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2025,
45(5):
051001.
doi: 10.11883/bzycj-2024-0250
Abstract:
In the process of deep penetration of the earth penetration weapon (EPW) attacking the underground target, the non-ideal penetration attitude with an initial attack angle is inevitable, which will introduce transverse overload with a large peak value for the earth penetrator. It 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 considered the influence of transverse overload, making it difficult to effectively reduce the transverse overload. In order to overcome this problem, a numerical simulation method was used to study the special transverse overload shedding effect and its mechanism of a new type of earth-penetrating projectile with a serrated configuration penetrating concrete targets at non-zero attack angles. The influences of the initial attack angle and the coefficient of the center of mass of the projectile were studied, and the motion, contact force, contact moment, and contact area of the projectile were analyzed using a conventional smooth projectile for 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%, respectively, 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 compete and control the reduction effects of the transverse overload of the whole projectile in the process of deep penetration with an initial attack angle. When optimizations of structural design are used to suppress the ballistic deflection of the serrated projectile, the transverse overload shedding efficiency of serrated projectiles 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 an initial attack angle is inevitable, which will introduce transverse overload with a large peak value for the earth penetrator. It 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 considered the influence of transverse overload, making it difficult to effectively reduce the transverse overload. In order to overcome this problem, a numerical simulation method was used to study the special transverse overload shedding effect and its mechanism of a new type of earth-penetrating projectile with a serrated configuration penetrating concrete targets at non-zero attack angles. The influences of the initial attack angle and the coefficient of the center of mass of the projectile were studied, and the motion, contact force, contact moment, and contact area of the projectile were analyzed using a conventional smooth projectile for 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%, respectively, 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 compete and control the reduction effects of the transverse overload of the whole projectile in the process of deep penetration with an initial attack angle. When optimizations of structural design are used to suppress the ballistic deflection of the serrated projectile, the transverse overload shedding efficiency of serrated projectiles can be effectively improved.
2025,
45(5):
051101.
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.
2025,
45(5):
052301.
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, with large-scale explosive dispersal experiments being relatively scarce. The initiation state of the aerosol cloud determines the blast power, and the device structure and specific explosive charge are the main factors affecting the cloud morphology. 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. Three types of canisters were utilized, namely the basic canister, the compound canister, and the strengthen canister, with the primary difference being their radial restraint mechanisms. The specific central explosive 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 central explosive of 0.8% has the best aerosol performance for 125 kg fuel. On this basis, characteristics of the aerosol were further analyzed. The optimal secondary detonation delay time is 240 ms. The calculating aerosol 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, with large-scale explosive dispersal experiments being relatively scarce. The initiation state of the aerosol cloud determines the blast power, and the device structure and specific explosive charge are the main factors affecting the cloud morphology. 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. Three types of canisters were utilized, namely the basic canister, the compound canister, and the strengthen canister, with the primary difference being their radial restraint mechanisms. The specific central explosive 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 central explosive of 0.8% has the best aerosol performance for 125 kg fuel. On this basis, characteristics of the aerosol were further analyzed. The optimal secondary detonation delay time is 240 ms. The calculating aerosol concentration before burst is 64 g/m3 and the chemical equivalent ratio of fuel to oxygen in the air is 0.54.
2025,
45(5):
053101.
doi: 10.11883/bzycj-2024-0272
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 using a self-built high-speed infrared temperature measurement system. The time resolution of the high-speed infrared temperature measurement system is in the order of microsecond. The concrete temperature curve was fitted by static calibration test as a reference. 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 and substantial influences of the steel fiber content on both dynamic performance and temperature. Specifically, as the steel fiber content increases, the compressive strength of the concrete improves, reaching optimal mechanical performance at 1.5% steel fiber content. However, at 2.0% 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 the 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 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 using a self-built high-speed infrared temperature measurement system. The time resolution of the high-speed infrared temperature measurement system is in the order of microsecond. The concrete temperature curve was fitted by static calibration test as a reference. 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 and substantial influences of the steel fiber content on both dynamic performance and temperature. Specifically, as the steel fiber content increases, the compressive strength of the concrete improves, reaching optimal mechanical performance at 1.5% steel fiber content. However, at 2.0% 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 the 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 the evaluation of crack propagation behavior.
2025,
45(5):
053201.
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.
2025,
45(5):
053202.
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, dissipated energy and reflection energy remain consistent, which are characterized by transmission energy, dissipated 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, dissipated energy and reflection energy remain consistent, which are characterized by transmission energy, dissipated 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.
2025,
45(5):
053301.
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.
2025,
45(5):
053302.
doi: 10.11883/bzycj-2024-0177
Abstract:
High-strength steel has excellent mechanical properties, which has been utilized in the fields of explosion and impact. In order to study the blast resistance of high-strength steel plates, ANSYS/LS-DYNA software was first used to simulate the impact test on high-strength steel materials. By comparing with experimental results, the Johnson-Cook model parameters characterizing the dynamic constitutive behavior of high-strength steel are determined. Based on the above model parameters, the explosion simulation of high-strength steel plates under near-field explosions is further carried out. The interaction process between the explosion shock wave and the steel plate is systematically analyzed, and the size effects of the steel plate on its deformation characteristics and failure mode are explained. The results show that the Johnson-Cook model can effectively simulate the mechanical behavior of S690 high-strength steel at high strain rates. High-strength steel plates have a weakening effect on the propagation of shock waves. With the increase of steel plate thickness, the propagation range of shock wave through steel plate decreases gradually. For high-strength steel plates of different geometric dimensions, near-field explosions will cause three damage modes: petal-shaped fracture, small fracture and large deformation. It is found that the thickness is the decisive factor to determine the failure mode of steel plates under near-field explosions. For high-strength steel plates with large deformation, the increase of thickness and decrease of width will improve the ability of resistance to near-field explosions. In addition, there is a positive correlation between the ability of shock resistance of the high-strength steel plate and the width-thickness ratio. When the proportional distance is 0.13, a model can be provided to predict the maximum displacement range of the high-strength steel plate according to the steel plate size. The above conclusions can provide some guiding significance for the optimal design and engineering application of high-strength steel structures.
High-strength steel has excellent mechanical properties, which has been utilized in the fields of explosion and impact. In order to study the blast resistance of high-strength steel plates, ANSYS/LS-DYNA software was first used to simulate the impact test on high-strength steel materials. By comparing with experimental results, the Johnson-Cook model parameters characterizing the dynamic constitutive behavior of high-strength steel are determined. Based on the above model parameters, the explosion simulation of high-strength steel plates under near-field explosions is further carried out. The interaction process between the explosion shock wave and the steel plate is systematically analyzed, and the size effects of the steel plate on its deformation characteristics and failure mode are explained. The results show that the Johnson-Cook model can effectively simulate the mechanical behavior of S690 high-strength steel at high strain rates. High-strength steel plates have a weakening effect on the propagation of shock waves. With the increase of steel plate thickness, the propagation range of shock wave through steel plate decreases gradually. For high-strength steel plates of different geometric dimensions, near-field explosions will cause three damage modes: petal-shaped fracture, small fracture and large deformation. It is found that the thickness is the decisive factor to determine the failure mode of steel plates under near-field explosions. For high-strength steel plates with large deformation, the increase of thickness and decrease of width will improve the ability of resistance to near-field explosions. In addition, there is a positive correlation between the ability of shock resistance of the high-strength steel plate and the width-thickness ratio. When the proportional distance is 0.13, a model can be provided to predict the maximum displacement range of the high-strength steel plate according to the steel plate size. The above conclusions can provide some guiding significance for the optimal design and engineering application of high-strength steel structures.
2025,
45(5):
053401.
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. In conditions of lower crushed ice densities, jets point to the interior of the cavity when the cavity collapses. 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. 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 with those in 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. In conditions of lower crushed ice densities, jets point to the interior of the cavity when the cavity collapses. 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. 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 with those in ice-free environments.
2025,
45(5):
054101.
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 polyvinylidene difluoride (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 polyvinylidene difluoride (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.
2025,
45(5):
055201.
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.
2025,
45(5):
055202.
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 based on ANSYS/LS-DYNA and is also tested with the data before. Then, the model is combined 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 based on ANSYS/LS-DYNA and is also tested with the data before. Then, the model is combined 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.
2025,
45(5):
055401.
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.
