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, Available online ,
doi: 10.11883/bzycj-2024-0192
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Lattice columns are often used as the main load-bearing components in engineering structures, and are inevitably impacted by other unintentional loads under engineering service environments, and the evaluation of the protective performance and optimization of the design of the building structure under impact loading is a key issue of concern in the fields of national defense, civil engineering, and other military and civilian use. In this paper, 1:2 scaled-down secondary impact experiments were carried out on lattice columns along different impact directions with the same impact energy each time, and compared with single-impact lattice columns under the same total energy, to analyze the force and deformation characteristics of the lattice columns under the impact loads. Subsequently, based on the experimentally verified finite element model, a continuous secondary impact simulation was carried out on the foot-foot lattice column, and the results of the dynamic response of the lattice column subjected to two consecutive impacts with the same total energy were obtained, and the effects of different energy distribution on the impact force, residual displacement and residual kinetic energy were analyzed. The results show that under the same total energy, the displacement of lattice columns under a single impact is larger than that of a secondary impact. The optimal energy distribution obtained by numerical simulation can reduce the residual displacement of members impacted along different directions by about 12%; when the lattice column is subjected to a larger proportion of energy for the first time or a smaller proportion of impact energy for the second time, the total energy absorbed by the column is smaller. The results of the study can provide a reference for the design method of lattice steel columns under such loading conditions.
Lattice columns are often used as the main load-bearing components in engineering structures, and are inevitably impacted by other unintentional loads under engineering service environments, and the evaluation of the protective performance and optimization of the design of the building structure under impact loading is a key issue of concern in the fields of national defense, civil engineering, and other military and civilian use. In this paper, 1:2 scaled-down secondary impact experiments were carried out on lattice columns along different impact directions with the same impact energy each time, and compared with single-impact lattice columns under the same total energy, to analyze the force and deformation characteristics of the lattice columns under the impact loads. Subsequently, based on the experimentally verified finite element model, a continuous secondary impact simulation was carried out on the foot-foot lattice column, and the results of the dynamic response of the lattice column subjected to two consecutive impacts with the same total energy were obtained, and the effects of different energy distribution on the impact force, residual displacement and residual kinetic energy were analyzed. The results show that under the same total energy, the displacement of lattice columns under a single impact is larger than that of a secondary impact. The optimal energy distribution obtained by numerical simulation can reduce the residual displacement of members impacted along different directions by about 12%; when the lattice column is subjected to a larger proportion of energy for the first time or a smaller proportion of impact energy for the second time, the total energy absorbed by the column is smaller. The results of the study can provide a reference for the design method of lattice steel columns under such loading conditions.
, Available online ,
doi: 10.11883/bzycj-2024-0252
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In order to explore the explosion reaction effect of zirconium-based reactive material casing and the ignition effect of fragments on fuel fuel driven by explosion, the reactive material casings containing Zr, Cu, Ni, Al and Y as the main elements was prepared by alloy melting and casting, and the outer diameter of the casing was 40mm, the height was 80mm, and the wall thickness was 5mm. In order to compare the aftereffect damage effect, the 45 steel casing of the same mass was prepared, and the internal charge of the two casings was JH-2 column. Through the explosion drive test and high-speed photography technology, the duration of the explosion fireball, the wave velocity of the shock wave, and the ignition of the impact of the fragments on the fuel box were studied. The results of the test showed that, compared with the steel shell of equal mass, the flame duration and shock wave speed of the Zr-based active material shell are longer and faster under the explosion drive, and the Zr-based active material shell has a strengthening effect on the air shock wave under the explosion drive. The fragments of the two materials were driven by the explosion to scatter and hit the oil tank, and both materials caused structural damage to the oil tank, and the 45 steel material did not ignite the internal fuel. The chemical energy released by the impact of the Zr-based active material on the fuel tank can ignite the fuel, and it has the performance of igniting the fuel.
In order to explore the explosion reaction effect of zirconium-based reactive material casing and the ignition effect of fragments on fuel fuel driven by explosion, the reactive material casings containing Zr, Cu, Ni, Al and Y as the main elements was prepared by alloy melting and casting, and the outer diameter of the casing was 40mm, the height was 80mm, and the wall thickness was 5mm. In order to compare the aftereffect damage effect, the 45 steel casing of the same mass was prepared, and the internal charge of the two casings was JH-2 column. Through the explosion drive test and high-speed photography technology, the duration of the explosion fireball, the wave velocity of the shock wave, and the ignition of the impact of the fragments on the fuel box were studied. The results of the test showed that, compared with the steel shell of equal mass, the flame duration and shock wave speed of the Zr-based active material shell are longer and faster under the explosion drive, and the Zr-based active material shell has a strengthening effect on the air shock wave under the explosion drive. The fragments of the two materials were driven by the explosion to scatter and hit the oil tank, and both materials caused structural damage to the oil tank, and the 45 steel material did not ignite the internal fuel. The chemical energy released by the impact of the Zr-based active material on the fuel tank can ignite the fuel, and it has the performance of igniting the fuel.
, Available online ,
doi: 10.11883/bzycj-2024-0278
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In order to study the damage mechanism of Zr-based amorphous alloy fragments penetrating CFRP and the destructive ability of the target material, a ballistic gun test was carried out to examine the ballistic performance of spherical Zr-based amorphous alloy. The area of the post-effect target of LY12 was analyzed using image recognition technology, with the aim of determining the extent of damage caused by the penetration of Zr-based amorphous alloy fragments through the laminated target and interstitial target, which was composed of 6mm-thick CFRP and 2mm-thick LY12. The results demonstrate that the damage area of the CFRP target is proportional to the fragmentation speed. There is no discernible reaction on the remaining portion of the target, with damage observed on the facing side, characterized by fiber shear and compression deformation, and on the backside, exhibiting tensile tearing and inter laminar failure. As the speed increases, the proportion of shear damage to the CFRP gradually increases. When a fragment impacts a target plate of the same setup, the damaged area of the LY12 target increases with the speed. When the speed is below 954.7 m·s-1, the damaged area of the interstitial target post-effect LY12 target is smaller than that of the laminated target post-effect LY12 target. With the increase of speed, the damaged area of the interstitial target post-effect LY12 target improves rapidly, while the damaged area of the laminated target post-effect LY12 target increases rapidly. The growth of the damaged area of the interstitial target post-effect LY12 target tends to slow down, and the former is much larger than the latter. Therefore, it is more favorable to set up interstitial targets for post-effect damage in high-speed impacts.
In order to study the damage mechanism of Zr-based amorphous alloy fragments penetrating CFRP and the destructive ability of the target material, a ballistic gun test was carried out to examine the ballistic performance of spherical Zr-based amorphous alloy. The area of the post-effect target of LY12 was analyzed using image recognition technology, with the aim of determining the extent of damage caused by the penetration of Zr-based amorphous alloy fragments through the laminated target and interstitial target, which was composed of 6mm-thick CFRP and 2mm-thick LY12. The results demonstrate that the damage area of the CFRP target is proportional to the fragmentation speed. There is no discernible reaction on the remaining portion of the target, with damage observed on the facing side, characterized by fiber shear and compression deformation, and on the backside, exhibiting tensile tearing and inter laminar failure. As the speed increases, the proportion of shear damage to the CFRP gradually increases. When a fragment impacts a target plate of the same setup, the damaged area of the LY12 target increases with the speed. When the speed is below 954.7 m·s-1, the damaged area of the interstitial target post-effect LY12 target is smaller than that of the laminated target post-effect LY12 target. With the increase of speed, the damaged area of the interstitial target post-effect LY12 target improves rapidly, while the damaged area of the laminated target post-effect LY12 target increases rapidly. The growth of the damaged area of the interstitial target post-effect LY12 target tends to slow down, and the former is much larger than the latter. Therefore, it is more favorable to set up interstitial targets for post-effect damage in high-speed impacts.
, Available online ,
doi: 10.11883/bzycj-2024-0244
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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, based on the scenario of NSC target against 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, and the superimposed effect of the penetration and explosion stress field, as well as 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 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 1.33m, 2.70m, 2.35m and 0.79m, 1.76m, 1.70m, 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 integrated penetration and moving charge explosion finite element analysis method 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, based on the scenario of NSC target against 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, and the superimposed effect of the penetration and explosion stress field, as well as 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 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 1.33m, 2.70m, 2.35m and 0.79m, 1.76m, 1.70m, 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 integrated penetration and moving charge explosion finite element analysis method are about 5%-30% higher than those calculated by the traditional penetration and static charge explosion method.
, Available online ,
doi: 10.11883/bzycj-2024-0280
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Aiming to investigate the performance and design approach of the carbon fiber reinforced polymer (CFRP) sheet strengthened masonry infilled walls subjected to blast loads, the commercial finite element program LS-DYNA is firstly used to develop the simplified micro-finite element model of masonry infilled walls and the corresponding blast-resistant analysis model of CFRP sheet strengthened walls. By comparing with the nine groups field explosion test results of unstrengthening and CFRP sheet strengthened masonry infilled walls, the applicability of the present simplified micro-modeling approach, as well as the material models and parameters of masonry and CFRP sheet, is verified. Furthermore, referring to the CFRP seismic strengthening methods recommended by Chinese standard GB 50608-2020, the dynamic behaviors of the prototype masonry infilled walls strengthened with CFRP sheets under blast loads are analyzed and compared. It is recommended to prioritize the diagonal two-way strengthening method, followed by vertical two-way and horizontal full-cover strengthening methods, and vertical full-cover and mixed three-way strengthening methods are not recommended. Finally, to simultaneously satisfy the CFRP is basically intact, no scattering debris and the peak central deflection less than wall thickness as the blast-resistant design goal, the ranges of scaled distance of prototype masonry infilled walls with different arrangements of tie bar (non-/cut-off/full-length tie bar) that need to be strengthened under typical sedan (227 kg equivalent TNT) and briefcase bombs (23 kg equivalent TNT) explode at different scaled distances are determined as 0.8-2 m/kg1/3 and 0.2-1.2 m/kg1/3, respectively. The suggestions for the optimal number of CFRP sheet layers for blast-resistant design are further given.
Aiming to investigate the performance and design approach of the carbon fiber reinforced polymer (CFRP) sheet strengthened masonry infilled walls subjected to blast loads, the commercial finite element program LS-DYNA is firstly used to develop the simplified micro-finite element model of masonry infilled walls and the corresponding blast-resistant analysis model of CFRP sheet strengthened walls. By comparing with the nine groups field explosion test results of unstrengthening and CFRP sheet strengthened masonry infilled walls, the applicability of the present simplified micro-modeling approach, as well as the material models and parameters of masonry and CFRP sheet, is verified. Furthermore, referring to the CFRP seismic strengthening methods recommended by Chinese standard GB 50608-2020, the dynamic behaviors of the prototype masonry infilled walls strengthened with CFRP sheets under blast loads are analyzed and compared. It is recommended to prioritize the diagonal two-way strengthening method, followed by vertical two-way and horizontal full-cover strengthening methods, and vertical full-cover and mixed three-way strengthening methods are not recommended. Finally, to simultaneously satisfy the CFRP is basically intact, no scattering debris and the peak central deflection less than wall thickness as the blast-resistant design goal, the ranges of scaled distance of prototype masonry infilled walls with different arrangements of tie bar (non-/cut-off/full-length tie bar) that need to be strengthened under typical sedan (227 kg equivalent TNT) and briefcase bombs (23 kg equivalent TNT) explode at different scaled distances are determined as 0.8-2 m/kg1/3 and 0.2-1.2 m/kg1/3, respectively. The suggestions for the optimal number of CFRP sheet layers for blast-resistant design are further given.
, Available online ,
doi: 10.11883/bzycj-2024-0214
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, Available online ,
doi: 10.11883/bzycj-2024-0335
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The influence mechanism the crack on the dynamic mechanical property of the rockmass is always an important and difficult problem in the field of rock mechanics. However, the establishment of the dynamic damage model for the fractured rockmass is the key to solve this problem, which has attracted much attention. At present, most of the dynamic damage models for the fractured rockmass are aimed at the flat cracks, which cannot take into account the influence of the crack roughness. To address this shortcoming, on basis of the calculation model for the rockmass macroscopic damage variable which can take into account the crack geometry parameter, strength parameter and deformation parameter, a calculation model for the rockmass macroscopic damage variable is proposed by introducing the JRC-JCS shear strength model for the rough crack established by Barton, which can consider the crack roughness. Secondly, the proposed calculation model is introduced into the uniaxial compressive dynamic damage model for the rock mass with the non-persistent crack, which both considers the coupling of the macroscopic and microscopic defects, and then a uniaxial compressive dynamic damage model for the rock mass with the non-persistent crack is established which can consider the crack roughness at the same time. Finally, the effect of crack roughness JRC and crack basic friction angle φb and crack length 2a on rockmass dynamic mechanical property is studied with the parametric sensitivity analysis. Taking the rockmass dynamic climax strength as an example, the calculation example shows that the rockmass dynamic climax strength increases from 26.42MPa to 27.28MPa and 28.37MPa with JRC increasing from 0 to 10 and 20 respectively. The rockmass dynamic climax strength increases from 26.42MPa to 27.28MPa and 28.80MPa with φb increasing from 0º to 15º and 30º respectively. The rockmass dynamic climax strength decreases from 31.37MPa to 27.28MPa and 23.90MPa with 2a increasing from 1cm to 2cm and 3cm respectively. At the same time, in order to describe the influence of the crack roughness more accurately, the crack fractal dimension is introduced into the dynamic damage model for the rock mass, which not only improves the calculation accuracy of the model, but also broadens its application range, which is more convenient for practical engineering application.
The influence mechanism the crack on the dynamic mechanical property of the rockmass is always an important and difficult problem in the field of rock mechanics. However, the establishment of the dynamic damage model for the fractured rockmass is the key to solve this problem, which has attracted much attention. At present, most of the dynamic damage models for the fractured rockmass are aimed at the flat cracks, which cannot take into account the influence of the crack roughness. To address this shortcoming, on basis of the calculation model for the rockmass macroscopic damage variable which can take into account the crack geometry parameter, strength parameter and deformation parameter, a calculation model for the rockmass macroscopic damage variable is proposed by introducing the JRC-JCS shear strength model for the rough crack established by Barton, which can consider the crack roughness. Secondly, the proposed calculation model is introduced into the uniaxial compressive dynamic damage model for the rock mass with the non-persistent crack, which both considers the coupling of the macroscopic and microscopic defects, and then a uniaxial compressive dynamic damage model for the rock mass with the non-persistent crack is established which can consider the crack roughness at the same time. Finally, the effect of crack roughness JRC and crack basic friction angle φb and crack length 2a on rockmass dynamic mechanical property is studied with the parametric sensitivity analysis. Taking the rockmass dynamic climax strength as an example, the calculation example shows that the rockmass dynamic climax strength increases from 26.42MPa to 27.28MPa and 28.37MPa with JRC increasing from 0 to 10 and 20 respectively. The rockmass dynamic climax strength increases from 26.42MPa to 27.28MPa and 28.80MPa with φb increasing from 0º to 15º and 30º respectively. The rockmass dynamic climax strength decreases from 31.37MPa to 27.28MPa and 23.90MPa with 2a increasing from 1cm to 2cm and 3cm respectively. At the same time, in order to describe the influence of the crack roughness more accurately, the crack fractal dimension is introduced into the dynamic damage model for the rock mass, which not only improves the calculation accuracy of the model, but also broadens its application range, which is more convenient for practical engineering application.
, Available online ,
doi: 10.11883/bzycj-2024-0307
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Biological soft materials, often with high water content and ultra-softness, display mechanical properties that non-linearly enhance over a broad range of strain rates. However, existing experimental constraints make it challenging to perform large deformation tests on these materials at intermediate strain rates. This study introduces a 15-meter-long Long Split Hopkinson Pressure Bar (LSHPB) system, driven by a dual-bullet electromagnetic mechanism, designed for large deformation intermediate strain rate testing of ultra-soft materials. Comparative tests conducted using both the LSHPB and a high-speed SHPB system validated the reliability of the newly developed system. The LSHPB system was then applied to measure the dynamic mechanical performance of polyvinyl alcohol (PVA) hydrogel at intermediate strain rates. The results, combined with existing data from low and high strain rate analyses, underscore the necessity for intermediate strain rate dynamic performance testing. This work not only broadens our understanding of the mechanical behavior of ultra-soft materials like PVA hydrogel across various strain rates but also introduces an innovative experimental technique for studying materials under intermediate strain conditions, thereby advancing the field of soft material dynamics.
Biological soft materials, often with high water content and ultra-softness, display mechanical properties that non-linearly enhance over a broad range of strain rates. However, existing experimental constraints make it challenging to perform large deformation tests on these materials at intermediate strain rates. This study introduces a 15-meter-long Long Split Hopkinson Pressure Bar (LSHPB) system, driven by a dual-bullet electromagnetic mechanism, designed for large deformation intermediate strain rate testing of ultra-soft materials. Comparative tests conducted using both the LSHPB and a high-speed SHPB system validated the reliability of the newly developed system. The LSHPB system was then applied to measure the dynamic mechanical performance of polyvinyl alcohol (PVA) hydrogel at intermediate strain rates. The results, combined with existing data from low and high strain rate analyses, underscore the necessity for intermediate strain rate dynamic performance testing. This work not only broadens our understanding of the mechanical behavior of ultra-soft materials like PVA hydrogel across various strain rates but also introduces an innovative experimental technique for studying materials under intermediate strain conditions, thereby advancing the field of soft material dynamics.
, Available online ,
doi: 10.11883/bzycj-2024-0336
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The dynamic constitutive model of rocks plays an important role in understanding the mechanical behavior of rocks under dynamic loads and solving rock dynamics problems. A dynamic constitutive model of rock with elastoplastic damage coupling based on continuum damage mechanics was established. This model uses the unified strength theory as the yield criterion and introduces a dynamic ratio of tension to compression to fully reflect the strain rate effect. The compressive damage variable is expressed with effective plastic strain and volumetric plastic strain, and the tensile damage variable with effective plastic strain to reflect the different damage evolution laws of rocks under tensile and compressive conditions. Using piecewise functions to characterize different plastic hardening behaviors of rocks under tensile and compressive conditions. The established constitutive model is numerically implemented of based on Fortran language and LS-DYNA user material customization interface (Umat). The established constitutive model is validated through three classic examples, namely, uniaxial and triaxial compression tests, uniaxial tensile tests, and ballistic tests on rocks. The results indicate that the constitutive model can comprehensively characterize the dynamic and static mechanical behavior of rocks.
The dynamic constitutive model of rocks plays an important role in understanding the mechanical behavior of rocks under dynamic loads and solving rock dynamics problems. A dynamic constitutive model of rock with elastoplastic damage coupling based on continuum damage mechanics was established. This model uses the unified strength theory as the yield criterion and introduces a dynamic ratio of tension to compression to fully reflect the strain rate effect. The compressive damage variable is expressed with effective plastic strain and volumetric plastic strain, and the tensile damage variable with effective plastic strain to reflect the different damage evolution laws of rocks under tensile and compressive conditions. Using piecewise functions to characterize different plastic hardening behaviors of rocks under tensile and compressive conditions. The established constitutive model is numerically implemented of based on Fortran language and LS-DYNA user material customization interface (Umat). The established constitutive model is validated through three classic examples, namely, uniaxial and triaxial compression tests, uniaxial tensile tests, and ballistic tests on rocks. The results indicate that the constitutive model can comprehensively characterize the dynamic and static mechanical behavior of rocks.
, Available online ,
doi: 10.11883/bzycj-2024-0309
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Abstract: This study investigates the dynamic response characteristics of silica sand under dynamic loading using the modified Split Hopkinson pressure bar (SHPB) to understand its crushing characteristics and energy-absorbing effects. Four different grain groups were examined, and the results demonstrate that the dynamic stress-strain behavior of the sand is influenced by grain size and strain rate. The deformation process of the sand can be categorized into three stages: elastic, yielding, and plastic. Plastic compaction dominates during the yielding stage, while crushing compaction is significant in the plastic stage. The relative crushing index of particles shows a direct relationship with both strain rate and effective particle size, while it is inversely related to the fractal dimension. The impact of particle size on energy absorption efficiency varies based on particle characteristics such as mineral composition, particle size, and degree of differentiation. At the same stress level, larger particle sizes exhibit higher energy absorption efficiency, and under the same loading strain rate conditions, larger particles experience lower peak stress. To enhance the energy absorption efficiency of sand and decrease the required loading level, it is advisable to utilize sand with larger particle sizes.
Abstract: This study investigates the dynamic response characteristics of silica sand under dynamic loading using the modified Split Hopkinson pressure bar (SHPB) to understand its crushing characteristics and energy-absorbing effects. Four different grain groups were examined, and the results demonstrate that the dynamic stress-strain behavior of the sand is influenced by grain size and strain rate. The deformation process of the sand can be categorized into three stages: elastic, yielding, and plastic. Plastic compaction dominates during the yielding stage, while crushing compaction is significant in the plastic stage. The relative crushing index of particles shows a direct relationship with both strain rate and effective particle size, while it is inversely related to the fractal dimension. The impact of particle size on energy absorption efficiency varies based on particle characteristics such as mineral composition, particle size, and degree of differentiation. At the same stress level, larger particle sizes exhibit higher energy absorption efficiency, and under the same loading strain rate conditions, larger particles experience lower peak stress. To enhance the energy absorption efficiency of sand and decrease the required loading level, it is advisable to utilize sand with larger particle sizes.
, Available online ,
doi: 10.11883/bzycj-2024-0294
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Cylindrical casing filled with charge under central point detonation at one end is the frequently-used structure for fragment weapons, whose fragment initial velocity produced by its fracture serves as an important parameter for evaluating the lethal power and the protective structures. To accurately predict the initial velocity distribution of cylindrical casing with different length-diameter ratios (L/D), it studied the impact of L/D ratios on the initial velocity of fragments and the applicability of existing empirical models for the initial velocity of fragments founded on the numerical model of experimental verification. On this basis, a correction term related to L/D ratio, which was often influenced by the axial rarefaction waves, was added to the fragment initial velocity index model. By fitting the data obtained from numerical simulations, the function expression of the correction term was derived and the calculation model for the initial velocity distribution of cylindrical casing with L/D ratio≥1 was obtained. Finally, the applicability of the established fragment initial velocity calculation model was validated through experimental data and numerical simulations. The research results indicate that the initial velocity distribution of fragments under different L/D ratios exhibits a trend where the initial velocities are lower at both ends and higher in the middle. Additionally, as the L/D ratio raises, the initial velocity of the fragment also increases. When the L/D ratio reaches 5, the relative error between the maximum initial velocity of the fragments and the calculated result using the Gurney formula is only 1.99%. However, the existing models for calculating initial velocities of fragment display significant errors when predicting smaller L/D ratios in cylindrical casing. The average error between the formula calculation results and the experimental and numerical simulation results does not exceed 6%, indicating that the proposed model is reliable for predicting the initial velocity distribution of fragments under different L/D ratios. The research work provides valuable insights for assessing the lethal power of fragment weapons and the structural design of protective devices in anti-terrorism projects.
Cylindrical casing filled with charge under central point detonation at one end is the frequently-used structure for fragment weapons, whose fragment initial velocity produced by its fracture serves as an important parameter for evaluating the lethal power and the protective structures. To accurately predict the initial velocity distribution of cylindrical casing with different length-diameter ratios (L/D), it studied the impact of L/D ratios on the initial velocity of fragments and the applicability of existing empirical models for the initial velocity of fragments founded on the numerical model of experimental verification. On this basis, a correction term related to L/D ratio, which was often influenced by the axial rarefaction waves, was added to the fragment initial velocity index model. By fitting the data obtained from numerical simulations, the function expression of the correction term was derived and the calculation model for the initial velocity distribution of cylindrical casing with L/D ratio≥1 was obtained. Finally, the applicability of the established fragment initial velocity calculation model was validated through experimental data and numerical simulations. The research results indicate that the initial velocity distribution of fragments under different L/D ratios exhibits a trend where the initial velocities are lower at both ends and higher in the middle. Additionally, as the L/D ratio raises, the initial velocity of the fragment also increases. When the L/D ratio reaches 5, the relative error between the maximum initial velocity of the fragments and the calculated result using the Gurney formula is only 1.99%. However, the existing models for calculating initial velocities of fragment display significant errors when predicting smaller L/D ratios in cylindrical casing. The average error between the formula calculation results and the experimental and numerical simulation results does not exceed 6%, indicating that the proposed model is reliable for predicting the initial velocity distribution of fragments under different L/D ratios. The research work provides valuable insights for assessing the lethal power of fragment weapons and the structural design of protective devices in anti-terrorism projects.
, Available online ,
doi: 10.11883/bzycj-2024-0272
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Abstract:
In order to study the dynamic mechanical properties of concrete and the dynamic temperature at the crack under impact, steel-polypropylene fiber reinforced concrete ( SPFRC ) was taken as the research object, and a self-built high-speed infrared temperature measurement system was used. The response rate of the system reached the microsecond level, and the concrete temperature curve was fitted by static calibration test. Combined with the Hopkinson pressure bar test device, the dynamic properties of SPFRC specimens with different steel fiber contents and the dynamic temperature change at the crack were studied. The results indicate a significant coupling effect between the temperature evolution and mechanical properties of the concrete specimens, with the steel fiber content substantially influencing both dynamic performance and temperature. Specifically, as the steel fiber content increases, the compressive strength of the concrete improves, reaching optimal mechanical performance at a 1.5% steel fiber content. However, at a 2% steel fiber content, the mechanical performance slightly decreases due to an increase in internal voids within the concrete. During impact, the dynamic temperature effect at the crack location exhibits a "stepped" pattern, with temperature change occurring in two distinct stages: an initial slow rise during early crack formation, followed by a sharp increase as friction and shear effects intensify with crack propagation. The influence of varying steel fiber content on temperature change is limited, with peak temperature and peak stress showing similar trends. The primary temperature variations are driven by crack propagation and frictional effects. After impact, the overall temperature in SPFRC specimens continues to rise within the first 300 μs. Due to thermal lag, the temperature does not decrease immediately after unloading. The high-speed infrared temperature measurement system provides a new method for real-time monitoring of temperature changes at concrete crack locations, offering a basis for assessing temperature evolution at cracks and aiding in the evaluation of crack propagation behavior.
In order to study the dynamic mechanical properties of concrete and the dynamic temperature at the crack under impact, steel-polypropylene fiber reinforced concrete ( SPFRC ) was taken as the research object, and a self-built high-speed infrared temperature measurement system was used. The response rate of the system reached the microsecond level, and the concrete temperature curve was fitted by static calibration test. Combined with the Hopkinson pressure bar test device, the dynamic properties of SPFRC specimens with different steel fiber contents and the dynamic temperature change at the crack were studied. The results indicate a significant coupling effect between the temperature evolution and mechanical properties of the concrete specimens, with the steel fiber content substantially influencing both dynamic performance and temperature. Specifically, as the steel fiber content increases, the compressive strength of the concrete improves, reaching optimal mechanical performance at a 1.5% steel fiber content. However, at a 2% steel fiber content, the mechanical performance slightly decreases due to an increase in internal voids within the concrete. During impact, the dynamic temperature effect at the crack location exhibits a "stepped" pattern, with temperature change occurring in two distinct stages: an initial slow rise during early crack formation, followed by a sharp increase as friction and shear effects intensify with crack propagation. The influence of varying steel fiber content on temperature change is limited, with peak temperature and peak stress showing similar trends. The primary temperature variations are driven by crack propagation and frictional effects. After impact, the overall temperature in SPFRC specimens continues to rise within the first 300 μs. Due to thermal lag, the temperature does not decrease immediately after unloading. The high-speed infrared temperature measurement system provides a new method for real-time monitoring of temperature changes at concrete crack locations, offering a basis for assessing temperature evolution at cracks and aiding in the evaluation of crack propagation behavior.
, Available online ,
doi: 10.11883/bzycj-2024-0191
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Abstract:
For the estimation of blast loading on complex structures, traditional numerical simulation methods were computationally intensive, while rapid estimation methods based on neural networks could only provide point estimates without offering confidence intervals for the results. To achieve fast and reliable estimation of blast loading on complex structures during explosions, Bayesian theory was integrated with deep learning to develop a Bayesian deep learning approach for rapid estimation of blast loading on complex structures. The approach initially utilized open-source numerical simulation software to generate a dataset of blast loading on complex structures, encompassing a wide range of parameters such as explosion equivalents, locations, and velocities. During this process, mesh sizes that balanced computational accuracy and speed were determined through mesh sensitivity analysis and numerical simulation accuracy verification. On this foundation, the deep learning model was extended into a Bayesian deep learning model based on Bayesian theory. By introducing probability distributions over the weights of the neural network, the model parameters were treated as random variables. Variational Bayesian inference was then employed to efficiently train the model, ensuring the accuracy of rapid blast loading estimation while also equipping the model with the ability to quantify uncertainty. Finally, metrics such as Mean Absolute Percentage Error (MAPE), Normalized Mean Prediction Interval Width (NMPIW), and Prediction Interval Coverage Probability (PICP) were adopted to quantitatively assess the model's estimated accuracy and uncertainty quantification precision. Additionally, an error decomposition of the estimation results was conducted, analyzing model performance based on target parameters and scaled distance. The results indicate that the proposed method achieved an estimation error of approximately 12.2% on the test set, with a confidence interval covering over 81.6% of true values, and the estimation time for a single sample point did not exceed 20 milliseconds. This method enables fast and accurate estimation of blast loading on complex structures while providing confidence information for the estimation results, representing a novel approach for achieving rapid and reliable estimation of blast loading on complex structures.
For the estimation of blast loading on complex structures, traditional numerical simulation methods were computationally intensive, while rapid estimation methods based on neural networks could only provide point estimates without offering confidence intervals for the results. To achieve fast and reliable estimation of blast loading on complex structures during explosions, Bayesian theory was integrated with deep learning to develop a Bayesian deep learning approach for rapid estimation of blast loading on complex structures. The approach initially utilized open-source numerical simulation software to generate a dataset of blast loading on complex structures, encompassing a wide range of parameters such as explosion equivalents, locations, and velocities. During this process, mesh sizes that balanced computational accuracy and speed were determined through mesh sensitivity analysis and numerical simulation accuracy verification. On this foundation, the deep learning model was extended into a Bayesian deep learning model based on Bayesian theory. By introducing probability distributions over the weights of the neural network, the model parameters were treated as random variables. Variational Bayesian inference was then employed to efficiently train the model, ensuring the accuracy of rapid blast loading estimation while also equipping the model with the ability to quantify uncertainty. Finally, metrics such as Mean Absolute Percentage Error (MAPE), Normalized Mean Prediction Interval Width (NMPIW), and Prediction Interval Coverage Probability (PICP) were adopted to quantitatively assess the model's estimated accuracy and uncertainty quantification precision. Additionally, an error decomposition of the estimation results was conducted, analyzing model performance based on target parameters and scaled distance. The results indicate that the proposed method achieved an estimation error of approximately 12.2% on the test set, with a confidence interval covering over 81.6% of true values, and the estimation time for a single sample point did not exceed 20 milliseconds. This method enables fast and accurate estimation of blast loading on complex structures while providing confidence information for the estimation results, representing a novel approach for achieving rapid and reliable estimation of blast loading on complex structures.
, Available online ,
doi: 10.11883/bzycj-2024-0181
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Abstract:
To investigate the stress wave characteristics within concrete targets under ultra-high velocity impact conditions, a stress wave testing system based on PVDF piezoelectric stress gauges was established, and research on the calibration method for PVDF piezoelectric stress gauges was conducted. The stress waveforms within concrete targets impacted by kilogram-scale cylindrical 93W tungsten alloy projectiles at ultra-high velocity 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, yielding 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 ultra-high velocity 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, with the maximum deviation of the stress wave peak values between simulation and experimental results not exceeding 20%, providing a useful tool for mechanism exploration; (4) The characteristics of stress waves within the target and the mechanisms of generation and attenuation were further understood using numerical simulation methods.
To investigate the stress wave characteristics within concrete targets under ultra-high velocity impact conditions, a stress wave testing system based on PVDF piezoelectric stress gauges was established, and research on the calibration method for PVDF piezoelectric stress gauges was conducted. The stress waveforms within concrete targets impacted by kilogram-scale cylindrical 93W tungsten alloy projectiles at ultra-high velocity 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, yielding 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 ultra-high velocity 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, with the maximum deviation of the stress wave peak values between simulation and experimental results not exceeding 20%, providing a useful tool for mechanism exploration; (4) The characteristics of stress waves within the target and the mechanisms of generation and attenuation were further understood using numerical simulation methods.
, Available online ,
doi: 10.11883/bzycj-2024-0262
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Abstract:
For a long time, the research on the mechanical mechanism of lung injuries under explosive shock waves was not sufficient. Due to the complexity of human injury test, the researches based on animal tests as well as the validated animal finite element models are of great importance. This study first establishes a finite element model of the chest of a small pig and uses a newly developed PVDF flexible shock wave pressure sensor to test the surface pressure of animals in shock tube experiments, verifying the accuracy of the finite element model. Secondly, the validated model was used to study the characteristics of lung injury in pigs at different blast distances, analyzing the lung injury properties under different intensities of shock waves. Moreover, the relationship between the peak pressure on the surface of chest and the grade of lung injury is established. Finally, blast tests are performed to obtain the lung injury of pig as well as the chest surface pressure history at different blast distances, which can be used to verify the correctness of the established relationship between the pressure peak on chest surface and the grade of lung injury.
For a long time, the research on the mechanical mechanism of lung injuries under explosive shock waves was not sufficient. Due to the complexity of human injury test, the researches based on animal tests as well as the validated animal finite element models are of great importance. This study first establishes a finite element model of the chest of a small pig and uses a newly developed PVDF flexible shock wave pressure sensor to test the surface pressure of animals in shock tube experiments, verifying the accuracy of the finite element model. Secondly, the validated model was used to study the characteristics of lung injury in pigs at different blast distances, analyzing the lung injury properties under different intensities of shock waves. Moreover, the relationship between the peak pressure on the surface of chest and the grade of lung injury is established. Finally, blast tests are performed to obtain the lung injury of pig as well as the chest surface pressure history at different blast distances, which can be used to verify the correctness of the established relationship between the pressure peak on chest surface and the grade of lung injury.
, Available online ,
doi: 10.11883/bzycj-2024-0248
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Abstract:
Scaled testing is an important method to study the penetration law. The size effect between the model test results and the prototype is a problem that must be solved to establish the calculation method of penetration. The penetration depth of the earth-penetrating projectile is a basic problem in the design of protection engineering. Based on the existing basic theory, the stress and strain state evolution of the rock-like target medium subjected to the penetration of earth-penetrating weapons and the penetration resistance function of the projectiles are derived. The formula for the caliber coefficient characterizing the size effect is obtained, and a simplified analysis of the nose shape coefficient and caliber coefficient is conducted within the penetration velocity range of the conventional earth-penetrating weapons. A practical calculation formula for the penetration depth of conventional earth-penetrating weapons into rock-like media is proposed, whose coefficients can be directly determined by parameters of target and projectiles. The results show that the main influencing factor of projectile impedance is target wave impedance. The source of the size effect is that the ranges of the target damage zones do not satisfy the geometric similarity law. The nose shape coefficient can be simplified as a linear function of warhead aspect ratio, and the nose shape coefficient of a flat-nosed projectile is 0.57. The caliber coefficient of the projectile is determined by the ratio of the cavity radius of the penetration to the radius of the fracture zone and can be taken as 1.2~1.4 for conventional earth-penetrating weapons. The theoretical calculation formula of penetration depth is in good agreement with experimental results, and thus has high reliability.
Scaled testing is an important method to study the penetration law. The size effect between the model test results and the prototype is a problem that must be solved to establish the calculation method of penetration. The penetration depth of the earth-penetrating projectile is a basic problem in the design of protection engineering. Based on the existing basic theory, the stress and strain state evolution of the rock-like target medium subjected to the penetration of earth-penetrating weapons and the penetration resistance function of the projectiles are derived. The formula for the caliber coefficient characterizing the size effect is obtained, and a simplified analysis of the nose shape coefficient and caliber coefficient is conducted within the penetration velocity range of the conventional earth-penetrating weapons. A practical calculation formula for the penetration depth of conventional earth-penetrating weapons into rock-like media is proposed, whose coefficients can be directly determined by parameters of target and projectiles. The results show that the main influencing factor of projectile impedance is target wave impedance. The source of the size effect is that the ranges of the target damage zones do not satisfy the geometric similarity law. The nose shape coefficient can be simplified as a linear function of warhead aspect ratio, and the nose shape coefficient of a flat-nosed projectile is 0.57. The caliber coefficient of the projectile is determined by the ratio of the cavity radius of the penetration to the radius of the fracture zone and can be taken as 1.2~1.4 for conventional earth-penetrating weapons. The theoretical calculation formula of penetration depth is in good agreement with experimental results, and thus has high reliability.
, Available online ,
doi: 10.11883/bzycj-2024-0203
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Abstract:
The equation of state for the detonation products of explosives is one of the foundations in explosion physics, and the JWL state equation were widely applied to study of various explosive properties. In order to obtain the equation state of explosive detonation products, in this paper, an underwater explosion method were used to study JWL equation state of detonation for RDX, the method were analyzed though the explosion bubble expansion process based on the conservation of energy, the energy include Es0 (Initial shock wave energy), Ept(Potential energy of water), Ec(The kinetic energy of water) and Er(energy loss by bubble expansion). And these energy were related to the change with underwater explosion bubble radius R-t and shock wave front Rs-t, which were got form the underwater explosion experiments. Based on the experiments result and using a similar processing experimental data method to cylindrical experiment, the function relationship of explosion bubble expansion radius R-t and variation of shock wave front position Rs-t were fitted, and the parameters of the JWL state equation of RDX explosive detonation products were got finally. Which compare with the parameters obtained from cylindrical experiments, it has a good agreement with underwater explosion bubble expansion bubble radius experiment result and bubble pulsation period got from the pool explosion experiment. This method provides a testing approach for the state equation of detonation products with low cost, few size limitations, and a wide pressure range.
The equation of state for the detonation products of explosives is one of the foundations in explosion physics, and the JWL state equation were widely applied to study of various explosive properties. In order to obtain the equation state of explosive detonation products, in this paper, an underwater explosion method were used to study JWL equation state of detonation for RDX, the method were analyzed though the explosion bubble expansion process based on the conservation of energy, the energy include Es0 (Initial shock wave energy), Ept(Potential energy of water), Ec(The kinetic energy of water) and Er(energy loss by bubble expansion). And these energy were related to the change with underwater explosion bubble radius R-t and shock wave front Rs-t, which were got form the underwater explosion experiments. Based on the experiments result and using a similar processing experimental data method to cylindrical experiment, the function relationship of explosion bubble expansion radius R-t and variation of shock wave front position Rs-t were fitted, and the parameters of the JWL state equation of RDX explosive detonation products were got finally. Which compare with the parameters obtained from cylindrical experiments, it has a good agreement with underwater explosion bubble expansion bubble radius experiment result and bubble pulsation period got from the pool explosion experiment. This method provides a testing approach for the state equation of detonation products with low cost, few size limitations, and a wide pressure range.
, Available online ,
doi: 10.11883/bzycj-2024-0142
Abstract:
Numerical simulation was carried out by using the Fluent simulation software and combining it with the situation of the working face3906 in a mine to investigate the propagation law of gas explosion in a U-shaped ventilation coal mining face and to explore the sensitivities of the overpressure attenuation of a gas explosion to different influencing factors. The relative errors between the numerically-simulated results and experimental ones are less than 15%, which verifies the reliability of the mathematical model developed in this paper. Then, the key parameters, namely, grid size, iteration time step, and ignition temperature are optimized to 0.2 m, 0.05 ms, and 1900 K, respectively. Numerical simulation indicates that the relationship between the peak of the explosion overpressure and the distance away from the explosion center of the coal face meets an exponential function relationship. The relationship between the arrival time of the peak explosion overpressure and the distance away from the explosion center meets a linear function. By designing an orthogonal array, 16 sets of data were obtained through simulation, and the following analyses were conducted based on this data. The extreme difference values of the three main control factors were obtained by using extreme difference analysis. The extreme difference value of the temperature is the greatest, the one of the gas concentration take the second, and the one of the gas accumulation area pressure is the least. The most significant impact of the temperature on the explosion overpressure attenuation in the numerical simulation, in which the R-value reaches 5.928. ANOVA analysis was carried out to study the significances of the main control factors affecting the explosion overpressure attenuation rate. In the three main control factors, the significance of the temperature is the most, the one of the gas accumulation zone pressure comes second, and the one of the gas concentration is the weakest. And the temperature shows a significance level of 31.835, while the other two factors are not significant.
Numerical simulation was carried out by using the Fluent simulation software and combining it with the situation of the working face
, Available online ,
doi: 10.11883/bzycj-2024-0132
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Abstract:
The sheet explosive loading technology is the main method to evaluate the dynamic response of the space structure under the X-ray radiation in laboratory. In order to realize the explosive loading with ultra-low specific impulse for structural examination of new space vehicles, the sheet explosive using PETN as the main explosive and polymer rubber as the binder has been developed. The mass fraction of PETN is 90% ~ 92%, the thickness range is 0.15~0.20 mm, the density range is 1.63~1.68 g/cm3 and the explosive velocity range is 7.44~7.71 km/s. In order to verify the high-impact initiation sensitivity of the sheet explosive, three rounds of verification experiments were designed based on the blast marketing method. In the experiment, the sheet explosive was directly applied to the effect plate or a certain air gap was reserved between the sheet explosive and the effect plate. By observing the explosive marks formed after the explosion on the effect plate, it is judged whether the explosive is detonated. The experimental results show that: the sheet explosive with thickness of 0.15~0.50 mm can be reliably detonated by the mild detonating fuse with a charge line density of 0.2g/m,
The sheet explosive loading technology is the main method to evaluate the dynamic response of the space structure under the X-ray radiation in laboratory. In order to realize the explosive loading with ultra-low specific impulse for structural examination of new space vehicles, the sheet explosive using PETN as the main explosive and polymer rubber as the binder has been developed. The mass fraction of PETN is 90% ~ 92%, the thickness range is 0.15~0.20 mm, the density range is 1.63~1.68 g/cm3 and the explosive velocity range is 7.44~7.71 km/s. In order to verify the high-impact initiation sensitivity of the sheet explosive, three rounds of verification experiments were designed based on the blast marketing method. In the experiment, the sheet explosive was directly applied to the effect plate or a certain air gap was reserved between the sheet explosive and the effect plate. By observing the explosive marks formed after the explosion on the effect plate, it is judged whether the explosive is detonated. The experimental results show that: the sheet explosive with thickness of 0.15~0.50 mm can be reliably detonated by the mild detonating fuse with a charge line density of 0.2g/m,
, Available online ,
doi: 10.11883/bzycj-2024-0136
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Abstract:
Aiming at the resistance evaluation and engineering design of the rock-rubble concrete shield under the combination of penetration and explosion of Earth Penetrating Weapons, firstly, this paper proposed a finite element modeling method for rock-rubble concrete shields. By conducting numerical simulations of quasi-static and penetration tests on ultra-high performance concrete targets containing different coarse aggregate types (corundum and basalt), particle sizes (5-15 mm, 5-20 mm, 35-45 mm, and 65-75 mm), and volume fractions (15% and 30%), the reliability of the modeling method, material constitutive models and corresponding parameters, as well as finite element analysis approach was thoroughly verified. Then, using the semi-infinite rock-rubble concrete shield penetrated by the SDB as a case study, the quantitative influence of type (corundum, basalt, and granite) and dimensionless particle size of rock-rubble (ranging from 0.3 to 2.2 times the projectile diameter) on the penetration depth was analyzed, and optimal design recommendations were determined. Furthermore, the penetration analyses of three typical prototype warheads, i.e., SDB, WDU-43/B, and BLU-109/B, were carried out, and the corresponding penetration resistances of normal strength concrete (NSC), ultra-high performance concrete (UHPC), and corundum rubble concrete (CRC) shields against the above three warheads were quantitatively compared. Finally, the engineering design method for the CRC shield under the combined effects of penetration and explosion of prototype warheads was proposed. The results indicate that the CRC shield containing the particle size of 1.3 to 1.7 times the projectile diameter exhibits the most excellent penetration resistance. Under the penetration of three types of warheads, the penetration depths in CRC shield were 0.29 m, 0.78 m, and 0.68 m, respectively, which are reduced by 61.8%-64.1% and 43.3%-58.0% compared to those in NSC and UHPC shields. Under the combined effects of penetration and explosion, the perforation limits of the CRC shield are 0.52 m, 1.22 m, and 1.50 m, while the scabbing limits are 1.11 m, 2.26 m, and 3.17 m. Compared with NSC and UHPC shields, the perforation limits are reduced by 60.5%-64.0% and 43.3%-58.0%, respectively, and the corresponding scabbing limits are reduced by 61.8%-69.1% and 34.7%-40.5%, respectively.
Aiming at the resistance evaluation and engineering design of the rock-rubble concrete shield under the combination of penetration and explosion of Earth Penetrating Weapons, firstly, this paper proposed a finite element modeling method for rock-rubble concrete shields. By conducting numerical simulations of quasi-static and penetration tests on ultra-high performance concrete targets containing different coarse aggregate types (corundum and basalt), particle sizes (5-15 mm, 5-20 mm, 35-45 mm, and 65-75 mm), and volume fractions (15% and 30%), the reliability of the modeling method, material constitutive models and corresponding parameters, as well as finite element analysis approach was thoroughly verified. Then, using the semi-infinite rock-rubble concrete shield penetrated by the SDB as a case study, the quantitative influence of type (corundum, basalt, and granite) and dimensionless particle size of rock-rubble (ranging from 0.3 to 2.2 times the projectile diameter) on the penetration depth was analyzed, and optimal design recommendations were determined. Furthermore, the penetration analyses of three typical prototype warheads, i.e., SDB, WDU-43/B, and BLU-109/B, were carried out, and the corresponding penetration resistances of normal strength concrete (NSC), ultra-high performance concrete (UHPC), and corundum rubble concrete (CRC) shields against the above three warheads were quantitatively compared. Finally, the engineering design method for the CRC shield under the combined effects of penetration and explosion of prototype warheads was proposed. The results indicate that the CRC shield containing the particle size of 1.3 to 1.7 times the projectile diameter exhibits the most excellent penetration resistance. Under the penetration of three types of warheads, the penetration depths in CRC shield were 0.29 m, 0.78 m, and 0.68 m, respectively, which are reduced by 61.8%-64.1% and 43.3%-58.0% compared to those in NSC and UHPC shields. Under the combined effects of penetration and explosion, the perforation limits of the CRC shield are 0.52 m, 1.22 m, and 1.50 m, while the scabbing limits are 1.11 m, 2.26 m, and 3.17 m. Compared with NSC and UHPC shields, the perforation limits are reduced by 60.5%-64.0% and 43.3%-58.0%, respectively, and the corresponding scabbing limits are reduced by 61.8%-69.1% and 34.7%-40.5%, respectively.
, Available online ,
doi: 10.11883/bzycj-2024-0232
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Abstract:
Addressing the buffering and load reduction challenges during high-speed water entry vehicle, applicable buffer head covers and various open-cell buffer foam configurations were designed. In the Arbitrary Lagrangian-Euler method, as the material flows within the spatial grid, the grid itself is able to move. This unique feature allows the Arbitrary Lagrangian-Euler method to harness the advantages of both the Lagrangian and Euler methods. It not only overcomes numerical calculation challenges stemming from element distortion but also facilitates accurate computation of large deformations and displacements in solids and fluids. This makes it particularly well-suited for addressing high-speed water buffer load reduction problems. Based on the Arbitrary Lagrangian-Eulerian method and considering the large deformation of the buffer foam and the hood, a numerical calculation model for buffering and load reduction during high-speed water entry of navigational bodies was established. Through numerical simulations, an in-depth study was conducted on the load reduction performance of buffer foams with different open-cell patterns. The results indicate that open-cell buffer foam exhibits significant advantages in dispersing the impact force and absorbing impact energy during water entry of navigational bodies, offering better buffering effects. Simultaneously, the buffer head cover experiences local progressive fragmentation upon water entry. The deformation and rupture of the outer wall surface of the buffer head cover at the connector between the buffer shell and the navigational body are caused by the stress concentration distribution generated during water impact. When the open-cell foam contacts the water surface, the front part enters the collapse stage, absorbing a large amount of energy and undergoing plastic deformation, resulting in a reduction of pores. This stage is the primary energy absorption phase for the buffer foam. In comparison, closed-cell foam exhibits poorer load reduction performance. Therefore, the adoption of open-cell foam represents a superior solution for buffering and load reduction during high-speed water entry of navigational bodies.
Addressing the buffering and load reduction challenges during high-speed water entry vehicle, applicable buffer head covers and various open-cell buffer foam configurations were designed. In the Arbitrary Lagrangian-Euler method, as the material flows within the spatial grid, the grid itself is able to move. This unique feature allows the Arbitrary Lagrangian-Euler method to harness the advantages of both the Lagrangian and Euler methods. It not only overcomes numerical calculation challenges stemming from element distortion but also facilitates accurate computation of large deformations and displacements in solids and fluids. This makes it particularly well-suited for addressing high-speed water buffer load reduction problems. Based on the Arbitrary Lagrangian-Eulerian method and considering the large deformation of the buffer foam and the hood, a numerical calculation model for buffering and load reduction during high-speed water entry of navigational bodies was established. Through numerical simulations, an in-depth study was conducted on the load reduction performance of buffer foams with different open-cell patterns. The results indicate that open-cell buffer foam exhibits significant advantages in dispersing the impact force and absorbing impact energy during water entry of navigational bodies, offering better buffering effects. Simultaneously, the buffer head cover experiences local progressive fragmentation upon water entry. The deformation and rupture of the outer wall surface of the buffer head cover at the connector between the buffer shell and the navigational body are caused by the stress concentration distribution generated during water impact. When the open-cell foam contacts the water surface, the front part enters the collapse stage, absorbing a large amount of energy and undergoing plastic deformation, resulting in a reduction of pores. This stage is the primary energy absorption phase for the buffer foam. In comparison, closed-cell foam exhibits poorer load reduction performance. Therefore, the adoption of open-cell foam represents a superior solution for buffering and load reduction during high-speed water entry of navigational bodies.
, Available online ,
doi: 10.11883/bzycj-2024-0217
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Abstract:
Penetration resistance is a crucial issue in the study of armor's anti-penetration performance and the optimization design of projectile structures. Through the analysis of the mechanical response of reinforcing bars under the dynamic constraint of both the projectile and concrete, the limitation of existing finite-length rigid beam models have been obtained. Based on this foundation, a shear-plastic hinge model was used to analyze the case of a projectile directly hitting the reinforcing bars, and a plastic string model was used to analyze the case of a projectile colliding with the side of the reinforcing bars, resulting in a more accurate equation for penetration resistance. In the shear plastic hinge model, stress analysis was performed based on the shear sliding of the reinforcing bar before fracture, and energy dissipation was calculated based on the deformation of the plastic hinge after the reinforcing bar fractures. In the plastic string model, the yield criterion of reinforcing bars under the combined action of bending moment and axial force was analyzed, and the plastic energy dissipation equations for reinforcing bar tension and bending were established. At the same time, the influence of changes in reinforcing bar kinetic energy was considered. Based on the theoretical model of cavity expansion and the empirical formula for the depth of projectile penetration, the concrete resistance equation under the indirect influence of steel reinforcement was obtained. By comparing with existing experimental data, the rationality of the theoretical models was verified. By analyzing the yield strength, diameter, mesh size of reinforcing bars, as well as the impact location of projectile, suggestions for the reinforcement design of the bulletproof layer were given. The adjacent two layers of reinforcing bars mesh should be staggered. The ratio of steel mesh to projectile diameter should be set between 0.5 and 0.8. It is not advisable to simply pursue high-strength reinforcing bars, and the ultimate plastic strain of reinforcing bars should also be considered as an important factor.
Penetration resistance is a crucial issue in the study of armor's anti-penetration performance and the optimization design of projectile structures. Through the analysis of the mechanical response of reinforcing bars under the dynamic constraint of both the projectile and concrete, the limitation of existing finite-length rigid beam models have been obtained. Based on this foundation, a shear-plastic hinge model was used to analyze the case of a projectile directly hitting the reinforcing bars, and a plastic string model was used to analyze the case of a projectile colliding with the side of the reinforcing bars, resulting in a more accurate equation for penetration resistance. In the shear plastic hinge model, stress analysis was performed based on the shear sliding of the reinforcing bar before fracture, and energy dissipation was calculated based on the deformation of the plastic hinge after the reinforcing bar fractures. In the plastic string model, the yield criterion of reinforcing bars under the combined action of bending moment and axial force was analyzed, and the plastic energy dissipation equations for reinforcing bar tension and bending were established. At the same time, the influence of changes in reinforcing bar kinetic energy was considered. Based on the theoretical model of cavity expansion and the empirical formula for the depth of projectile penetration, the concrete resistance equation under the indirect influence of steel reinforcement was obtained. By comparing with existing experimental data, the rationality of the theoretical models was verified. By analyzing the yield strength, diameter, mesh size of reinforcing bars, as well as the impact location of projectile, suggestions for the reinforcement design of the bulletproof layer were given. The adjacent two layers of reinforcing bars mesh should be staggered. The ratio of steel mesh to projectile diameter should be set between 0.5 and 0.8. It is not advisable to simply pursue high-strength reinforcing bars, and the ultimate plastic strain of reinforcing bars should also be considered as an important factor.
, Available online ,
doi: 10.11883/bzycj-2024-0218
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Abstract:
The post ignition effect of explosives will release more energy by reacting with air, resulting in an increase in quasi-static pressure. In order to predict the quasi-static pressure of internal explosion in a closed environment composed of aluminum containing active materials and explosive rings, this paper proposes an optimization method for the quasi-static pressure calculation model applicable to the internal explosion of aluminum containing composite charges, based on summarizing the existing quasi-static pressure calculation models of hydrogen, oxygen, and nitrogen explosives that consider the post ignition effect. Then, active materials and explosives composite charges and aluminum containing explosives internal explosion tests are carried out, and the experimental data are compared and analyzed with the quasi-static pressure results calculated by the established optimization model. At the same time, the internal explosion results of the two types of explosives are compared, and the calculation model is extended to general aluminum containing explosives and the accuracy is verified. The research results indicate that the established quasi-static pressure correction model for post combustion of composite explosives is in good agreement with experimental and literature data, with an average error of 10.2% and a maximum error of 16.0%; The average error of the calculation results for general aluminum containing explosives is 12.1%, with a maximum error
The post ignition effect of explosives will release more energy by reacting with air, resulting in an increase in quasi-static pressure. In order to predict the quasi-static pressure of internal explosion in a closed environment composed of aluminum containing active materials and explosive rings, this paper proposes an optimization method for the quasi-static pressure calculation model applicable to the internal explosion of aluminum containing composite charges, based on summarizing the existing quasi-static pressure calculation models of hydrogen, oxygen, and nitrogen explosives that consider the post ignition effect. Then, active materials and explosives composite charges and aluminum containing explosives internal explosion tests are carried out, and the experimental data are compared and analyzed with the quasi-static pressure results calculated by the established optimization model. At the same time, the internal explosion results of the two types of explosives are compared, and the calculation model is extended to general aluminum containing explosives and the accuracy is verified. The research results indicate that the established quasi-static pressure correction model for post combustion of composite explosives is in good agreement with experimental and literature data, with an average error of 10.2% and a maximum error of 16.0%; The average error of the calculation results for general aluminum containing explosives is 12.1%, with a maximum error
, Available online ,
doi: 10.11883/bzycj-2024-0163
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Abstract:
Abstract: In order to discuss the gap size effect of flyer to the initiating behavior for TATB based explosives, initiation experiments for PBX-6 and PBXL-7 were performed. The target velocity and shape of the flyer to explosives were obtained using by 1550nm Photon Doppler velocimetry. The running distance to detonation of explosive samples were gained by Terahertz-wave Doppler interferometric velocimetry. The relationship between the experiment data captured above were analyzed. It reveals that the running distance to detonation of the TATB based explosive change non-monotonously with the increase of the gap size. With the increase of gap size from zero to 20 mm, the target velocity of the flyer stay at the gap layer initiation stage named S0, the velocity declining stage named S1 for the flyer, the free running stage of spallation named S2, the remerging stage of the flyer with its spallation named S3 and united as one flyer stage named S4 respectively. The running distance to detonation for TATB based explosives is the smallest when the flyer velocity stay at the stage S4, the result at the stage S0 which means the gap layer initiating status is the next, the results at the velocity declining stage S1 and remerging stage S3 are the worst together. These experiment results suggest that the initiating performance of flyer to explosives is not always better than gap layer. The initiation mechanism of flyer to explosives with different gap sizes probably is related to the target velocity together with the structure of flyer.
Abstract: In order to discuss the gap size effect of flyer to the initiating behavior for TATB based explosives, initiation experiments for PBX-6 and PBXL-7 were performed. The target velocity and shape of the flyer to explosives were obtained using by 1550nm Photon Doppler velocimetry. The running distance to detonation of explosive samples were gained by Terahertz-wave Doppler interferometric velocimetry. The relationship between the experiment data captured above were analyzed. It reveals that the running distance to detonation of the TATB based explosive change non-monotonously with the increase of the gap size. With the increase of gap size from zero to 20 mm, the target velocity of the flyer stay at the gap layer initiation stage named S0, the velocity declining stage named S1 for the flyer, the free running stage of spallation named S2, the remerging stage of the flyer with its spallation named S3 and united as one flyer stage named S4 respectively. The running distance to detonation for TATB based explosives is the smallest when the flyer velocity stay at the stage S4, the result at the stage S0 which means the gap layer initiating status is the next, the results at the velocity declining stage S1 and remerging stage S3 are the worst together. These experiment results suggest that the initiating performance of flyer to explosives is not always better than gap layer. The initiation mechanism of flyer to explosives with different gap sizes probably is related to the target velocity together with the structure of flyer.
, Available online ,
doi: 10.11883/bzycj-2024-0096
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Abstract:
For studying the trajectories’ characteristics of elliptical cross-section projectiles penetrating multi-layer spaced steel targets, experimental investigation of typical projectiles penetrating multi-layer spaced Q355B steel targets has been conducted. Numerical simulations have been performed on LS-DYNA finite element software and typical results obtained have been validated by experimental results. The attitude and trajectory parameters in the penetration process and the deflection mechanism of the projectile were obtained. The influence of cross-section shape, the minor-to-major axis length ratios of the projectile cross-section, initial velocity, rotation angle and incident angle on the penetration trajectories and attitude deflection was investigated. The research results show that the penetration trajectory stability of the circular cross-section projectile is better than the elliptical and asymmetric elliptical cross-section projectile when the rotation angle is 0°. As the minor-to-major axis length ratios increase, the trajectory is more stable. The trajectory deflection reduces with higher initial velocity. When rotation angle is 90°, the penetration trajectory of both symmetric and asymmetric elliptical cross-section projectile in the incident plane is the most stable, and the trajectory deflection of the two projectiles in the horizontal plane reaches its maximum at rotation angles of 45° and 90°, respectively. The trajectory stability of asymmetric elliptical projectile when the rotation angle is obtuse is better than that at the acute angle. When the incident angle is in the range of [0°,50°], the trajectory instability and attitude deflection of projectile increase with the increase of incident angle and then decrease, and both reach the largest when incident angle is about 30°. It is also found that the projectile will separate from the target during the penetration stage of projectile nose when penetrating thin steel target in a stable attitude. When the projectile penetrates thin steel target in a large attack angle, the attachment of projectile and target mainly occurs on the upper surface of
For studying the trajectories’ characteristics of elliptical cross-section projectiles penetrating multi-layer spaced steel targets, experimental investigation of typical projectiles penetrating multi-layer spaced Q355B steel targets has been conducted. Numerical simulations have been performed on LS-DYNA finite element software and typical results obtained have been validated by experimental results. The attitude and trajectory parameters in the penetration process and the deflection mechanism of the projectile were obtained. The influence of cross-section shape, the minor-to-major axis length ratios of the projectile cross-section, initial velocity, rotation angle and incident angle on the penetration trajectories and attitude deflection was investigated. The research results show that the penetration trajectory stability of the circular cross-section projectile is better than the elliptical and asymmetric elliptical cross-section projectile when the rotation angle is 0°. As the minor-to-major axis length ratios increase, the trajectory is more stable. The trajectory deflection reduces with higher initial velocity. When rotation angle is 90°, the penetration trajectory of both symmetric and asymmetric elliptical cross-section projectile in the incident plane is the most stable, and the trajectory deflection of the two projectiles in the horizontal plane reaches its maximum at rotation angles of 45° and 90°, respectively. The trajectory stability of asymmetric elliptical projectile when the rotation angle is obtuse is better than that at the acute angle. When the incident angle is in the range of [0°,50°], the trajectory instability and attitude deflection of projectile increase with the increase of incident angle and then decrease, and both reach the largest when incident angle is about 30°. It is also found that the projectile will separate from the target during the penetration stage of projectile nose when penetrating thin steel target in a stable attitude. When the projectile penetrates thin steel target in a large attack angle, the attachment of projectile and target mainly occurs on the upper surface of
, Available online ,
doi: 10.11883/bzycj-2024-0128
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Abstract:
In the near-field explosion of improvised explosive device, the protective structure is often subjected to the combined action of blast wave and fragments. To improve the protection performance of the structure, a composite structural material containing foamed aluminum/fiber sandwich was designed and prepared. The "explosion + penetration" experiment was carried out to study the failure mode of the composite structure under the combined action of explosion shock wave and high-speed fragments. The influence of the two loading’s timing sequence of explosion shock wave and fragment on the failure mode was discussed, and the energy absorption mechanism of different materials was analyzed. The results show that the change of detonation distance directly affects the timing sequence of the action of explosion shock wave and fragment. In the conditions discussed in this paper, when the detonation distance is greater than 600mm, the fragment acts before the shock wave. Under the combined action of shock wave and fragment, the aluminum plate is accompanied by local sag deformation in addition to the penetration failure of fragments. The cellular structure of foamed aluminum was crushed and deformed under the impact load. The fibers at the bullet hole are stretched and fractured under the penetration of fragments, and are accompanied by high temperature failure. Under the two sequential effects, the existence of bullet holes weakens the effect of shock wave on the front aluminum plate, and the deformation and damage degree of the later sandwich structural material and the rear aluminum plate are more serious than that of the previous material. This research provides a technical basis for the application and functional design of lightweight composite structural materials in the field of near-burst protection in limited space.
In the near-field explosion of improvised explosive device, the protective structure is often subjected to the combined action of blast wave and fragments. To improve the protection performance of the structure, a composite structural material containing foamed aluminum/fiber sandwich was designed and prepared. The "explosion + penetration" experiment was carried out to study the failure mode of the composite structure under the combined action of explosion shock wave and high-speed fragments. The influence of the two loading’s timing sequence of explosion shock wave and fragment on the failure mode was discussed, and the energy absorption mechanism of different materials was analyzed. The results show that the change of detonation distance directly affects the timing sequence of the action of explosion shock wave and fragment. In the conditions discussed in this paper, when the detonation distance is greater than 600mm, the fragment acts before the shock wave. Under the combined action of shock wave and fragment, the aluminum plate is accompanied by local sag deformation in addition to the penetration failure of fragments. The cellular structure of foamed aluminum was crushed and deformed under the impact load. The fibers at the bullet hole are stretched and fractured under the penetration of fragments, and are accompanied by high temperature failure. Under the two sequential effects, the existence of bullet holes weakens the effect of shock wave on the front aluminum plate, and the deformation and damage degree of the later sandwich structural material and the rear aluminum plate are more serious than that of the previous material. This research provides a technical basis for the application and functional design of lightweight composite structural materials in the field of near-burst protection in limited space.
, Available online ,
doi: 10.11883/bzycj-2024-0089
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Plasma rock breaking technology has the characteristics of being green, efficient, and controllable, and has great application prospects in deep rock breaking. This article conducted four sets of plasma sandstone blasting experiments under different confining pressures. Through CT scanning and 3D reconstruction, the morphology, structure, and distribution of internal fractures in rocks were compared and analyzed. The rock breaking effect of plasma rock breaking technology under different confining pressures was studied. LS-DYNA was used for numerical simulation to explore the mechanism of plasma rock breaking under different confining pressures and the expansion of internal fractures in rocks during blasting Distribution and damage evolution patterns. The results show that under the same voltage, as the three-dimensional confining pressure increases, the number and distribution range of surface cracks on the rock gradually decrease. The complexity and connectivity of internal cracks in sandstone significantly decrease. Secondly, in the dynamic stress field generated by plasma blasting and the static stress coupling field generated by confining pressure, the shock wave generated by plasma blasting has a greater effect in the initial stage of the explosion, There is no significant difference in the crack morphology and central expansion area of rocks under different confining pressures. As the shock wave attenuates, confining pressure plays a decisive role in the later stage of plasma blasting, inhibiting the crack propagation and damage evolution of the rock
Plasma rock breaking technology has the characteristics of being green, efficient, and controllable, and has great application prospects in deep rock breaking. This article conducted four sets of plasma sandstone blasting experiments under different confining pressures. Through CT scanning and 3D reconstruction, the morphology, structure, and distribution of internal fractures in rocks were compared and analyzed. The rock breaking effect of plasma rock breaking technology under different confining pressures was studied. LS-DYNA was used for numerical simulation to explore the mechanism of plasma rock breaking under different confining pressures and the expansion of internal fractures in rocks during blasting Distribution and damage evolution patterns. The results show that under the same voltage, as the three-dimensional confining pressure increases, the number and distribution range of surface cracks on the rock gradually decrease. The complexity and connectivity of internal cracks in sandstone significantly decrease. Secondly, in the dynamic stress field generated by plasma blasting and the static stress coupling field generated by confining pressure, the shock wave generated by plasma blasting has a greater effect in the initial stage of the explosion, There is no significant difference in the crack morphology and central expansion area of rocks under different confining pressures. As the shock wave attenuates, confining pressure plays a decisive role in the later stage of plasma blasting, inhibiting the crack propagation and damage evolution of the rock
, Available online ,
doi: 10.11883/bzycj-2024-0119
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H-section steel columns have been widely employed in industrial buildings and parking lots, etc., which are vulnerable to crane-loading or vehicle collisions. Based on above background, the lateral impact model and residual load-carrying capacity model were established using Abaqus finite element software to analyze the performance of H-section steel columns during and after impact loading, following previous experimental studies. Firstly, the working mechanism, including the deformation characteristics, stress evolution and energy dissipation, was analyzed. Results indicated that under impact loading, the deformation pattern is mainly dominated by the global deformation, with the local deformation of the upper flange and out-of-plane buckling of web. The time history curve of impact force presents an obvious plateau phase, and the existence of the pre-axial loading obviously reduces the impact resistance of the specimens. In general, H-section steel columns exhibited favorable ductility performance during impact loading. Subsequently, a total of 108 parametric models were developed, and the influences of load parameters (impact mass, impact velocity and axial load ratio), material parameter (steel yield strength) and geometric parameters (sectional area and specimen length) on the impact force, deformation, and residual load-carrying capacity were emphatically studied. The results showed that as the impact mass, impact velocity, and pre-axial loading ratio increased, both the global and local deformations of H-section steel column increased, while the residual bearing capacity decreased. Finally, by considering the multi-factor interactions, the formulas for predicting global deformation and local deformation during impact and the residual load performance after impact were presented by using response surface method. Results showed that pre-axial loading was a key factor affecting global deformation, while the impact velocity affected local deformation. In addition, both the pre-axial loading and impact velocity significantly interact with other parameters. The proposed formulas can be employed for the damage evaluation and design of H-section steel columns during the whole impact process.
H-section steel columns have been widely employed in industrial buildings and parking lots, etc., which are vulnerable to crane-loading or vehicle collisions. Based on above background, the lateral impact model and residual load-carrying capacity model were established using Abaqus finite element software to analyze the performance of H-section steel columns during and after impact loading, following previous experimental studies. Firstly, the working mechanism, including the deformation characteristics, stress evolution and energy dissipation, was analyzed. Results indicated that under impact loading, the deformation pattern is mainly dominated by the global deformation, with the local deformation of the upper flange and out-of-plane buckling of web. The time history curve of impact force presents an obvious plateau phase, and the existence of the pre-axial loading obviously reduces the impact resistance of the specimens. In general, H-section steel columns exhibited favorable ductility performance during impact loading. Subsequently, a total of 108 parametric models were developed, and the influences of load parameters (impact mass, impact velocity and axial load ratio), material parameter (steel yield strength) and geometric parameters (sectional area and specimen length) on the impact force, deformation, and residual load-carrying capacity were emphatically studied. The results showed that as the impact mass, impact velocity, and pre-axial loading ratio increased, both the global and local deformations of H-section steel column increased, while the residual bearing capacity decreased. Finally, by considering the multi-factor interactions, the formulas for predicting global deformation and local deformation during impact and the residual load performance after impact were presented by using response surface method. Results showed that pre-axial loading was a key factor affecting global deformation, while the impact velocity affected local deformation. In addition, both the pre-axial loading and impact velocity significantly interact with other parameters. The proposed formulas can be employed for the damage evaluation and design of H-section steel columns during the whole impact process.
, Available online ,
doi: 10.11883/bzycj-2024-0102
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In order to reduce the great threat of gas explosion to coal mine operators and coal safety mining, the law of explosion overpressure and impact gas velocity attenuation with the propagation distance of different volumes of gas-air mixed gas in roadway was deeply studied. Firstly, based on dimensional analysis and energy similarity law, a dimensionless formula for the attenuation of gas explosion overpressure and impact gas velocity with propagation distance is established, considering the factors affecting the attenuation of gas explosion overpressure and impact gas velocity with propagation distance. Secondly, by regression analysis of the experimental data in large roadway, the attenuation models of overpressure and impact airflow velocity and their relations are obtained. Finally, the attenuation model and relation are verified. The results show that the energy of gas mixture, the amount of gas accumulation, the distance of measuring point, the hydraulic diameter and the cross-sectional area of roadway are the main factors affecting the attenuation of overpressure and impact gas velocity. Both overpressure and impact gas velocity are positively correlated with the accumulation of mixed gas. The greater the initial overpressure and impact gas velocity, the faster the attenuation. The relative errors between the theoretical value and the test value of the attenuation model and the relative errors between the theoretical value and the test value of the relation are controlled at about 10%, and the overall consistency of the data is high, which verifies the reliability of the data, and can describe the law of gas explosion propagation more simply and intuitively, and realize the rapid calculation of overpressure and gas velocity.
In order to reduce the great threat of gas explosion to coal mine operators and coal safety mining, the law of explosion overpressure and impact gas velocity attenuation with the propagation distance of different volumes of gas-air mixed gas in roadway was deeply studied. Firstly, based on dimensional analysis and energy similarity law, a dimensionless formula for the attenuation of gas explosion overpressure and impact gas velocity with propagation distance is established, considering the factors affecting the attenuation of gas explosion overpressure and impact gas velocity with propagation distance. Secondly, by regression analysis of the experimental data in large roadway, the attenuation models of overpressure and impact airflow velocity and their relations are obtained. Finally, the attenuation model and relation are verified. The results show that the energy of gas mixture, the amount of gas accumulation, the distance of measuring point, the hydraulic diameter and the cross-sectional area of roadway are the main factors affecting the attenuation of overpressure and impact gas velocity. Both overpressure and impact gas velocity are positively correlated with the accumulation of mixed gas. The greater the initial overpressure and impact gas velocity, the faster the attenuation. The relative errors between the theoretical value and the test value of the attenuation model and the relative errors between the theoretical value and the test value of the relation are controlled at about 10%, and the overall consistency of the data is high, which verifies the reliability of the data, and can describe the law of gas explosion propagation more simply and intuitively, and realize the rapid calculation of overpressure and gas velocity.
, Available online ,
doi: 10.11883/bzycj-2024-0071
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There are many microcracks and micropores in the rock, which will initiate, propagate, and coalescence under dynamic loading, leading to rock instability and failure. When blasting excavation is carried out, the retained rock mass will be subjected to the dynamic loading generated by cyclic blasting, resulting in cumulative damage, which will lead to the reduction of the rock mass strength, and even failure. In order to simulate this physical process, this study embeds the existing rock dynamic damage constitutive model, which can perfectly describe the rock dynamic damage induced by blasting, into FLAC through secondary development to analyze the cumulative damage of rock mass under cyclic blasting. And then it is adopted to simulate the dynamic response of the rock slope with the locked segment under cyclic blasting. The results show that the slope stability gradually decreases with increasing the number of cyclic blasting after considering the cumulative damage effect of the rock slope. For the rock slope with the locked segment, the damage of the locked segment firstly occurs at both ends, and then propagates to the middle, in which the rock mass shows a progressive failure mode. Because the cumulative damage of the rock slope is considered, the stability factor of the slope will decrease after each blasting. When the cumulative damage is not considered, the stability factor of the slope is basically unchanged. The failure mode of the rock slope with a locked segment under cyclic blasting is the combination of dynamic tensile failure and shear failure caused by rock mass slip. The location of the locked segment in the weak interlayer affects the failure mode and stability of the slope. Therefore, when carrying out similar engineering activities, the cumulative damage effect of rock mass should be considered to avoid engineering accidents.
There are many microcracks and micropores in the rock, which will initiate, propagate, and coalescence under dynamic loading, leading to rock instability and failure. When blasting excavation is carried out, the retained rock mass will be subjected to the dynamic loading generated by cyclic blasting, resulting in cumulative damage, which will lead to the reduction of the rock mass strength, and even failure. In order to simulate this physical process, this study embeds the existing rock dynamic damage constitutive model, which can perfectly describe the rock dynamic damage induced by blasting, into FLAC through secondary development to analyze the cumulative damage of rock mass under cyclic blasting. And then it is adopted to simulate the dynamic response of the rock slope with the locked segment under cyclic blasting. The results show that the slope stability gradually decreases with increasing the number of cyclic blasting after considering the cumulative damage effect of the rock slope. For the rock slope with the locked segment, the damage of the locked segment firstly occurs at both ends, and then propagates to the middle, in which the rock mass shows a progressive failure mode. Because the cumulative damage of the rock slope is considered, the stability factor of the slope will decrease after each blasting. When the cumulative damage is not considered, the stability factor of the slope is basically unchanged. The failure mode of the rock slope with a locked segment under cyclic blasting is the combination of dynamic tensile failure and shear failure caused by rock mass slip. The location of the locked segment in the weak interlayer affects the failure mode and stability of the slope. Therefore, when carrying out similar engineering activities, the cumulative damage effect of rock mass should be considered to avoid engineering accidents.
, Available online ,
doi: 10.11883/bzycj-2023-0343
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Abstract:
Facing the challenges of accurate and effective prediction under extreme loads, machine learning has gradually demonstrated its potential to replace traditional methods. Existing approaches primarily focus on predicting the peak overpressure or impulse of explosive shock waves, with limited research on predicting the reflected overpressure time history. Load-time history prediction encompasses not only the peak overpressure but also embraces various multi-dimensional information including duration, waveform, and impulse, thereby offering a more comprehensive depiction of the dynamic temporal and spatial characteristics of shock waves. To address this issue, a prediction model for bridge surface reflected overpressure time history is proposed, targeting a planar shock wave diffracting around a bridge section. This model is based on Principal Component Analysis (PCA) and Backpropagation Neural Network (BPNN) algorithm with multi-task learning. A loss function considering the impact of peak overpressure and maximum impulse is introduced to fully consider the potential correlations between different modes after PCA dimension reduction. This enables the
Facing the challenges of accurate and effective prediction under extreme loads, machine learning has gradually demonstrated its potential to replace traditional methods. Existing approaches primarily focus on predicting the peak overpressure or impulse of explosive shock waves, with limited research on predicting the reflected overpressure time history. Load-time history prediction encompasses not only the peak overpressure but also embraces various multi-dimensional information including duration, waveform, and impulse, thereby offering a more comprehensive depiction of the dynamic temporal and spatial characteristics of shock waves. To address this issue, a prediction model for bridge surface reflected overpressure time history is proposed, targeting a planar shock wave diffracting around a bridge section. This model is based on Principal Component Analysis (PCA) and Backpropagation Neural Network (BPNN) algorithm with multi-task learning. A loss function considering the impact of peak overpressure and maximum impulse is introduced to fully consider the potential correlations between different modes after PCA dimension reduction. This enables the
, Available online ,
doi: 10.11883/bzycj-2023-0395
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Abstract:
Propellers serve as pivotal components within ship propulsion systems, directly influencing a vessel's performance through their stability and efficiency. Current research on the resilience of propulsion shafts often simplifies propellers to homogenous discs, neglecting their structural intricacies. This approach fails to accurately capture the transient damage features of propellers under the effects of underwater explosion. Therefore, this paper takes into consideration the propeller's structural characteristics. By initially employing wet modal analysis, the study determines that solid modeling outperforms shell modeling. It investigates the response and damage characteristics of propeller surfaces under the influence of far-field shockwaves while considering the propeller's structural attributes. The paper also analyzes the transient damage characteristics of propellers in conjunction with the hydrodynamic cavitation state generated during high-speed propeller rotation. The research findings demonstrate that at attack angles of 0 degrees and 90 degrees, surface loads on the propeller due to shockwave incidence are higher, but they exhibit an upper limit that correlates with the propeller's structural features. When accounting for the hydrodynamic cavitation state, stress levels on the blades remain consistently uniform. The primary plastic damage zone on the blades is near the root, showcasing both local and complete plastic deformation modes. This paper delves into the damage and cavitation characteristics of propellers under far-field explosions, and its results offer valuable insights for protecting propulsion shafts and propellers against shock impacts.
Propellers serve as pivotal components within ship propulsion systems, directly influencing a vessel's performance through their stability and efficiency. Current research on the resilience of propulsion shafts often simplifies propellers to homogenous discs, neglecting their structural intricacies. This approach fails to accurately capture the transient damage features of propellers under the effects of underwater explosion. Therefore, this paper takes into consideration the propeller's structural characteristics. By initially employing wet modal analysis, the study determines that solid modeling outperforms shell modeling. It investigates the response and damage characteristics of propeller surfaces under the influence of far-field shockwaves while considering the propeller's structural attributes. The paper also analyzes the transient damage characteristics of propellers in conjunction with the hydrodynamic cavitation state generated during high-speed propeller rotation. The research findings demonstrate that at attack angles of 0 degrees and 90 degrees, surface loads on the propeller due to shockwave incidence are higher, but they exhibit an upper limit that correlates with the propeller's structural features. When accounting for the hydrodynamic cavitation state, stress levels on the blades remain consistently uniform. The primary plastic damage zone on the blades is near the root, showcasing both local and complete plastic deformation modes. This paper delves into the damage and cavitation characteristics of propellers under far-field explosions, and its results offer valuable insights for protecting propulsion shafts and propellers against shock impacts.
, Available online
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Abstract:
To enhance the service safety of nodular cast iron structures such as the spent nuclear fuel storage and transportation vessel under low temperature and dynamic loads, the mode I dynamic fracture toughness of nodular cast iron was experimentally investigated at ambient and cryogenic temperatures (20℃, -40℃, -60℃ and -80℃) using an improved split Hopkinson pressure bar technique. The ductile-brittle transition behavior of the material was specially investigated. The crack initiation time of the specimen was determined by the strain gauge method. The dynamic stress intensity factor (DSIF) at the crack tip and the mode I dynamic fracture toughness (DFT) of the material were determined by the experimental-numerical method. The results show that under the same impact velocity, the DFT and fracture initiation time of nodular cast iron decrease significantly with the decrease in temperature. Through quantitative analysis of the microscopic fracture morphologies, it is revealed that there is a failure mechanism transition at different temperatures. As the temperature decreases, the number of dimples on the fracture surface decreases, while the river patterns as well as cleavage steps increase, which indicates that the ductility of the material is weakened but the brittleness is enhanced at low temperatures. This ductile-brittle transition phenomenon is consistent with the tendency of the measured toughness of the material.
To enhance the service safety of nodular cast iron structures such as the spent nuclear fuel storage and transportation vessel under low temperature and dynamic loads, the mode I dynamic fracture toughness of nodular cast iron was experimentally investigated at ambient and cryogenic temperatures (20℃, -40℃, -60℃ and -80℃) using an improved split Hopkinson pressure bar technique. The ductile-brittle transition behavior of the material was specially investigated. The crack initiation time of the specimen was determined by the strain gauge method. The dynamic stress intensity factor (DSIF) at the crack tip and the mode I dynamic fracture toughness (DFT) of the material were determined by the experimental-numerical method. The results show that under the same impact velocity, the DFT and fracture initiation time of nodular cast iron decrease significantly with the decrease in temperature. Through quantitative analysis of the microscopic fracture morphologies, it is revealed that there is a failure mechanism transition at different temperatures. As the temperature decreases, the number of dimples on the fracture surface decreases, while the river patterns as well as cleavage steps increase, which indicates that the ductility of the material is weakened but the brittleness is enhanced at low temperatures. This ductile-brittle transition phenomenon is consistent with the tendency of the measured toughness of the material.
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, Available online ,
doi: 10.11883/bzycj-2024-0117
Abstract:
In this paper, the microspheres in fly ash are used as sensitizer and inert additive to prepare the low detonation velocity emulsion explosives. The detonation velocity and the parameters of explosion shock wave in the air of emulsion explosives were measured by the probe method, the lead column compression method and the air explosion method, respectively, and the safety of emulsion explosives was tested by the storage life experiment and thermal analysis experiment. The experimental results show that the detonation velocity, the brisance, the peak pressure, the positive impulse and the positive pressure action time of shock wave of emulsion explosives increased first and then decreased with the increase of the content of fly ash microspheres. When the content of fly ash microspheres was 15%, the detonation performance of emulsion explosive was the best, and when the content of fly ash microspheres was 45% , the detonation velocity of the explosive decreased obviously, and the detonation velocity ranged from2191 to 2312 m/s, which can satisfy the use condition of explosive for explosive welding. In addition, it is found that the detonation performance of emulsion explosives with D50=79 μm fly ash microspheres was higher than those of fly ash microspheres with D50=116 μm and 47 μm. The storage life and thermal analysis results show that the storage life of low detonation velocity emulsion explosives with fly ash microspheres is significantly better than that of traditional low detonation velocity emulsion explosive with clay particles, the activation energy of thermal decomposition of the emulsion explosive with 15% fly ash microspheres was only 0.3% higher than that of emulsion matrix, and the results showed that the addition of fly ash microspheres had no obvious effect on the thermal stability of the emulsion matrix. The research results have important reference value for green resource disposal of coal-based solid waste and formulation design of the low detonation velocity emulsion explosive.
In this paper, the microspheres in fly ash are used as sensitizer and inert additive to prepare the low detonation velocity emulsion explosives. The detonation velocity and the parameters of explosion shock wave in the air of emulsion explosives were measured by the probe method, the lead column compression method and the air explosion method, respectively, and the safety of emulsion explosives was tested by the storage life experiment and thermal analysis experiment. The experimental results show that the detonation velocity, the brisance, the peak pressure, the positive impulse and the positive pressure action time of shock wave of emulsion explosives increased first and then decreased with the increase of the content of fly ash microspheres. When the content of fly ash microspheres was 15%, the detonation performance of emulsion explosive was the best, and when the content of fly ash microspheres was 45% , the detonation velocity of the explosive decreased obviously, and the detonation velocity ranged from
, Available online ,
doi: 10.11883/bzycj-2024-0173
Abstract:
In order to better understand the mechanical response and injury mechanism of the head under the action of explosive shock wave, the geometric information of the head was obtained through computerized tomography and magnetic resonance imaging, and a finite element model of the head with fine cranial bone and brain tissue was developed. Based on the existing blast tube cadaver experiments, forward, side, and backward explosive shock numerical simulations were conducted, and the cranial pressure-time history curves and peak cranial pressure were compared to validate the finite element model. The results show that the peak pressures of the four regions in the cranium under the three impact directions are in good agreement with the experimental and simulated data in the literature; there is obvious stress concentration at the suture line of the cranial bone in the simulated blast simulation; the head has a greater risk of injury at the suture line; and the front and back impacts cause more serious head injuries than the side impact under the same explosive shock intensity. The head model established can be used in the study of head injury under explosive loading, and the influence of suture on the biomechanical response of the head can be explored, which has important research significance for blast injury research.
In order to better understand the mechanical response and injury mechanism of the head under the action of explosive shock wave, the geometric information of the head was obtained through computerized tomography and magnetic resonance imaging, and a finite element model of the head with fine cranial bone and brain tissue was developed. Based on the existing blast tube cadaver experiments, forward, side, and backward explosive shock numerical simulations were conducted, and the cranial pressure-time history curves and peak cranial pressure were compared to validate the finite element model. The results show that the peak pressures of the four regions in the cranium under the three impact directions are in good agreement with the experimental and simulated data in the literature; there is obvious stress concentration at the suture line of the cranial bone in the simulated blast simulation; the head has a greater risk of injury at the suture line; and the front and back impacts cause more serious head injuries than the side impact under the same explosive shock intensity. The head model established can be used in the study of head injury under explosive loading, and the influence of suture on the biomechanical response of the head can be explored, which has important research significance for blast injury research.
, Available online ,
doi: 10.11883/bzycj-2024-0221
Abstract:
Due to the complexity of mild traumatic brain injury (mTBI) and the limitations of data measurement methods, it is often not feasible to directly determine the damage status of the brain based on the brain tissue damage threshold. The damage mechanism of brain tissue involves a variety of complex mechanical, biochemical, and physiological processes that vary significantly between individuals. In addition, existing measurement techniques still have limitations in temporal and spatial resolution, making it difficult to accurately capture the dynamic response of brain tissue. Therefore, establishing the relationship between head motion and brain tissue damage has become a key step in understanding the mechanical mechanism of mild traumatic brain injury. By studying the relationship between head motion and brain tissue damage, researchers can better understand the specific effects of different types of head motion (such as linear acceleration, rotational acceleration, rotational velocity) on brain tissue. This understanding not only helps reveal the basic mechanical mechanisms of mild traumatic brain injury, but also provides a scientific basis for the development of more effective protective equipment. For example, based on these findings, the design of protective helmets can be optimized to better disperse impact energy, reduce stress concentrations in brain tissue, and reduce the risk of trauma. However, there are still many challenges in assessing injury risk directly from kinematic measurements of the head. This article summarizes and reviews in detail the load characteristics related to mild traumatic brain injury and their corresponding brain tissue response, including the stress and strain effects of head kinematic parameters on brain tissue. In addition, this article also explores the head models used in studying brain injury mechanisms and their characteristics, such as high-precision finite element models and multi-scale models, which play an important role in simulating the deformation response of brain tissue. By comprehensively analyzing the relationship between head kinematic parameters and brain tissue deformation response, this article provides important reference and guidance for the prevention, assessment and treatment of mild traumatic brain injury.
Due to the complexity of mild traumatic brain injury (mTBI) and the limitations of data measurement methods, it is often not feasible to directly determine the damage status of the brain based on the brain tissue damage threshold. The damage mechanism of brain tissue involves a variety of complex mechanical, biochemical, and physiological processes that vary significantly between individuals. In addition, existing measurement techniques still have limitations in temporal and spatial resolution, making it difficult to accurately capture the dynamic response of brain tissue. Therefore, establishing the relationship between head motion and brain tissue damage has become a key step in understanding the mechanical mechanism of mild traumatic brain injury. By studying the relationship between head motion and brain tissue damage, researchers can better understand the specific effects of different types of head motion (such as linear acceleration, rotational acceleration, rotational velocity) on brain tissue. This understanding not only helps reveal the basic mechanical mechanisms of mild traumatic brain injury, but also provides a scientific basis for the development of more effective protective equipment. For example, based on these findings, the design of protective helmets can be optimized to better disperse impact energy, reduce stress concentrations in brain tissue, and reduce the risk of trauma. However, there are still many challenges in assessing injury risk directly from kinematic measurements of the head. This article summarizes and reviews in detail the load characteristics related to mild traumatic brain injury and their corresponding brain tissue response, including the stress and strain effects of head kinematic parameters on brain tissue. In addition, this article also explores the head models used in studying brain injury mechanisms and their characteristics, such as high-precision finite element models and multi-scale models, which play an important role in simulating the deformation response of brain tissue. By comprehensively analyzing the relationship between head kinematic parameters and brain tissue deformation response, this article provides important reference and guidance for the prevention, assessment and treatment of mild traumatic brain injury.
, Available online ,
doi: 10.11883/bzycj-2024-0239
Abstract:
In order to explore the underwater anti-explosion protection effect of steel fiber reinforced cellular concrete materials, the damage process of reinforced concrete slabs under underwater contact explosion was reproduced by the coupling method of smoothed particle hydrodynamics and finite element method (SPH-FEM). The validity of the simulation method was verified by comparing with the experimental results. On this basis, a three-dimensional refined simulation model of water-explosive-protective layer-reinforced concrete slab was established by the SPH-FEM coupling method. The damage evolution process, failure mode and failure mechanism of protective layer of steel fiber reinforced cellular concrete (SAP10S5, SAP10S10, SAP10S15 and SAP10S20) with different fiber ratios and explosive mass were studied, and the prediction curve of damage level of reinforced concrete slabs was constructed. The results show that the numerical simulation results are in good agreement with the experimental results, which verifies the effectiveness of the simulation method. Under the underwater contact explosion, the addition of protective layer of steel fiber reinforced cellular concrete can effectively reduce the damage degree of protected reinforced concrete (RC) slab, and its influence on the damage degree of RC slab decreases first and then increases with the increase of steel fiber volume fraction in the protective layer. Among them, the anti-explosion protection effect of protective layer of SAP10S15 ratio is the best. When the amount of explosive increases within a certain range, the protective layer of SAP10S15 ratio can still maintain a high proportion of energy consumption and effectively reduce the damage degree of the RC plate. When the amount of explosive is 0.25 kg, the damage index of RC slabs strengthened with protective layer of SAP10S15 has the most obvious attenuation compared with the unprotected scheme, which is 42.5%, and the damage level is reduced from serious damage to moderate damage. The prediction curve of constructed damage level can directly evaluate the influence of steel fiber volume fraction/explosive amount on the damage degree of RC panel. The above research results can provide reference for the anti-explosion protection design of wading concrete structures.
In order to explore the underwater anti-explosion protection effect of steel fiber reinforced cellular concrete materials, the damage process of reinforced concrete slabs under underwater contact explosion was reproduced by the coupling method of smoothed particle hydrodynamics and finite element method (SPH-FEM). The validity of the simulation method was verified by comparing with the experimental results. On this basis, a three-dimensional refined simulation model of water-explosive-protective layer-reinforced concrete slab was established by the SPH-FEM coupling method. The damage evolution process, failure mode and failure mechanism of protective layer of steel fiber reinforced cellular concrete (SAP10S5, SAP10S10, SAP10S15 and SAP10S20) with different fiber ratios and explosive mass were studied, and the prediction curve of damage level of reinforced concrete slabs was constructed. The results show that the numerical simulation results are in good agreement with the experimental results, which verifies the effectiveness of the simulation method. Under the underwater contact explosion, the addition of protective layer of steel fiber reinforced cellular concrete can effectively reduce the damage degree of protected reinforced concrete (RC) slab, and its influence on the damage degree of RC slab decreases first and then increases with the increase of steel fiber volume fraction in the protective layer. Among them, the anti-explosion protection effect of protective layer of SAP10S15 ratio is the best. When the amount of explosive increases within a certain range, the protective layer of SAP10S15 ratio can still maintain a high proportion of energy consumption and effectively reduce the damage degree of the RC plate. When the amount of explosive is 0.25 kg, the damage index of RC slabs strengthened with protective layer of SAP10S15 has the most obvious attenuation compared with the unprotected scheme, which is 42.5%, and the damage level is reduced from serious damage to moderate damage. The prediction curve of constructed damage level can directly evaluate the influence of steel fiber volume fraction/explosive amount on the damage degree of RC panel. The above research results can provide reference for the anti-explosion protection design of wading concrete structures.
, Available online ,
doi: 10.11883/bzycj-2024-0318
Abstract:
The battery pack of electric vehicles is highly susceptible to failure under side pole collision. To accurately and quickly evaluate the safety of battery packs under such conditions, this paper introduces a local region refined battery pack model that can effectively characterize the deformation and mechanical response of the jellyroll of battery. Simulation analyses were conducted under varying impact velocity, angles, positions, and vehicle loading configuration, with the latter achieved by uniformly applying mass compensation to the side wall of the battery pack. A simulation matrix was designed using an optimized Latin hypercube sampling (LHS) strategy, and a dataset was generated through image recognition methods. This dataset includes parameters such as the maximum intrusion depth, intrusion location, intrusion width of the battery pack side wall, and the deformation of the jellyroll of battery. New features, including collision energy and velocity components in the x and y directions, were derived and selected as input features for model training through correlation analysis. Support vector machine (SVM), random forest (RF), and back propagation neural networks (BPNN) were employed to build a data-driven predictive model. The SVM model demonstrated superior performance, achieving an average R2 of 0.96 across prediction parameters. The prediction of the maximum intrusion depth of the battery pack side wall was particularly accurate, with an R2 exceeding 0.95 for all three models. Additionally, the robustness of the models was tested by introducing Gaussian noise, where the BP neural network exhibited better robustness. Even with the addition of Gaussian noise with a standard deviation of 0.5, the BP model maintained an average R2 of 0.91 for the prediction parameters. The established data-driven model can effectively predict mechanical response of battery packs under side pole collisions and provide a reliable tool for evaluating battery pack safety.
The battery pack of electric vehicles is highly susceptible to failure under side pole collision. To accurately and quickly evaluate the safety of battery packs under such conditions, this paper introduces a local region refined battery pack model that can effectively characterize the deformation and mechanical response of the jellyroll of battery. Simulation analyses were conducted under varying impact velocity, angles, positions, and vehicle loading configuration, with the latter achieved by uniformly applying mass compensation to the side wall of the battery pack. A simulation matrix was designed using an optimized Latin hypercube sampling (LHS) strategy, and a dataset was generated through image recognition methods. This dataset includes parameters such as the maximum intrusion depth, intrusion location, intrusion width of the battery pack side wall, and the deformation of the jellyroll of battery. New features, including collision energy and velocity components in the x and y directions, were derived and selected as input features for model training through correlation analysis. Support vector machine (SVM), random forest (RF), and back propagation neural networks (BPNN) were employed to build a data-driven predictive model. The SVM model demonstrated superior performance, achieving an average R2 of 0.96 across prediction parameters. The prediction of the maximum intrusion depth of the battery pack side wall was particularly accurate, with an R2 exceeding 0.95 for all three models. Additionally, the robustness of the models was tested by introducing Gaussian noise, where the BP neural network exhibited better robustness. Even with the addition of Gaussian noise with a standard deviation of 0.5, the BP model maintained an average R2 of 0.91 for the prediction parameters. The established data-driven model can effectively predict mechanical response of battery packs under side pole collisions and provide a reliable tool for evaluating battery pack safety.
, Available online ,
doi: 10.11883/bzycj-2024-0256
Abstract:
A realistic blast injury model was developed for simulating auditory damage in the inner ears of miniature pigs under controlled explosion conditions to investigate the impact of varying blast shockwave pressures on auditory impairment. Fourteen healthy miniature pigs were selected and underwent auditory brainstem response (ABR) testing prior to exposure to explosions. A free-field explosion platform was constructed utilizing 1.9 kg and 8.0 kg of TNT, with the explosive source 1.8 meters above the ground. The pigs were securely fixed in protective devices, exposing only their head, and placed at varying distances from the blast source. Peak shockwave pressures were measured, and immediate mortality rates were calculated accordingly. Post-explosion ABR tests were conducted, followed by examination of cochlear tissues using scanning electron microscopy to analyze hair cell damage. Shockwave peak pressures ranged from 96.3 kPa to 628.3 kPa over a distance range of 1.8 m to 3.8 m, with pressure decreasing as distance increased. At a distance of 2.6 m, a peak pressure of 628.3 kPa resulted in a mortality ratio of 50%. ABR threshold comparisons before and after the explosion revealed significant increases across all tested frequencies (P < 0.05), with the most notable changes at a frequency of 4 kHz. Scanning electron microscopy analysis demonstrated that inner hair cells exhibited greater susceptibility to damage compared to outer hair cells, with higher shockwave pressure leading to more sever damage. Blast shockwaves caused substantial auditory system damage to miniature pigs as evidenced by elevated ABR thresholds and destruction of cochlear hair cell. Inner hair cells proved more vulnerable to blast shockwaves. The established model can provide a valuable experimental foundation for further studies on blast injury mechanisms and protective strategies.
A realistic blast injury model was developed for simulating auditory damage in the inner ears of miniature pigs under controlled explosion conditions to investigate the impact of varying blast shockwave pressures on auditory impairment. Fourteen healthy miniature pigs were selected and underwent auditory brainstem response (ABR) testing prior to exposure to explosions. A free-field explosion platform was constructed utilizing 1.9 kg and 8.0 kg of TNT, with the explosive source 1.8 meters above the ground. The pigs were securely fixed in protective devices, exposing only their head, and placed at varying distances from the blast source. Peak shockwave pressures were measured, and immediate mortality rates were calculated accordingly. Post-explosion ABR tests were conducted, followed by examination of cochlear tissues using scanning electron microscopy to analyze hair cell damage. Shockwave peak pressures ranged from 96.3 kPa to 628.3 kPa over a distance range of 1.8 m to 3.8 m, with pressure decreasing as distance increased. At a distance of 2.6 m, a peak pressure of 628.3 kPa resulted in a mortality ratio of 50%. ABR threshold comparisons before and after the explosion revealed significant increases across all tested frequencies (P < 0.05), with the most notable changes at a frequency of 4 kHz. Scanning electron microscopy analysis demonstrated that inner hair cells exhibited greater susceptibility to damage compared to outer hair cells, with higher shockwave pressure leading to more sever damage. Blast shockwaves caused substantial auditory system damage to miniature pigs as evidenced by elevated ABR thresholds and destruction of cochlear hair cell. Inner hair cells proved more vulnerable to blast shockwaves. The established model can provide a valuable experimental foundation for further studies on blast injury mechanisms and protective strategies.
, Available online ,
doi: 10.11883/bzycj-2024-0204
Abstract:
Shock tubes can simulate blast waves in laboratory settings, offering advantages such as easily controlled parameters and varied measurement methods. It is widely used in the research of blast wave effects. However, in comparison to real blast, particularly in near-field blast, the blast waves generated by shock tubes has challenges in achieving shorter positive pressure durations and higher overpressure values. Through analysis of shock tube theory and numerical simulations, it has been determined that reducing positive pressure durations hinges on ensuring a swift catch-up by the reflected rarefaction wave with the incident shock wave. Similarly, increasing peak overpressure relies on enhancing the driving capability of the driving gas. Therefore, a conical cross-section driving approach is proposed to reduce the positive pressure durations, which allows the reflected rarefaction wave to catch up with the incident shock wave faster. By employing forward detonation driving technology and utilizing chemical energy to replace high-pressure air to increase the sound speed of the driving gas, high peak overpressure can be achieved at low detonation initial pressure. Numerical simulations show that under the same conditions of the incident shock Mach number (MS=2.0), the positive pressure durations can be reduced by nearly half and the device length can be reduced to nearly one-third by implementing the conical section-driven approach. Experimental results from the shock tube show blast wave characteristics, with peak overpressures ranging from 64.7 kPa to 813.4 kPa and positive pressure durations ranging from 1.7 ms to 4.8 ms. In blast wave simulation experiments, it is important to maintain the peak overpressure within a reasonable range to prevent the interface from reaching the test position. However, when the interface does reach the test position, it is possible to simulate the temperature field of the fireball in near-field blast waves. This research provides the necessary experimental conditions for evaluating the impact of near-field blast waves on injuries and investigating the protective performance of equipment.
Shock tubes can simulate blast waves in laboratory settings, offering advantages such as easily controlled parameters and varied measurement methods. It is widely used in the research of blast wave effects. However, in comparison to real blast, particularly in near-field blast, the blast waves generated by shock tubes has challenges in achieving shorter positive pressure durations and higher overpressure values. Through analysis of shock tube theory and numerical simulations, it has been determined that reducing positive pressure durations hinges on ensuring a swift catch-up by the reflected rarefaction wave with the incident shock wave. Similarly, increasing peak overpressure relies on enhancing the driving capability of the driving gas. Therefore, a conical cross-section driving approach is proposed to reduce the positive pressure durations, which allows the reflected rarefaction wave to catch up with the incident shock wave faster. By employing forward detonation driving technology and utilizing chemical energy to replace high-pressure air to increase the sound speed of the driving gas, high peak overpressure can be achieved at low detonation initial pressure. Numerical simulations show that under the same conditions of the incident shock Mach number (MS=2.0), the positive pressure durations can be reduced by nearly half and the device length can be reduced to nearly one-third by implementing the conical section-driven approach. Experimental results from the shock tube show blast wave characteristics, with peak overpressures ranging from 64.7 kPa to 813.4 kPa and positive pressure durations ranging from 1.7 ms to 4.8 ms. In blast wave simulation experiments, it is important to maintain the peak overpressure within a reasonable range to prevent the interface from reaching the test position. However, when the interface does reach the test position, it is possible to simulate the temperature field of the fireball in near-field blast waves. This research provides the necessary experimental conditions for evaluating the impact of near-field blast waves on injuries and investigating the protective performance of equipment.
, Available online ,
doi: 10.11883/bzycj-2024-0339
Abstract:
The deformation and failure of the internal separator in lithium-ion batteries under external impact are key factors in triggering internal short circuits. The surface of the battery electrodes is usually not smooth, which can cause stress concentration in the separator, affecting the mechanical stability of the battery. Therefore, this study, based on numerical simulation and theoretical analysis, deeply explores the mechanical behavior of the battery separator under compression on uneven surfaces and its short-circuit safety boundary. The model is established using the finite element software ABAQUS, selecting a section of a separator with a width of 50 μm and the nearby positive and negative electrode coatings as a representative unit cell for two-dimensional finite element modeling and numerical calculation. The study compares the surface morphology of three forms: (1) ideal plane; (2) densely packed granular surface; (3) single granular protrusion plane, as well as the effects of particle size, separator thickness, and loading rate. By analyzing the stress-strain curve of the separator, it is found that the separator compressed by uneven surfaces exhibits a "softening phenomenon" compared to compression on an ideal plane. For the ideal plane case, the strain distribution is very uniform, so the battery’s load-bearing capacity is larger. However, for densely packed granular and single granular protrusion cases, under the same loading displacement, the loaded area is smaller, and the generated reaction force is also smaller. As the loading progresses, the gaps are gradually filled, the loaded area increases, and gradually tends to be loaded on the entire surface, and the load difference gradually decreases. Through parametric analysis of the failure stress, it is found that as the particle diameter increases, the separator thickness decreases, or within a certain range of loading rates increases, the separator exhibits a softening behavior, that is, the average stress decreases, the yield point shifts backward, and the short-circuit failure stress also decreases. Furthermore, this study also establishes an equivalent compression constitutive model of the separator under compression on uneven surfaces, thereby theoretically explaining the effect of roughness on failure stress and deriving a quantitative relationship between the two.
The deformation and failure of the internal separator in lithium-ion batteries under external impact are key factors in triggering internal short circuits. The surface of the battery electrodes is usually not smooth, which can cause stress concentration in the separator, affecting the mechanical stability of the battery. Therefore, this study, based on numerical simulation and theoretical analysis, deeply explores the mechanical behavior of the battery separator under compression on uneven surfaces and its short-circuit safety boundary. The model is established using the finite element software ABAQUS, selecting a section of a separator with a width of 50 μm and the nearby positive and negative electrode coatings as a representative unit cell for two-dimensional finite element modeling and numerical calculation. The study compares the surface morphology of three forms: (1) ideal plane; (2) densely packed granular surface; (3) single granular protrusion plane, as well as the effects of particle size, separator thickness, and loading rate. By analyzing the stress-strain curve of the separator, it is found that the separator compressed by uneven surfaces exhibits a "softening phenomenon" compared to compression on an ideal plane. For the ideal plane case, the strain distribution is very uniform, so the battery’s load-bearing capacity is larger. However, for densely packed granular and single granular protrusion cases, under the same loading displacement, the loaded area is smaller, and the generated reaction force is also smaller. As the loading progresses, the gaps are gradually filled, the loaded area increases, and gradually tends to be loaded on the entire surface, and the load difference gradually decreases. Through parametric analysis of the failure stress, it is found that as the particle diameter increases, the separator thickness decreases, or within a certain range of loading rates increases, the separator exhibits a softening behavior, that is, the average stress decreases, the yield point shifts backward, and the short-circuit failure stress also decreases. Furthermore, this study also establishes an equivalent compression constitutive model of the separator under compression on uneven surfaces, thereby theoretically explaining the effect of roughness on failure stress and deriving a quantitative relationship between the two.
, Available online ,
doi: 10.11883/bzycj-2024-0329
Abstract:
As a crucial component to ensure the safety and reliability of lithium-ion batteries (LIBs), the polymer separator plays a significant role in ensuring the mechanical abuse safety of the battery, and its mechanical properties have become an important indicator of battery safety performance. This study focuses on the compressive mechanical behavior of separators in prismatic power batteries under coupled strain rate and temperature conditions. A comprehensive experiment has been conducted including quasi-static and dynamic compression tests across a wide range of strain rates and temperatures. These tests assessed the separator’s mechanical behavior under different strain rates and temperature conditions, with a specific focus on properties and damage mechanism at elevated temperatures and different strain rates. The mechanical response of the separator was meticulously explored, involving an in-depth analysis of strain rate-dependent and temperature-dependent mechanical properties. The results indicated that the separator's mechanical behavior is highly sensitive to both strain rate and temperature. As the strain rate increases, the yield point is reached earlier, causing the separator to yield sooner. Additionally, both the elastic modulus and the yield stress of the separator decrease as the temperature rises. At low strain rates, the yield point shifts forward, whereas at high strain rates, the yield strain increases with temperature. Additionally, the coupled effects of temperature and strain rate were found to alter the damage failure modes, subsequently affecting the separator’s mechanical properties and structural integrity. At low strain rates, the failure of the separator is primarily characterized by plastic deformation and local buckling, whereas complex dynamic failure modes may occur at high strain rates. Based on experimental data, a nonlinear viscoelastic constitutive model was developed, incorporating the effects of temperature-strain rate coupling. This model offers essential insights for the safe and optimized design of lithium-ion batteries. The comprehensive experimental analysis and model developed in this study provide critical references for advancing the design, manufacturing, and practical application of LIB separators, enhancing their reliability and safety across a diverse range of operational conditions.
As a crucial component to ensure the safety and reliability of lithium-ion batteries (LIBs), the polymer separator plays a significant role in ensuring the mechanical abuse safety of the battery, and its mechanical properties have become an important indicator of battery safety performance. This study focuses on the compressive mechanical behavior of separators in prismatic power batteries under coupled strain rate and temperature conditions. A comprehensive experiment has been conducted including quasi-static and dynamic compression tests across a wide range of strain rates and temperatures. These tests assessed the separator’s mechanical behavior under different strain rates and temperature conditions, with a specific focus on properties and damage mechanism at elevated temperatures and different strain rates. The mechanical response of the separator was meticulously explored, involving an in-depth analysis of strain rate-dependent and temperature-dependent mechanical properties. The results indicated that the separator's mechanical behavior is highly sensitive to both strain rate and temperature. As the strain rate increases, the yield point is reached earlier, causing the separator to yield sooner. Additionally, both the elastic modulus and the yield stress of the separator decrease as the temperature rises. At low strain rates, the yield point shifts forward, whereas at high strain rates, the yield strain increases with temperature. Additionally, the coupled effects of temperature and strain rate were found to alter the damage failure modes, subsequently affecting the separator’s mechanical properties and structural integrity. At low strain rates, the failure of the separator is primarily characterized by plastic deformation and local buckling, whereas complex dynamic failure modes may occur at high strain rates. Based on experimental data, a nonlinear viscoelastic constitutive model was developed, incorporating the effects of temperature-strain rate coupling. This model offers essential insights for the safe and optimized design of lithium-ion batteries. The comprehensive experimental analysis and model developed in this study provide critical references for advancing the design, manufacturing, and practical application of LIB separators, enhancing their reliability and safety across a diverse range of operational conditions.
, Available online ,
doi: 10.11883/bzycj-2024-0138
Abstract:
In this study, AlSi10Mg alloy was prepared by selective laser melting (SLM) first, and then subjected to stress relieved annealing treatment. The microstructures of the alloy were analyzed by optical microscope (OM), scanning electron microscope (SEM) and electron backscatter diffraction (EBSD) technology. To understand the influence of coupling effects on the mechanical behavior of AlSi10Mg alloy under wide strain rates and wide temperatures, the mechanical behavior of the alloy under extreme conditions (high and low temperatures, high strain-rate) were analyzed by universal testing machine with an environmental chamber and split Hopkinson pressure bar. The results show that AlSi10Mg alloy possesses fine cellular dendritic microstructure, mainly including α-Al and Si phases, and annealing treatment can result in the discontinuous distribution of eutectic Si particles. The average grain size is 3.7 μm. AlSi10Mg alloy displays strain-rate strengthening effect under room temperature condition at 0.002–4 800 s−1, and has different strain-rate sensitivity in different strain-rate ranges. Under high strain-rate conditions, strain hardening effect still dominates. The material has higher yield strength and flow stress at 173 K. When the strain-rate is 0.002 s−1, the SLM AlSi10Mg alloy has different temperature sensitivities in different temperature ranges. The alloy does not have temperature sensitivity in the range of 173–243 K; the material exhibits temperature sensitivity ranging from 293 K to 573 K, and the softening effect due to temperature on the material intensifies with increasing temperature. Based on the J-C constitutive model, a modified J-C constitutive model expressed by piecewise functions is constructed and the experimental results are fitted. In addition, experimental verification was conducted on the modified J-C constitutive model, and the predicted results are basically consistent with the experimental results. Within the scope of the study, the modified J-C constitutive model effectively reflects the mechanical behavior of the alloy at high and low temperatures and under different strain-rate.
In this study, AlSi10Mg alloy was prepared by selective laser melting (SLM) first, and then subjected to stress relieved annealing treatment. The microstructures of the alloy were analyzed by optical microscope (OM), scanning electron microscope (SEM) and electron backscatter diffraction (EBSD) technology. To understand the influence of coupling effects on the mechanical behavior of AlSi10Mg alloy under wide strain rates and wide temperatures, the mechanical behavior of the alloy under extreme conditions (high and low temperatures, high strain-rate) were analyzed by universal testing machine with an environmental chamber and split Hopkinson pressure bar. The results show that AlSi10Mg alloy possesses fine cellular dendritic microstructure, mainly including α-Al and Si phases, and annealing treatment can result in the discontinuous distribution of eutectic Si particles. The average grain size is 3.7 μm. AlSi10Mg alloy displays strain-rate strengthening effect under room temperature condition at 0.002–4 800 s−1, and has different strain-rate sensitivity in different strain-rate ranges. Under high strain-rate conditions, strain hardening effect still dominates. The material has higher yield strength and flow stress at 173 K. When the strain-rate is 0.002 s−1, the SLM AlSi10Mg alloy has different temperature sensitivities in different temperature ranges. The alloy does not have temperature sensitivity in the range of 173–243 K; the material exhibits temperature sensitivity ranging from 293 K to 573 K, and the softening effect due to temperature on the material intensifies with increasing temperature. Based on the J-C constitutive model, a modified J-C constitutive model expressed by piecewise functions is constructed and the experimental results are fitted. In addition, experimental verification was conducted on the modified J-C constitutive model, and the predicted results are basically consistent with the experimental results. Within the scope of the study, the modified J-C constitutive model effectively reflects the mechanical behavior of the alloy at high and low temperatures and under different strain-rate.
, Available online ,
doi: 10.11883/bzycj-2024-0216
Abstract:
To investigate the mechanism of post-synaptic scaffold protein Preso in the exacerbation of post-traumatic stress disorder (PTSD) by blast-related traumatic brain injury (bTBI), thirty-six male C57 mice were randomly divided into the control group (Sham group), 3.5 MPa bTBI group, 4.5 MPa bTBI group, 5.5 MPa bTBI group, 4.5 MPa bTBI+saline group, 4.5 MPa bTBI+small molecule interfering peptide (TAT-FERM) group, and 6 mice in each group. And twelve Preso-/- mice were randomly divided into Sham group and 4.5 MPa bTBI group, with 6 mice in each group. The mice were subjected to bTBI modelling and were routinely kept for 2 weeks after completion. 4.5 MPa bTBI+saline group and 4.5 MPa bTBI+TAT-FERM group were administered once a day through the tail vein for 5 consecutive days after bTBI modelling. Compared with the control group, the anxiety and depression behavior of 3.5 MPa bTBI mice was not significantly changed. Mice in the 4.5 MPa bTBI and 5.5 MPa bTBI groups showed significant PTSD symptoms and promoted the formation of the Preso/mGluR1 complex. The use of TAT-FERM blocked the interaction between Preso and mGluR1, inhibited the formation of Preso/mGluR1 complex without altering the expression of Preso/mGluR1 complex component proteins, and ameliorated PTSD symptoms caused by bTBI. Results display that the promotion of Preso/mGluR1 complex formation by bTBI is an important molecular pathological mechanism by which bTBI induces PTSD symptoms. The effect of bTBI on PTSD can be attenuated by blocking the interaction between Preso and mGluR1, providing a potential target for the treatment of bTBI-associated PTSD.
To investigate the mechanism of post-synaptic scaffold protein Preso in the exacerbation of post-traumatic stress disorder (PTSD) by blast-related traumatic brain injury (bTBI), thirty-six male C57 mice were randomly divided into the control group (Sham group), 3.5 MPa bTBI group, 4.5 MPa bTBI group, 5.5 MPa bTBI group, 4.5 MPa bTBI+saline group, 4.5 MPa bTBI+small molecule interfering peptide (TAT-FERM) group, and 6 mice in each group. And twelve Preso-/- mice were randomly divided into Sham group and 4.5 MPa bTBI group, with 6 mice in each group. The mice were subjected to bTBI modelling and were routinely kept for 2 weeks after completion. 4.5 MPa bTBI+saline group and 4.5 MPa bTBI+TAT-FERM group were administered once a day through the tail vein for 5 consecutive days after bTBI modelling. Compared with the control group, the anxiety and depression behavior of 3.5 MPa bTBI mice was not significantly changed. Mice in the 4.5 MPa bTBI and 5.5 MPa bTBI groups showed significant PTSD symptoms and promoted the formation of the Preso/mGluR1 complex. The use of TAT-FERM blocked the interaction between Preso and mGluR1, inhibited the formation of Preso/mGluR1 complex without altering the expression of Preso/mGluR1 complex component proteins, and ameliorated PTSD symptoms caused by bTBI. Results display that the promotion of Preso/mGluR1 complex formation by bTBI is an important molecular pathological mechanism by which bTBI induces PTSD symptoms. The effect of bTBI on PTSD can be attenuated by blocking the interaction between Preso and mGluR1, providing a potential target for the treatment of bTBI-associated PTSD.
, Available online ,
doi: 10.11883/bzycj-2024-0321
Abstract:
This investigation seeks to elucidate the impact of various discharge states on the dynamic mechanical responses and failure mechanisms of lithium-ion batteries through a comprehensive experimental study. Employing quasi-static compression tests, the research systematically analyzes the compression characteristics and safety performance of lithium-ion batteries preset to specific discharge levels. These tests were conducted at critical junctures: during discharge, following a 1-hour rest period, and after a 24-hour rest period. This methodology enabled a detailed examination of the force-displacement response characteristics, ultimate load-bearing capacity, and overall safety behaviors under varying electrochemical states. The experimental findings indicate that batteries in a discharged state exhibit lower force-displacement curves, suggesting a decrease in structural stiffness attributable to the electro-chemical reaction inside the battery during the discharge process. Notably, these batteries demonstrated a higher maximum load-bearing capacity compared to those tested after rest periods. Additionally, batteries undergoing compression tests in the midst of discharge were more susceptible to catastrophic failures, such as explosions, whereas those allowed to rest showed significantly enhanced safety characteristics. Further microscopic analysis using Scanning Electron Microscopy (SEM) provided insights into the internal structural changes, revealing extensive damage to electrode particles in batteries tested in the discharged state compared to those tested post-rest. The observed damage and increased risk of mechanical failure are primarily attributed to diffusive stresses generated during the discharge process, which accumulate and intensify the vulnerability of the battery structure under mechanical loads. This study contributes valuable experimental evidence and theoretical insights that are crucial for advancing the understanding of the mechanical integrity and safety of lithium-ion batteries under operational stresses. The findings underscore the importance of considering discharge states in the safety design and evaluation of lithium-ion batteries, potentially leading to enhanced durability and safer application in practical scenarios.
This investigation seeks to elucidate the impact of various discharge states on the dynamic mechanical responses and failure mechanisms of lithium-ion batteries through a comprehensive experimental study. Employing quasi-static compression tests, the research systematically analyzes the compression characteristics and safety performance of lithium-ion batteries preset to specific discharge levels. These tests were conducted at critical junctures: during discharge, following a 1-hour rest period, and after a 24-hour rest period. This methodology enabled a detailed examination of the force-displacement response characteristics, ultimate load-bearing capacity, and overall safety behaviors under varying electrochemical states. The experimental findings indicate that batteries in a discharged state exhibit lower force-displacement curves, suggesting a decrease in structural stiffness attributable to the electro-chemical reaction inside the battery during the discharge process. Notably, these batteries demonstrated a higher maximum load-bearing capacity compared to those tested after rest periods. Additionally, batteries undergoing compression tests in the midst of discharge were more susceptible to catastrophic failures, such as explosions, whereas those allowed to rest showed significantly enhanced safety characteristics. Further microscopic analysis using Scanning Electron Microscopy (SEM) provided insights into the internal structural changes, revealing extensive damage to electrode particles in batteries tested in the discharged state compared to those tested post-rest. The observed damage and increased risk of mechanical failure are primarily attributed to diffusive stresses generated during the discharge process, which accumulate and intensify the vulnerability of the battery structure under mechanical loads. This study contributes valuable experimental evidence and theoretical insights that are crucial for advancing the understanding of the mechanical integrity and safety of lithium-ion batteries under operational stresses. The findings underscore the importance of considering discharge states in the safety design and evaluation of lithium-ion batteries, potentially leading to enhanced durability and safer application in practical scenarios.
, Available online ,
doi: 10.11883/bzycj-2024-0108
Abstract:
Based on the Euler-Lagrangian coupling method (CEL), a fluid-solid coupling model of gunpowder gas-barrel/cannonball-air is established. Numerical simulations are carried out on the launching process of large-caliber artillery shells in low altitude (altitude 0 m), medium altitude (altitude1000 m), sub-high altitude (altitude 3000 m) and high altitude (altitude 5000 m) environments, and the comparative studies are conducted on the influence mechanism of altitudes on the dynamic evolution characteristics of muzzle shock waves. The simulation results show that the dynamic evolution process of the muzzle shock wave has significant direction dependence. The peak pressure of the muzzle shock wave will decrease as the altitude increases (namely the ambient pressure decreases), and the decrease of peak pressure is approximately linear to the change of ambient pressure . Increasing altitude will reduce the pressure peak of the muzzle shock wave for the same position (same distance and direction). The lateral muzzle shock wave, formed at the muzzle brake, dominates the pressure peak in the typical operating zone of the artillery operators (3–5 m behind the muzzle). The pressure peak value and effective action time at different altitudes can cause damage to the hearing organs, and induce the threat to the non-hearing organs. Therefore, the protection capabilities of artillery operators’ equipment is urgently needed to be improved, providing the effective protection for the important organs, such as ears, eyes, lungs and brains.
Based on the Euler-Lagrangian coupling method (CEL), a fluid-solid coupling model of gunpowder gas-barrel/cannonball-air is established. Numerical simulations are carried out on the launching process of large-caliber artillery shells in low altitude (altitude 0 m), medium altitude (altitude
, Available online ,
doi: 10.11883/bzycj-2024-0242
Abstract:
In military operations, terrorist attacks, accidents and other situations, blast injury has become the main mode of casualties, among which the proportion of blast-induced traumatic brain injury (bTBI) has increased significantly, but the specific injury mechanism is still unclear. In order to obtain the acceleration response of human head under the action of explosion shock wave, establish the internal relationship between acceleration and explosion shock wave overpressure, and evaluate the head injury evaluation criteria based on acceleration parameters, this study carried out the air static explosion test of various TNT equivalent spherical charges by using the dummy model with standard body level, on which the acceleration time history curves and the free field overpressure curves of the model head at different scaled distances were obtained. Based on peak linear acceleration, head injury criterion (HIC) and head impact power (HIP), the risk level of head injury was quantitatively analyzed, and the applicability and effectiveness of the three injury assessment indexes were evaluated in the explosion scene. The results show that the acceleration of the dummy head at 4.2 m from the detonation center increases rapidly with the increase of TNT equivalent. In the range from 1 to 4 kg TNT mass, the peak acceleration in the direction of detonation increases from 16.29g to 70.11g. The peak acceleration in each direction is linearly correlated with the peak overpressure. Under the experimental conditions, the maximum risk of mild traumatic brain injury (mTBI) predicted by the three evaluation indexes was 25%, 10%, and 5%, where HIP index evaluated the lower risk of mTBI. When the three evaluation indexes reached the threshold of severe head injury, the corresponding peak overpressure was 0.322, 0.300 and 0.332 MPa, respectively. The peak overpressure corresponding to the HIC index was the lowest, indicating that it had the strongest sensitivity to predict severe head injury.
In military operations, terrorist attacks, accidents and other situations, blast injury has become the main mode of casualties, among which the proportion of blast-induced traumatic brain injury (bTBI) has increased significantly, but the specific injury mechanism is still unclear. In order to obtain the acceleration response of human head under the action of explosion shock wave, establish the internal relationship between acceleration and explosion shock wave overpressure, and evaluate the head injury evaluation criteria based on acceleration parameters, this study carried out the air static explosion test of various TNT equivalent spherical charges by using the dummy model with standard body level, on which the acceleration time history curves and the free field overpressure curves of the model head at different scaled distances were obtained. Based on peak linear acceleration, head injury criterion (HIC) and head impact power (HIP), the risk level of head injury was quantitatively analyzed, and the applicability and effectiveness of the three injury assessment indexes were evaluated in the explosion scene. The results show that the acceleration of the dummy head at 4.2 m from the detonation center increases rapidly with the increase of TNT equivalent. In the range from 1 to 4 kg TNT mass, the peak acceleration in the direction of detonation increases from 16.29g to 70.11g. The peak acceleration in each direction is linearly correlated with the peak overpressure. Under the experimental conditions, the maximum risk of mild traumatic brain injury (mTBI) predicted by the three evaluation indexes was 25%, 10%, and 5%, where HIP index evaluated the lower risk of mTBI. When the three evaluation indexes reached the threshold of severe head injury, the corresponding peak overpressure was 0.322, 0.300 and 0.332 MPa, respectively. The peak overpressure corresponding to the HIC index was the lowest, indicating that it had the strongest sensitivity to predict severe head injury.
, Available online ,
doi: 10.11883/bzycj-2024-0211
Abstract:
The impact from under-body blast (UBB) can easily cause spinal injuries to armored vehicle occupants. In order to comprehensively understand the injury behavior and risk of different spine segment of the occupant under UBB impacts, numerical simulations using a high biofidelity fidelity human finite element model were conducted to simulate the dynamic response process of the occupant spine under typical UBB impacts. Then kinematic, dynamic, and biomechanical response were integrated to study the potential damage behavior of each segment of the spine, and biomechanical indicators were used to analyze spinal injury risk under different loading conditions and protective seat design parameters. The results indicate that: the over extension of the C4-T3 segment is the main reason for injuries to the spinous process, transverse process, and intervertebral disc annulus fibrosus; injuries of the T7-T12 segment are mainly associated with the forward over bending combined with axial compression; the axial compression of the lumbar spine results in a high injury risk at the anterior aspect of the vertebral body and the nucleus pulposus of the intervertebral disc; the risk of spinal segment injury increases with the increase of peak load acceleration, and the risk of thoracolumbar spine injury under anti-blast seat protection is lower, but there is a high risk of cervical spine fracture; reducing the stiffness of the seat suspension can reduce the risk of spinal injury for passengers, but changing the damping parameter of the seat suspension in the range of 0.6−1.2 kN·s/m has no significant effect on the spinal injury risk of occupants.
The impact from under-body blast (UBB) can easily cause spinal injuries to armored vehicle occupants. In order to comprehensively understand the injury behavior and risk of different spine segment of the occupant under UBB impacts, numerical simulations using a high biofidelity fidelity human finite element model were conducted to simulate the dynamic response process of the occupant spine under typical UBB impacts. Then kinematic, dynamic, and biomechanical response were integrated to study the potential damage behavior of each segment of the spine, and biomechanical indicators were used to analyze spinal injury risk under different loading conditions and protective seat design parameters. The results indicate that: the over extension of the C4-T3 segment is the main reason for injuries to the spinous process, transverse process, and intervertebral disc annulus fibrosus; injuries of the T7-T12 segment are mainly associated with the forward over bending combined with axial compression; the axial compression of the lumbar spine results in a high injury risk at the anterior aspect of the vertebral body and the nucleus pulposus of the intervertebral disc; the risk of spinal segment injury increases with the increase of peak load acceleration, and the risk of thoracolumbar spine injury under anti-blast seat protection is lower, but there is a high risk of cervical spine fracture; reducing the stiffness of the seat suspension can reduce the risk of spinal injury for passengers, but changing the damping parameter of the seat suspension in the range of 0.6−1.2 kN·s/m has no significant effect on the spinal injury risk of occupants.
, Available online ,
doi: 10.11883/bzycj-2024-0279
Abstract:
Prefabricated concrete bursting layer has a very important application prospect in the field of protective engineering attributed to its technical advantages including high construction efficiency and construction quality. However, compared with the monolithic cast-in-situ concrete bursting layer, the impact resistance of the prefabricated concrete bursting layer may be significantly reduced because of the interfaces between the prefabricated blocks and the cast-in-situ part. Therefore, it is important for engineers to reasonably design the prefabricated concrete bursting layer to make its penetration resistance comparable to the monolithic one. To this end, a kind of prefabricated bursting layer connected by wet joints and rebars was proposed in our previous study. In order to apply the prefabricated bursting layer in protective engineering, a series of numerical models were developed to further study its penetration resistance. Firstly, based on the Kong-Fang model and smoothed particle Galerkin (SPG) method, the numerical models were developed and validated against the experimental data of projectile penetrating monolithic and prefabricated targets. Then, the validated numerical models were further used to investigate the influences of prefabricated block size, wet joint width and anchorage length, spacing and diameter of rebars on the penetration resistance of prefabricated targets. Numerical results indicate that increasing the width of wet joints, reducing the spacing between rebars, and extending the anchorage length of rebars can significantly enhance the penetration resistance of prefabricated targets. After clarifying the influences of these parameters, an engineering design method for a prefabricated concrete bursting layer was proposed. Finally, based on this method, two prefabricated high performance concrete targets subjected to two typical types of warhead penetration were designed. Numerical results show that the penetration resistances of two prefabricated targets were comparable to monolithic targets. The proposed engineering design method can provide a reference for engineering applications of prefabricated concrete bursting layers connected by the wet joints and rebars.
Prefabricated concrete bursting layer has a very important application prospect in the field of protective engineering attributed to its technical advantages including high construction efficiency and construction quality. However, compared with the monolithic cast-in-situ concrete bursting layer, the impact resistance of the prefabricated concrete bursting layer may be significantly reduced because of the interfaces between the prefabricated blocks and the cast-in-situ part. Therefore, it is important for engineers to reasonably design the prefabricated concrete bursting layer to make its penetration resistance comparable to the monolithic one. To this end, a kind of prefabricated bursting layer connected by wet joints and rebars was proposed in our previous study. In order to apply the prefabricated bursting layer in protective engineering, a series of numerical models were developed to further study its penetration resistance. Firstly, based on the Kong-Fang model and smoothed particle Galerkin (SPG) method, the numerical models were developed and validated against the experimental data of projectile penetrating monolithic and prefabricated targets. Then, the validated numerical models were further used to investigate the influences of prefabricated block size, wet joint width and anchorage length, spacing and diameter of rebars on the penetration resistance of prefabricated targets. Numerical results indicate that increasing the width of wet joints, reducing the spacing between rebars, and extending the anchorage length of rebars can significantly enhance the penetration resistance of prefabricated targets. After clarifying the influences of these parameters, an engineering design method for a prefabricated concrete bursting layer was proposed. Finally, based on this method, two prefabricated high performance concrete targets subjected to two typical types of warhead penetration were designed. Numerical results show that the penetration resistances of two prefabricated targets were comparable to monolithic targets. The proposed engineering design method can provide a reference for engineering applications of prefabricated concrete bursting layers connected by the wet joints and rebars.
, Available online ,
doi: 10.11883/bzycj-2024-0207
Abstract:
To investigate the dynamic mechanical characterization of non-pure and non-intact ice materials under impact loads, a modified split Hopkinson pressure bar (SHPB) was used. Rapid loading, rod end cooling and waveform shaping techniques were used to ensure the stability of the ice material and achieve dynamic stress balance during loading. The impact mechanical properties of complete ice (pure water, containing 2.5%, 3.5%, 4.5% salt, containing 2.0%, 4.5%, 8.5% coconut) and spliced ice (splicing interface inclination 30°, 60°) at freezing temperature of −10 ℃ were studied. The strain rate ranges from 150~250 s−1. The failure process was recorded by using the high-speed camera triggered simultaneously with the pressure rod. The correlation between the stress and strain of the sample, along with the failure process, was determined by analyzing the time history curve of sample. The failure mode of the spliced ice sample was analyzed by combining the Mohr-Coulomb strength criterion. The results show that the pure water ice exhibits the highest compressive strength, followed by the ice with coconut shreds, and both of them show a positive strain rate effect. However, the compressive strength of the ice with salt addition decreases significantly due to its loose structure and the strain rate effect is not obvious. The dynamic compressive strength of ice samples added with coconut fiber increases firstly and then decreases with the increase of coconut fiber content. Ice samples with high coconut fiber content are prone to "double peak" phenomenon due to the binding effect of coconut fiber on broken ice with small particle size. The splicing plane affects the crack growth, resulting in lower compressive strength than the intact ice sample, and affects the failure mode as well. The ice with small interface inclination is mainly damaged by interface slip, while the ice with large interface inclination is mainly damaged by whole ice, which is similar to the intact ice. The research results provide theoretical basis and method reference for the dynamic mechanical properties of non-pure and non-intact ice materials under impact loads.
To investigate the dynamic mechanical characterization of non-pure and non-intact ice materials under impact loads, a modified split Hopkinson pressure bar (SHPB) was used. Rapid loading, rod end cooling and waveform shaping techniques were used to ensure the stability of the ice material and achieve dynamic stress balance during loading. The impact mechanical properties of complete ice (pure water, containing 2.5%, 3.5%, 4.5% salt, containing 2.0%, 4.5%, 8.5% coconut) and spliced ice (splicing interface inclination 30°, 60°) at freezing temperature of −10 ℃ were studied. The strain rate ranges from 150~250 s−1. The failure process was recorded by using the high-speed camera triggered simultaneously with the pressure rod. The correlation between the stress and strain of the sample, along with the failure process, was determined by analyzing the time history curve of sample. The failure mode of the spliced ice sample was analyzed by combining the Mohr-Coulomb strength criterion. The results show that the pure water ice exhibits the highest compressive strength, followed by the ice with coconut shreds, and both of them show a positive strain rate effect. However, the compressive strength of the ice with salt addition decreases significantly due to its loose structure and the strain rate effect is not obvious. The dynamic compressive strength of ice samples added with coconut fiber increases firstly and then decreases with the increase of coconut fiber content. Ice samples with high coconut fiber content are prone to "double peak" phenomenon due to the binding effect of coconut fiber on broken ice with small particle size. The splicing plane affects the crack growth, resulting in lower compressive strength than the intact ice sample, and affects the failure mode as well. The ice with small interface inclination is mainly damaged by interface slip, while the ice with large interface inclination is mainly damaged by whole ice, which is similar to the intact ice. The research results provide theoretical basis and method reference for the dynamic mechanical properties of non-pure and non-intact ice materials under impact loads.
, Available online ,
doi: 10.11883/bzycj-2024-0423
Abstract:
, Available online ,
doi: 10.11883/bzycj-2024-0257
Abstract:
We firstly verified the protective performance of eye equipment (goggles) based on a head dynamic test system and shock tube and field live blast test environments. The results show that goggles have better protective performance and suggest that duty personnel should be equipped with goggles that have combined functions of anti-ultraviolet, anti-glare, anti-smoke and anti-fragmentation in to improve eye protection capabilities. After that, we investigated the tissue damage and functional impairment changes after explosive eye blast injury, and the protective effect and mechanism of the goggles for animal experimental version. This may provide a theoretical basis for prevention and treatment, and also have important implications for the design and improvement of protective goggles. Beagles and C57 mice were used for related animal experiments, and the changes in retinal layer thickness and cell apoptosis were observed after blast injury by HE, Tunel, Nissl staining, visual electrophysiology detection and other methods. It was found that with the increase of blast intensity and the extension of time after explosion, both the degree of retinal injury and cell apoptosis increased, among which the ganglion cell layer and photoreceptor inner and outer segments suffered the most severe damage. Further research on molecular changes indicates that the expression levels of autophagy-related regulatory proteins SQSTM1/p62 (P <0.0001 ) and LC3-II (P = 0.8437 ), as well as LC3-I (P = 0.003), are significantly increased, suggesting that retinal damage is, to some extent, induced by autophagic mechanisms. The protective goggles could effectively reduce the damage of blast wave to retina, protect the structural integrity of retinal nerve fiber layer, inner and outer nuclear layer, ganglion cell layer and photoreceptor inner and outer segments. At the same time, compared with that of other groups, the difference in retinal layer thickness and cell apoptosis was most significant in the 3.5 MPa group, suggesting that the glasses played the maximum protective effect at this intensity, which may be related to the reduction in the retinal autophagy.
We firstly verified the protective performance of eye equipment (goggles) based on a head dynamic test system and shock tube and field live blast test environments. The results show that goggles have better protective performance and suggest that duty personnel should be equipped with goggles that have combined functions of anti-ultraviolet, anti-glare, anti-smoke and anti-fragmentation in to improve eye protection capabilities. After that, we investigated the tissue damage and functional impairment changes after explosive eye blast injury, and the protective effect and mechanism of the goggles for animal experimental version. This may provide a theoretical basis for prevention and treatment, and also have important implications for the design and improvement of protective goggles. Beagles and C57 mice were used for related animal experiments, and the changes in retinal layer thickness and cell apoptosis were observed after blast injury by HE, Tunel, Nissl staining, visual electrophysiology detection and other methods. It was found that with the increase of blast intensity and the extension of time after explosion, both the degree of retinal injury and cell apoptosis increased, among which the ganglion cell layer and photoreceptor inner and outer segments suffered the most severe damage. Further research on molecular changes indicates that the expression levels of autophagy-related regulatory proteins SQSTM1/p62 (P <
, Available online ,
doi: 10.11883/bzycj-2024-0229
Abstract:
To investigate the influence of the density of crushed ice region on the cavity evolution of a structure, an oblique water-entry experiment of the structure was conducted by high-speed photography technology under different crushed ice cover densities. Moreover, by comparing the water-entry process of the oblique structure in varying densities of crushed ice cover, the influence of crushed ice cover density on cavity evolution during the oblique water-entry process of the structure was obtained. Results indicate that during the cavity expansion, the presence of crushed ice reduces the cavity diameter by impeding the outward expansion of the fluid near the free surface, compared with the ice-free environment. When the cavity closes, crushed ice also impedes the inward contraction of the free surface fluid and prolongs the cavity expansion time. The augmentation in the total volume of air within the cavity results in a decrement of the pressure differential between the inside and outside of the cavity, ultimately leading to a retardation in the cavity closure time. As the coverage density of crushed ice gradually increases, the impedance exerted by the crushed ice on the inward contraction of fluid at the free surface progressively intensifies. This enhanced obstruction from the crushed ice further prolongs the cavity closure time and concurrently augments its length and maximum diameter. In conditions of lower crushed ice densities, jets point to the interior of the cavity when the cavity collapses. Besides, under conditions of higher crushed ice cover densities, the cavity wall is wrinkled by the irregular impact of the fluid. As the submerged depth of the structure increases, the cavity undergoes a deep necking under the influence of ambient pressure. As the coverage density of crushed ice gradually increases, the velocity of the underwater motion of the structure shows a trend of faster decay compared to ice-free environments.
To investigate the influence of the density of crushed ice region on the cavity evolution of a structure, an oblique water-entry experiment of the structure was conducted by high-speed photography technology under different crushed ice cover densities. Moreover, by comparing the water-entry process of the oblique structure in varying densities of crushed ice cover, the influence of crushed ice cover density on cavity evolution during the oblique water-entry process of the structure was obtained. Results indicate that during the cavity expansion, the presence of crushed ice reduces the cavity diameter by impeding the outward expansion of the fluid near the free surface, compared with the ice-free environment. When the cavity closes, crushed ice also impedes the inward contraction of the free surface fluid and prolongs the cavity expansion time. The augmentation in the total volume of air within the cavity results in a decrement of the pressure differential between the inside and outside of the cavity, ultimately leading to a retardation in the cavity closure time. As the coverage density of crushed ice gradually increases, the impedance exerted by the crushed ice on the inward contraction of fluid at the free surface progressively intensifies. This enhanced obstruction from the crushed ice further prolongs the cavity closure time and concurrently augments its length and maximum diameter. In conditions of lower crushed ice densities, jets point to the interior of the cavity when the cavity collapses. Besides, under conditions of higher crushed ice cover densities, the cavity wall is wrinkled by the irregular impact of the fluid. As the submerged depth of the structure increases, the cavity undergoes a deep necking under the influence of ambient pressure. As the coverage density of crushed ice gradually increases, the velocity of the underwater motion of the structure shows a trend of faster decay compared to ice-free environments.
, Available online ,
doi: 10.11883/bzycj-2024-0099
Abstract:
Artificial intelligence/machine learning methods can discover hidden physical patterns in data. By constructing an end-to-end surrogate model between state parameters and dynamic results, many complex engineering problems such as strong coupling, nonlinearity, and multiphysics can be efficiently solved. In the field of highly nonlinear explosion and shock dynamics, a classic detonation driving problem was chosen as the research object. Using numerical simulation results as training data for machine learning surrogate models, and combining forward simulation and reverse design organically. Based on deep neural network technology, an end-to-end surrogate model was constructed between feature position velocity profiles, material dynamic deformation, and engineering factors. And the calculation accuracy of the surrogate model was provided, verifying the ability to invert engineering factors from velocity profiles. The research results indicate that the end-to-end surrogate model has high predictive ability, with relative errors of less than 1% in both velocity profile prediction and engineering factor estimation. It can be applied to the rapid design, high-precision prediction, and agile iteration of highly nonlinear explosion and impact dynamics problems.
Artificial intelligence/machine learning methods can discover hidden physical patterns in data. By constructing an end-to-end surrogate model between state parameters and dynamic results, many complex engineering problems such as strong coupling, nonlinearity, and multiphysics can be efficiently solved. In the field of highly nonlinear explosion and shock dynamics, a classic detonation driving problem was chosen as the research object. Using numerical simulation results as training data for machine learning surrogate models, and combining forward simulation and reverse design organically. Based on deep neural network technology, an end-to-end surrogate model was constructed between feature position velocity profiles, material dynamic deformation, and engineering factors. And the calculation accuracy of the surrogate model was provided, verifying the ability to invert engineering factors from velocity profiles. The research results indicate that the end-to-end surrogate model has high predictive ability, with relative errors of less than 1% in both velocity profile prediction and engineering factor estimation. It can be applied to the rapid design, high-precision prediction, and agile iteration of highly nonlinear explosion and impact dynamics problems.
, Available online ,
doi: 10.11883/bzycj-2024-0197
Abstract:
Explosion shock injury is a major public health problem facing China, characterized by high incidence rate, mass occurrence, and difficulty in prevention, with many critical injuries, high infection rates, and difficult diagnosis and treatment. Effective protection against explosive shock injuries is superior to any reliable treatment. Explosion shock injury protection is a complex problem involving multiple disciplines such as medicine, materials science, and explosion shock mechanics. It requires establishing relationships between the propagation of explosion shock waves, injury assessment, material design and preparation, and evaluation of material attenuation performance. Based on this, starting from the generation, propagation of explosion shock wave and the occurrence mechanism of explosion shock injury, this paper introduces the injury mechanism of lung and brain explosion injury, gives the injury mechanics indexes of different degrees of lung and brain explosion injury, systematically reviews the research status and progress of protective materials for explosion shock injury, discusses the protection mechanism of different materials, and focuses on the widely used protective materials for explosion shock wave, such as porous materials, hydrogels, polyurea, etc. In addition, in response to the problem of inconsistent evaluation methods for the attenuation of explosive shock wave performance of protective materials, a comprehensive investigation was conducted on the evaluation methods of material attenuation of explosive shock wave performance, such as biological evaluation method, lead testing method, etc., and the advantages and disadvantages of various evaluation methods were analyzed. Finally, the development trends in the evaluation of explosion shock wave protection performance, the scale relationship between animal explosion shock injury severity and material protection performance and personnel protection, and the relationship between material mechanics indicators and protection performance were discussed. This article aims to provide technical and theoretical references for the design, preparation, application, and testing of protective materials for personnel explosion and impact injuries.
Explosion shock injury is a major public health problem facing China, characterized by high incidence rate, mass occurrence, and difficulty in prevention, with many critical injuries, high infection rates, and difficult diagnosis and treatment. Effective protection against explosive shock injuries is superior to any reliable treatment. Explosion shock injury protection is a complex problem involving multiple disciplines such as medicine, materials science, and explosion shock mechanics. It requires establishing relationships between the propagation of explosion shock waves, injury assessment, material design and preparation, and evaluation of material attenuation performance. Based on this, starting from the generation, propagation of explosion shock wave and the occurrence mechanism of explosion shock injury, this paper introduces the injury mechanism of lung and brain explosion injury, gives the injury mechanics indexes of different degrees of lung and brain explosion injury, systematically reviews the research status and progress of protective materials for explosion shock injury, discusses the protection mechanism of different materials, and focuses on the widely used protective materials for explosion shock wave, such as porous materials, hydrogels, polyurea, etc. In addition, in response to the problem of inconsistent evaluation methods for the attenuation of explosive shock wave performance of protective materials, a comprehensive investigation was conducted on the evaluation methods of material attenuation of explosive shock wave performance, such as biological evaluation method, lead testing method, etc., and the advantages and disadvantages of various evaluation methods were analyzed. Finally, the development trends in the evaluation of explosion shock wave protection performance, the scale relationship between animal explosion shock injury severity and material protection performance and personnel protection, and the relationship between material mechanics indicators and protection performance were discussed. This article aims to provide technical and theoretical references for the design, preparation, application, and testing of protective materials for personnel explosion and impact injuries.
, Available online ,
doi: 10.11883/bzycj-2024-0118
Abstract:
With the wide application of new types of ammunition and large-caliber heavy artillery, the non-contact killing mode caused by explosive shock is rapidly replacing the original direct contact killing caused by bullets, fragments, etc., and its killing power, precision, etc., on the combat personnel and equipment is more threatening. This paper will start from the introduction of the typical test environment and methods of explosive shock wave, through an overview of the explosive impact monitoring and sensing technology and explosive impact flow field reconstruction technology analysis to summarize the development trend, and finally the application of portable explosive shock wave sensing system in the foreign military was briefly introduced for the research and development of China's related products to provide reference experience. At present, the most commonly used sensors in explosion impact tests are overpressure sensors and acceleration sensors. Among them, overpressure sensors can be divided into piezoresistive sensor, piezoelectric sensor and fiber-optic sensor; acceleration sensors cloud be divided into piezoresistive acceleration sensors, piezoelectric acceleration sensors, capacitive acceleration sensors, resonance acceleration sensors, electron tunneling acceleration sensors, thermal convection acceleration sensors and optical acceleration sensors (space light acceleration sensors, fiber-optic acceleration sensors). accelerometers, fiber optic accelerometers). The demanding testing environment requires all sensors to have high frequency response , good detection linear characteristics, high signal-to-noise ratio, high sensitivity, good anti-interference performance, and excellent characteristics such as small size and light weight. Shock wave over-pressure sensor toward miniaturization, standardization, integration and intelligent research direction, while vigorously developing new sensing technology research. Based on CFD data and experimental data, artificial intelligence technology is introduced into the explosion wave signal processing and flow field reconstruction; portable explosion impact detection and evaluation system with independent intellectual property rights in China is developed to provide rapid classification and rapid diagnosis and treatment basis for the protection and rescue of special industry practitioners in extreme environments.
With the wide application of new types of ammunition and large-caliber heavy artillery, the non-contact killing mode caused by explosive shock is rapidly replacing the original direct contact killing caused by bullets, fragments, etc., and its killing power, precision, etc., on the combat personnel and equipment is more threatening. This paper will start from the introduction of the typical test environment and methods of explosive shock wave, through an overview of the explosive impact monitoring and sensing technology and explosive impact flow field reconstruction technology analysis to summarize the development trend, and finally the application of portable explosive shock wave sensing system in the foreign military was briefly introduced for the research and development of China's related products to provide reference experience. At present, the most commonly used sensors in explosion impact tests are overpressure sensors and acceleration sensors. Among them, overpressure sensors can be divided into piezoresistive sensor, piezoelectric sensor and fiber-optic sensor; acceleration sensors cloud be divided into piezoresistive acceleration sensors, piezoelectric acceleration sensors, capacitive acceleration sensors, resonance acceleration sensors, electron tunneling acceleration sensors, thermal convection acceleration sensors and optical acceleration sensors (space light acceleration sensors, fiber-optic acceleration sensors). accelerometers, fiber optic accelerometers). The demanding testing environment requires all sensors to have high frequency response , good detection linear characteristics, high signal-to-noise ratio, high sensitivity, good anti-interference performance, and excellent characteristics such as small size and light weight. Shock wave over-pressure sensor toward miniaturization, standardization, integration and intelligent research direction, while vigorously developing new sensing technology research. Based on CFD data and experimental data, artificial intelligence technology is introduced into the explosion wave signal processing and flow field reconstruction; portable explosion impact detection and evaluation system with independent intellectual property rights in China is developed to provide rapid classification and rapid diagnosis and treatment basis for the protection and rescue of special industry practitioners in extreme environments.
, Available online ,
doi: 10.11883/bzycj-2024-0254
Abstract:
To address the issues of over-excavation at the tunnel arch foot due to the difficulty of forming the perimeter hole blasting and under-excavation at the tunnel face bottom, the damage characteristics of surrounding rock caused by perimeter hole blasting at the arch foot of a horseshoe-shaped tunnel were studied through a combination of theoretical calculations and numerical simulations. On the theoretical level, an in-depth analysis of the stress distribution and crack radius in the arch foot area was conducted based on the principles of blasting mechanics, and the theoretical charge length for the perimeter holes at the arch foot was derived. Building on this, a 3D numerical model of the perimeter holes at the arch foot was established through numerical simulation. During the modeling process, the damage evolution in the surrounding rock during blasting was simulated by introducing an appropriate damage model, and post-blast damage cloud maps were generated. By comparing the damage cloud maps under different conditions, the relationship between blasting effectiveness and parameters such as free surface shape, charge amount, and void deflection angle was analyzed, further revealing the mechanisms by which these parameters influence the blasting formation results, which were validated through field experiments. The research results indicate that the shape of the free surface significantly impacts the extent of surrounding rock damage and the energy utilization efficiency of explosives. A concave free surface results in a smaller damage range compared to a flat free surface, with greater rock confinement, making it difficult for the explosives to effectively fracture the surrounding rock, leading to an energy utilization rate of only 78%. The blasting effectiveness shows a trend of first increasing and then decreasing with the increase in charge amount, with the optimal blasting effectiveness achieved when the linear charge density of the perimeter holes at the arch foot is 0.624. Additionally, by setting voids and adjusting the void deflection angle, the blasting effectiveness of the perimeter holes at the arch foot can be improved. With the optimized blasting parameters, the maximum linear over-excavation at the arch foot was reduced by 53.1%, resulting in a smooth tunnel contour. The research outcomes are engineeringly feasible and provide valuable insights for similar projects.
To address the issues of over-excavation at the tunnel arch foot due to the difficulty of forming the perimeter hole blasting and under-excavation at the tunnel face bottom, the damage characteristics of surrounding rock caused by perimeter hole blasting at the arch foot of a horseshoe-shaped tunnel were studied through a combination of theoretical calculations and numerical simulations. On the theoretical level, an in-depth analysis of the stress distribution and crack radius in the arch foot area was conducted based on the principles of blasting mechanics, and the theoretical charge length for the perimeter holes at the arch foot was derived. Building on this, a 3D numerical model of the perimeter holes at the arch foot was established through numerical simulation. During the modeling process, the damage evolution in the surrounding rock during blasting was simulated by introducing an appropriate damage model, and post-blast damage cloud maps were generated. By comparing the damage cloud maps under different conditions, the relationship between blasting effectiveness and parameters such as free surface shape, charge amount, and void deflection angle was analyzed, further revealing the mechanisms by which these parameters influence the blasting formation results, which were validated through field experiments. The research results indicate that the shape of the free surface significantly impacts the extent of surrounding rock damage and the energy utilization efficiency of explosives. A concave free surface results in a smaller damage range compared to a flat free surface, with greater rock confinement, making it difficult for the explosives to effectively fracture the surrounding rock, leading to an energy utilization rate of only 78%. The blasting effectiveness shows a trend of first increasing and then decreasing with the increase in charge amount, with the optimal blasting effectiveness achieved when the linear charge density of the perimeter holes at the arch foot is 0.624. Additionally, by setting voids and adjusting the void deflection angle, the blasting effectiveness of the perimeter holes at the arch foot can be improved. With the optimized blasting parameters, the maximum linear over-excavation at the arch foot was reduced by 53.1%, resulting in a smooth tunnel contour. The research outcomes are engineeringly feasible and provide valuable insights for similar projects.
, Available online ,
doi: 10.11883/bzycj-2024-0224
Abstract:
To reasonably describe the reaction evolution behavior of explosives after ignition under mechanical confinement, we conduct in-depth analysis of the deformation and movement characteristics of the shell, and divide the response process of the shell into three stages: elastoplastic stage, complete yield stage, and shell rupture stage with inertial motion constraint. The combustion rate theory and the combustion crack-network theory are employed as pivotal parameters for the reaction evolution of the explosives. In the initial stage, the mechanical properties of the shell are taken into consideration, with the material properties serving as the upper limit for structural constraint strength. During this stage, the deformation of the shell remains relatively small. In the second stage, a generalized equivalent stiffness concept is introduced in order to account for the inertial confinement effect of the shell movement. Furthermore, a mechanical deformation analysis of cylindrical shells and end caps is conducted, which takes into account the coupled effects of combustion crack network reaction evolution and shell deformation movement based on a kinematic theory. The third stage is building upon the foundation established in preceding stages, the impact of gas leakage following shell rupture on the progression of the explosive reaction process is considered, The integration of these three stages yields a formula for pressure, shell velocity, and time in the non-impact ignition reaction evolution process of solid explosives. A model for explosives reaction evolution is established to characterize the inertial confinement effects of the shell movement. This model and the related parameters are verified by comparing the calculating results with typical experimental data. It is found that the velocity of shell motion and the changes in internal pressure fundamentally characterize the relationship between the energy release of the explosives and the work done by the product gas. Considering the inertial confinement effects of shell motion is more indicative for the evolution process of explosives reaction, by using this model, the internal pressure of the shell, reaction rate and reaction degree of solid explosives can be calculated based on the historical changes in the velocity of the shell’s motion, thus providing a theoretical method for the explosive safety design and for evaluation under unexpected stimuli.
To reasonably describe the reaction evolution behavior of explosives after ignition under mechanical confinement, we conduct in-depth analysis of the deformation and movement characteristics of the shell, and divide the response process of the shell into three stages: elastoplastic stage, complete yield stage, and shell rupture stage with inertial motion constraint. The combustion rate theory and the combustion crack-network theory are employed as pivotal parameters for the reaction evolution of the explosives. In the initial stage, the mechanical properties of the shell are taken into consideration, with the material properties serving as the upper limit for structural constraint strength. During this stage, the deformation of the shell remains relatively small. In the second stage, a generalized equivalent stiffness concept is introduced in order to account for the inertial confinement effect of the shell movement. Furthermore, a mechanical deformation analysis of cylindrical shells and end caps is conducted, which takes into account the coupled effects of combustion crack network reaction evolution and shell deformation movement based on a kinematic theory. The third stage is building upon the foundation established in preceding stages, the impact of gas leakage following shell rupture on the progression of the explosive reaction process is considered, The integration of these three stages yields a formula for pressure, shell velocity, and time in the non-impact ignition reaction evolution process of solid explosives. A model for explosives reaction evolution is established to characterize the inertial confinement effects of the shell movement. This model and the related parameters are verified by comparing the calculating results with typical experimental data. It is found that the velocity of shell motion and the changes in internal pressure fundamentally characterize the relationship between the energy release of the explosives and the work done by the product gas. Considering the inertial confinement effects of shell motion is more indicative for the evolution process of explosives reaction, by using this model, the internal pressure of the shell, reaction rate and reaction degree of solid explosives can be calculated based on the historical changes in the velocity of the shell’s motion, thus providing a theoretical method for the explosive safety design and for evaluation under unexpected stimuli.
, Available online ,
doi: 10.11883/bzycj-2024-0222
Abstract:
Post-traumatic stress disorder (PTSD) is a complex mental health condition that can arise after a person experiences or witnesses a traumatic event. These events can range from combat situations in military conflicts to natural disasters or personal assaults. The impact of PTSD on individuals and society as a whole is profound, often leading to significant emotional distress and functional impairment. Despite its prevalence, accurately diagnosing PTSD remains a challenge due to the lack of standardized diagnostic criteria. Recent advancements in PTSD research have focused on identifying biomarkers that can aid in the diagnosis and monitoring of the disorder. These biomarkers include genetic susceptibility markers, changes in brain structure and function detected through neuroimaging techniques, alterations in the autonomic nervous system, and specific fluid markers that may indicate biological changes associated with PTSD. By studying these biomarkers, researchers hope to gain a better understanding of the underlying neurobiological mechanisms of PTSD, ultimately leading to more effective screening and treatment strategies. The development of PTSD biomarkers involves a rigorous process of validation, from initial target selection to internal and external validation experiments. Currently, researchers are working towards confirming the clinical utility of these biomarkers through large-scale studies involving multiple research centers and diverse patient populations. By integrating biomarkers with clinical data and demographic risk factors, there is potential to create a comprehensive diagnostic model for PTSD that surpasses traditional questionnaire-based assessments. In the future, a multi-protein diagnostic model based on fluid proteomics profiling could revolutionize the way PTSD is diagnosed and managed. This approach holds promise for providing clinicians with a more reliable and objective tool for identifying and treating individuals with PTSD, ultimately improving outcomes for patients and reducing the burden of this debilitating condition on society.
Post-traumatic stress disorder (PTSD) is a complex mental health condition that can arise after a person experiences or witnesses a traumatic event. These events can range from combat situations in military conflicts to natural disasters or personal assaults. The impact of PTSD on individuals and society as a whole is profound, often leading to significant emotional distress and functional impairment. Despite its prevalence, accurately diagnosing PTSD remains a challenge due to the lack of standardized diagnostic criteria. Recent advancements in PTSD research have focused on identifying biomarkers that can aid in the diagnosis and monitoring of the disorder. These biomarkers include genetic susceptibility markers, changes in brain structure and function detected through neuroimaging techniques, alterations in the autonomic nervous system, and specific fluid markers that may indicate biological changes associated with PTSD. By studying these biomarkers, researchers hope to gain a better understanding of the underlying neurobiological mechanisms of PTSD, ultimately leading to more effective screening and treatment strategies. The development of PTSD biomarkers involves a rigorous process of validation, from initial target selection to internal and external validation experiments. Currently, researchers are working towards confirming the clinical utility of these biomarkers through large-scale studies involving multiple research centers and diverse patient populations. By integrating biomarkers with clinical data and demographic risk factors, there is potential to create a comprehensive diagnostic model for PTSD that surpasses traditional questionnaire-based assessments. In the future, a multi-protein diagnostic model based on fluid proteomics profiling could revolutionize the way PTSD is diagnosed and managed. This approach holds promise for providing clinicians with a more reliable and objective tool for identifying and treating individuals with PTSD, ultimately improving outcomes for patients and reducing the burden of this debilitating condition on society.
, Available online ,
doi: 10.11883/bzycj-2024-0175
Abstract:
The safety of propulsion lithium batteries is a technical bottleneck problem restricting the operation and airworthiness certification of electric aircraft and affects the development of electric aviation worldwide. Failure events such as combustion and explosion triggered by thermal runaway of lithium batteries will cause the catastrophic consequences of aircraft destruction and casualties. This paper aims to introduce the status of aircraft lithium battery thermal runaway explosion characteristics for relevant researchers from three aspects, respectively, lithium-ion battery thermal runaway combustion and explosion behavior, thermal runaway gas explosion limit and thermal runaway gas explosion hazard assessment. In terms of lithium-ion battery thermal runaway explosion behaviors, introduced the lithium-ion battery thermal runaway development process, analyzed the determination of the parameters of the thermal runaway impact characteristics, summarized the evolution of the thermal jet mechanism and the simulation of jet flame and experimental methods; For the thermal runaway gas explosion limit, compared with national and international testing standards for the explosion limit of gases, concluded the theoretical calculation of the explosion limit of thermal runaway gas, as well as in-situ detection of the explosion limit of innovative methods are introduced; In the thermal runaway gas explosion risk assessment, a method of ageing lithium-ion battery risk assessment is proposed by innovatively combining CT non-destructive testing technology with explosion limit in-situ testing method. Based on the characteristics of lithium-ion battery thermal runaway gas explosion limit and pressure rise rate, the factors of explosion danger and explosion severity are obtained, and the explosion risk calculation formula explosion danger parameter indicators are innovated. It proposes that future research will focus on areas such as advanced diagnostic techniques, enhanced electrolyte stability, multi-scale modelling, advanced inhibition techniques, and the establishment of standardized testing processes and safety regulations. It proposes that future research will focus on areas such as advanced diagnostic techniques, enhanced electrolyte stability, multi-scale modeling, advanced inhibition techniques, and the establishment of standardized test procedures and technical regulations.
The safety of propulsion lithium batteries is a technical bottleneck problem restricting the operation and airworthiness certification of electric aircraft and affects the development of electric aviation worldwide. Failure events such as combustion and explosion triggered by thermal runaway of lithium batteries will cause the catastrophic consequences of aircraft destruction and casualties. This paper aims to introduce the status of aircraft lithium battery thermal runaway explosion characteristics for relevant researchers from three aspects, respectively, lithium-ion battery thermal runaway combustion and explosion behavior, thermal runaway gas explosion limit and thermal runaway gas explosion hazard assessment. In terms of lithium-ion battery thermal runaway explosion behaviors, introduced the lithium-ion battery thermal runaway development process, analyzed the determination of the parameters of the thermal runaway impact characteristics, summarized the evolution of the thermal jet mechanism and the simulation of jet flame and experimental methods; For the thermal runaway gas explosion limit, compared with national and international testing standards for the explosion limit of gases, concluded the theoretical calculation of the explosion limit of thermal runaway gas, as well as in-situ detection of the explosion limit of innovative methods are introduced; In the thermal runaway gas explosion risk assessment, a method of ageing lithium-ion battery risk assessment is proposed by innovatively combining CT non-destructive testing technology with explosion limit in-situ testing method. Based on the characteristics of lithium-ion battery thermal runaway gas explosion limit and pressure rise rate, the factors of explosion danger and explosion severity are obtained, and the explosion risk calculation formula explosion danger parameter indicators are innovated. It proposes that future research will focus on areas such as advanced diagnostic techniques, enhanced electrolyte stability, multi-scale modelling, advanced inhibition techniques, and the establishment of standardized testing processes and safety regulations. It proposes that future research will focus on areas such as advanced diagnostic techniques, enhanced electrolyte stability, multi-scale modeling, advanced inhibition techniques, and the establishment of standardized test procedures and technical regulations.
, Available online ,
doi: 10.11883/bzycj-2024-0179
Abstract:
Blast-induced traumatic brain injury (bTBI) is defined as the damaging effect of the shock wave on the brain, which may cause behavioral impairment, physical symptoms and long-term cognitive impairment. Statistically, bTBI is the most common type of traumatic brain injury in combatants, but the mechanism has not been fully elucidated so far because of the high complexity of bTBI. When the shock wave produced during explosions acts on the surface of the skull and propagates within the head, it can lead to a diffuse damage to the brain. In terms of pathological mechanism, bTBI includes two aspects: primary injury and secondary injury. The mechanical injury effect of the shock wave generated by explosions can cause the primary injury of craniocerebral structures, which is usually irreversible and can be only prevented with effective measures. And the secondary injuries will be triggered by the primary injury after bTBI, which involve a series of complex cascades including synaptic dysfunction, excitotoxic injury, blood-brain barrier disruption, meningeal lymphatic system dysfunction, neuroinflammation, mitochondrial dysfunction, oxidative stress, tau protein hyperphosphorylation and amyloid-β pathological changes. And it can last for some time or even extend into the chronic stage after injury, providing a critical window for intervention. It is difficult to diagnose mild bTBI due to the high heterogeneity of clinical symptoms and the positive imaging manifestations. However, great progresses have been made in the research of blood biomarkers of bTBI in recent years, such as ubiquitin carboxyl-terminal hydrolase L1, neuron-specific enolase, neurofilament protein-light, hyperphosphorylated tau protein, myelin basic protein, glial fibrillary acidic protein, S100 calcium-binding protein β and neurogenic exosomes. All of the above-mentioned biomarkers are expected to be effective means of early diagnosis and prognosis judgment of imaging-negative bTBI. In conclusion, this review focuses on the frontier progress of the pathogenesis and biomarkers of bTBI, and looks forward to future research directions in order to provide more new ideas for exploring the pathogenesis, early diagnosis strategies as well as intervention targets of bTBI.
Blast-induced traumatic brain injury (bTBI) is defined as the damaging effect of the shock wave on the brain, which may cause behavioral impairment, physical symptoms and long-term cognitive impairment. Statistically, bTBI is the most common type of traumatic brain injury in combatants, but the mechanism has not been fully elucidated so far because of the high complexity of bTBI. When the shock wave produced during explosions acts on the surface of the skull and propagates within the head, it can lead to a diffuse damage to the brain. In terms of pathological mechanism, bTBI includes two aspects: primary injury and secondary injury. The mechanical injury effect of the shock wave generated by explosions can cause the primary injury of craniocerebral structures, which is usually irreversible and can be only prevented with effective measures. And the secondary injuries will be triggered by the primary injury after bTBI, which involve a series of complex cascades including synaptic dysfunction, excitotoxic injury, blood-brain barrier disruption, meningeal lymphatic system dysfunction, neuroinflammation, mitochondrial dysfunction, oxidative stress, tau protein hyperphosphorylation and amyloid-β pathological changes. And it can last for some time or even extend into the chronic stage after injury, providing a critical window for intervention. It is difficult to diagnose mild bTBI due to the high heterogeneity of clinical symptoms and the positive imaging manifestations. However, great progresses have been made in the research of blood biomarkers of bTBI in recent years, such as ubiquitin carboxyl-terminal hydrolase L1, neuron-specific enolase, neurofilament protein-light, hyperphosphorylated tau protein, myelin basic protein, glial fibrillary acidic protein, S100 calcium-binding protein β and neurogenic exosomes. All of the above-mentioned biomarkers are expected to be effective means of early diagnosis and prognosis judgment of imaging-negative bTBI. In conclusion, this review focuses on the frontier progress of the pathogenesis and biomarkers of bTBI, and looks forward to future research directions in order to provide more new ideas for exploring the pathogenesis, early diagnosis strategies as well as intervention targets of bTBI.
, Available online ,
doi: 10.11883/bzycj-2024-0069
Abstract:
In relation to the application of high-entropy alloy systems containing high-density and high-calorific value elements in the liner of shaped charge warheads, the Ta-Hf-Nb-Zr high-entropy alloy system is investigated. The study employed an INSTRON material testing machine and a split Hopkinson pressure bar testing platform to explore the mechanical response of this high-entropy alloy across a wide range of strain rates from 10−3 to 103 s−1, temperatures ranging from 25 to 900 °C, and stress triaxiality values ranging from 0.33 to 0.89. Yield strength and failure strain data were obtained from static round bar tensile tests and dynamic compression tests conducted under these varying conditions. By using least squares fitting, the parameters of the Johnson-Cook (J-C) constitutive equation as well as the damage failure model parameters, are derived. Subsequently, a simulation model for explosively formed projectile (EFP) made from high-entropy alloys under explosive loading conditions was developed. Pulse X-ray tests of the EFP formation were performed, and numerical simulations of the EFP formation process are conducted using LS-DYNA software. The results show that at 117 μs, the high-entropy alloy EFP remains largely intact, with a length of 51.1 mm and a diameter of 12.27 mm. At 187 μs, three fractures are observed at the tail of the EFP, with the head length measuring 24.3 mm, the diameter at 12.27 mm, and the EFP speed recorded at2496.3 m/s. The numerical simulations demonstrate that the EFP length, diameter, and velocity at these time instants match the test data with errors of less than 8.2%. Moreover, the fracture patterns observed experimentally align closely with those predicted by the simulations. This consistency indicates that the J-C model effectively predicts the formation characteristics of high-entropy alloy EFPs under explosive loading conditions, confirming its utility in accurately simulating the EFP formation process.
In relation to the application of high-entropy alloy systems containing high-density and high-calorific value elements in the liner of shaped charge warheads, the Ta-Hf-Nb-Zr high-entropy alloy system is investigated. The study employed an INSTRON material testing machine and a split Hopkinson pressure bar testing platform to explore the mechanical response of this high-entropy alloy across a wide range of strain rates from 10−3 to 103 s−1, temperatures ranging from 25 to 900 °C, and stress triaxiality values ranging from 0.33 to 0.89. Yield strength and failure strain data were obtained from static round bar tensile tests and dynamic compression tests conducted under these varying conditions. By using least squares fitting, the parameters of the Johnson-Cook (J-C) constitutive equation as well as the damage failure model parameters, are derived. Subsequently, a simulation model for explosively formed projectile (EFP) made from high-entropy alloys under explosive loading conditions was developed. Pulse X-ray tests of the EFP formation were performed, and numerical simulations of the EFP formation process are conducted using LS-DYNA software. The results show that at 117 μs, the high-entropy alloy EFP remains largely intact, with a length of 51.1 mm and a diameter of 12.27 mm. At 187 μs, three fractures are observed at the tail of the EFP, with the head length measuring 24.3 mm, the diameter at 12.27 mm, and the EFP speed recorded at
, Available online ,
doi: 10.11883/bzycj-2024-0255
Abstract:
Mechanical damage to components of the auditory system is the main cause of hearing loss after exposure to blast overpressure waves. There still exist some controversies in high level impulse sound Damage Risk Criteria (DRC). For example, whether average energy or peak overpressure should be used as a main criterion, whether positive duration is important or not, etc. Based on the free-field air explosion, we designed and established a platform for studying blast injuries in large animals. We studied the effect of different explosion parameters on the rupture of the tympanic membrane (TM) and established a relationship between the probability of TM rupture and the dose of the blast wave in terms of peak overpressure and positive duration. The free-field overpressure time history was measured by a pen-shaped pressure sensor. The overpressure time-history curves were fitted by the modified Friedlander equation, thus the peak pressure and positive duration of the blast wave were determined. The impulse pressure energy spectra analysis is performed on the recorded waveforms to determine the signal energy distribution over the frequencies under different explosion parameters. The degree of TM rupture of miniature pigs was recorded after dissection. A two-variable logistic regression was performed on the resulting experimental TM rupture ratio for damage risk curves in terms of peak overpressure and positive duration. The study found that when peak overpressure was lower than 170kPa, there was no obvious damage to the TM; when peak overpressure was greater than 237 kPa, some of the TMs ruptured or were congested with varying severity. As the distance from the explosion center became smaller, the peak pressure became larger, while the severity of TM damage did not increase monotonically. In the 8.0-kg-TNT equivalent explosion, the severity of TM rupture showed a tendency to increase and then decrease as the distance became smaller. Through the analysis of the blast wave characteristics, we found that the smaller the distance away from the center, the shorter the positive duration and the increase in the high-frequency component of the blast wave. The probability of TM rupture of miniature pigs may decrease, but significant hearing loss and inner ear damage still occur at this time. As a viscoelastic membrane structure that transmits sound through vibration, the dynamic response of the eardrum may be closely related to the frequency spectrum of loads. In addition to the peak pressure, the blast wave waveform may have a significant impact on the degree of TM rupture.
Mechanical damage to components of the auditory system is the main cause of hearing loss after exposure to blast overpressure waves. There still exist some controversies in high level impulse sound Damage Risk Criteria (DRC). For example, whether average energy or peak overpressure should be used as a main criterion, whether positive duration is important or not, etc. Based on the free-field air explosion, we designed and established a platform for studying blast injuries in large animals. We studied the effect of different explosion parameters on the rupture of the tympanic membrane (TM) and established a relationship between the probability of TM rupture and the dose of the blast wave in terms of peak overpressure and positive duration. The free-field overpressure time history was measured by a pen-shaped pressure sensor. The overpressure time-history curves were fitted by the modified Friedlander equation, thus the peak pressure and positive duration of the blast wave were determined. The impulse pressure energy spectra analysis is performed on the recorded waveforms to determine the signal energy distribution over the frequencies under different explosion parameters. The degree of TM rupture of miniature pigs was recorded after dissection. A two-variable logistic regression was performed on the resulting experimental TM rupture ratio for damage risk curves in terms of peak overpressure and positive duration. The study found that when peak overpressure was lower than 170kPa, there was no obvious damage to the TM; when peak overpressure was greater than 237 kPa, some of the TMs ruptured or were congested with varying severity. As the distance from the explosion center became smaller, the peak pressure became larger, while the severity of TM damage did not increase monotonically. In the 8.0-kg-TNT equivalent explosion, the severity of TM rupture showed a tendency to increase and then decrease as the distance became smaller. Through the analysis of the blast wave characteristics, we found that the smaller the distance away from the center, the shorter the positive duration and the increase in the high-frequency component of the blast wave. The probability of TM rupture of miniature pigs may decrease, but significant hearing loss and inner ear damage still occur at this time. As a viscoelastic membrane structure that transmits sound through vibration, the dynamic response of the eardrum may be closely related to the frequency spectrum of loads. In addition to the peak pressure, the blast wave waveform may have a significant impact on the degree of TM rupture.
, Available online ,
doi: 10.11883/bzycj-2024-0095
Abstract:
As an environmentally friendly energy-absorbing material, shear-thickening fluid (STF) can be applied to protective structures to improve impact resistance. STF was obtained by mixing fumed silica particles with polyethylene glycol solution. It was then filled into a honeycomb core layer to make STF-filled honeycomb sandwich panels. Finally, the effect of STF on the impact resistance of the structure was explored. The impact force-displacement curves were obtained by using the drop weight impact experiment, and the effects of impact velocity (1.0, 1.5, 2.0 m/s), honeycomb aperture diameter (2.0, 2.5, 3.0 mm), and wall thickness (0.04, 0.06, 0.08 mm) on the mechanical properties of the sandwich panel were studied. At the same time, digital image correlation technology was utilized, which is an optical method for measuring the deformation of the surface of an object. By comparing the pixel displacements in multiple images, the strain history and deflection field distribution of the back panel of the structure were obtained, and the low-velocity impact response process of the structure was discussed. The experimental results show that under low-velocity impact, there is bump deformation in the center area of the back panel of the STF-unfilled honeycomb sandwich panel, and there is obvious bulging deformation in the surrounding area. The central area of the back panel of the STF-filled honeycomb sandwich panels has a wider range of bump deformations and no bulging around it. The shear-thickening effect of STF can increase the honeycomb elements involved in energy absorption, expand the local deformation area of the structure, and reduce the deflection of the back panel of the structure. Increasing the impact velocity, increasing the honeycomb aperture diameter, or decreasing the wall thickness are all more conducive to the shear-thickening effect of STF. The results provide a reference for the application of STF in protective structures.
As an environmentally friendly energy-absorbing material, shear-thickening fluid (STF) can be applied to protective structures to improve impact resistance. STF was obtained by mixing fumed silica particles with polyethylene glycol solution. It was then filled into a honeycomb core layer to make STF-filled honeycomb sandwich panels. Finally, the effect of STF on the impact resistance of the structure was explored. The impact force-displacement curves were obtained by using the drop weight impact experiment, and the effects of impact velocity (1.0, 1.5, 2.0 m/s), honeycomb aperture diameter (2.0, 2.5, 3.0 mm), and wall thickness (0.04, 0.06, 0.08 mm) on the mechanical properties of the sandwich panel were studied. At the same time, digital image correlation technology was utilized, which is an optical method for measuring the deformation of the surface of an object. By comparing the pixel displacements in multiple images, the strain history and deflection field distribution of the back panel of the structure were obtained, and the low-velocity impact response process of the structure was discussed. The experimental results show that under low-velocity impact, there is bump deformation in the center area of the back panel of the STF-unfilled honeycomb sandwich panel, and there is obvious bulging deformation in the surrounding area. The central area of the back panel of the STF-filled honeycomb sandwich panels has a wider range of bump deformations and no bulging around it. The shear-thickening effect of STF can increase the honeycomb elements involved in energy absorption, expand the local deformation area of the structure, and reduce the deflection of the back panel of the structure. Increasing the impact velocity, increasing the honeycomb aperture diameter, or decreasing the wall thickness are all more conducive to the shear-thickening effect of STF. The results provide a reference for the application of STF in protective structures.
, Available online ,
doi: 10.11883/bzycj-2024-0023
Abstract:
Simultaneous or slightly different explosions at multiple points in the concrete medium can generate a complex superposition and aggregation effect of ground shock waves, significantly enhancing the pressure of ground shock waves in a specific area and greatly improving the destructive power of the explosion. In order to obtain the explosion aggregation effect and ground shock propagation attenuation law under the different arrangement of multi-point explosive sources. Firstly, field tests were carried out on single and seven-point aggregated explosions in concrete. Then, the reliability of the RHT material model parameters and the SPH numerical algorithm were verified based on experimental data. On this basis through the orthogonal design method and gray system theory on the multi-point detonation parameters for the optimization of design. Gray correlation coefficients and gray correlations between scaled charge spacing, scaled active charge height, scaled detonation time difference and peak pressure at different proportional bursting center distances were established. Finally, single-objective factor optimization and multi-objective factor optimization were identified, a set of preferred combinations of each factor was determined, and simulation tests were conducted to verify the results. The analysis results show that the concrete material model of RHT and the SPH algorithm can reasonably predict the shock wave propagation attenuation characteristics of multipoint charge explosions at different scaled bursting center distances as well as the induced damage and destruction of concrete; The main factors affecting the impact of the ground shock aggregation of explosive effect, in order of magnitude: scaled charge spacing, scaled detonation time difference and scaled active charge height. The use of optimized detonation parameters, that is, in the case of this test, in the proportional charge spacing 0.549 m/kg1/3, the proportional detonation time difference of 0.239 m/kg1/3, the proportional active charge height of 0, the ground shock aggregation effect to achieve the best, up to the same amount of single-point group charging the same amount of ground shock pressure of 4.7 times.
Simultaneous or slightly different explosions at multiple points in the concrete medium can generate a complex superposition and aggregation effect of ground shock waves, significantly enhancing the pressure of ground shock waves in a specific area and greatly improving the destructive power of the explosion. In order to obtain the explosion aggregation effect and ground shock propagation attenuation law under the different arrangement of multi-point explosive sources. Firstly, field tests were carried out on single and seven-point aggregated explosions in concrete. Then, the reliability of the RHT material model parameters and the SPH numerical algorithm were verified based on experimental data. On this basis through the orthogonal design method and gray system theory on the multi-point detonation parameters for the optimization of design. Gray correlation coefficients and gray correlations between scaled charge spacing, scaled active charge height, scaled detonation time difference and peak pressure at different proportional bursting center distances were established. Finally, single-objective factor optimization and multi-objective factor optimization were identified, a set of preferred combinations of each factor was determined, and simulation tests were conducted to verify the results. The analysis results show that the concrete material model of RHT and the SPH algorithm can reasonably predict the shock wave propagation attenuation characteristics of multipoint charge explosions at different scaled bursting center distances as well as the induced damage and destruction of concrete; The main factors affecting the impact of the ground shock aggregation of explosive effect, in order of magnitude: scaled charge spacing, scaled detonation time difference and scaled active charge height. The use of optimized detonation parameters, that is, in the case of this test, in the proportional charge spacing 0.549 m/kg1/3, the proportional detonation time difference of 0.239 m/kg1/3, the proportional active charge height of 0, the ground shock aggregation effect to achieve the best, up to the same amount of single-point group charging the same amount of ground shock pressure of 4.7 times.
, Available online ,
doi: 10.11883/bzycj-2024-0312
Abstract:
Lithium-ion battery combustion accidents are known for their rapid onset and difficulty in extinguishment, raising significant safety concerns in environments with collision risks. These risks highlight the need for stringent damage assessment and failure prediction methods for power batteries. While severe collisions can cause immediate catastrophic damage and thermal runaway, most collisions occur at low speeds, where the impact may result in only minor external deformation without immediate failure. However, the potential safety risks associated with continued use of batteries after such minor collisions are not well understood. Current research and battery safety standards primarily focus on immediate or short-term failure after impact, leaving a gap in understanding the long-term effects of low-energy collisions on battery safety. This study addresses this gap by investigating the impact of low-energy collisions on the safety and reliability of lithium-ion batteries. A shock-compression sequential loading experiment was used to evaluate the mechanical response and failure behavior of pouch batteries under dynamic loading. The study also explored the deterioration of batteries subjected to weaker impact loads through electrochemical performance testing and internal structural damage analysis. The results reveal that even if a battery does not fail immediately under low-impact energy, its internal mechanical integrity may still be compromised, leading to a lower failure threshold under subsequent loads. Significant deterioration in capacity and internal resistance was observed, with the battery’s ability to withstand secondary loads and its electrochemical performance declining as impact energy increased. This indicates a clear correlation between impact-induced deformation and overall battery performance. The study also proposes a quantitative evaluation method for assessing the battery's condition after minor impacts, offering a valuable tool for predicting the risks associated with reusing impacted batteries. These insights are essential for understanding the response mechanisms of lithium-ion batteries under low-energy collision conditions and for optimizing safety standards for their continued use in collision-prone environments.
Lithium-ion battery combustion accidents are known for their rapid onset and difficulty in extinguishment, raising significant safety concerns in environments with collision risks. These risks highlight the need for stringent damage assessment and failure prediction methods for power batteries. While severe collisions can cause immediate catastrophic damage and thermal runaway, most collisions occur at low speeds, where the impact may result in only minor external deformation without immediate failure. However, the potential safety risks associated with continued use of batteries after such minor collisions are not well understood. Current research and battery safety standards primarily focus on immediate or short-term failure after impact, leaving a gap in understanding the long-term effects of low-energy collisions on battery safety. This study addresses this gap by investigating the impact of low-energy collisions on the safety and reliability of lithium-ion batteries. A shock-compression sequential loading experiment was used to evaluate the mechanical response and failure behavior of pouch batteries under dynamic loading. The study also explored the deterioration of batteries subjected to weaker impact loads through electrochemical performance testing and internal structural damage analysis. The results reveal that even if a battery does not fail immediately under low-impact energy, its internal mechanical integrity may still be compromised, leading to a lower failure threshold under subsequent loads. Significant deterioration in capacity and internal resistance was observed, with the battery’s ability to withstand secondary loads and its electrochemical performance declining as impact energy increased. This indicates a clear correlation between impact-induced deformation and overall battery performance. The study also proposes a quantitative evaluation method for assessing the battery's condition after minor impacts, offering a valuable tool for predicting the risks associated with reusing impacted batteries. These insights are essential for understanding the response mechanisms of lithium-ion batteries under low-energy collision conditions and for optimizing safety standards for their continued use in collision-prone environments.
, Available online ,
doi: 10.11883/bzycj-2024-0240
Abstract:
The thermal shock caused by thermal runaway of lithium batteries will damage the installation structure and pose a threat to the safety of surrounding personnel and equipment, which is a key issue limiting their aviation applications. Through a self-built high-temperature impact experimental platform for lithium battery thermal runaway, it was found that the impact pressure on the battery pack top plate from single-cell thermal shock can reach up to 13.23 kPa, causing the external surface temperature to exceed 274 ℃. The combined effect of high temperature and impact pressure increases the risk of the casing undergoing plastic deformation, buckling, or even failure. To effectively mitigate such risks, a passive protection method of coating the top plate of the battery pack with fireproof coating is proposed. Through large panel combustion experiments and cone calorimeter tests, it was found that the epoxy resin-based intumescent fireproof coatings can effectively block the impact pressure of lithium battery thermal runaway by expanding, and they absorb heat, reducing and delaying the temperature rise of the battery pack top plate, demonstrating excellent thermal shock resistance. By comparing the containment effects of fireproof coatings of different thicknesses, it was found that the 1mm coating is more suitable for practical application needs. Referring to relevant airworthiness regulations, verification tests were conducted on the containment of lithium battery thermal runaway. The analysis of the experiment results shows that the 1.0 mm thick E80S20 coating and E85S15B3 coating reduced the maximum temperature of the battery pack top plate by 52.16% and 55.80%, respectively. Additionally, the maximum structural deformation decreased by 72.2% and 44.4%, respectively. The study indicates that passive protection technology of fireproof coating can effectively enhance the containment of high temperatures and impact hazards caused by thermal runaway. This approach can serve as an effective measure in the safety design of aviation power lithium battery systems.
The thermal shock caused by thermal runaway of lithium batteries will damage the installation structure and pose a threat to the safety of surrounding personnel and equipment, which is a key issue limiting their aviation applications. Through a self-built high-temperature impact experimental platform for lithium battery thermal runaway, it was found that the impact pressure on the battery pack top plate from single-cell thermal shock can reach up to 13.23 kPa, causing the external surface temperature to exceed 274 ℃. The combined effect of high temperature and impact pressure increases the risk of the casing undergoing plastic deformation, buckling, or even failure. To effectively mitigate such risks, a passive protection method of coating the top plate of the battery pack with fireproof coating is proposed. Through large panel combustion experiments and cone calorimeter tests, it was found that the epoxy resin-based intumescent fireproof coatings can effectively block the impact pressure of lithium battery thermal runaway by expanding, and they absorb heat, reducing and delaying the temperature rise of the battery pack top plate, demonstrating excellent thermal shock resistance. By comparing the containment effects of fireproof coatings of different thicknesses, it was found that the 1mm coating is more suitable for practical application needs. Referring to relevant airworthiness regulations, verification tests were conducted on the containment of lithium battery thermal runaway. The analysis of the experiment results shows that the 1.0 mm thick E80S20 coating and E85S15B3 coating reduced the maximum temperature of the battery pack top plate by 52.16% and 55.80%, respectively. Additionally, the maximum structural deformation decreased by 72.2% and 44.4%, respectively. The study indicates that passive protection technology of fireproof coating can effectively enhance the containment of high temperatures and impact hazards caused by thermal runaway. This approach can serve as an effective measure in the safety design of aviation power lithium battery systems.
, Available online ,
doi: 10.11883/bzycj-2024-0188
Abstract:
To improve the safety performance of cylindrical lithium-ion batteries under radial dynamic impacting, the dynamic response characteristics of the batteries under large deformation were investigated based on the membrane factor method. Firstly, the battery was simplified to sandwich beam including the casing and inner core. The plastic yield criterion and membrane factor of the battery cross-section were established based on tensile yield strengths. The membrane factor was introduced into the motion equation to solve the dynamic response under large deformation. Furthermore, the mechanical properties of the battery components were determined based on tensile and compression tests. Then the finite element (FE) model of the battery was developed. It has been shown that the theoretical results and FE results of the displacement responses and velocity responses of the battery were in good agreement. The larger the initial velocity of the battery under impact loading, the larger the effect of axial force effect on the dynamic response. The maximum deflection of the battery increases approximately linearly with initial velocity, and the actual response time shows saturation. The maximum deflection of the battery increases with the decrease of the ratio of casing yield strength to core yield strength. The effect of yield strength is significant under thin battery casings. The maximum deflection of the battery decreases with the increase of the casing thickness. Under high yield strength ratio, the effect of casing thickness is significant. The research can provide technical support for the failure prediction and structural safety design of the battery.
To improve the safety performance of cylindrical lithium-ion batteries under radial dynamic impacting, the dynamic response characteristics of the batteries under large deformation were investigated based on the membrane factor method. Firstly, the battery was simplified to sandwich beam including the casing and inner core. The plastic yield criterion and membrane factor of the battery cross-section were established based on tensile yield strengths. The membrane factor was introduced into the motion equation to solve the dynamic response under large deformation. Furthermore, the mechanical properties of the battery components were determined based on tensile and compression tests. Then the finite element (FE) model of the battery was developed. It has been shown that the theoretical results and FE results of the displacement responses and velocity responses of the battery were in good agreement. The larger the initial velocity of the battery under impact loading, the larger the effect of axial force effect on the dynamic response. The maximum deflection of the battery increases approximately linearly with initial velocity, and the actual response time shows saturation. The maximum deflection of the battery increases with the decrease of the ratio of casing yield strength to core yield strength. The effect of yield strength is significant under thin battery casings. The maximum deflection of the battery decreases with the increase of the casing thickness. Under high yield strength ratio, the effect of casing thickness is significant. The research can provide technical support for the failure prediction and structural safety design of the battery.
, Available online ,
doi: 10.11883/bzycj-2024-0158
Abstract:
Combined with the actual distribution characteristics of tungsten fibers and metallic glass matrix, a three-dimensional (3D) mesoscale finite element (FE) geometric model of a long rod of tungsten fiber-reinforced metallic glass composite was established, and the coupled thermo-mechanical constitutive model was used to describe the high strength and high shear sensitivity of metallic glass matrix. FE simulations on the oblique penetration/perforation of composite and tungsten alloy long rods into steel targets were carried out combined with related oblique penetrating tests, and comparative analyses on the deformation and failure characteristics of projectiles and targets were conducted. Furthermore, the influences of oblique angle and impact velocity on the ‘self-sharpening’ behavior of composite long rods and the corresponding ballistic performance were investigated in detail. Related analysis shows that in the oblique impact condition, due to the asymmetrical characteristics of target resistance on the rod, the rod nose gradually sharpens into an asymmetrical pointed configuration, and certain deflection occurs in the trajectory. Consequently, the ‘self-sharpening’ behavior in the composite long rod is weakened to a certain extent, and thus a decay occurs in its penetrating property. Besides, the impact velocity also contributes to the ‘self-sharpening’ characteristics and the corresponding ballistic behavior in the oblique impact condition, and the decay of penetrating capability derived from the oblique angle is more remarkable at lower impact velocities. When the oblique angle increases to 50°, the composite long rod is hard to effectively penetrate the target at an impact velocity lower than 900 m/s, and ricochet becomes easy when it impacts under a higher oblique angle. The results are of good significance in predicting the penetrating ability of tungsten fiber-reinforced metallic glass matrix composite long rods and optimizing its impact attitude.
Combined with the actual distribution characteristics of tungsten fibers and metallic glass matrix, a three-dimensional (3D) mesoscale finite element (FE) geometric model of a long rod of tungsten fiber-reinforced metallic glass composite was established, and the coupled thermo-mechanical constitutive model was used to describe the high strength and high shear sensitivity of metallic glass matrix. FE simulations on the oblique penetration/perforation of composite and tungsten alloy long rods into steel targets were carried out combined with related oblique penetrating tests, and comparative analyses on the deformation and failure characteristics of projectiles and targets were conducted. Furthermore, the influences of oblique angle and impact velocity on the ‘self-sharpening’ behavior of composite long rods and the corresponding ballistic performance were investigated in detail. Related analysis shows that in the oblique impact condition, due to the asymmetrical characteristics of target resistance on the rod, the rod nose gradually sharpens into an asymmetrical pointed configuration, and certain deflection occurs in the trajectory. Consequently, the ‘self-sharpening’ behavior in the composite long rod is weakened to a certain extent, and thus a decay occurs in its penetrating property. Besides, the impact velocity also contributes to the ‘self-sharpening’ characteristics and the corresponding ballistic behavior in the oblique impact condition, and the decay of penetrating capability derived from the oblique angle is more remarkable at lower impact velocities. When the oblique angle increases to 50°, the composite long rod is hard to effectively penetrate the target at an impact velocity lower than 900 m/s, and ricochet becomes easy when it impacts under a higher oblique angle. The results are of good significance in predicting the penetrating ability of tungsten fiber-reinforced metallic glass matrix composite long rods and optimizing its impact attitude.
, Available online ,
doi: 10.11883/bzycj-2024-0205
Abstract:
Lung blast injury is the most common cause of death from primary blast injuries, and effective protection is crucial for mitigating injuries and improving treatment outcomes. Research on polyurea materials as body armor is still in its early stages. This study conducted numerical simulations to investigate the mechanical response of lungs protected by polyurea under blast wave conditions and the attenuation characteristics of polyurea against blast waves. LS-DYNA was used to simulate the direct damage process of blast waves on the thorax of goats wearing protective materials, and the validity was verified through field pressure data and gross lung injury observations. Finally, the finite element model of blast wave protection effects was used to evaluate the protective effects of polyurea materials on human lung blast injuries. The results showed that when the right lung faces the blast center, the stress from lung injuries is mainly concentrated in the lower lobe of the right lung. The overall stress in the protected lung model is lower, and the lung overtraction effect caused by the negative pressure is weakened. Polyurea materials can effectively attenuate the peak overpressure on the skin and lung surface by approximately 58.8%, reduce the maximum velocity of the sternum by about 22.4%, and enhance attenuation capacity with increasing blast wave pressure, thereby effectively reducing the incidence and severity of lung blast injuries. The established computer simulation evaluation model for personnel protection effects provides a method for evaluating the protective efficacy of new protective materials against lung blast injuries and predicting post-protection injury severity, with significant military and social implications.
Lung blast injury is the most common cause of death from primary blast injuries, and effective protection is crucial for mitigating injuries and improving treatment outcomes. Research on polyurea materials as body armor is still in its early stages. This study conducted numerical simulations to investigate the mechanical response of lungs protected by polyurea under blast wave conditions and the attenuation characteristics of polyurea against blast waves. LS-DYNA was used to simulate the direct damage process of blast waves on the thorax of goats wearing protective materials, and the validity was verified through field pressure data and gross lung injury observations. Finally, the finite element model of blast wave protection effects was used to evaluate the protective effects of polyurea materials on human lung blast injuries. The results showed that when the right lung faces the blast center, the stress from lung injuries is mainly concentrated in the lower lobe of the right lung. The overall stress in the protected lung model is lower, and the lung overtraction effect caused by the negative pressure is weakened. Polyurea materials can effectively attenuate the peak overpressure on the skin and lung surface by approximately 58.8%, reduce the maximum velocity of the sternum by about 22.4%, and enhance attenuation capacity with increasing blast wave pressure, thereby effectively reducing the incidence and severity of lung blast injuries. The established computer simulation evaluation model for personnel protection effects provides a method for evaluating the protective efficacy of new protective materials against lung blast injuries and predicting post-protection injury severity, with significant military and social implications.
, Available online ,
doi: 10.11883/bzycj-2024-0073
Abstract:
To improve the accuracy and robustness of the explicit FEM algorithm based on penalty method for simulating large deformation contact-impact problem, a new large-deformation non-penetration contact algorithm based on forward incremental displacement central difference (FIDCD) was developed. On the one hand, according to FIDCD, the solving step of the dynamic equation was decomposed into an estimated step without considering contact and a correction step considering contact constraint. At the current moment, a contact force was applied thorough the penalty method to make the deformation of entities satisfy the non-penetration condition. The contact force was calculated by a soft constraint penalty stiffness, which helped to maintain stability of contact localization. It enhanced the numerical accuracy of the explicit contact computation. On the other hand, to accurately calculate the large-deformation internal force of the next moment while only obtaining the displacement, the internal force term of the dynamic equation was mapped to a known configuration for solution based on the arbitrary reference configurations (ARC) theory. It avoided using the values of variables at intermediate configuration to approximate them, thereby improving the numerical accuracy of the large deformation computation. More rigorous contact algorithms and geometric nonlinear solution strategy can effectively suppress mesh distortion and non-physical penetration between entities during large-deformation impact simulation. This thus improved the robustness of the new explicit algorithm. Finally, the computational program written according to the new developed algorithm was applied to simulate several impact and penetration examples with different impact velocities. By comparing the simulation results with those obtained from commercial software, the correctness of the developed algorithm and computational program was verified. At the same time, it can also be proven that the algorithm proposed is more robust in simulating high-speed and large-deformation impact problems than the classical explicit contact-impact algorithm based on the frog jump center difference scheme combining with penalty method.
To improve the accuracy and robustness of the explicit FEM algorithm based on penalty method for simulating large deformation contact-impact problem, a new large-deformation non-penetration contact algorithm based on forward incremental displacement central difference (FIDCD) was developed. On the one hand, according to FIDCD, the solving step of the dynamic equation was decomposed into an estimated step without considering contact and a correction step considering contact constraint. At the current moment, a contact force was applied thorough the penalty method to make the deformation of entities satisfy the non-penetration condition. The contact force was calculated by a soft constraint penalty stiffness, which helped to maintain stability of contact localization. It enhanced the numerical accuracy of the explicit contact computation. On the other hand, to accurately calculate the large-deformation internal force of the next moment while only obtaining the displacement, the internal force term of the dynamic equation was mapped to a known configuration for solution based on the arbitrary reference configurations (ARC) theory. It avoided using the values of variables at intermediate configuration to approximate them, thereby improving the numerical accuracy of the large deformation computation. More rigorous contact algorithms and geometric nonlinear solution strategy can effectively suppress mesh distortion and non-physical penetration between entities during large-deformation impact simulation. This thus improved the robustness of the new explicit algorithm. Finally, the computational program written according to the new developed algorithm was applied to simulate several impact and penetration examples with different impact velocities. By comparing the simulation results with those obtained from commercial software, the correctness of the developed algorithm and computational program was verified. At the same time, it can also be proven that the algorithm proposed is more robust in simulating high-speed and large-deformation impact problems than the classical explicit contact-impact algorithm based on the frog jump center difference scheme combining with penalty method.
, Available online ,
doi: 10.11883/bzycj-2023-0452
Abstract:
To predict precisely the lower explosion limit of thermal runaway products of lithium iron phosphate batteries, thermal runaway tests of lithium iron phosphate batteries were carried out in a closed pressure vessel. The experiments were carried out at 25 ℃ and 0.1 MPa, and the method was used to analyze the thermal runaway gas production. The vent gas species composition of lithium iron phosphate batteries was analyzed by gas chromatography and mass spectrometry. Combined with the thermal runaway characteristics of the battery and gas chromatography-mass spectrometry (GC-MS) technology, the gas composition of thermal runaway products of lithium iron phosphate batteries was calculated. It was assumed that the thermal runway products released from the relief valve to the first injection were all dimethyl carbonate (DMC), and the secondary injection gas was the mixed gas generated by the internal chemical reaction, which is mainly composed of H2, CO2, CO, CH4, and C2H4. A prediction model of the lower explosion limit of thermal runaway products was established based on the energy conservation equation and adiabatic flame temperature. The prediction methods of lower explosion limit of multicomponent gases based on adiabatic flame temperature, Le Chatelier law method, and Jones method were verified, and the influence of electrolyte vapor on the lower explosion limit of thermal runaway production was also investigated. The smallest deviation of the lower explosion limit calculated by the Le Chatelier law method at normal temperature and pressure was 1.14%, and the largest deviation of the lower explosion limit calculated by the adiabatic flame temperature method was 10.02%. Within the range from 60% SOC to 100% SOC, the lower explosion limit of the thermal runaway gases increases first and then decreases. When the electrolyte vapor is considered in the thermal runaway products, the lower explosion limit of thermal runaway products of lithium iron phosphate batteries with 60% SOC is only 3.93%, which is 22.49% lower than that of the thermal runaway gas without considering the electrolyte vapor. Actually, the electrolyte vapor is contained in the thermal runaway products of lithium iron phosphate batteries. These results indicate that the addition of electrolyte vapor increases the explosion risk of thermal runaway production of lithium iron phosphate batteries.
To predict precisely the lower explosion limit of thermal runaway products of lithium iron phosphate batteries, thermal runaway tests of lithium iron phosphate batteries were carried out in a closed pressure vessel. The experiments were carried out at 25 ℃ and 0.1 MPa, and the method was used to analyze the thermal runaway gas production. The vent gas species composition of lithium iron phosphate batteries was analyzed by gas chromatography and mass spectrometry. Combined with the thermal runaway characteristics of the battery and gas chromatography-mass spectrometry (GC-MS) technology, the gas composition of thermal runaway products of lithium iron phosphate batteries was calculated. It was assumed that the thermal runway products released from the relief valve to the first injection were all dimethyl carbonate (DMC), and the secondary injection gas was the mixed gas generated by the internal chemical reaction, which is mainly composed of H2, CO2, CO, CH4, and C2H4. A prediction model of the lower explosion limit of thermal runaway products was established based on the energy conservation equation and adiabatic flame temperature. The prediction methods of lower explosion limit of multicomponent gases based on adiabatic flame temperature, Le Chatelier law method, and Jones method were verified, and the influence of electrolyte vapor on the lower explosion limit of thermal runaway production was also investigated. The smallest deviation of the lower explosion limit calculated by the Le Chatelier law method at normal temperature and pressure was 1.14%, and the largest deviation of the lower explosion limit calculated by the adiabatic flame temperature method was 10.02%. Within the range from 60% SOC to 100% SOC, the lower explosion limit of the thermal runaway gases increases first and then decreases. When the electrolyte vapor is considered in the thermal runaway products, the lower explosion limit of thermal runaway products of lithium iron phosphate batteries with 60% SOC is only 3.93%, which is 22.49% lower than that of the thermal runaway gas without considering the electrolyte vapor. Actually, the electrolyte vapor is contained in the thermal runaway products of lithium iron phosphate batteries. These results indicate that the addition of electrolyte vapor increases the explosion risk of thermal runaway production of lithium iron phosphate batteries.
, Available online ,
doi: 10.11883/bzycj-2024-0150
Abstract:
The protection level and domestic standard test level of commonly used passive flexible barriers against rockfall impact are not higher than 5 000 kJ, while bridges in mountains and other important transportation infrastructures are facing rockfall disaster threats with higher impact energy levels. Considering that the design method for passive flexible barriers with higher impact energy levels is lacking, to provide a feasible and reliable tool for the infrastructure engineers, the analysis and design of 8 000 kJ-level passive flexible barrier against rockfall impact were carried out at present based on the numerical simulation method. Firstly, by adopting the explicit dynamic software ANSYS/LS-DYNA, quasi-static tests, including the tensile test on single wire ring and three-ring chain, net puncturing test, and the dynamic impact test, i.e., 2 000 kJ rockfall impacting the full-scale passive flexible barrier, were numerically reproduced, and the reliability of the numerical simulation method was fully verified by comparing with the experimental data, i.e., the maximum breaking force and breaking displacement of the wire ring and its failure characteristics, the whole impact process of rockfall, and the cable force-time history curves. The influencing factors, i.e., the inclining angle, span, and height of the steel post and different specifications of energy dissipating devices ranging from 50 kJ to 70 kJ, on the dynamic behavior of the passive flexible barrier were further analyzed. The results show that the specification of the energy dissipation device is the most critical parameter controlling the internal force and displacement of the passive flexible barrier. The inclining angle of the steel post is recommended to be 10°. An increase in the post spacing can reduce the in-plane stiffness of the structure while having less effect on the transverse anchorage. An increase in the post height will cause a significant increase in the support reaction force at the post bottom. A reasonable adjustment of the anchorage position of each wire rope is required when the post height and spacing are changed. Finally, based on the results of parameter analysis, two design schemes for a passive flexible barrier against 8 000 kJ rockfall impact were given by adjusting the geometry of the structure, the specification of the energy dissipating device, and the addition of transmission support ropes. Both of them passed the test of the European standard EAD 340059-00-0106.
The protection level and domestic standard test level of commonly used passive flexible barriers against rockfall impact are not higher than 5 000 kJ, while bridges in mountains and other important transportation infrastructures are facing rockfall disaster threats with higher impact energy levels. Considering that the design method for passive flexible barriers with higher impact energy levels is lacking, to provide a feasible and reliable tool for the infrastructure engineers, the analysis and design of 8 000 kJ-level passive flexible barrier against rockfall impact were carried out at present based on the numerical simulation method. Firstly, by adopting the explicit dynamic software ANSYS/LS-DYNA, quasi-static tests, including the tensile test on single wire ring and three-ring chain, net puncturing test, and the dynamic impact test, i.e., 2 000 kJ rockfall impacting the full-scale passive flexible barrier, were numerically reproduced, and the reliability of the numerical simulation method was fully verified by comparing with the experimental data, i.e., the maximum breaking force and breaking displacement of the wire ring and its failure characteristics, the whole impact process of rockfall, and the cable force-time history curves. The influencing factors, i.e., the inclining angle, span, and height of the steel post and different specifications of energy dissipating devices ranging from 50 kJ to 70 kJ, on the dynamic behavior of the passive flexible barrier were further analyzed. The results show that the specification of the energy dissipation device is the most critical parameter controlling the internal force and displacement of the passive flexible barrier. The inclining angle of the steel post is recommended to be 10°. An increase in the post spacing can reduce the in-plane stiffness of the structure while having less effect on the transverse anchorage. An increase in the post height will cause a significant increase in the support reaction force at the post bottom. A reasonable adjustment of the anchorage position of each wire rope is required when the post height and spacing are changed. Finally, based on the results of parameter analysis, two design schemes for a passive flexible barrier against 8 000 kJ rockfall impact were given by adjusting the geometry of the structure, the specification of the energy dissipating device, and the addition of transmission support ropes. Both of them passed the test of the European standard EAD 340059-00-0106.
, Available online ,
doi: 10.11883/bzycj-2024-0152
Abstract:
To investigate the dynamic mechanical properties of sandstone in deep strata under impact loads, an improved Hopkinson pressure bar experimental system was established. The traditional Hopkinson pressure bar's transmission rod was replaced with a long rod specimen made of gray sandstone to better simulate deep geological conditions. Point spalling treatment was applied to the specimen, and strain gauges were meticulously affixed at critical measurement points.Dynamic compression experiments were meticulously conducted on the gray sandstone long rod specimen at various loading rates (9.57 m/s, 14.78 m/s, 19.32 m/s, and 27.60 m/s). Utilizing high-speed digital image correlation (DIC) technology, the evolution of displacement and strain fields on the surface of the specimen throughout each test was closely monitored. This advanced technique enabled a detailed exploration of how the gray sandstone responded to near-field impact loading, particularly focusing on its tensile failure characteristics.Employing the Lagrangian analysis method, displacement-time curves for different mass points derived from the DIC analysis of displacement fields were extracted. These curves provided critical data to compute the stress-strain behavior of the gray sandstone material under dynamic loading conditions. The study reveals several key findings: the gray sandstone long rod specimen predominantly exhibits tensile failure, with distinct patterns of fragmentation near the loading end and layer cracking away from it. Moreover, the dynamic compressive strength factor of the gray sandstone long rod specimen shows a notable increase with higher strain rates, indicating a significant strain rate effect. Correspondingly, both stress and strain peaks observe an upward trend at various measurement points with increasing loading rates.Remarkably, under identical loading rates, stress-strain curves of the gray sandstone long rod specimen exhibit a unique phenomenon where curves from measurement points closer to the loading end envelop those from points farther away. This observation underscores the complex nature of dynamic loading responses in geological materials.Overall, this comprehensive investigation provides essential theoretical insights and methodological references for understanding the dynamic behavior of sandstone within deep geological formations under impact loads. The findings offer valuable contributions to engineering practices concerned with the stability and resilience of underground structures subjected to dynamic loading conditions.
To investigate the dynamic mechanical properties of sandstone in deep strata under impact loads, an improved Hopkinson pressure bar experimental system was established. The traditional Hopkinson pressure bar's transmission rod was replaced with a long rod specimen made of gray sandstone to better simulate deep geological conditions. Point spalling treatment was applied to the specimen, and strain gauges were meticulously affixed at critical measurement points.Dynamic compression experiments were meticulously conducted on the gray sandstone long rod specimen at various loading rates (9.57 m/s, 14.78 m/s, 19.32 m/s, and 27.60 m/s). Utilizing high-speed digital image correlation (DIC) technology, the evolution of displacement and strain fields on the surface of the specimen throughout each test was closely monitored. This advanced technique enabled a detailed exploration of how the gray sandstone responded to near-field impact loading, particularly focusing on its tensile failure characteristics.Employing the Lagrangian analysis method, displacement-time curves for different mass points derived from the DIC analysis of displacement fields were extracted. These curves provided critical data to compute the stress-strain behavior of the gray sandstone material under dynamic loading conditions. The study reveals several key findings: the gray sandstone long rod specimen predominantly exhibits tensile failure, with distinct patterns of fragmentation near the loading end and layer cracking away from it. Moreover, the dynamic compressive strength factor of the gray sandstone long rod specimen shows a notable increase with higher strain rates, indicating a significant strain rate effect. Correspondingly, both stress and strain peaks observe an upward trend at various measurement points with increasing loading rates.Remarkably, under identical loading rates, stress-strain curves of the gray sandstone long rod specimen exhibit a unique phenomenon where curves from measurement points closer to the loading end envelop those from points farther away. This observation underscores the complex nature of dynamic loading responses in geological materials.Overall, this comprehensive investigation provides essential theoretical insights and methodological references for understanding the dynamic behavior of sandstone within deep geological formations under impact loads. The findings offer valuable contributions to engineering practices concerned with the stability and resilience of underground structures subjected to dynamic loading conditions.
, Available online ,
doi: 10.11883/bzycj-2024-0064
Abstract:
Sympathetic detonation is defined as the phenomenon where the detonation pressure in one borehole causes explosives in another adjacent borehole to be detonated through an inert medium. It can increase the stress wave and the value of peak particle velocity, even causing fly rock to be thrown far away. These effects can impact the safety of blasting operation, slope stability, and blasting effects. Sympathetic detonation was identified by comparing the fluctuation difference of recorded blast-induced vibration signals. To investigate the mechanism of sympathetic detonation and methods of preventing sympathetic detonation in water-rich fissure open-pit mines, numerical simulation and field tests were adopted to analyze the effects of parameters on the occurrence of sympathetic detonation, such as the quantity of donor charge, crack width, and distance between charges. These results indicated that the borehole pressure increased with the decrease in decoupled charge coefficient, the increase of the crack width between boreholes (0.25-1.00 cm), and the decrease in the distance between boreholes. By using a wave-blocking tube, filling rock power, or setting up an air gap, the impact pressure produced by the donor charge was transmitted to the acceptor charge through the water-rich cracks. These methods made impact pressure lower than the critical detonation pressure of the emulsion explosive, which could prevent the sympathetic detonation of the accepted charge. Based on the field tests and simulated results, rock power filling was the best method of preventing sympathetic detonation when there was a single crack between the boreholes. Meanwhile, using a wave-blocking tube with a thickness of 2.6 mm was the best method of preventing sympathetic detonation when there were multiple cracks between the boreholes. Above all, the proposed detection method and obtained technologies provide the theory and guidance for preventing sympathetic detonation, which leads to improved blasting effects and the safety of blasting operations.
Sympathetic detonation is defined as the phenomenon where the detonation pressure in one borehole causes explosives in another adjacent borehole to be detonated through an inert medium. It can increase the stress wave and the value of peak particle velocity, even causing fly rock to be thrown far away. These effects can impact the safety of blasting operation, slope stability, and blasting effects. Sympathetic detonation was identified by comparing the fluctuation difference of recorded blast-induced vibration signals. To investigate the mechanism of sympathetic detonation and methods of preventing sympathetic detonation in water-rich fissure open-pit mines, numerical simulation and field tests were adopted to analyze the effects of parameters on the occurrence of sympathetic detonation, such as the quantity of donor charge, crack width, and distance between charges. These results indicated that the borehole pressure increased with the decrease in decoupled charge coefficient, the increase of the crack width between boreholes (0.25-1.00 cm), and the decrease in the distance between boreholes. By using a wave-blocking tube, filling rock power, or setting up an air gap, the impact pressure produced by the donor charge was transmitted to the acceptor charge through the water-rich cracks. These methods made impact pressure lower than the critical detonation pressure of the emulsion explosive, which could prevent the sympathetic detonation of the accepted charge. Based on the field tests and simulated results, rock power filling was the best method of preventing sympathetic detonation when there was a single crack between the boreholes. Meanwhile, using a wave-blocking tube with a thickness of 2.6 mm was the best method of preventing sympathetic detonation when there were multiple cracks between the boreholes. Above all, the proposed detection method and obtained technologies provide the theory and guidance for preventing sympathetic detonation, which leads to improved blasting effects and the safety of blasting operations.
, Available online ,
doi: 10.11883/bzycj-2024-0109
Abstract:
For the launch safety problem of the typical CL-20-based high detonation velocity pressed explosive (C-1, 94.5% CL-20+5.5% additive), the impact response characteristics of the explosive were studied by a large-scale hammer test with 400 kg, which has an impact loading curve similar to the loading characteristics of artillery chamber pressure. Meanwhile, the improved stress rate characterization method, the lower limit method, and the drop height method were used to characterize the drop hammer impact response characteristics of the explosive, and compared with the same kind of pressed explosives JO-8 and JH-2. The improved stress rate characterization method is obtained by improving the data processing process based on existing criteria and weakening the sensitivity of the original criterion formula to oscillatory waveforms. The measured stress curves and characterization parameters of the bottom of the three pressed explosives under different drop heights are obtained by tests, and the impact sensitivity differences of the explosives and influence factors of the impact sensitivity of C-1 are discussed. The results show that the improved stress rate characterization method has certain effectiveness and universality for characterizing the impact sensitivity of explosives. Meanwhile, the improved stress rate characterization method is consistent with other methods in reflecting the law. The drop height of C-1 (H50) is 1.0 m, which is 62.5% and 50.0% of JO-8 and JH-2, respectively; the peak stress of the backseat corresponding to non-detonation (σ0) is 748.90 MPa, which is 85.42% and 64.33% of JO-8 and JH-2, respectively; the safety stress rate parameter (C0) is 344 GPa2/s, which is 45.87% and 39.14% of JO-8 and JH-2, respectively. The molecular structure of CL-20, the mechanical properties, and the thermal-chemical characteristics of the C-1 explosive cylinder are the main factors that make its impact sensitivity higher than JO-8 and JH-2. The research results can provide a reference for the application and design calculation of CL-20-based high detonation velocity pressed explosives in a high overload environment.
For the launch safety problem of the typical CL-20-based high detonation velocity pressed explosive (C-1, 94.5% CL-20+5.5% additive), the impact response characteristics of the explosive were studied by a large-scale hammer test with 400 kg, which has an impact loading curve similar to the loading characteristics of artillery chamber pressure. Meanwhile, the improved stress rate characterization method, the lower limit method, and the drop height method were used to characterize the drop hammer impact response characteristics of the explosive, and compared with the same kind of pressed explosives JO-8 and JH-2. The improved stress rate characterization method is obtained by improving the data processing process based on existing criteria and weakening the sensitivity of the original criterion formula to oscillatory waveforms. The measured stress curves and characterization parameters of the bottom of the three pressed explosives under different drop heights are obtained by tests, and the impact sensitivity differences of the explosives and influence factors of the impact sensitivity of C-1 are discussed. The results show that the improved stress rate characterization method has certain effectiveness and universality for characterizing the impact sensitivity of explosives. Meanwhile, the improved stress rate characterization method is consistent with other methods in reflecting the law. The drop height of C-1 (H50) is 1.0 m, which is 62.5% and 50.0% of JO-8 and JH-2, respectively; the peak stress of the backseat corresponding to non-detonation (σ0) is 748.90 MPa, which is 85.42% and 64.33% of JO-8 and JH-2, respectively; the safety stress rate parameter (C0) is 344 GPa2/s, which is 45.87% and 39.14% of JO-8 and JH-2, respectively. The molecular structure of CL-20, the mechanical properties, and the thermal-chemical characteristics of the C-1 explosive cylinder are the main factors that make its impact sensitivity higher than JO-8 and JH-2. The research results can provide a reference for the application and design calculation of CL-20-based high detonation velocity pressed explosives in a high overload environment.
, Available online ,
doi: 10.11883/bzycj-2024-0074
Abstract:
The annular shaped charges serve as the precursor of a tandem warhead, prized for its ability to create large diameter perforation in targets. In an effort to enhance the penetration capacity of the annular shaped charge jet and mitigate the impact of the inner casing on subsequent sections induced by a reversed penetrator, a novel approach was taken to implement the investigation. Four different combinations of inner and outer casing materials based on steel and aluminum alloy were explored. It was found that when the inner casing was made of aluminum alloy, the average penetration depth in the rear target was 36.13% lower than that when the inner casing was made of steel. Selecting an inner casing of aluminum alloy and an outer casing of steel, the effects of tip offset, liner thickness, and standoff distance on the formation and penetration characteristics of the annular jet were further investigated. The results show that the jet formed by the non-eccentric liner exhibits radial offset, negatively influencing its penetration capability. However, by offsetting the liner tip to the outer side by 0.05d (where d represents the radial thickness of the annular shaped charge), both the forming and penetration performances of the jet are significantly improved. In addition, as the liner thickness increases, the velocity of the jet tip gradually decreases. Notably, the annular jet formed by an eccentric conical liner with a thickness of 0.045d exhibits superior penetration performance. Furthermore, the standoff distance emerges as a critical factor influencing the penetration capability of the annular jet. Optimal performance is achieved at a standoff distance of 1.12d. Under the same scenario, jet penetration tests were implemented. The difference between the radius of the penetration tunnel from numerical and experimental study lies within 12%. Subsequently, the reliability of the numerical simulation model and the conclusions are verified.
The annular shaped charges serve as the precursor of a tandem warhead, prized for its ability to create large diameter perforation in targets. In an effort to enhance the penetration capacity of the annular shaped charge jet and mitigate the impact of the inner casing on subsequent sections induced by a reversed penetrator, a novel approach was taken to implement the investigation. Four different combinations of inner and outer casing materials based on steel and aluminum alloy were explored. It was found that when the inner casing was made of aluminum alloy, the average penetration depth in the rear target was 36.13% lower than that when the inner casing was made of steel. Selecting an inner casing of aluminum alloy and an outer casing of steel, the effects of tip offset, liner thickness, and standoff distance on the formation and penetration characteristics of the annular jet were further investigated. The results show that the jet formed by the non-eccentric liner exhibits radial offset, negatively influencing its penetration capability. However, by offsetting the liner tip to the outer side by 0.05d (where d represents the radial thickness of the annular shaped charge), both the forming and penetration performances of the jet are significantly improved. In addition, as the liner thickness increases, the velocity of the jet tip gradually decreases. Notably, the annular jet formed by an eccentric conical liner with a thickness of 0.045d exhibits superior penetration performance. Furthermore, the standoff distance emerges as a critical factor influencing the penetration capability of the annular jet. Optimal performance is achieved at a standoff distance of 1.12d. Under the same scenario, jet penetration tests were implemented. The difference between the radius of the penetration tunnel from numerical and experimental study lies within 12%. Subsequently, the reliability of the numerical simulation model and the conclusions are verified.
, Available online ,
doi: 10.11883/bzycj-2024-0130
Abstract:
The high reactivity of hydrogen and oxygen poses a huge challenge to the stable propagation of rotating detonation waves. To study the propagation instability of hydrogen-oxygen rotating detonation waves, based on the RYrhoCentralFoam solver developed by OpenFOAM, numerical simulations were conducted on two-dimensional hydrogen-oxygen rotating detonation waves in small scale model by changing the equivalence ratio. The complex and variable propagation characteristics of hydrogen-oxygen rotating detonation waves were revealed, and the typical flow field was analyzed. The instability of propagation modes and the quenching and re-initiation mechanisms of detonation waves were explored. The results show that as the equivalence ratio increases, the flow field exhibits three propagation modes: extinction, single wave, and hybrid waves. The detonation wave velocity increases almost linearly with the increase of equivalence ratio, with a velocity deficit of 5% to 8%. The disturbance of shock waves causes significant distortion and wrinkling on the deflagration surface, while the high reactivity of hydrogen and oxygen results in obvious layering on the deflagration surface and different instability at the two interfaces. The upper interface exhibits Kelvin-Helmholt (K-H) instability, while the lower interface exhibits Rayleigh-Taylor (R-T) instability. As for the hybrid waves, the detonation wave is extremely unstable, maintaining a cycle between three states: quenching, single wave, and double wave collision. There are two ways in which detonation waves can be extinguished: firstly, the collision of two waves leads to the quenching of the detonation wave, and secondly, the intensification of combustion on the deflagration surface leads to the downward movement of the deflagration surface, ultimately resulting in the quenching of the detonation wave. The main reason for re-initiation is that the R-T instability induces detonation products and fresh premixed gas squeezing each other on the deflagration surface. The interaction between fresh premixed gas and products produces spikes and bubbles, enhances the reaction heat release on the deflagration surface, and generates local hotspots. The hotspots gradually increase into detonation waves, achieving the transition from deflagration to detonation.
The high reactivity of hydrogen and oxygen poses a huge challenge to the stable propagation of rotating detonation waves. To study the propagation instability of hydrogen-oxygen rotating detonation waves, based on the RYrhoCentralFoam solver developed by OpenFOAM, numerical simulations were conducted on two-dimensional hydrogen-oxygen rotating detonation waves in small scale model by changing the equivalence ratio. The complex and variable propagation characteristics of hydrogen-oxygen rotating detonation waves were revealed, and the typical flow field was analyzed. The instability of propagation modes and the quenching and re-initiation mechanisms of detonation waves were explored. The results show that as the equivalence ratio increases, the flow field exhibits three propagation modes: extinction, single wave, and hybrid waves. The detonation wave velocity increases almost linearly with the increase of equivalence ratio, with a velocity deficit of 5% to 8%. The disturbance of shock waves causes significant distortion and wrinkling on the deflagration surface, while the high reactivity of hydrogen and oxygen results in obvious layering on the deflagration surface and different instability at the two interfaces. The upper interface exhibits Kelvin-Helmholt (K-H) instability, while the lower interface exhibits Rayleigh-Taylor (R-T) instability. As for the hybrid waves, the detonation wave is extremely unstable, maintaining a cycle between three states: quenching, single wave, and double wave collision. There are two ways in which detonation waves can be extinguished: firstly, the collision of two waves leads to the quenching of the detonation wave, and secondly, the intensification of combustion on the deflagration surface leads to the downward movement of the deflagration surface, ultimately resulting in the quenching of the detonation wave. The main reason for re-initiation is that the R-T instability induces detonation products and fresh premixed gas squeezing each other on the deflagration surface. The interaction between fresh premixed gas and products produces spikes and bubbles, enhances the reaction heat release on the deflagration surface, and generates local hotspots. The hotspots gradually increase into detonation waves, achieving the transition from deflagration to detonation.
, Available online ,
doi: 10.11883/bzycj-2024-0097
Abstract:
Concrete materials are widely used in the construction of infrastructure and defense facilities. In order to study the dynamic mechanical properties of high-temperature concrete with different cooling methods, the dynamic mechanical properties of C30 cylindrical concrete samples at different temperatures with different cooling methods were tested by\begin{document}$\varnothing $\end{document} ![]()
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Concrete materials are widely used in the construction of infrastructure and defense facilities. In order to study the dynamic mechanical properties of high-temperature concrete with different cooling methods, the dynamic mechanical properties of C30 cylindrical concrete samples at different temperatures with different cooling methods were tested by
, Available online ,
doi: 10.11883/bzycj-2024-0145
Abstract:
In order to explore the structural response characteristics of projectile obliquely penetrating granite target, based on a 30 mm ballistic gun platform, the tests of projectile obliquely penetrating granite target were carried out, and the damage parameters of projectile structure under non-normal penetration were obtained. On this basis, combined with the numerical simulation, the deformation and fracture mechanism of the projectile structure of the projectile obliquely penetrating the granite target are studied, and the influence of the initial conditions of penetration on the structural response of the projectile is analyzed. The results show that the projectile is prone to bending and fracture when it is not penetrating the granite target. The asymmetric force on the head and tail of the projectile is the main factor affecting the response characteristics of the projectile. The degree of deformation and failure of the projectile is determined by the peak value of the angular velocity difference between the head and tail of the projectile. As the yaw increases, the bending degree of the projectile increases linearly, and the projectile breaks when the yaw increases to 8°. With the increase of the impact angle, the bending degree of the projectile increases first, followed by decrease and then increase again. When the impact angle is 15°, the bending degree of the projectile is the smallest. When the impact angle reaches 30°, the projectile breaks. Compared with the impact angle, the yaw has a more significant effect on the response behavior of the projectile structure. When the yaw and impact angle are combined, the introduction of the impact angle will increase the critical fracture positive yaw of the projectile, and the negative yaw will weaken the ability of the projectile to resist bending deformation and fracture. When the impact velocity is greater than1600 m/s, the impact velocity of the projectile becomes the main controlling factor for the different response behaviors of the projectile.
In order to explore the structural response characteristics of projectile obliquely penetrating granite target, based on a 30 mm ballistic gun platform, the tests of projectile obliquely penetrating granite target were carried out, and the damage parameters of projectile structure under non-normal penetration were obtained. On this basis, combined with the numerical simulation, the deformation and fracture mechanism of the projectile structure of the projectile obliquely penetrating the granite target are studied, and the influence of the initial conditions of penetration on the structural response of the projectile is analyzed. The results show that the projectile is prone to bending and fracture when it is not penetrating the granite target. The asymmetric force on the head and tail of the projectile is the main factor affecting the response characteristics of the projectile. The degree of deformation and failure of the projectile is determined by the peak value of the angular velocity difference between the head and tail of the projectile. As the yaw increases, the bending degree of the projectile increases linearly, and the projectile breaks when the yaw increases to 8°. With the increase of the impact angle, the bending degree of the projectile increases first, followed by decrease and then increase again. When the impact angle is 15°, the bending degree of the projectile is the smallest. When the impact angle reaches 30°, the projectile breaks. Compared with the impact angle, the yaw has a more significant effect on the response behavior of the projectile structure. When the yaw and impact angle are combined, the introduction of the impact angle will increase the critical fracture positive yaw of the projectile, and the negative yaw will weaken the ability of the projectile to resist bending deformation and fracture. When the impact velocity is greater than
, Available online ,
doi: 10.11883/bzycj-2024-0083
Abstract:
Reinforced concrete slabs, as the main load-bearing components in the structure of construction projects, are very likely to suffer serious damage in explosive accidents, while polyurea elastomers, with their better anti-blast and anti-impact properties, have been widely used in the field of protective engineering. It is well known that the mechanical properties and deformation mechanisms of thin slabs in the range from 100 mm to 250 mm and thick concrete slabs above 250 mm are not the same, and the thickness of reinforced concrete substrates studied so far is generally concentrated in the range from 100 mm to 250 mm, and there are relatively few studies on thick slabs of polyurea-coated reinforced concrete with a slab thickness of 250 mm or more. In order to study the anti-blast performance of the polyurea/reinforced concrete thick slab composite structure, firstly, the contact explosion tests were carried out on the polyurea/reinforced concrete thick slab composite structure with different charges, while the overall and local damage characteristics were analyzed. Secondly, numerical simulations were carried out using LS-DYNA finite element simulation software to verify the correctness of the numerical model by comparing with the experimental results. Based on LS-DYNA finite element simulations, the damage process of polyurea/reinforced concrete thick plate composite structure and the evolution of shock wave inside the polyurea/reinforced concrete thick plate were investigated, which revealed the anti-blast mechanism of the polyurea coating, and further analyzed the damage mode and damage characteristics of the polyurea/reinforced concrete thick plate composite structure. The test and finite element results showed that the polyurea/steel-reinforced concrete composite structure exhibited six damage modes under the contact explosion load (i.e., crate; spall; spall and bulge; threshold spall, bulging deformation of the polyurea coating; severe spall, serious bulging deformation of the polyurea coating; perforation). The investigation also demonstrated that the backside polyurea-coated reinforced concrete thick slabs effectively improved the anti-blast performance of the composite structure. The results of the study can provide a basis and reference for the design of blast resistance of polyurea/reinforced concrete thick slab composite structures.
Reinforced concrete slabs, as the main load-bearing components in the structure of construction projects, are very likely to suffer serious damage in explosive accidents, while polyurea elastomers, with their better anti-blast and anti-impact properties, have been widely used in the field of protective engineering. It is well known that the mechanical properties and deformation mechanisms of thin slabs in the range from 100 mm to 250 mm and thick concrete slabs above 250 mm are not the same, and the thickness of reinforced concrete substrates studied so far is generally concentrated in the range from 100 mm to 250 mm, and there are relatively few studies on thick slabs of polyurea-coated reinforced concrete with a slab thickness of 250 mm or more. In order to study the anti-blast performance of the polyurea/reinforced concrete thick slab composite structure, firstly, the contact explosion tests were carried out on the polyurea/reinforced concrete thick slab composite structure with different charges, while the overall and local damage characteristics were analyzed. Secondly, numerical simulations were carried out using LS-DYNA finite element simulation software to verify the correctness of the numerical model by comparing with the experimental results. Based on LS-DYNA finite element simulations, the damage process of polyurea/reinforced concrete thick plate composite structure and the evolution of shock wave inside the polyurea/reinforced concrete thick plate were investigated, which revealed the anti-blast mechanism of the polyurea coating, and further analyzed the damage mode and damage characteristics of the polyurea/reinforced concrete thick plate composite structure. The test and finite element results showed that the polyurea/steel-reinforced concrete composite structure exhibited six damage modes under the contact explosion load (i.e., crate; spall; spall and bulge; threshold spall, bulging deformation of the polyurea coating; severe spall, serious bulging deformation of the polyurea coating; perforation). The investigation also demonstrated that the backside polyurea-coated reinforced concrete thick slabs effectively improved the anti-blast performance of the composite structure. The results of the study can provide a basis and reference for the design of blast resistance of polyurea/reinforced concrete thick slab composite structures.
, Available online ,
doi: 10.11883/bzycj-2024-0053
Abstract:
Damage assessment of building structures plays an important role in military operations and engineering protection design. However, there is a lack of high-efficiency and validated damage assessment methods due to the complexity, variety, and large size of building structures. Therefore, a structural damage assessment method was proposed based on the high-precision numerical simulation analysis, in which the blast loadings, as well as the damage degrees of members, rooms, and building structures, were comprehensively considered. Firstly, the typical explosion tests and collapse accidents of reinforced concrete (RC) structures and masonry walls were numerically reproduced to verify the reliability of the numerical simulation approach for masonry-infilled RC frame structures. Subsequently, the blast-resistant analysis of a typical three-story masonry-infilled RC frame structure was conducted under internal explosions of different charge weights (25−200kg TNT), including the propagation of blast waves, structural damage, and scattering of infilled walls. Besides, the proposed high-efficiency assessment method exhibited four key characteristics: (1) the concept of mirror explosion source and the non-linear shock addition rules were combined to predict the internal blast loadings in central and adjacent rooms; (2) the damage degrees of structural and non-structural members, i.e., beams, slabs, columns, and infilled walls, were determined by the equivalent single degree of freedom method; (3) the importance factor of members was considered and weighted to evaluate the damage degree of the room; (4) the influence of usage and location of each room on the damage degree of the building structure was considered. Finally, the proposed assessment method was employed to predict the aforementioned explosion scenarios. It derives that the RC frame structures exhibit slight, moderate, and severe damage under the explosions of 25, 100, and 200 kg TNT, respectively. The predicted damage degrees are identical to the simulation results, while the calculation time is reduced by over 99%. Therefore, the proposed method possesses reliability and timeliness in damage assessment of building structures.
Damage assessment of building structures plays an important role in military operations and engineering protection design. However, there is a lack of high-efficiency and validated damage assessment methods due to the complexity, variety, and large size of building structures. Therefore, a structural damage assessment method was proposed based on the high-precision numerical simulation analysis, in which the blast loadings, as well as the damage degrees of members, rooms, and building structures, were comprehensively considered. Firstly, the typical explosion tests and collapse accidents of reinforced concrete (RC) structures and masonry walls were numerically reproduced to verify the reliability of the numerical simulation approach for masonry-infilled RC frame structures. Subsequently, the blast-resistant analysis of a typical three-story masonry-infilled RC frame structure was conducted under internal explosions of different charge weights (25−200kg TNT), including the propagation of blast waves, structural damage, and scattering of infilled walls. Besides, the proposed high-efficiency assessment method exhibited four key characteristics: (1) the concept of mirror explosion source and the non-linear shock addition rules were combined to predict the internal blast loadings in central and adjacent rooms; (2) the damage degrees of structural and non-structural members, i.e., beams, slabs, columns, and infilled walls, were determined by the equivalent single degree of freedom method; (3) the importance factor of members was considered and weighted to evaluate the damage degree of the room; (4) the influence of usage and location of each room on the damage degree of the building structure was considered. Finally, the proposed assessment method was employed to predict the aforementioned explosion scenarios. It derives that the RC frame structures exhibit slight, moderate, and severe damage under the explosions of 25, 100, and 200 kg TNT, respectively. The predicted damage degrees are identical to the simulation results, while the calculation time is reduced by over 99%. Therefore, the proposed method possesses reliability and timeliness in damage assessment of building structures.
, Available online ,
doi: 10.11883/bzycj-2024-0061
Abstract:
Due to the high compressive/tensile strengths and fracture toughness, ultra-high performance concrete (UHPC) has great application potential in protective structures against the attack of earth penetrating weapons. Accurately evaluating the damage and failure and establishing reliable design methods of UHPC shields against the combination of penetration and explosion of warheads can provide a helpful reference for protective structure design and resistance improvement. In this study, combined tests of 105 mm-caliber projectile penetration test and 5 kg TNT explosion test on semi-infinite UHPC target were conducted first. The detailed test data of the projectile and target under penetration and the combined effect of penetration and explosion were recorded. Then, a finite element model of UHPC under penetration and explosion was established. By conducting the numerical simulations of the above-conducted test and the existing prefabricated hole charge explosion test on the finite UHPC slab, as well as comprehensively comparing the destroy depth and cracking dimension of the target, the reliability of the established finite element model and the corresponding analysis approach in predicting the damage and failure of UHPC shield against the combination of penetration and explosion of warheads were validated. Finally, the perforation limit and scabbing limit of the UHPC shield under the combination of penetration and explosion of three typical prototype warheads, i.e., SDB, WDU-43/B, and BLU-109/B, were determined and compared with those of normal strength concrete shield. The results show that, the perforation limit and scabbing limit of the UHPC shield against the above three warheads are in ranges of 1.30−2.60 m and 1.70−5.00 m, respectively. The corresponding critical perforation and scabbing coefficients are in the ranges of 1.81−2.17 and 2.46−4.17, respectively. Compared with the normal strength concrete shield, the cracking diameter of the UHPC shield is reduced by 34.4%−42.4%. The perforation limit and scabbing limit are reduced by 7.1%−31.6% and 39.7%−52.8%, respectively. The present work can provide an analysis method and reference for the resistance evaluation and design of the UHPC shield.
Due to the high compressive/tensile strengths and fracture toughness, ultra-high performance concrete (UHPC) has great application potential in protective structures against the attack of earth penetrating weapons. Accurately evaluating the damage and failure and establishing reliable design methods of UHPC shields against the combination of penetration and explosion of warheads can provide a helpful reference for protective structure design and resistance improvement. In this study, combined tests of 105 mm-caliber projectile penetration test and 5 kg TNT explosion test on semi-infinite UHPC target were conducted first. The detailed test data of the projectile and target under penetration and the combined effect of penetration and explosion were recorded. Then, a finite element model of UHPC under penetration and explosion was established. By conducting the numerical simulations of the above-conducted test and the existing prefabricated hole charge explosion test on the finite UHPC slab, as well as comprehensively comparing the destroy depth and cracking dimension of the target, the reliability of the established finite element model and the corresponding analysis approach in predicting the damage and failure of UHPC shield against the combination of penetration and explosion of warheads were validated. Finally, the perforation limit and scabbing limit of the UHPC shield under the combination of penetration and explosion of three typical prototype warheads, i.e., SDB, WDU-43/B, and BLU-109/B, were determined and compared with those of normal strength concrete shield. The results show that, the perforation limit and scabbing limit of the UHPC shield against the above three warheads are in ranges of 1.30−2.60 m and 1.70−5.00 m, respectively. The corresponding critical perforation and scabbing coefficients are in the ranges of 1.81−2.17 and 2.46−4.17, respectively. Compared with the normal strength concrete shield, the cracking diameter of the UHPC shield is reduced by 34.4%−42.4%. The perforation limit and scabbing limit are reduced by 7.1%−31.6% and 39.7%−52.8%, respectively. The present work can provide an analysis method and reference for the resistance evaluation and design of the UHPC shield.
, Available online ,
doi: 10.11883/bzycj-2024-0070
Abstract:
Silicone rubber has been widely used as a typical sandwich-structure or cushion-structure material in various high pressure loading environments. Under pressure loading of up to tens of GPa, silicone rubber may undergo shock decomposition reaction, and the decomposition products contain gas-solid mixture. Numerical simulation without the shock decomposition of silicone rubber can’t interpret some complex physical phenomena observed in detonation driven experiment. In order to illustrate the shock decomposition effect of silicone rubber, a simple shock decomposition model for silicone rubber is proposed based on the existing physical knowledge. By using the simple shock decomposition model for silicone rubber, the simulations of the experiment setup of detonation driven silicone rubber foam are carried out, and the simulated free surface velocities are compared with the experiments. The results show that the shock decomposition of silicone rubber can reasonably interpret the two grotesque phenomena observed in the experiment. During the shock decomposition process, the first incident pressure of silicone rubber would relax around the critical shock decomposition pressure for a period of time. As a result, the free surface velocity of steel plate exhibits a platform as observed in the experiment during the first take-off process. The compressibility of gas phase products of silicone rubber after shock decomposition is much higher than the solid/fluid materials, so more energy in the first incident wave is consumed to compress gas products to do work, leading to energy attenuation and peak pressure reduction when the first incident wave propagates to the outer surface of steel plate. Consequently, the peak value of the first take-off free surface velocity of steel plate decreases. Insight into the dynamic behavior of silicone rubber at high pressures is particularly valuable for predicting their response to extreme conditions, and it contributes to a deeper understanding of such experimental phenomena and to the proposal of a more refined shock decomposition model for silicone rubber.
Silicone rubber has been widely used as a typical sandwich-structure or cushion-structure material in various high pressure loading environments. Under pressure loading of up to tens of GPa, silicone rubber may undergo shock decomposition reaction, and the decomposition products contain gas-solid mixture. Numerical simulation without the shock decomposition of silicone rubber can’t interpret some complex physical phenomena observed in detonation driven experiment. In order to illustrate the shock decomposition effect of silicone rubber, a simple shock decomposition model for silicone rubber is proposed based on the existing physical knowledge. By using the simple shock decomposition model for silicone rubber, the simulations of the experiment setup of detonation driven silicone rubber foam are carried out, and the simulated free surface velocities are compared with the experiments. The results show that the shock decomposition of silicone rubber can reasonably interpret the two grotesque phenomena observed in the experiment. During the shock decomposition process, the first incident pressure of silicone rubber would relax around the critical shock decomposition pressure for a period of time. As a result, the free surface velocity of steel plate exhibits a platform as observed in the experiment during the first take-off process. The compressibility of gas phase products of silicone rubber after shock decomposition is much higher than the solid/fluid materials, so more energy in the first incident wave is consumed to compress gas products to do work, leading to energy attenuation and peak pressure reduction when the first incident wave propagates to the outer surface of steel plate. Consequently, the peak value of the first take-off free surface velocity of steel plate decreases. Insight into the dynamic behavior of silicone rubber at high pressures is particularly valuable for predicting their response to extreme conditions, and it contributes to a deeper understanding of such experimental phenomena and to the proposal of a more refined shock decomposition model for silicone rubber.
, Available online ,
doi: 10.11883/bzycj-2024-0082
Abstract:
When X-rays generated by high-altitude nuclear detonation irradiates on the shell structure of missile, blow-off impulse (BOI) and thermal shock waves generated may produce dynamic response and damage on it. The existing three one-dimensional theoretical models, Whitener, BBAY, and MBBAY, can only provide approximate BOI values and accurate results of peak pressure and other information are inaccessible. Solving this problem requires numerical calculations based on real physical laws. The numerical simulation program TSHOCK3D for X-ray thermal excitation wave is used to calculate the BOI and peak pressure to make a comparative analysis. An aluminum plate with a length and width of 0.4 centimeters and a thickness of 0.1 centimeters is set as the target for X-ray radiation. The range of the working conditions is 0.1−3.0 keV for the Planck's blackbody temperatures and radiant energy flux are in the range of 220−400 J/cm2. The results indicate that the TSHOCK3D can give the results effectively and reliably. The simulation results are consistent with the theoretical models mentioned above. The BOI and peak pressure are approximately linear with the energy flux, while the maximum value exist for different blackbody temperatures.
When X-rays generated by high-altitude nuclear detonation irradiates on the shell structure of missile, blow-off impulse (BOI) and thermal shock waves generated may produce dynamic response and damage on it. The existing three one-dimensional theoretical models, Whitener, BBAY, and MBBAY, can only provide approximate BOI values and accurate results of peak pressure and other information are inaccessible. Solving this problem requires numerical calculations based on real physical laws. The numerical simulation program TSHOCK3D for X-ray thermal excitation wave is used to calculate the BOI and peak pressure to make a comparative analysis. An aluminum plate with a length and width of 0.4 centimeters and a thickness of 0.1 centimeters is set as the target for X-ray radiation. The range of the working conditions is 0.1−3.0 keV for the Planck's blackbody temperatures and radiant energy flux are in the range of 220−400 J/cm2. The results indicate that the TSHOCK3D can give the results effectively and reliably. The simulation results are consistent with the theoretical models mentioned above. The BOI and peak pressure are approximately linear with the energy flux, while the maximum value exist for different blackbody temperatures.
, Available online ,
doi: 10.11883/bzycj-2024-0036
Abstract:
X-ray diffraction test was used to analyze the changes in the mineral composition of the granite before and after filling with water to study the effects of saturated water and initial damage degree on macroscopic and microscopic failure characteristics of granite under impact load. The Hopkinson device was used to carry out dynamic mechanical tests on the granite samples under different states to analyze the dynamic mechanical properties of the granite and the block size characteristics under different states. In addition, some of the granite fragments after impact were selected for electron microscope scanning test to analyze the fracture failure characteristics. The fractal dimension was used to analyze the fragmentation degree of the granite fragments after impact and the scanning images of the fracture under electron microscopy. The influence of the image magnification selected during electron microscope scanning on the fractal dimension is discussed. The micro-cracking mechanism of granite induced by saturated water under impact load is briefly analyzed. The results show that the mineral composition of the saturated granite changes compared with the natural granite. The proportions of hornblende, albite, microcline, and quartz in the saturated granite decrease, while the proportion of kaolinite increases significantly. With the increase of initial damage, the dynamic peak stress of granite gradually decreases while the fragmentation degree and the fractal dimension of the block increase gradually, and the influence of initial damage on the fractal dimension of the block is greater than that of saturated water. With the increase of initial damage, more micro-cracks and debris appear in the fracture image, and the fractal dimension of the fracture image increases gradually. In a certain range, the fractal dimension of electron microscope scanning images increases with the increase of image magnification, but when the image exceeds a certain multiple, the fractal dimension will decrease. The research results can provide some theoretical and engineering references for the failure and instability mechanism analysis of disturbed water-saturated granite with initial damage in geotechnical engineering.
X-ray diffraction test was used to analyze the changes in the mineral composition of the granite before and after filling with water to study the effects of saturated water and initial damage degree on macroscopic and microscopic failure characteristics of granite under impact load. The Hopkinson device was used to carry out dynamic mechanical tests on the granite samples under different states to analyze the dynamic mechanical properties of the granite and the block size characteristics under different states. In addition, some of the granite fragments after impact were selected for electron microscope scanning test to analyze the fracture failure characteristics. The fractal dimension was used to analyze the fragmentation degree of the granite fragments after impact and the scanning images of the fracture under electron microscopy. The influence of the image magnification selected during electron microscope scanning on the fractal dimension is discussed. The micro-cracking mechanism of granite induced by saturated water under impact load is briefly analyzed. The results show that the mineral composition of the saturated granite changes compared with the natural granite. The proportions of hornblende, albite, microcline, and quartz in the saturated granite decrease, while the proportion of kaolinite increases significantly. With the increase of initial damage, the dynamic peak stress of granite gradually decreases while the fragmentation degree and the fractal dimension of the block increase gradually, and the influence of initial damage on the fractal dimension of the block is greater than that of saturated water. With the increase of initial damage, more micro-cracks and debris appear in the fracture image, and the fractal dimension of the fracture image increases gradually. In a certain range, the fractal dimension of electron microscope scanning images increases with the increase of image magnification, but when the image exceeds a certain multiple, the fractal dimension will decrease. The research results can provide some theoretical and engineering references for the failure and instability mechanism analysis of disturbed water-saturated granite with initial damage in geotechnical engineering.
, Available online ,
doi: 10.11883/bzycj-2023-0252
Abstract:
A numerical simulation study is carried out on the overall battle damage circumstances of structures and the residual behavior of fragments after the typical parts of aircraft are attacked by high-speed fragments. An adaptive FEM-SPH coupling simulation method is established by using LS-DYNA software and combining the advantages of Finite Element Method (FEM) and Smoothed Particle Hydrodynamics (SPH). Using this coupling simulation method, the computational model of two typical parts of the aircraft is set up, and the accurate simulation of the core position is realized by a local refinement method of hexahedral FEM grids. Experiments were carried out to verify the numerical model. A series of high-velocity impact (HVI) battle damage simulations are carried out. The debris cloud and crater appearance formed after fragment impacting on structure at high speed under different working conditions are compared, while the residual velocity and mass of the fragment are analyzed. The critical ricochet angles of the fragment on the skin are also determined. The major conclusions are given below. The calculation results of the adaptive FEM-SPH coupling algorithm are in good agreement with the experimental results, and it can simulate fragment HVI damage effectively and precisely. The distribution shape of debris cloud becomes narrow and long with the increase of fragment incident velocity, and the incidence angle can change the shape orientation of debris cloud and crater on the structure. The variation trends of height and spread velocity of debris cloud with incident velocity or angle are basically consistent and linear. The velocity reduction of the fragment does not change with the incident velocity, and the mass reduction is positively correlated with it, both of which are negatively correlated with the incidence angle. The critical ricochet angle of fragment varies almost linearly with the incident velocity. The research results can provide a reference for the damage prediction and rapid maintenance of aircraft after air combat.
A numerical simulation study is carried out on the overall battle damage circumstances of structures and the residual behavior of fragments after the typical parts of aircraft are attacked by high-speed fragments. An adaptive FEM-SPH coupling simulation method is established by using LS-DYNA software and combining the advantages of Finite Element Method (FEM) and Smoothed Particle Hydrodynamics (SPH). Using this coupling simulation method, the computational model of two typical parts of the aircraft is set up, and the accurate simulation of the core position is realized by a local refinement method of hexahedral FEM grids. Experiments were carried out to verify the numerical model. A series of high-velocity impact (HVI) battle damage simulations are carried out. The debris cloud and crater appearance formed after fragment impacting on structure at high speed under different working conditions are compared, while the residual velocity and mass of the fragment are analyzed. The critical ricochet angles of the fragment on the skin are also determined. The major conclusions are given below. The calculation results of the adaptive FEM-SPH coupling algorithm are in good agreement with the experimental results, and it can simulate fragment HVI damage effectively and precisely. The distribution shape of debris cloud becomes narrow and long with the increase of fragment incident velocity, and the incidence angle can change the shape orientation of debris cloud and crater on the structure. The variation trends of height and spread velocity of debris cloud with incident velocity or angle are basically consistent and linear. The velocity reduction of the fragment does not change with the incident velocity, and the mass reduction is positively correlated with it, both of which are negatively correlated with the incidence angle. The critical ricochet angle of fragment varies almost linearly with the incident velocity. The research results can provide a reference for the damage prediction and rapid maintenance of aircraft after air combat.
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2024, 44(11): 111001.
doi: 10.11883/bzycj-2023-0459
Abstract:
The layered protective structure composed of a bursting layer, distribution layer, and structure layer is usually used to resist the penetration and blast waves induced by advanced earth-penetrating weapons (EPWs). The defect of a traditional layered protective structure with medium/coarse sand as the distribution layer is that it is difficult to reliably control the load on the structure layer. To solve this issue, an alternative approach is presented by replacing the material of the distribution layer from the frequently used medium/coarse sand to foam concrete. A blast test on the layered composite target composed of a CF120 concrete (a fiber-reinforced high-strength concrete) bursting layer, a C5 foam concrete distribution layer, and a C40 reinforced concrete structure layer was first conducted in the present study to investigate the blast resistance of layered protective structure sandwiched by foam concrete (named composite protective structure), in which the damage and failure in the layered composite target and blast waves at specific locations were a major concern and were accurately recorded. Then, based on the concrete material model established by Kong and Fang and the smoothed particle Galerkin (SPG) algorithm available in the LS-DYNA, a corresponding numerical model was developed and validated against the test data. Using the validated numerical model, the propagation and attenuation of blast waves and damage and failure in the composite protective structure induced by cylindrical charge explosion are discussed in detail. It is found that the blast resistance mechanism of the composite protective structure is attributed to the extreme wave impedance mismatch between the bursting layer and the foam concrete layer, which greatly reduces the propagation of blast waves into the foam concrete layer, leading to a transformation of more blast energy to the bursting layer, so that the blast load and energy on the structure layer can be greatly reduced. The research results can provide an important reference for the design of protective structures against EPWs.
The layered protective structure composed of a bursting layer, distribution layer, and structure layer is usually used to resist the penetration and blast waves induced by advanced earth-penetrating weapons (EPWs). The defect of a traditional layered protective structure with medium/coarse sand as the distribution layer is that it is difficult to reliably control the load on the structure layer. To solve this issue, an alternative approach is presented by replacing the material of the distribution layer from the frequently used medium/coarse sand to foam concrete. A blast test on the layered composite target composed of a CF120 concrete (a fiber-reinforced high-strength concrete) bursting layer, a C5 foam concrete distribution layer, and a C40 reinforced concrete structure layer was first conducted in the present study to investigate the blast resistance of layered protective structure sandwiched by foam concrete (named composite protective structure), in which the damage and failure in the layered composite target and blast waves at specific locations were a major concern and were accurately recorded. Then, based on the concrete material model established by Kong and Fang and the smoothed particle Galerkin (SPG) algorithm available in the LS-DYNA, a corresponding numerical model was developed and validated against the test data. Using the validated numerical model, the propagation and attenuation of blast waves and damage and failure in the composite protective structure induced by cylindrical charge explosion are discussed in detail. It is found that the blast resistance mechanism of the composite protective structure is attributed to the extreme wave impedance mismatch between the bursting layer and the foam concrete layer, which greatly reduces the propagation of blast waves into the foam concrete layer, leading to a transformation of more blast energy to the bursting layer, so that the blast load and energy on the structure layer can be greatly reduced. The research results can provide an important reference for the design of protective structures against EPWs.
2024, 44(11): 111101.
doi: 10.11883/bzycj-2023-0418
Abstract:
Hydrogen is crucial in the global shift towards clean energy and is gaining significance in the energy industry, while its high flammability and explosive hazard make its safety a research hotspot. It is crucial to thoroughly investigate and assess the safety of hydrogen as it progresses toward commercialization in the energy sector. This article reviews the latest advancements in hydrogen explosion suppression conducted by researchers around the world, aiming at offering a scientific foundation and technical approach to efficiently manage and reduce the damaging impacts of hydrogen explosion incidents. The article focuses on the study of hydrogen explosion suppression materials and their suppression mechanisms, so as to provide scientific understanding and technical support for the safe application of hydrogen. Firstly, it systematically introduces the research progress in hydrogen explosion suppression by discussing four significant categories, i.e., gas, liquid, solid, and multiphase composite explosion suppression materials. By comparing and analyzing the effects, key performance parameters, and the variation rules of these materials, the current research status and effectiveness of various explosion suppression materials are sorted out, helping to deepen the understanding of the explosion suppression effects of these materials. Secondly, focusing on the suppression mechanism, the research delves into the vital role of explosion suppression materials in suppressing hydrogen explosions. Starting from three dimensions, i.e., physical suppression, chemical suppression, and physicochemical comprehensive suppression, it elucidates the mechanisms of action of explosion suppression materials in the suppression process, contributing to a deeper understanding of the role of explosion suppression materials in suppressing or mitigating hydrogen explosions. Finally, the article looks forward to the future development directions of hydrogen explosion suppression materials, especially emphasizing the importance of further studies on the high-efficiency explosion suppression materials and the challenges faced in practical applications. This review is aimed to provide scientific reference and inspiration for the research, development, and application of new hydrogen explosion suppression materials.
Hydrogen is crucial in the global shift towards clean energy and is gaining significance in the energy industry, while its high flammability and explosive hazard make its safety a research hotspot. It is crucial to thoroughly investigate and assess the safety of hydrogen as it progresses toward commercialization in the energy sector. This article reviews the latest advancements in hydrogen explosion suppression conducted by researchers around the world, aiming at offering a scientific foundation and technical approach to efficiently manage and reduce the damaging impacts of hydrogen explosion incidents. The article focuses on the study of hydrogen explosion suppression materials and their suppression mechanisms, so as to provide scientific understanding and technical support for the safe application of hydrogen. Firstly, it systematically introduces the research progress in hydrogen explosion suppression by discussing four significant categories, i.e., gas, liquid, solid, and multiphase composite explosion suppression materials. By comparing and analyzing the effects, key performance parameters, and the variation rules of these materials, the current research status and effectiveness of various explosion suppression materials are sorted out, helping to deepen the understanding of the explosion suppression effects of these materials. Secondly, focusing on the suppression mechanism, the research delves into the vital role of explosion suppression materials in suppressing hydrogen explosions. Starting from three dimensions, i.e., physical suppression, chemical suppression, and physicochemical comprehensive suppression, it elucidates the mechanisms of action of explosion suppression materials in the suppression process, contributing to a deeper understanding of the role of explosion suppression materials in suppressing or mitigating hydrogen explosions. Finally, the article looks forward to the future development directions of hydrogen explosion suppression materials, especially emphasizing the importance of further studies on the high-efficiency explosion suppression materials and the challenges faced in practical applications. This review is aimed to provide scientific reference and inspiration for the research, development, and application of new hydrogen explosion suppression materials.
2024, 44(11): 112101.
doi: 10.11883/bzycj-2023-0404
Abstract:
To study the explosion process of carbon-iron nanomaterials synthesized by gaseous detonation, the effects of different molar ratios of hydrogen to oxygen (2∶1, 3∶1, 4∶1) on the peak value time-history curve of detonation parameters (detonation velocity, detonation temperature, and detonation pressure) and the morphology of carbon-iron nanomaterials were studied by combination of hydrogen-oxygen experiments and numerical simulations. The explosion experiments used hydrogen and oxygen with a purity of 99.999% in a closed detonation tube. The precursor was ferrocene with a purity of 99%. A high-speed camera was used to observe in the middle of the tube. After the experiments, the samples were collected and characterized by transmission electron microscopy. The numerical simulation used ICEM software for modeling and meshing and then used Fluent software to verify the rationality of the mesh size, and then performed simulation calculations after confirming the optimal mesh size. The results indicate that hydrogen-oxygen explosion inside a detonation tube involves two processes: the propagation of detonation waves and the attenuation of combustion waves, and the hydrogen-oxygen molar ratio has a significant impact on the peak time history curves of detonation velocity, detonation temperature, and detonation pressure. With the increase of the molar ratio of hydrogen to oxygen, the detonation velocity, detonation temperature, detonation pressure, and attenuation rate of the detonation wave all decrease. The molar ratio of hydrogen to oxygen affects the morphology growth of carbon-iron nanomaterials by influencing the propagation and attenuation of detonation waves. At zero oxygen balance, the sample consists of carbon-coated iron nanoparticles. As the hydrogen-oxygen molar ratio increases, the number of carbon nanotubes in the sample gradually increases. Adjusting the molar ratio of hydrogen to oxygen can achieve control over the propagation and attenuation process of detonation waves, and also achieve the goal of controlling the preparation of carbon iron nanomaterials with specific morphologies through gaseous detonation.
To study the explosion process of carbon-iron nanomaterials synthesized by gaseous detonation, the effects of different molar ratios of hydrogen to oxygen (2∶1, 3∶1, 4∶1) on the peak value time-history curve of detonation parameters (detonation velocity, detonation temperature, and detonation pressure) and the morphology of carbon-iron nanomaterials were studied by combination of hydrogen-oxygen experiments and numerical simulations. The explosion experiments used hydrogen and oxygen with a purity of 99.999% in a closed detonation tube. The precursor was ferrocene with a purity of 99%. A high-speed camera was used to observe in the middle of the tube. After the experiments, the samples were collected and characterized by transmission electron microscopy. The numerical simulation used ICEM software for modeling and meshing and then used Fluent software to verify the rationality of the mesh size, and then performed simulation calculations after confirming the optimal mesh size. The results indicate that hydrogen-oxygen explosion inside a detonation tube involves two processes: the propagation of detonation waves and the attenuation of combustion waves, and the hydrogen-oxygen molar ratio has a significant impact on the peak time history curves of detonation velocity, detonation temperature, and detonation pressure. With the increase of the molar ratio of hydrogen to oxygen, the detonation velocity, detonation temperature, detonation pressure, and attenuation rate of the detonation wave all decrease. The molar ratio of hydrogen to oxygen affects the morphology growth of carbon-iron nanomaterials by influencing the propagation and attenuation of detonation waves. At zero oxygen balance, the sample consists of carbon-coated iron nanoparticles. As the hydrogen-oxygen molar ratio increases, the number of carbon nanotubes in the sample gradually increases. Adjusting the molar ratio of hydrogen to oxygen can achieve control over the propagation and attenuation process of detonation waves, and also achieve the goal of controlling the preparation of carbon iron nanomaterials with specific morphologies through gaseous detonation.
2024, 44(11): 112201.
doi: 10.11883/bzycj-2023-0440
Abstract:
There is a lack of reliable calculation theory for the transmission and reflection pressures of shock waves at the water-soil interface. Using the mass conservation equation, momentum conservation equation, and the equations of state of water and soil, the Hugoniot relationship and p-u curve of the propagation of shock waves in water and soil medium are derived, and then the transmission and reflection pressures of the shock wave at the water-soil interface can be analyzed theoretically. Two-dimensional numerical models of the free field in water and water-soil layered medium field are established, in which the water and soil parameters are consistent with those in the three-phase medium saturated soil model used in the theoretical derivation. The calculation results show that the theoretical and numerical solutions of the water-soil interface transmission and reflection pressures are highly consistent. When using 80 g TNT explosives and exploding at 0.1–0.9 m from the water-soil interface (proportional burst distance of 0.232–2.089 m/kg1/3), the error of the theoretical and numerical solutions for transmission and reflection pressures is less than 7%, and the coefficient of the reflection pressure is in the range of 1.6–1.8 according to the analytical solution of the reflection pressure and the ratio of the incident pressure in the water. When exploding at 0.5 m from the water-soil interface and the gas content of the saturated soil varies in the range of 0–10%, the transmission and reflection pressures are 63.8–70.0 MPa, and the reflection pressure coefficients are in the range of 1.55–1.70 at this time. The calculation method for the shock wave transmission and reflection pressure at the water-soil interface has a clear physical meaning and high precision and can provide a theoretical basis for the soil damage assessment of engineering structures in submerged soil caused by underwater explosions.
There is a lack of reliable calculation theory for the transmission and reflection pressures of shock waves at the water-soil interface. Using the mass conservation equation, momentum conservation equation, and the equations of state of water and soil, the Hugoniot relationship and p-u curve of the propagation of shock waves in water and soil medium are derived, and then the transmission and reflection pressures of the shock wave at the water-soil interface can be analyzed theoretically. Two-dimensional numerical models of the free field in water and water-soil layered medium field are established, in which the water and soil parameters are consistent with those in the three-phase medium saturated soil model used in the theoretical derivation. The calculation results show that the theoretical and numerical solutions of the water-soil interface transmission and reflection pressures are highly consistent. When using 80 g TNT explosives and exploding at 0.1–0.9 m from the water-soil interface (proportional burst distance of 0.232–2.089 m/kg1/3), the error of the theoretical and numerical solutions for transmission and reflection pressures is less than 7%, and the coefficient of the reflection pressure is in the range of 1.6–1.8 according to the analytical solution of the reflection pressure and the ratio of the incident pressure in the water. When exploding at 0.5 m from the water-soil interface and the gas content of the saturated soil varies in the range of 0–10%, the transmission and reflection pressures are 63.8–70.0 MPa, and the reflection pressure coefficients are in the range of 1.55–1.70 at this time. The calculation method for the shock wave transmission and reflection pressure at the water-soil interface has a clear physical meaning and high precision and can provide a theoretical basis for the soil damage assessment of engineering structures in submerged soil caused by underwater explosions.
2024, 44(11): 112202.
doi: 10.11883/bzycj-2023-0342
Abstract:
Based on the Kong-Fang concrete material model and the multi-material arbitrary Lagrangian-Eulerian (MM-ALE) algorithm available in the LS-DYNA, the attenuation law of stress waves in CF120 concrete subjected to cylindrical cased charge explosion was numerically investigated in this paper. Firstly, the numerical algorithm and material model parameters were validated against two sets of cylindrical charge explosion tests. Then a series of fully enclosed and partially buried cylindrical charge explosion numerical models were established, in which different aspect ratios, shell thicknesses, and charge buried depths were considered to analyze the influence of charge shape and shell thickness on stress waves in concrete. Finally, an empirical formula for peak stress of compression wave in concrete induced by cylindrical cased charge explosion was presented based on curve-fitting the numerical data. Numerical results demonstrate that the larger the aspect ratio, the higher the peak stress in the near region, while the opposite law takes on in the far region. Besides, increasing the shell thickness will make the peak stress higher, but there is a threshold. The influence of charge shape, shell thickness, and charge buried depth on the peak stress can be quantified by defining the length-diameter ratio, thickness-diameter ratio, and coupling factor of peak stress. The empirical formula for peak stress of compression wave in concrete is valid for varied aspect ratio, shell thickness, and charge buried depth, which can provide a reliable estimation the peak stress induced by cylindrical cased charge explosion.
Based on the Kong-Fang concrete material model and the multi-material arbitrary Lagrangian-Eulerian (MM-ALE) algorithm available in the LS-DYNA, the attenuation law of stress waves in CF120 concrete subjected to cylindrical cased charge explosion was numerically investigated in this paper. Firstly, the numerical algorithm and material model parameters were validated against two sets of cylindrical charge explosion tests. Then a series of fully enclosed and partially buried cylindrical charge explosion numerical models were established, in which different aspect ratios, shell thicknesses, and charge buried depths were considered to analyze the influence of charge shape and shell thickness on stress waves in concrete. Finally, an empirical formula for peak stress of compression wave in concrete induced by cylindrical cased charge explosion was presented based on curve-fitting the numerical data. Numerical results demonstrate that the larger the aspect ratio, the higher the peak stress in the near region, while the opposite law takes on in the far region. Besides, increasing the shell thickness will make the peak stress higher, but there is a threshold. The influence of charge shape, shell thickness, and charge buried depth on the peak stress can be quantified by defining the length-diameter ratio, thickness-diameter ratio, and coupling factor of peak stress. The empirical formula for peak stress of compression wave in concrete is valid for varied aspect ratio, shell thickness, and charge buried depth, which can provide a reliable estimation the peak stress induced by cylindrical cased charge explosion.
2024, 44(11): 113101.
doi: 10.11883/bzycj-2-23-0466
Abstract:
Coral concrete is a material with severely asymmetric tensile and compressive strengths. Therefore, studying the dynamic tensile mechanical properties of coral concrete is of great significance for island reef protective engineering. To investigate the dynamic tensile mechanical properties of carbon fiber (CF) and stainless steel fiber (SSF) reinforced coral sand cement mortar under impact loading, dynamic splitting tests were conducted using a 100 mm diameter split Hopkinson pressure bar (SHPB) device. Comparative analysis was carried out on the dynamic tensile strength and energy dissipation patterns of coral sand cement mortars with different fiber contents at various strain rates. In the SHPB tests, cement mortar specimens with different fiber contents were prepared: no fiber, 1.5% CF, 1.5% CF with 0.5% SSF, 1.5% CF with 1.0% SSF, and 1.5% CF with 1.5% SSF. The specimens were subjected to four impact velocities: 3.45, 4.86, 6.54, and 7.34 m/s. This allowed for impact-splitting tests conducted at different strain-rate ranges. In addition, scanning electron microscope (SEM) tests were performed to reveal the action mechanism of the hybrid fibers. The results indicate that the static and dynamic tensile strengths of CF and SSF-reinforced coral sand cement mortar specimens are significantly improved, with a maximum dynamic tensile strength increase ratio of 66.03%. At the same strain rate, the dynamic tensile strength of the specimens positively correlates with the fiber content, while the fragmentation degree negatively correlates with the fiber content. The fiber bridging effect effectively suppresses the development of cracks in the specimens. Under the same fiber content, the dynamic increase factor increases significantly with the increase of strain rate, with a maximum increase factor of 2.44, demonstrating a clear tensile strain rate effect. The fragmentation degree and dissipated energy of coral sand cement mortar specimens positively correlate with the strain rate, and samples with higher fiber dosages require more energy to dissipate during failure.
Coral concrete is a material with severely asymmetric tensile and compressive strengths. Therefore, studying the dynamic tensile mechanical properties of coral concrete is of great significance for island reef protective engineering. To investigate the dynamic tensile mechanical properties of carbon fiber (CF) and stainless steel fiber (SSF) reinforced coral sand cement mortar under impact loading, dynamic splitting tests were conducted using a 100 mm diameter split Hopkinson pressure bar (SHPB) device. Comparative analysis was carried out on the dynamic tensile strength and energy dissipation patterns of coral sand cement mortars with different fiber contents at various strain rates. In the SHPB tests, cement mortar specimens with different fiber contents were prepared: no fiber, 1.5% CF, 1.5% CF with 0.5% SSF, 1.5% CF with 1.0% SSF, and 1.5% CF with 1.5% SSF. The specimens were subjected to four impact velocities: 3.45, 4.86, 6.54, and 7.34 m/s. This allowed for impact-splitting tests conducted at different strain-rate ranges. In addition, scanning electron microscope (SEM) tests were performed to reveal the action mechanism of the hybrid fibers. The results indicate that the static and dynamic tensile strengths of CF and SSF-reinforced coral sand cement mortar specimens are significantly improved, with a maximum dynamic tensile strength increase ratio of 66.03%. At the same strain rate, the dynamic tensile strength of the specimens positively correlates with the fiber content, while the fragmentation degree negatively correlates with the fiber content. The fiber bridging effect effectively suppresses the development of cracks in the specimens. Under the same fiber content, the dynamic increase factor increases significantly with the increase of strain rate, with a maximum increase factor of 2.44, demonstrating a clear tensile strain rate effect. The fragmentation degree and dissipated energy of coral sand cement mortar specimens positively correlate with the strain rate, and samples with higher fiber dosages require more energy to dissipate during failure.
2024, 44(11): 113102.
doi: 10.11883/bzycj-2023-0296
Abstract:
The dynamic mechanical behavior of a metallic hierarchical corrugated sandwich beam subjected to foam projectile impact was systematically studied. After verifying the reliability of the numerical method, the dynamic deformation evolution, quantitative deflection results, deformation failure modes, and energy absorption characteristics of the metallic hierarchical corrugated sandwich beam under different projectile momentum levels were analyzed using Abaqus-Explicit simulations. Subsequently, three metallic single-layer empty corrugated sandwich beams with different geometric parameters were designed, aiming to compare the shock resistance between single-layer and hierarchical corrugated sandwich beams under equal mass conditions. The results showed that the degree of crushing of the secondary corrugated core on the impact side and the first-order corrugated core of the hierarchical sandwich beam was always greater than that of the rear sandwich’s secondary corrugated core. The final mid-span deflection of the rear face of the hierarchical corrugated sandwich beam was always smaller than the corresponding deflection value of the equivalent mass single-level empty corrugated sandwich beam, demonstrating the superior impact protection performance of the hierarchical sandwich beam. This enhancement mechanism is mainly attributed to the increased energy absorption because of the added cellular cores, which protects the rear face sheet. Besides, the plastic longitudinal stretching strength of the hierarchical sandwich beam remains almost unchanged, while the plastic bending strength increases due to the increase in the total beam thickness, thereby enlarging the plastic yield surface of the sandwich structure.
The dynamic mechanical behavior of a metallic hierarchical corrugated sandwich beam subjected to foam projectile impact was systematically studied. After verifying the reliability of the numerical method, the dynamic deformation evolution, quantitative deflection results, deformation failure modes, and energy absorption characteristics of the metallic hierarchical corrugated sandwich beam under different projectile momentum levels were analyzed using Abaqus-Explicit simulations. Subsequently, three metallic single-layer empty corrugated sandwich beams with different geometric parameters were designed, aiming to compare the shock resistance between single-layer and hierarchical corrugated sandwich beams under equal mass conditions. The results showed that the degree of crushing of the secondary corrugated core on the impact side and the first-order corrugated core of the hierarchical sandwich beam was always greater than that of the rear sandwich’s secondary corrugated core. The final mid-span deflection of the rear face of the hierarchical corrugated sandwich beam was always smaller than the corresponding deflection value of the equivalent mass single-level empty corrugated sandwich beam, demonstrating the superior impact protection performance of the hierarchical sandwich beam. This enhancement mechanism is mainly attributed to the increased energy absorption because of the added cellular cores, which protects the rear face sheet. Besides, the plastic longitudinal stretching strength of the hierarchical sandwich beam remains almost unchanged, while the plastic bending strength increases due to the increase in the total beam thickness, thereby enlarging the plastic yield surface of the sandwich structure.
2024, 44(11): 113103.
doi: 10.11883/bzycj-2023-0460
Abstract:
To address the issue of peak load reduction for impact loads in engineering technology, the energy absorption characteristics of axial series energy absorbing tubes was investigated through a combination of numerical simulation and experimentation. Firstly, the Johnson-Cook dynamic constitutive parameters of the material 06Cr18Ni11Ti GB/T1220-2007 of energy absorbing tubes were established and evaluated based on high-speed tensile tests which indicates 06Cr18Ni11Ti has obvious strain rate hardening effect. Subsequently, numerical simulation and high-speed impact tests were conducted to examine the energy absorption characteristics of energy absorption tubes, with an evaluation of consistency between numerical simulation and test results. The numerical simulation was based on the time-step ABAQUS/Explicit finite element simulation platform. The high speed impact test system used the high pressure gas inside the air actuated piston cylinder as the power source, which could accelerate the mass block to a speed of 30 m/s. Finally, the energy absorption evaluation indexes between the axial series configuration and the single configuration of the energy absorption tube were compared and analyzed by numerical simulation. The analysis demonstrates that deformation mode, load curve, and energy absorption evaluation indexes from both numerical simulations and impact tests exhibit good agreement. The accuracy of material performance parameters confirms the effectiveness of simulation prediction methods while validating reasonability and reliability of high-speed impact test schemes. Compared to axial series configurations with identical structural parameters, single-tube configurations display asymmetric and unstable twist deformations during compression processes. Single-tube configurations experience a 13% reduction in effective compression stroke along with a 33.4% increase in peak load, 15% increase in instantaneous impact load, 13% increase in average compression force, as well as a 17.7% increase in peak-to-average load ratio. Consequently, axial series configurations prove to be more ideal energy absorbing structures.
To address the issue of peak load reduction for impact loads in engineering technology, the energy absorption characteristics of axial series energy absorbing tubes was investigated through a combination of numerical simulation and experimentation. Firstly, the Johnson-Cook dynamic constitutive parameters of the material 06Cr18Ni11Ti GB/T1220-2007 of energy absorbing tubes were established and evaluated based on high-speed tensile tests which indicates 06Cr18Ni11Ti has obvious strain rate hardening effect. Subsequently, numerical simulation and high-speed impact tests were conducted to examine the energy absorption characteristics of energy absorption tubes, with an evaluation of consistency between numerical simulation and test results. The numerical simulation was based on the time-step ABAQUS/Explicit finite element simulation platform. The high speed impact test system used the high pressure gas inside the air actuated piston cylinder as the power source, which could accelerate the mass block to a speed of 30 m/s. Finally, the energy absorption evaluation indexes between the axial series configuration and the single configuration of the energy absorption tube were compared and analyzed by numerical simulation. The analysis demonstrates that deformation mode, load curve, and energy absorption evaluation indexes from both numerical simulations and impact tests exhibit good agreement. The accuracy of material performance parameters confirms the effectiveness of simulation prediction methods while validating reasonability and reliability of high-speed impact test schemes. Compared to axial series configurations with identical structural parameters, single-tube configurations display asymmetric and unstable twist deformations during compression processes. Single-tube configurations experience a 13% reduction in effective compression stroke along with a 33.4% increase in peak load, 15% increase in instantaneous impact load, 13% increase in average compression force, as well as a 17.7% increase in peak-to-average load ratio. Consequently, axial series configurations prove to be more ideal energy absorbing structures.
2024, 44(11): 113301.
doi: 10.11883/bzycj-2023-0208
Abstract:
In order to solve the problem of high-performance lightweight bulletproof inserts protection of penetration of light weapon killing elements, this paper carried out penetration experiments on ultra-high molecular weight polyethylene (UHMWPE) laminated sheet, analyzed the deformation and failure characteristics of the UHMWPE sheet after penetration and compared the damage morphology of light weapon killing element. A numerical model of UHMWPE laminate against the penetration of light weapon killers was established by using the finite element software LS-DYNA, and the validity of the numerical model was verified by the experimental results of the damage morphology of the target plate, the depth of the depression and the deformation of the warhead. On this basis, the failure mode of the UHMWPE thin plate subjected to oblique penetration by the projectile is investigated by numerical methods, and the influence of the incidence angle on the ricochet phenomenon and the damage morphology of UHMWPE thin plate under the penetration of three kinds of light weapon killing elements is revealed. The results show that the ricochet angles of 7.62 mm×25 mm steel-core bullets and 7.62 mm×39 mm ordinary bullets (steel-core) obliquely penetrating UHMWPE plates are located in the range of 45°–50°; 7.62 mm×25 mm lead-core bullets can be completely ricocheted out when the angle of incidence is greater than 70°, and the rest of the bullets are in the form of broken shrapnel splinters, and the destruction of the bullet body has an effect on the ricochet condition; the oblique penetration bullets produce a large area and a large number of damage patterns at a smaller angle of incidence; the oblique penetration bullets produce a larger area and a larger number of damage patterns in the UHMWPE plates. When the angle of incidence is small, the oblique penetration bullet will produce a larger area and a certain depth of the crater, the next bullet will be easier to penetrate the crater weakness of the fiber plate, and the oblique penetration effect on the thin plate by the secondary penetration of the negative impact, the angle of incidence is larger, the bullet will be more complete ricochet and has a high residual velocity, which will produce a secondary killing of personnel. The research results can be used for UHMWPE thin plate for lightweight military bulletproof insert design to provide reference.
In order to solve the problem of high-performance lightweight bulletproof inserts protection of penetration of light weapon killing elements, this paper carried out penetration experiments on ultra-high molecular weight polyethylene (UHMWPE) laminated sheet, analyzed the deformation and failure characteristics of the UHMWPE sheet after penetration and compared the damage morphology of light weapon killing element. A numerical model of UHMWPE laminate against the penetration of light weapon killers was established by using the finite element software LS-DYNA, and the validity of the numerical model was verified by the experimental results of the damage morphology of the target plate, the depth of the depression and the deformation of the warhead. On this basis, the failure mode of the UHMWPE thin plate subjected to oblique penetration by the projectile is investigated by numerical methods, and the influence of the incidence angle on the ricochet phenomenon and the damage morphology of UHMWPE thin plate under the penetration of three kinds of light weapon killing elements is revealed. The results show that the ricochet angles of 7.62 mm×25 mm steel-core bullets and 7.62 mm×39 mm ordinary bullets (steel-core) obliquely penetrating UHMWPE plates are located in the range of 45°–50°; 7.62 mm×25 mm lead-core bullets can be completely ricocheted out when the angle of incidence is greater than 70°, and the rest of the bullets are in the form of broken shrapnel splinters, and the destruction of the bullet body has an effect on the ricochet condition; the oblique penetration bullets produce a large area and a large number of damage patterns at a smaller angle of incidence; the oblique penetration bullets produce a larger area and a larger number of damage patterns in the UHMWPE plates. When the angle of incidence is small, the oblique penetration bullet will produce a larger area and a certain depth of the crater, the next bullet will be easier to penetrate the crater weakness of the fiber plate, and the oblique penetration effect on the thin plate by the secondary penetration of the negative impact, the angle of incidence is larger, the bullet will be more complete ricochet and has a high residual velocity, which will produce a secondary killing of personnel. The research results can be used for UHMWPE thin plate for lightweight military bulletproof insert design to provide reference.
2024, 44(11): 113302.
doi: 10.11883/bzycj-2024-0063
Abstract:
Reactive fragments are composed of multifunctional impact reactive structural materials. After reactive fragments penetrate the front target of warhead, the debris cloud generated by the sufficient reaction of reactive material will damage the medium behind the target in the form of kinetic energy-chemical energy coupling damage. Ballistic impact experiments and finite element simulations were conducted to investigate the impact damage effect of reactive fragments on cased charge. Based on the criteria for failure levels of cased charge characterized by equivalent fragments initial velocity and equivalent gurney velocity, the ratio of the equivalent gurney velocity under abnormal detonation conditions to gurney velocity or the ratio of the equivalent fragments initial velocity under abnormal detonation conditions to the fragments initial velocity is used to measure the reaction violence of the cased charge. Equivalent gurney velocity of cased charge under impact of inert fragments and reactive fragments, response duration of cased charge, the damage of the authentication target, and the peak pressure of explosive layer are compared. The influence of energy release characteristics of reactive fragments on the failure of cased charge is also analyzed. The results show that explosive detonate under the impact of inert fragments, while explosive deflagrate or explode under the impact of reactive fragments. The steel verification target only presents significant circular pit during explosive detonation. The explosive detonation process captured by high-speed photography is on the microsecond scale, while the explosive explosion or deflagration process is on the millisecond scale. Under the penetration of six reactive fragments, the corresponding ratio of equivalent gurney velocity to gurney velocity ranges from 0.014 to 0.233, which is far below the ratio of equivalent gurney velocity to gurney velocity under the condition of inert fragments penetrating cased charges. By using AUTODYN, the peak pressure at the observation point on the axis of the cased charge during detonation failure under the penetration of inert fragments ranges from 17.3 to 34.5 GPa, while the peak pressure of cased charge during deflagration failure under the penetration of reactive fragments ranges from 1.04 to 3.62 GPa, which is far below the critical detonation pressure. Based on the ratio of the equivalent gurney velocity to gurney velocity, the peak pressure of explosive and superimposed effect of kinetic energy and chemical energy of reactive fragments, the idea that it is difficult to detonate cased charge under the penetration of reactive fragments is proposed.
Reactive fragments are composed of multifunctional impact reactive structural materials. After reactive fragments penetrate the front target of warhead, the debris cloud generated by the sufficient reaction of reactive material will damage the medium behind the target in the form of kinetic energy-chemical energy coupling damage. Ballistic impact experiments and finite element simulations were conducted to investigate the impact damage effect of reactive fragments on cased charge. Based on the criteria for failure levels of cased charge characterized by equivalent fragments initial velocity and equivalent gurney velocity, the ratio of the equivalent gurney velocity under abnormal detonation conditions to gurney velocity or the ratio of the equivalent fragments initial velocity under abnormal detonation conditions to the fragments initial velocity is used to measure the reaction violence of the cased charge. Equivalent gurney velocity of cased charge under impact of inert fragments and reactive fragments, response duration of cased charge, the damage of the authentication target, and the peak pressure of explosive layer are compared. The influence of energy release characteristics of reactive fragments on the failure of cased charge is also analyzed. The results show that explosive detonate under the impact of inert fragments, while explosive deflagrate or explode under the impact of reactive fragments. The steel verification target only presents significant circular pit during explosive detonation. The explosive detonation process captured by high-speed photography is on the microsecond scale, while the explosive explosion or deflagration process is on the millisecond scale. Under the penetration of six reactive fragments, the corresponding ratio of equivalent gurney velocity to gurney velocity ranges from 0.014 to 0.233, which is far below the ratio of equivalent gurney velocity to gurney velocity under the condition of inert fragments penetrating cased charges. By using AUTODYN, the peak pressure at the observation point on the axis of the cased charge during detonation failure under the penetration of inert fragments ranges from 17.3 to 34.5 GPa, while the peak pressure of cased charge during deflagration failure under the penetration of reactive fragments ranges from 1.04 to 3.62 GPa, which is far below the critical detonation pressure. Based on the ratio of the equivalent gurney velocity to gurney velocity, the peak pressure of explosive and superimposed effect of kinetic energy and chemical energy of reactive fragments, the idea that it is difficult to detonate cased charge under the penetration of reactive fragments is proposed.
2024, 44(11): 113901.
doi: 10.11883/bzycj-2023-0260
Abstract:
Based on the computational fluid dynamics (CFD) numerical methods, a set of reliable and effective numerical methods for investigating the flow field and evolution characteristics of motion during the process of falling vehicle with boost floatation aids impacting the water in wave environment was established coupled with volume of fluid (VOF) multiphase flow model, k-ω SST turbulence model, Schnerr-Sauer cavitation model and Stokes fifth-order nonlinear wave theory. The numerical simulation of the process of falling into water under a horizontal cylinder showed that the difference between the experimental results and the numerical results in falling displacement was small, which verifies the validity of the numerical method of water falling impact. The wave generation results obtained by the velocity boundary numerical wave generation method were in good agreement with Stokes fifth-order nonlinear wave theory. Based on the established numerical method, numerical simulation was carried out on the water falling impact process of the vehicle with boost floatation aids under different wave sea states. The kinematic and dynamic parameters of the vehicle and evolution of water-entry cavity flow field during the impact process were analyzed, and the water falling impact characteristics of the vehicle with boost floatation aids under wave environment were summarized. The results show that the impact of wave environment on the falling impact process is mainly reflected in the motion attenuation section. The horizontal impact is much more affected by the wave environment than the vertical impact and the influence of different sea conditions on the horizontal impact of the vehicle is mainly achieved by influencing the formation and collapse of the water-entry cavity. The calculated displacement, velocity, acceleration and boost floatation aids force during the impact process of vehicle with boost floatation aids can be provided as a reference for the structural design and safety test guidance of the vehicle recovery under wave environment.
Based on the computational fluid dynamics (CFD) numerical methods, a set of reliable and effective numerical methods for investigating the flow field and evolution characteristics of motion during the process of falling vehicle with boost floatation aids impacting the water in wave environment was established coupled with volume of fluid (VOF) multiphase flow model, k-ω SST turbulence model, Schnerr-Sauer cavitation model and Stokes fifth-order nonlinear wave theory. The numerical simulation of the process of falling into water under a horizontal cylinder showed that the difference between the experimental results and the numerical results in falling displacement was small, which verifies the validity of the numerical method of water falling impact. The wave generation results obtained by the velocity boundary numerical wave generation method were in good agreement with Stokes fifth-order nonlinear wave theory. Based on the established numerical method, numerical simulation was carried out on the water falling impact process of the vehicle with boost floatation aids under different wave sea states. The kinematic and dynamic parameters of the vehicle and evolution of water-entry cavity flow field during the impact process were analyzed, and the water falling impact characteristics of the vehicle with boost floatation aids under wave environment were summarized. The results show that the impact of wave environment on the falling impact process is mainly reflected in the motion attenuation section. The horizontal impact is much more affected by the wave environment than the vertical impact and the influence of different sea conditions on the horizontal impact of the vehicle is mainly achieved by influencing the formation and collapse of the water-entry cavity. The calculated displacement, velocity, acceleration and boost floatation aids force during the impact process of vehicle with boost floatation aids can be provided as a reference for the structural design and safety test guidance of the vehicle recovery under wave environment.
2024, 44(11): 114101.
doi: 10.11883/bzycj-2023-0195
Abstract:
Based on the basic principles of electromagnetic induction, an impact device is proposed that generates high-amplitude and long-pulse acceleration loads driven by electromagnetic forces. The impact device goes to make up for the shortcomings of the current stage of ground impact test technology. The disadvantages of the current stage of ground impact test technology include mainly time-consuming, high cost, low repeatability and controllability, and it is difficult to continuously improve the pulse width of acceleration load. Acceleration impact tests were performed using an electromagnetic Hopkinson bar, and the working process of the device from the generation of electromagnetic force to its transformation into impact load was analyzed. In the acceleration impact test, the stress on the bar was obtained by strain gauges and the acceleration loads at the end of the bar were obtained by acceleration transducers. A plurality of test results without loss of repeatability. The classical one-dimensional stress wave theory for predicting the relationship between acceleration and stress in slender bars is developed. Comparative analysis against experimental data are presented to demonstrate the effectiveness of the present approach. The electromagnetic Hopkinson bar acceleration impact test was numerically simulated using COMSOL finite element software, and the simulation results showed good consistency with the experimental results, indicating that the numerical model could simulate this kind of impact test more accurately and verifying the accuracy of the numerical model. Based on this finite element model, an impact device that generates high-amplitude, long-pulse acceleration is proposed, and numerical simulations of the device are carried out at different voltages and capacitances. The simulation results show that the device is able to generate the required acceleration. The acceleration amplitude increases with increasing capacitance voltage and the acceleration pulse width increases with increasing capacitance value. By regulating the values of the circuit parameters, the device can generate acceleration loads with different amplitudes and pulse widths.
Based on the basic principles of electromagnetic induction, an impact device is proposed that generates high-amplitude and long-pulse acceleration loads driven by electromagnetic forces. The impact device goes to make up for the shortcomings of the current stage of ground impact test technology. The disadvantages of the current stage of ground impact test technology include mainly time-consuming, high cost, low repeatability and controllability, and it is difficult to continuously improve the pulse width of acceleration load. Acceleration impact tests were performed using an electromagnetic Hopkinson bar, and the working process of the device from the generation of electromagnetic force to its transformation into impact load was analyzed. In the acceleration impact test, the stress on the bar was obtained by strain gauges and the acceleration loads at the end of the bar were obtained by acceleration transducers. A plurality of test results without loss of repeatability. The classical one-dimensional stress wave theory for predicting the relationship between acceleration and stress in slender bars is developed. Comparative analysis against experimental data are presented to demonstrate the effectiveness of the present approach. The electromagnetic Hopkinson bar acceleration impact test was numerically simulated using COMSOL finite element software, and the simulation results showed good consistency with the experimental results, indicating that the numerical model could simulate this kind of impact test more accurately and verifying the accuracy of the numerical model. Based on this finite element model, an impact device that generates high-amplitude, long-pulse acceleration is proposed, and numerical simulations of the device are carried out at different voltages and capacitances. The simulation results show that the device is able to generate the required acceleration. The acceleration amplitude increases with increasing capacitance voltage and the acceleration pulse width increases with increasing capacitance value. By regulating the values of the circuit parameters, the device can generate acceleration loads with different amplitudes and pulse widths.
2024, 44(11): 115401.
doi: 10.11883/bzycj-2023-0340
Abstract:
In order to improve the explosion suppression efficiency of liquefied petroleum gas (LPG), a self-designed semi-open organic glass pipeline was used to build the N2/water mist explosion suppression experimental platform. The explosion suppression effect of N2/water mist containing modified chlorine compounds was analyzed from four aspects: explosion overpressure, flame propagation velocity and its peak arrival time, and flame structure. The results show that the chlorine compounds are selective to surfactants. The synergistic effect between KCl, NaCl and NH4Cl and fatty alcohol polyoxyethylene ether (AeO9) and silicone surfactant (Sicare2235) is better. The maximum explosion overpressure and flame propagation velocity are obviously reduced, and their arrival time is obviously prolonged. When sodium dodecyl sulfate (SDS) only interacts with NaCl, the explosion suppression effect is significantly improved. While when SDS interacts with the other three chloride salts, there is no synergistic effect or even explosion-promoting effect. Explosion enhancement occurs when FeCl2 cooperates with surfactants. When the chlorine compound and the surfactant act together, there is an optimal value for the surface tension value, when the surface tension is 20 mN/m, the explosion suppression efficiency is the best. The numerical simulation results of chemical kinetics show that the modified chlorine compound N2 water mist can effectively reduce the adiabatic flame temperature, consume key free radicals, and interrupt the combustion chain reaction. The synergistic mechanism of explosion suppression is mainly reflected in three aspects: N2 inerting dilution, surfactant regulation of water mist particle size increase cooling effect and inhibition of chain reaction. The research results will provide technical guidance for the prevention and suppression of liquefied petroleum gas explosion accidents in China.
In order to improve the explosion suppression efficiency of liquefied petroleum gas (LPG), a self-designed semi-open organic glass pipeline was used to build the N2/water mist explosion suppression experimental platform. The explosion suppression effect of N2/water mist containing modified chlorine compounds was analyzed from four aspects: explosion overpressure, flame propagation velocity and its peak arrival time, and flame structure. The results show that the chlorine compounds are selective to surfactants. The synergistic effect between KCl, NaCl and NH4Cl and fatty alcohol polyoxyethylene ether (AeO9) and silicone surfactant (Sicare2235) is better. The maximum explosion overpressure and flame propagation velocity are obviously reduced, and their arrival time is obviously prolonged. When sodium dodecyl sulfate (SDS) only interacts with NaCl, the explosion suppression effect is significantly improved. While when SDS interacts with the other three chloride salts, there is no synergistic effect or even explosion-promoting effect. Explosion enhancement occurs when FeCl2 cooperates with surfactants. When the chlorine compound and the surfactant act together, there is an optimal value for the surface tension value, when the surface tension is 20 mN/m, the explosion suppression efficiency is the best. The numerical simulation results of chemical kinetics show that the modified chlorine compound N2 water mist can effectively reduce the adiabatic flame temperature, consume key free radicals, and interrupt the combustion chain reaction. The synergistic mechanism of explosion suppression is mainly reflected in three aspects: N2 inerting dilution, surfactant regulation of water mist particle size increase cooling effect and inhibition of chain reaction. The research results will provide technical guidance for the prevention and suppression of liquefied petroleum gas explosion accidents in China.
Founded in 1981 monthly
Sponsored byChinese Society of Theoretical and Applied Mechanics
Institude of Fluid Physics, CAEP
Editor-in-ChiefCangli Liu
