. For internal explosion occurring between main girders, structural damage presents a more severe and extensive pattern. In addition to concrete spalling and fragmentation on the bottom surface of the bridge deck, obvious outward bulging deformation, concrete crushing and local collapse failure occur on the webs and transverse diaphragms of T-girders. Among the three typical blast damage states, the combined blast condition with deck central explosion followed by secondary inter-girder explosion causes the most significant degradation of structural ultimate load-bearing capacity due to the superimposed synergistic damage effect. Reasonable optimization of live load layout effectively avoids severe damage areas of blast-affected bridges, eliminates the adverse influence of blast-induced structural defects, and achieves a remarkable improvement in the ultimate load-bearing capacity of damaged bridges. An integrated evaluation system covering the whole process from blast damage characterization to ultimate load-bearing capacity quantification is established in this research. The proposed evaluation method provides a systematic theoretical basis and feasible technical support for residual load-bearing capacity assessment, damage prediction and blast-resistant reinforcement design of prestressed concrete T-girder bridges suffering blast loads.
To clarify the ultimate load-bearing capacity characteristics of prestressed concrete T-girder bridges under typical blast loads and address the technical difficulties in the residual load-bearing capacity evaluation of blast-damaged bridge structures, a two-stage test method combining blast damage test and post-blast static loading test is adopted in this study. A full-scale (1:1) prestressed concrete T-girder bridge specimen consistent with practical engineering structural parameters is taken as the test object to carry out large-equivalent field blast tests. Multi-stage graded static loading tests are further implemented on the blast-damaged specimen to obtain structural damage evolution features and deflection response data under post-blast service conditions. Based on the measured damage morphologies, deformation data and mechanical response laws acquired from physical tests, a refined three-dimensional finite element (FE) numerical simulation model for prestressed concrete T-girder bridges is established. Key structural characteristics including concrete and reinforcement strain-rate effects, material nonlinearity, prestress loss and structural contact interaction are fully considered in model establishment. The accuracy and reliability of the numerical model are validated through comparative calibration with experimental results. The validated model is subsequently employed to quantitatively investigate the ultimate load-bearing performance of bridges under three typical blast working conditions, including deck central contact blast, combined blast of deck central explosion and inter-girder internal explosion, and bilateral inter-girder internal explosion. The research results demonstrate distinct structural damage and bearing degradation characteristics under different blast scenarios. Contact blast acting on the bridge deck mainly induces local slab perforation failure and concentrated plastic deformation of deck concrete. For internal explosion occurring between main girders, structural damage presents a more severe and extensive pattern. In addition to concrete spalling and fragmentation on the bottom surface of the bridge deck, obvious outward bulging deformation, concrete crushing and local collapse failure occur on the webs and transverse diaphragms of T-girders. Among the three typical blast damage states, the combined blast condition with deck central explosion followed by secondary inter-girder explosion causes the most significant degradation of structural ultimate load-bearing capacity due to the superimposed synergistic damage effect. Reasonable optimization of live load layout effectively avoids severe damage areas of blast-affected bridges, eliminates the adverse influence of blast-induced structural defects, and achieves a remarkable improvement in the ultimate load-bearing capacity of damaged bridges. An integrated evaluation system covering the whole process from blast damage characterization to ultimate load-bearing capacity quantification is established in this research. The proposed evaluation method provides a systematic theoretical basis and feasible technical support for residual load-bearing capacity assessment, damage prediction and blast-resistant reinforcement design of prestressed concrete T-girder bridges suffering blast loads.
, Available online , doi: 10.11883/bzycj-2025-0294
Abstract:
Magnesium powder, as a commonly used metallic material, poses a significant explosion risk during its production process, necessitating the urgent development of efficient and targeted explosion suppressants. In this study, different types of bimetallic supramolecular compound suppressants were successfully synthesized via the coprecipitation method, and their suppression effects on magnesium powder explosions were investigated using Hartmann tube experiments. It was found that the bimetallic supramolecular compounds exhibited superior explosion suppression performance compared to the traditional suppressant sodium bicarbonate. Moreover, when the metal cations were identical, carbonate ions demonstrated better suppression efficiency than chloride ions. The suppression effectiveness followed the order: CaFe-carbonate > CuAl-carbonate > MgAl-carbonate > CaFe-chloride > ZnCr-carbonate > MgAl-chloride materials. The suppression mechanism was identified as a combination of endothermic decomposition, physical encapsulation, inert gas dilution, and synergistic scavenging of key free radicals by metal cations and interlayer anions, thereby achieving a dual physical–chemical explosion suppression effect. This study compares the suppression performance of different bimetallic supramolecular compounds on magnesium powder deflagration, offering new insights for the safety protection against accidental magnesium powder explosions.
Magnesium powder, as a commonly used metallic material, poses a significant explosion risk during its production process, necessitating the urgent development of efficient and targeted explosion suppressants. In this study, different types of bimetallic supramolecular compound suppressants were successfully synthesized via the coprecipitation method, and their suppression effects on magnesium powder explosions were investigated using Hartmann tube experiments. It was found that the bimetallic supramolecular compounds exhibited superior explosion suppression performance compared to the traditional suppressant sodium bicarbonate. Moreover, when the metal cations were identical, carbonate ions demonstrated better suppression efficiency than chloride ions. The suppression effectiveness followed the order: CaFe-carbonate > CuAl-carbonate > MgAl-carbonate > CaFe-chloride > ZnCr-carbonate > MgAl-chloride materials. The suppression mechanism was identified as a combination of endothermic decomposition, physical encapsulation, inert gas dilution, and synergistic scavenging of key free radicals by metal cations and interlayer anions, thereby achieving a dual physical–chemical explosion suppression effect. This study compares the suppression performance of different bimetallic supramolecular compounds on magnesium powder deflagration, offering new insights for the safety protection against accidental magnesium powder explosions.
, Available online , doi: 10.11883/bzycj-2025-0313
Abstract:
Traditional homogenization models have difficulty accurately capturing the mesoscale effects of aggregate distribution, aggregate particle size, and reinforcement configuration on stress-wave propagation paths and energy-dissipation mechanisms in concrete, thereby limiting an in-depth understanding of the blast-induced failure mechanisms of reinforced concrete slabs. To address this issue, a three-dimensional mesoscale finite element model of reinforced concrete slabs incorporating reinforcement, aggregates, and mortar matrix was established through the combined use of MATLAB and LS-DYNA. The aggregates were modeled according to actual aggregate gradation characteristics, the reinforcing bars were accurately arranged based on practical engineering layout parameters, and appropriate contact algorithms were adopted among the matrix, aggregates, and reinforcing bars to simulate interfacial effects. The model was validated against contact explosion tests, and the results show that it can predict the failure modes and crater dimensions of reinforced concrete slabs subjected to contact explosion loads with reasonable accuracy. On this basis, the effects of aggregate characteristics, including distribution pattern and particle size, and reinforcement arrangement on the blast resistance and stress-wave propagation behavior of reinforced concrete were investigated through parametric mesoscale numerical simulations. Regarding the aggregate parameters, the particle-size distribution pattern and aggregate size govern the evolution of stress waves and energy-dissipation characteristics, thereby affecting the geometric dimensions of the craters on the top surface and the spalling craters on the bottom surface of the concrete slab. When the aggregate particle size decreases from the top surface to the bottom surface, the expansion of the top-surface crater and the development of bottom-surface spalling can be effectively suppressed; in contrast, an increasing particle-size distribution aggravates surface cratering and internal spalling damage. In terms of aggregate size, the bottom-surface spalling craters of slabs containing small aggregates exhibit shallow and wide characteristics, whereas those containing large aggregates exhibit deep and narrow morphologies. Compared with aggregates, reinforcing bars exert a weaker influence on the overall failure mode and stress-wave propagation behavior of the slab. At a low reinforcement ratio, the reinforcing bars have little effect on the dynamic transmission of compressive stress peaks, whereas under high explosion loads, they suppress slab fragmentation, mitigate flexural damage, and improve the structural integrity and damage resistance of the slab.
Traditional homogenization models have difficulty accurately capturing the mesoscale effects of aggregate distribution, aggregate particle size, and reinforcement configuration on stress-wave propagation paths and energy-dissipation mechanisms in concrete, thereby limiting an in-depth understanding of the blast-induced failure mechanisms of reinforced concrete slabs. To address this issue, a three-dimensional mesoscale finite element model of reinforced concrete slabs incorporating reinforcement, aggregates, and mortar matrix was established through the combined use of MATLAB and LS-DYNA. The aggregates were modeled according to actual aggregate gradation characteristics, the reinforcing bars were accurately arranged based on practical engineering layout parameters, and appropriate contact algorithms were adopted among the matrix, aggregates, and reinforcing bars to simulate interfacial effects. The model was validated against contact explosion tests, and the results show that it can predict the failure modes and crater dimensions of reinforced concrete slabs subjected to contact explosion loads with reasonable accuracy. On this basis, the effects of aggregate characteristics, including distribution pattern and particle size, and reinforcement arrangement on the blast resistance and stress-wave propagation behavior of reinforced concrete were investigated through parametric mesoscale numerical simulations. Regarding the aggregate parameters, the particle-size distribution pattern and aggregate size govern the evolution of stress waves and energy-dissipation characteristics, thereby affecting the geometric dimensions of the craters on the top surface and the spalling craters on the bottom surface of the concrete slab. When the aggregate particle size decreases from the top surface to the bottom surface, the expansion of the top-surface crater and the development of bottom-surface spalling can be effectively suppressed; in contrast, an increasing particle-size distribution aggravates surface cratering and internal spalling damage. In terms of aggregate size, the bottom-surface spalling craters of slabs containing small aggregates exhibit shallow and wide characteristics, whereas those containing large aggregates exhibit deep and narrow morphologies. Compared with aggregates, reinforcing bars exert a weaker influence on the overall failure mode and stress-wave propagation behavior of the slab. At a low reinforcement ratio, the reinforcing bars have little effect on the dynamic transmission of compressive stress peaks, whereas under high explosion loads, they suppress slab fragmentation, mitigate flexural damage, and improve the structural integrity and damage resistance of the slab.
, Available online , doi: 10.11883/bzycj-2025-0139
Abstract:
In order to compare the similarities and differences among the ‘self-sharpening’ behavior as well as the corresponding ballistic performance of tungsten fiber / metallic glass matrix (WF/MG) composite long rods with different fiber diameters, the deformation and failure characteristics of various WF/MG composite long rods were investigated systematically integrated with related penetrating test results and mesoscopic finite element (FE) simulation analysis, in which the two-dimensional (2D) and three-dimensional (3D) meso-scale FE geometric models of WF/MG composite long rod were established according to the actual distribution characteristics of metallic glass matrix and tungsten fibers, and a coupled ‘thermo-mechanical-free volume’ constitutive model was applied to characterize the high shear sensitivity as well as high strength of metallic glass matrix. Moreover, the transformation of deformation and failure modes of projectiles under different impact velocities was analyzed in detail. Related analysis demonstrated that due to the differences in the mechanical properties among the tungsten fibers with different diameters, i.e., bending resistance and shear resistance, etc., the corresponding composite long rods exhibit different failure characteristics during the penetration process, and it further affects their penetration / perforation performance. The impact velocity also plays an important role on the deformation and failure modes of composite long rods and the corresponding penetration / perforation performance: when the impact velocity is relatively low, the fibers in the nose of composite rod projectile exhibits unstable buckling phenomenon and gradually disperse during the penetration process, which makes the projectile nose blunt at a certain extent, and induces the increase in the penetration resistance and decrease in the penetration performance; along with the impact velocity increases, in the case that the fiber diameter is small, the fibers on the outer side of projectile nose refluxes back, and when the fiber diameter is large, the fibers mainly behave as shear failure, and it further strengthen the ‘self-sharpening’ behavior as well as the penetration performance of projectile; when the impact velocity and fiber diameter reach a certain upper threshold values, The thickness of ‘edge layer’ in the rod nose is sharply reduced, and thus the ‘self-sharpening’ performance is weakened, and the penetration capability of projectile is decayed again. Related research is beneficial to predicting the penetration / perforation performance of WF/MG composite long rods with different fiber diameters under different impact velocities, and optimizing the structural design of projectile as well as the impact velocity, etc.
In order to compare the similarities and differences among the ‘self-sharpening’ behavior as well as the corresponding ballistic performance of tungsten fiber / metallic glass matrix (WF/MG) composite long rods with different fiber diameters, the deformation and failure characteristics of various WF/MG composite long rods were investigated systematically integrated with related penetrating test results and mesoscopic finite element (FE) simulation analysis, in which the two-dimensional (2D) and three-dimensional (3D) meso-scale FE geometric models of WF/MG composite long rod were established according to the actual distribution characteristics of metallic glass matrix and tungsten fibers, and a coupled ‘thermo-mechanical-free volume’ constitutive model was applied to characterize the high shear sensitivity as well as high strength of metallic glass matrix. Moreover, the transformation of deformation and failure modes of projectiles under different impact velocities was analyzed in detail. Related analysis demonstrated that due to the differences in the mechanical properties among the tungsten fibers with different diameters, i.e., bending resistance and shear resistance, etc., the corresponding composite long rods exhibit different failure characteristics during the penetration process, and it further affects their penetration / perforation performance. The impact velocity also plays an important role on the deformation and failure modes of composite long rods and the corresponding penetration / perforation performance: when the impact velocity is relatively low, the fibers in the nose of composite rod projectile exhibits unstable buckling phenomenon and gradually disperse during the penetration process, which makes the projectile nose blunt at a certain extent, and induces the increase in the penetration resistance and decrease in the penetration performance; along with the impact velocity increases, in the case that the fiber diameter is small, the fibers on the outer side of projectile nose refluxes back, and when the fiber diameter is large, the fibers mainly behave as shear failure, and it further strengthen the ‘self-sharpening’ behavior as well as the penetration performance of projectile; when the impact velocity and fiber diameter reach a certain upper threshold values, The thickness of ‘edge layer’ in the rod nose is sharply reduced, and thus the ‘self-sharpening’ performance is weakened, and the penetration capability of projectile is decayed again. Related research is beneficial to predicting the penetration / perforation performance of WF/MG composite long rods with different fiber diameters under different impact velocities, and optimizing the structural design of projectile as well as the impact velocity, etc.
, Available online , doi: 10.11883/bzycj-2026-0054
Abstract:
Impact fatigue refers to the phenomenon in which materials or structures, subjected to repeated impact loading, experience localized stress concentrations and rapid strain accumulation, leading to the initiation of internal micro-damage and ultimately the fracture failure. Impact fatigue loads are characterized by their short duration, rapid loading rates and significantly elevated strain-rates, which has greater threat than conventional fatigue. The wheel-rail dynamic contact forces of high-speed trains exhibit typical characteristics of impact fatigue loading, which induces the accumulation of impact fatigue damage, accelerates the deterioration of material’s mechanical properties; and consequently, compromises the operational safety of high-speed trains. The present study integrates a material-based impact fatigue damage-coupled constitutive model to develop a comprehensive three-dimensional wheel-rail rolling contact finite element model. The stress-strain states and adhesion-slip characteristics of wheel-rail rolling/sliding contact are clarified, and the distribution features and accumulation evolution of wheel-rail impact fatigue damage are analyzed. Meanwhile, the effects of train speed, friction coefficient, and traction coefficient on impact fatigue damage are studied, and the influence of material constitutive model on typical wheel-rail contact mechanical behavior is examined. The results clearly indicate that the proposed impact fatigue model is able to well represent the wheel-rail contact responses, adhesion-slip distribution characteristics and damage accumulation. Under repeated rolling contact, the impact fatigue damage of the rail exhibits a nonlinear cumulative increasing trend with the increase of rolling cycles; however, the growth rate gradually decreases and eventually tends to stabilize approximately. Compared with the elastoplastic constitutive model, the wheel-rail contact mechanical responses predicted by the impact fatigue constitutive model are more severe and dangerous. Moreover, the coupling effect of impact fatigue damage gradually intensifies with the increase of wheel passages. These findings provide valuable theoretical insights and technical support for fatigue damage assessment and life prediction of high-speed wheel-rail systems.
Impact fatigue refers to the phenomenon in which materials or structures, subjected to repeated impact loading, experience localized stress concentrations and rapid strain accumulation, leading to the initiation of internal micro-damage and ultimately the fracture failure. Impact fatigue loads are characterized by their short duration, rapid loading rates and significantly elevated strain-rates, which has greater threat than conventional fatigue. The wheel-rail dynamic contact forces of high-speed trains exhibit typical characteristics of impact fatigue loading, which induces the accumulation of impact fatigue damage, accelerates the deterioration of material’s mechanical properties; and consequently, compromises the operational safety of high-speed trains. The present study integrates a material-based impact fatigue damage-coupled constitutive model to develop a comprehensive three-dimensional wheel-rail rolling contact finite element model. The stress-strain states and adhesion-slip characteristics of wheel-rail rolling/sliding contact are clarified, and the distribution features and accumulation evolution of wheel-rail impact fatigue damage are analyzed. Meanwhile, the effects of train speed, friction coefficient, and traction coefficient on impact fatigue damage are studied, and the influence of material constitutive model on typical wheel-rail contact mechanical behavior is examined. The results clearly indicate that the proposed impact fatigue model is able to well represent the wheel-rail contact responses, adhesion-slip distribution characteristics and damage accumulation. Under repeated rolling contact, the impact fatigue damage of the rail exhibits a nonlinear cumulative increasing trend with the increase of rolling cycles; however, the growth rate gradually decreases and eventually tends to stabilize approximately. Compared with the elastoplastic constitutive model, the wheel-rail contact mechanical responses predicted by the impact fatigue constitutive model are more severe and dangerous. Moreover, the coupling effect of impact fatigue damage gradually intensifies with the increase of wheel passages. These findings provide valuable theoretical insights and technical support for fatigue damage assessment and life prediction of high-speed wheel-rail systems.
, Available online , doi: 10.11883/bzycj-2025-0357
Abstract:
Because of the difficulty in obtaining granite materials and the high cost of conducting penetration tests on granite targets, an equivalence study between reinforced concrete and granite targets was carried out. To establish the equivalence relationship between the two target types, dimensional analysis and a modified compensation method were adopted, with the projectile residual velocity taken as the equivalence criterion, and a computational method for determining equivalent thickness was derived. Based on existing experimental data, numerical models for medium-velocity projectile penetration into reinforced concrete and granite targets were developed and validated using the LS-DYNA software. By varying the projectile impact velocity and target thickness in the numerical simulations, the similarities in damage characteristics between reinforced concrete and granite targets were systematically investigated, and the corresponding failure regions were classified. On the basis of the simulation results, specific equivalent design formulas for granite and reinforced concrete targets were obtained through data fitting. The results show that the established numerical models can accurately predict the projectile residual velocity and reproduce the failure characteristics of both target types during penetration. Compared with reinforced concrete, granite exhibits a smaller compaction zone and tunnel diameter, finer and longer cracks with higher propagation velocities, larger surface crack areas, and a greater tendency to form large spallation craters. Under identical penetration conditions, granite targets and reinforced concrete targets of equivalent thickness display similar failure characteristics, and both can be divided into five distinct failure regions. Through dimensional analysis and compensation correction, a dimensionless residual-velocity function for projectile penetration into reinforced concrete and granite targets was derived, together with an equivalent thickness formula relating the two materials. The fitted equivalent thickness coefficient between granite and reinforced concrete was determined to be 1.69966. Validation of the proposed equivalence formula indicates that the residual-velocity error between the prototype and equivalent model targets is less than 5%. These results provide a useful reference for the equivalent design of rock targets subjected to medium-velocity projectile penetration and offer a systematic methodology for substituting reinforced concrete for granite in related experimental and engineering applications.
Because of the difficulty in obtaining granite materials and the high cost of conducting penetration tests on granite targets, an equivalence study between reinforced concrete and granite targets was carried out. To establish the equivalence relationship between the two target types, dimensional analysis and a modified compensation method were adopted, with the projectile residual velocity taken as the equivalence criterion, and a computational method for determining equivalent thickness was derived. Based on existing experimental data, numerical models for medium-velocity projectile penetration into reinforced concrete and granite targets were developed and validated using the LS-DYNA software. By varying the projectile impact velocity and target thickness in the numerical simulations, the similarities in damage characteristics between reinforced concrete and granite targets were systematically investigated, and the corresponding failure regions were classified. On the basis of the simulation results, specific equivalent design formulas for granite and reinforced concrete targets were obtained through data fitting. The results show that the established numerical models can accurately predict the projectile residual velocity and reproduce the failure characteristics of both target types during penetration. Compared with reinforced concrete, granite exhibits a smaller compaction zone and tunnel diameter, finer and longer cracks with higher propagation velocities, larger surface crack areas, and a greater tendency to form large spallation craters. Under identical penetration conditions, granite targets and reinforced concrete targets of equivalent thickness display similar failure characteristics, and both can be divided into five distinct failure regions. Through dimensional analysis and compensation correction, a dimensionless residual-velocity function for projectile penetration into reinforced concrete and granite targets was derived, together with an equivalent thickness formula relating the two materials. The fitted equivalent thickness coefficient between granite and reinforced concrete was determined to be 1.69966. Validation of the proposed equivalence formula indicates that the residual-velocity error between the prototype and equivalent model targets is less than 5%. These results provide a useful reference for the equivalent design of rock targets subjected to medium-velocity projectile penetration and offer a systematic methodology for substituting reinforced concrete for granite in related experimental and engineering applications.
, Available online , doi: 10.11883/bzycj-2025-0348
Abstract:
The present investigation examines the effectiveness of a composite cushion charging structure, placed at the bottom of underwater boreholes, to mitigate bedrock damage induced by blasting excavation during cross-sea engineering. With reference to the embedded open caisson blasting project for a major cross-sea bridge, this research adopted a combined methodology of field sampling and controlled underwater explosion model tests. A piezoelectric ceramic detection system was employed to quantitatively analyze how the composite cushion, composed of iron-sand concrete layers with varying wave impedances, affects rock sample damage. Piezoelectric signals were processed via wavelet packet analysis to calculate the axial damage factor (DI) of the blast hole. Furthermore, by integrating fractal dimension theory with damage mechanics, a quantitative assessment was performed on the propagation behavior of cracks formed on the top surfaces of rock specimens under different test conditions. Results demonstrate that the implemented composite bottom cushion effectively mitigates blast-induced damage by significantly inhibiting macroscopic crack propagation, reducing surface crack density, and decreasing the axial penetration depth of cracks into the rock mass. Detailed analysis of axial damage reveals a clear trend, showing that the reduction in DI becomes more pronounced as the wave impedance of the cushion material increases. Specifically, within the borehole-affected zone (0–12 cm), the maximum achievable reduction in DI reaches 10.70%. In the adjacent bedrock zone, damage mitigation is even more evident, with DI decreasing by 95.7% to 95.8%, depending on the specific wave impedance. In conclusion, this work confirms that employing a composite cushion charging structure in underwater drilling and blasting operations can significantly alleviate blast-induced damage to foundational bedrock. The findings also establish that axial damage to the rock mass can be effectively controlled by adjusting the wave impedance of the iron-sand concrete in the cushion layer. These outcomes offer valuable insights for optimizing blasting design and enhancing damage control in marine engineering projects.
The present investigation examines the effectiveness of a composite cushion charging structure, placed at the bottom of underwater boreholes, to mitigate bedrock damage induced by blasting excavation during cross-sea engineering. With reference to the embedded open caisson blasting project for a major cross-sea bridge, this research adopted a combined methodology of field sampling and controlled underwater explosion model tests. A piezoelectric ceramic detection system was employed to quantitatively analyze how the composite cushion, composed of iron-sand concrete layers with varying wave impedances, affects rock sample damage. Piezoelectric signals were processed via wavelet packet analysis to calculate the axial damage factor (DI) of the blast hole. Furthermore, by integrating fractal dimension theory with damage mechanics, a quantitative assessment was performed on the propagation behavior of cracks formed on the top surfaces of rock specimens under different test conditions. Results demonstrate that the implemented composite bottom cushion effectively mitigates blast-induced damage by significantly inhibiting macroscopic crack propagation, reducing surface crack density, and decreasing the axial penetration depth of cracks into the rock mass. Detailed analysis of axial damage reveals a clear trend, showing that the reduction in DI becomes more pronounced as the wave impedance of the cushion material increases. Specifically, within the borehole-affected zone (0–12 cm), the maximum achievable reduction in DI reaches 10.70%. In the adjacent bedrock zone, damage mitigation is even more evident, with DI decreasing by 95.7% to 95.8%, depending on the specific wave impedance. In conclusion, this work confirms that employing a composite cushion charging structure in underwater drilling and blasting operations can significantly alleviate blast-induced damage to foundational bedrock. The findings also establish that axial damage to the rock mass can be effectively controlled by adjusting the wave impedance of the iron-sand concrete in the cushion layer. These outcomes offer valuable insights for optimizing blasting design and enhancing damage control in marine engineering projects.
, Available online , doi: 10.11883/bzycj-2025-0263
Abstract:
To evaluate the crater damage effect of cylinder charge contact explosion on steel fiber reinforced concrete (SFRC) structures, a numerical model of an SFRC target was developed by the using the smooth particle Galerkin method and a structured arbitrary Lagrange-Euler (SPG-S-ALE) fluid-structure interaction algorithm. The failure modes and damage of the SFRC target under different charge mass Q and length-to-diameter ratios l/d were investigated. Based on contact explosion theory and dimensional analysis, cratering coefficients K1 and K2 were introduced to develop predictive models for the crater diameter D and depth H as functions of the effective charge mass Qₑ. The results indicate that under the combined effects of charge mass and length-to-to-diameter ratio, the primary failure mode of the SFRC targets is cratering damage. Under constant charge mass conditions, as the l/d ratio increases from 1 to 5, both the crater diameter D and depth H decrease by approximately 50%. Within the range of effective charge Qₑ less than 16 kg, the K1 and\begin{document}$ \sqrt{{K}_{2}} $\end{document}
To evaluate the crater damage effect of cylinder charge contact explosion on steel fiber reinforced concrete (SFRC) structures, a numerical model of an SFRC target was developed by the using the smooth particle Galerkin method and a structured arbitrary Lagrange-Euler (SPG-S-ALE) fluid-structure interaction algorithm. The failure modes and damage of the SFRC target under different charge mass Q and length-to-diameter ratios l/d were investigated. Based on contact explosion theory and dimensional analysis, cratering coefficients K1 and K2 were introduced to develop predictive models for the crater diameter D and depth H as functions of the effective charge mass Qₑ. The results indicate that under the combined effects of charge mass and length-to-to-diameter ratio, the primary failure mode of the SFRC targets is cratering damage. Under constant charge mass conditions, as the l/d ratio increases from 1 to 5, both the crater diameter D and depth H decrease by approximately 50%. Within the range of effective charge Qₑ less than 16 kg, the K1 and
, Available online , doi: 10.11883/bzycj-2025-0336
Abstract:
To explore the feasibility of nano aluminum thermite as a detonator substitute for achieving stable detonation in mixed biomass blasting agent systems, and to clarify the differences in detonation effects relative to detonators, digital electronic detonators (S0), Al/CuO thermite (S1), and Al/Bi2O3 thermite (S2) were selected to detonate a mixed biomass blasting agent composed of wood powder and peanut shell powder (mass ratio 1∶1). Based on theoretical analysis, qualitative analysis and quantitative calculation were conducted for the total energy release and energy release power of different detonation methods to estimate detonation performance. Industrial explosive performance testing methods-including aluminum thermite detonation test, orthogonal tests of detonation velocity and intensity, underwater explosion tests, and blasting funnel tests-were used to systematically test and compare the detonation response characteristics of the mixed biomass blasting agent under different detonation conditions. The evolutionary laws of the explosive performance were explored from perspectives of impact effect, energy release intensity, and spatial damage effect. Results indicate that detonators and thermites belong to two distinct energy release power level systems: detonators enable instantaneous power output in the MW range, while thermites only reach the kW range. Aluminum thermite detonation is a typical high-temperature explosive energy release process with high energy density, which can achieve effective energy coupling under limited constraints and possesses reliable detonation capability. Oxygen pressure is the dominant factor affecting detonation velocity and intensity, followed by steel pipe wall thickness. The impact of detonation methods is relatively weak, and detonation methods are substitutable. Synergistic enhancement of detonation velocity and intensity can be achieved by increasing oxygen pressure and optimizing constraint conditions. The excitation efficiency of the three detonation methods follows a consistent ranking: S0 is the strongest, S2 ranks second, and S1 is slightly weaker. This ranking has been verified by shock wave parameters and crater volumes (0.33 m3, 0.24 m3, 0.21 m3). This research provides experimental support for the optimization and application of biomass blasting technology.
To explore the feasibility of nano aluminum thermite as a detonator substitute for achieving stable detonation in mixed biomass blasting agent systems, and to clarify the differences in detonation effects relative to detonators, digital electronic detonators (S0), Al/CuO thermite (S1), and Al/Bi2O3 thermite (S2) were selected to detonate a mixed biomass blasting agent composed of wood powder and peanut shell powder (mass ratio 1∶1). Based on theoretical analysis, qualitative analysis and quantitative calculation were conducted for the total energy release and energy release power of different detonation methods to estimate detonation performance. Industrial explosive performance testing methods-including aluminum thermite detonation test, orthogonal tests of detonation velocity and intensity, underwater explosion tests, and blasting funnel tests-were used to systematically test and compare the detonation response characteristics of the mixed biomass blasting agent under different detonation conditions. The evolutionary laws of the explosive performance were explored from perspectives of impact effect, energy release intensity, and spatial damage effect. Results indicate that detonators and thermites belong to two distinct energy release power level systems: detonators enable instantaneous power output in the MW range, while thermites only reach the kW range. Aluminum thermite detonation is a typical high-temperature explosive energy release process with high energy density, which can achieve effective energy coupling under limited constraints and possesses reliable detonation capability. Oxygen pressure is the dominant factor affecting detonation velocity and intensity, followed by steel pipe wall thickness. The impact of detonation methods is relatively weak, and detonation methods are substitutable. Synergistic enhancement of detonation velocity and intensity can be achieved by increasing oxygen pressure and optimizing constraint conditions. The excitation efficiency of the three detonation methods follows a consistent ranking: S0 is the strongest, S2 ranks second, and S1 is slightly weaker. This ranking has been verified by shock wave parameters and crater volumes (0.33 m3, 0.24 m3, 0.21 m3). This research provides experimental support for the optimization and application of biomass blasting technology.
, Available online , doi: 10.11883/bzycj-2025-0308
Abstract:
To investigate the complex wake flow characteristics of multi-motor parallel rocket sleds, this study focuses on the mechanisms by which the nozzle horizontal spacing and the impingement height influence the flow structure and ground effect. A three-dimensional physical model was constructed for a dual-rail rocket sled system featuring three nozzles arranged in a triangular pyramid configuration. Four operating conditions were established, including large spacing (l = 7d), small spacing (l = 1d), low impingement height (h = 2d), and high impingement height (h=5.5d). The effects of nozzle center distance and impingement height on the flow field structure and ground effect were comparatively analyzed. Numerical simulations were performed using a computational fluid dynamics (CFD) method based on the Reynolds-Averaged Navier-Stokes equations, coupled with the Realizable k-ε turbulence model for transient solutions. The combustion chamber pressure-time curve derived from interior ballistic theory was applied to the nozzle inlet via a user-defined function (UDF). The sled velocity-time curve, determined from the exterior ballistic particle trajectory equation, was assigned as the far-field pressure boundary condition, enabling a coupled simulation framework of interior ballistics, exterior ballistics and flow field. The computational domain utilized a structured grid with refinement in the jet interaction region and near the ground to ensure calculation accuracy. The velocity and pressure fields obtained from numerical simulations were compared and validated against jet morphology, impingement height, and vortex core positions recorded by high-speed photography (2000 Hz). The flow field structure, pressure distribution, and thermal erosion behavior on the ground under different configurations are systematically revealed. The results indicate that the small-spacing nozzle arrangement triggers intense jet interference without ground effect participation, leading to a multi-peak and slow-recovery pressure evolution feature and substantially delays the flow field relaxation process. The coupling relationship between ground effect and jet interference is dominated by impingement height. At low impingement height conditions, the jet impinging on the ground induces intense reorganization and fragmentation of vortex structures, generating wall jets with velocities up to 960 m/s. Consequently, the peak ground surface temperatures reaches 1286.6 K with sustained high temperatures, which significantly elevates the risk of rail ablation. Conversely, a high impingement height effectively suppresses the ground effect, resulting in a more homogeneous and stable flow field structure. In this case, the peak ground temperature reduced by approximately 65% and maximum velocity reduced by 58%, significantly mitigating ablation risk. The initial phase (0－8 m) of the rocket sled is identified as the critical region subjected to the most severe thermomechanical loads. During this stage, the average acceleration reaches 832.7 m/s2, and the specific action time per unit distance is prolonged to 1.84 ms/m. Coupled with the transient complex flow field, this constitutes an extremely high risk for rail ablation. The numerical simulation results show excellent agreement with high-speed photographic experimental data regarding flow field morphology, impingement height, and vortex core positions, thereby validating the reliability of the established coupled model. This study elucidates the complex flow mechanisms of multi-nozzle parallel systems under strongly constrained conditions, and provids important theoretical foundations and design parameters for structural layout optimization and thermal protection design in high-acceleration, heavy-load rocket sled test systems.
To investigate the complex wake flow characteristics of multi-motor parallel rocket sleds, this study focuses on the mechanisms by which the nozzle horizontal spacing and the impingement height influence the flow structure and ground effect. A three-dimensional physical model was constructed for a dual-rail rocket sled system featuring three nozzles arranged in a triangular pyramid configuration. Four operating conditions were established, including large spacing (l = 7d), small spacing (l = 1d), low impingement height (h = 2d), and high impingement height (h=5.5d). The effects of nozzle center distance and impingement height on the flow field structure and ground effect were comparatively analyzed. Numerical simulations were performed using a computational fluid dynamics (CFD) method based on the Reynolds-Averaged Navier-Stokes equations, coupled with the Realizable k-ε turbulence model for transient solutions. The combustion chamber pressure-time curve derived from interior ballistic theory was applied to the nozzle inlet via a user-defined function (UDF). The sled velocity-time curve, determined from the exterior ballistic particle trajectory equation, was assigned as the far-field pressure boundary condition, enabling a coupled simulation framework of interior ballistics, exterior ballistics and flow field. The computational domain utilized a structured grid with refinement in the jet interaction region and near the ground to ensure calculation accuracy. The velocity and pressure fields obtained from numerical simulations were compared and validated against jet morphology, impingement height, and vortex core positions recorded by high-speed photography (
, Available online , doi: 10.11883/bzycj-2025-0401
Abstract:
Coupling coefficients and stemming coefficients are essential for predicting ground shock magnitude and damage zones from underground explosions, yet their variation with burial depth and dependence on media and explosion types remain insufficiently compared. Experimental and theoretical methods for determining these coefficients in concrete, rock, and soil under both chemical and nuclear explosions were systematically reviewed. Based on collected data from published tests, definitions of different coupling coefficients (energy coupling, ground shock parameter coupling, equivalent yield, and stemming coefficients) were clarified, and conversion relationships among them were derived using energy conservation and wave attenuation principles. The critical burial depth for full coupling was analyzed separately for peak quantities (e.g., peak stress, particle velocity) and integral quantities (e.g., impulse, surface vibration). Experimental results show that peak quantities reach full coupling at a depth approximately equal to the contained explosion cavity radius, which is much shallower than the critical depth for contained explosions. In contrast, impulse and ground motion require depths close to the contained explosion threshold. The coupling energy is proportional to the volume of the damaged zone, and the evolution of coupling coefficients with scaled depth of burial follows a Boltzmann function, requiring only two parameters to define the entire curve. For chemical explosions, the fully coupled equivalent yield coefficient (relative to contained explosions) in concrete, limestone, and soils was quantified, with stemming coefficients ranging from 1.4~1.8 in rocks and 2.4~2.6 in soils. It is concluded that different ground shock parameters exhibit distinct coupling behaviors, challenging the assumption of a universal coupling coefficient. Proposed empirical formulas provide conservative estimates for engineering design, while the underlying mechanisms of free-surface unloading require further quantitative investigation.
Coupling coefficients and stemming coefficients are essential for predicting ground shock magnitude and damage zones from underground explosions, yet their variation with burial depth and dependence on media and explosion types remain insufficiently compared. Experimental and theoretical methods for determining these coefficients in concrete, rock, and soil under both chemical and nuclear explosions were systematically reviewed. Based on collected data from published tests, definitions of different coupling coefficients (energy coupling, ground shock parameter coupling, equivalent yield, and stemming coefficients) were clarified, and conversion relationships among them were derived using energy conservation and wave attenuation principles. The critical burial depth for full coupling was analyzed separately for peak quantities (e.g., peak stress, particle velocity) and integral quantities (e.g., impulse, surface vibration). Experimental results show that peak quantities reach full coupling at a depth approximately equal to the contained explosion cavity radius, which is much shallower than the critical depth for contained explosions. In contrast, impulse and ground motion require depths close to the contained explosion threshold. The coupling energy is proportional to the volume of the damaged zone, and the evolution of coupling coefficients with scaled depth of burial follows a Boltzmann function, requiring only two parameters to define the entire curve. For chemical explosions, the fully coupled equivalent yield coefficient (relative to contained explosions) in concrete, limestone, and soils was quantified, with stemming coefficients ranging from 1.4~1.8 in rocks and 2.4~2.6 in soils. It is concluded that different ground shock parameters exhibit distinct coupling behaviors, challenging the assumption of a universal coupling coefficient. Proposed empirical formulas provide conservative estimates for engineering design, while the underlying mechanisms of free-surface unloading require further quantitative investigation.
, Available online , doi: 10.11883/bzycj-2025-0140
Abstract:
Hydrogen energy, as a zero-carbon energy source, holds broad application prospects in critical defense systems because of its high energy density and zero carbon emissions. To enhance energy utilization efficiency and ensure operational safety, an integrated approach combining experimental and numerical simulations was adopted to systematically examine the effects of hydrogen concentration on explosion dynamics in a confined space. Experiments were carried out in a cylindrical chamber equipped with high-frequency pressure sensors and a high-speed camera to record transient overpressure and track flame propagation behavior. Complementing the experimental setup, computational fluid dynamics (CFD) simulations were implemented using a detailed 19-step hydrogen/air chemical reaction mechanism to accurately reproduce the spatiotemporal evolution of flow field velocity during the premixed gas explosion process. Results indicate that the maximum explosion pressure occurred at a hydrogen volume fraction of 30%, peaking at 0.623 94 MPa. The peak flame area was largest at both 30% and 45%, exceeding results at 15% and 60% by 14.6% and 6.3%, respectively. The 30 % condition also achieved the peak flame area in the shortest time, at 8.2 ms. Furthermore, geometric constraints at the junction of the cylindrical sidewall and the endwall led to accumulation of unburned hydrogen, causing localized increases in density and pressure and resulting in four clearly discernible high-velocity regions within the flow field. At 9 ms, the flow velocity profile along the centerline exhibited symmetry with a dual-peak structure appearing unilaterally. While the 45% condition showed an early transient velocity advantage due to intensified local heat release, the 30% condition demonstrated superior late-stage velocity recovery owing to more stable and sustained combustion near the stoichiometric ratio. These findings underscore the high combustion efficiency and stability achievable near stoichiometric conditions, providing a scientific foundation for the design and optimization of high-efficiency hydrogen combustion systems..
Hydrogen energy, as a zero-carbon energy source, holds broad application prospects in critical defense systems because of its high energy density and zero carbon emissions. To enhance energy utilization efficiency and ensure operational safety, an integrated approach combining experimental and numerical simulations was adopted to systematically examine the effects of hydrogen concentration on explosion dynamics in a confined space. Experiments were carried out in a cylindrical chamber equipped with high-frequency pressure sensors and a high-speed camera to record transient overpressure and track flame propagation behavior. Complementing the experimental setup, computational fluid dynamics (CFD) simulations were implemented using a detailed 19-step hydrogen/air chemical reaction mechanism to accurately reproduce the spatiotemporal evolution of flow field velocity during the premixed gas explosion process. Results indicate that the maximum explosion pressure occurred at a hydrogen volume fraction of 30%, peaking at 0.623 94 MPa. The peak flame area was largest at both 30% and 45%, exceeding results at 15% and 60% by 14.6% and 6.3%, respectively. The 30 % condition also achieved the peak flame area in the shortest time, at 8.2 ms. Furthermore, geometric constraints at the junction of the cylindrical sidewall and the endwall led to accumulation of unburned hydrogen, causing localized increases in density and pressure and resulting in four clearly discernible high-velocity regions within the flow field. At 9 ms, the flow velocity profile along the centerline exhibited symmetry with a dual-peak structure appearing unilaterally. While the 45% condition showed an early transient velocity advantage due to intensified local heat release, the 30% condition demonstrated superior late-stage velocity recovery owing to more stable and sustained combustion near the stoichiometric ratio. These findings underscore the high combustion efficiency and stability achievable near stoichiometric conditions, providing a scientific foundation for the design and optimization of high-efficiency hydrogen combustion systems..
