2024 Vol. 44, No. 4
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2024, 44(4): 041001.
doi: 10.11883/bzycj-2023-0375
Abstract:
The fiber back plate in ceramic/fiber composite armor cannot provide sufficient support for the ceramic panel due to its low stiffness, which weakens the erosion effect of the ceramic panel on the projectile. In order to enhance the overall structural stiffness of composite armor, a metal sandwich layer material was added to the ceramic/fiber composite armor. The ballistic performance of the sandwich composite armor against 12.7-mm incendiary projectiles was studied through experiments and numerical simulations. The experimental results indicate that the core of the penetrator exhibits a brittle fracture failure mode, while composite armor exhibits multiple failure modes, including petal-shaped expansion of the sandwich layer, delamination and protrusion deformation of the UHMWPE (ultra-high molecular weight polyethylene) laminate. A three-dimensional numerical model was established to analyze the evolution of the entire ballistic response, and the accuracy of the simulation was verified through experimental results. The simulation results indicate that the armor of the 12.7-mm penetrator will cause damage to the ceramic, which will erode the pointed oval head of the projectile core, making the core head blunt and weakening the penetration ability of the projectile core into the UHMWPE backing plate. Most of the kinetic energy of the residual projectile is absorbed by the UHMWPE layer, and the failure mode of the UHMWPE laminate will change from shear failure to tensile failure as the number of layers increases. In addition, as a sandwich layer, the porous TC4 board can provide support for the ceramic panel, increase the energy absorption of the ceramic panel and erosion of the projectile, and the 12-mm-pore-size TC4 sandwich layer can provide greater stiffness support, increase the energy absorption efficiency of the overall composite structure by 10%.
The fiber back plate in ceramic/fiber composite armor cannot provide sufficient support for the ceramic panel due to its low stiffness, which weakens the erosion effect of the ceramic panel on the projectile. In order to enhance the overall structural stiffness of composite armor, a metal sandwich layer material was added to the ceramic/fiber composite armor. The ballistic performance of the sandwich composite armor against 12.7-mm incendiary projectiles was studied through experiments and numerical simulations. The experimental results indicate that the core of the penetrator exhibits a brittle fracture failure mode, while composite armor exhibits multiple failure modes, including petal-shaped expansion of the sandwich layer, delamination and protrusion deformation of the UHMWPE (ultra-high molecular weight polyethylene) laminate. A three-dimensional numerical model was established to analyze the evolution of the entire ballistic response, and the accuracy of the simulation was verified through experimental results. The simulation results indicate that the armor of the 12.7-mm penetrator will cause damage to the ceramic, which will erode the pointed oval head of the projectile core, making the core head blunt and weakening the penetration ability of the projectile core into the UHMWPE backing plate. Most of the kinetic energy of the residual projectile is absorbed by the UHMWPE layer, and the failure mode of the UHMWPE laminate will change from shear failure to tensile failure as the number of layers increases. In addition, as a sandwich layer, the porous TC4 board can provide support for the ceramic panel, increase the energy absorption of the ceramic panel and erosion of the projectile, and the 12-mm-pore-size TC4 sandwich layer can provide greater stiffness support, increase the energy absorption efficiency of the overall composite structure by 10%.
Voltage transient characteristics and microscopic mechanism of tantalum capacitors under impact load
2024, 44(4): 043101.
doi: 10.11883/bzycj-2023-0232
Abstract:
To investigate the failure mechanism of tantalum capacitors under shock loads, shock experiments were conducted on tantalum capacitors using shock waves generated by underwater explosions with an electronic detonator. Five groups of experiments with different shock intensities were designed by varying the distance between the capacitor and the electronic detonator. The transient voltage characteristics of tantalum capacitors under different intensity shock loads were studied. The voltage variations of tantalum capacitors were explained based on the changes in internal leakage current and external charging current, and the failure modes of tantalum capacitors were analyzed. Scanning electron microscopy was utilized to observe the microstructure of damaged areas in tantalum capacitors and the micro-failure mechanisms of tantalum capacitors under shock loads were discussed. The results indicate that tantalum capacitors experience short-circuit failures after shocks, with a significant decrease in voltage initially, followed by a slow rise and self-recovery. As the shock wave overpressure increases, the probability of tantalum capacitor failure increases, with a critical overpressure threshold of approximately 32 MPa. Different types of voltage variations correspond to different failure modes, including instant self-recovery after breakdown, slow self-recovery after breakdown, and repetitive breakdown with self-recovery. Different types of voltage variations exhibit significant differences in the peak values of initial leakage currents, with the first type ranging from 2.5 A to 5 A, the second type ranging from 1 A to 2 A, and the third type ranging from 8 A to 9 A. Moreover, larger peak values of leakage currents result in narrower peak widths. The micro-failure mechanisms of tantalum capacitors under shock loads include the propagation of microcracks within the oxide film leading to excessive local electric field strength and breakdown, impurities and surrounding crystalline oxide film protruding to form conductive channels in the region of thinner oxide film, and the formation of through-cracks followed by gas ionization leading to breakdown.
To investigate the failure mechanism of tantalum capacitors under shock loads, shock experiments were conducted on tantalum capacitors using shock waves generated by underwater explosions with an electronic detonator. Five groups of experiments with different shock intensities were designed by varying the distance between the capacitor and the electronic detonator. The transient voltage characteristics of tantalum capacitors under different intensity shock loads were studied. The voltage variations of tantalum capacitors were explained based on the changes in internal leakage current and external charging current, and the failure modes of tantalum capacitors were analyzed. Scanning electron microscopy was utilized to observe the microstructure of damaged areas in tantalum capacitors and the micro-failure mechanisms of tantalum capacitors under shock loads were discussed. The results indicate that tantalum capacitors experience short-circuit failures after shocks, with a significant decrease in voltage initially, followed by a slow rise and self-recovery. As the shock wave overpressure increases, the probability of tantalum capacitor failure increases, with a critical overpressure threshold of approximately 32 MPa. Different types of voltage variations correspond to different failure modes, including instant self-recovery after breakdown, slow self-recovery after breakdown, and repetitive breakdown with self-recovery. Different types of voltage variations exhibit significant differences in the peak values of initial leakage currents, with the first type ranging from 2.5 A to 5 A, the second type ranging from 1 A to 2 A, and the third type ranging from 8 A to 9 A. Moreover, larger peak values of leakage currents result in narrower peak widths. The micro-failure mechanisms of tantalum capacitors under shock loads include the propagation of microcracks within the oxide film leading to excessive local electric field strength and breakdown, impurities and surrounding crystalline oxide film protruding to form conductive channels in the region of thinner oxide film, and the formation of through-cracks followed by gas ionization leading to breakdown.
2024, 44(4): 043102.
doi: 10.11883/bzycj-2023-0142
Abstract:
Cuttlefish bone is a biomineralized shell produced inside the cuttlefish that enables deep and shallow floating by adjusting the gas-liquid ratio. As a typical porous material with high specific stiffness, its light-weight and high rigidity make it well adapted to the deep-sea environment. Consequently, cuttlebone is often mimicked to design biomimetic porous materials with high porosity and high stiffness mechanical properties. However, the mechanical behavior of cuttlebone under dynamic loading is still unclear, which is extremely unfavorable for the dynamic design of cuttlebone. This study delves into an extensive exploration of cuttlebone's mechanical behavior under compressions with different loading strain rates using Instron material testing machine and split Hopkinson pressure bar experimental device. Under quasi-static loading conditions, the compressive stress-strain curves of cuttlebone were obtained and exhibited three typical stages, namely linear elastic stage, long plateau stage and densification stage. The specific energy absorption of cuttlebone calculated from the stress-strain curve is illustrated, showing that cuttlebone has a better energy absorption capability compared with other common bionic structures and porous materials. Under dynamic loading scenarios by using split Hopkinson pressure bar, the dynamic stress strain curves of cuttlebone were obtained at loading strain rates of approximate 400−530 s−1. Both the dynamic initial crushing stress and the plateau stress of cuttlebone exhibited a pronounced escalation with increasing loading strain rates, indicating that the cuttlebone structure is strongly sensitive to the loading strain rate. Furthermore, the mechanical attributes of cuttlebone with respect to different growth directions during quasi-static compression tests were investigated. As the growth direction increased, a discernible decline in both stiffness and energy absorption performance within the cuttlebone structure was observed, thus revealing the anisotropy of the compression behavior of cuttlefish bone. These insights not only deepen the understanding of cuttlebone's mechanical behavior but also offer valuable knowledge that can inform biomimetic and bioinspired engineering designs for a range of applications.
Cuttlefish bone is a biomineralized shell produced inside the cuttlefish that enables deep and shallow floating by adjusting the gas-liquid ratio. As a typical porous material with high specific stiffness, its light-weight and high rigidity make it well adapted to the deep-sea environment. Consequently, cuttlebone is often mimicked to design biomimetic porous materials with high porosity and high stiffness mechanical properties. However, the mechanical behavior of cuttlebone under dynamic loading is still unclear, which is extremely unfavorable for the dynamic design of cuttlebone. This study delves into an extensive exploration of cuttlebone's mechanical behavior under compressions with different loading strain rates using Instron material testing machine and split Hopkinson pressure bar experimental device. Under quasi-static loading conditions, the compressive stress-strain curves of cuttlebone were obtained and exhibited three typical stages, namely linear elastic stage, long plateau stage and densification stage. The specific energy absorption of cuttlebone calculated from the stress-strain curve is illustrated, showing that cuttlebone has a better energy absorption capability compared with other common bionic structures and porous materials. Under dynamic loading scenarios by using split Hopkinson pressure bar, the dynamic stress strain curves of cuttlebone were obtained at loading strain rates of approximate 400−530 s−1. Both the dynamic initial crushing stress and the plateau stress of cuttlebone exhibited a pronounced escalation with increasing loading strain rates, indicating that the cuttlebone structure is strongly sensitive to the loading strain rate. Furthermore, the mechanical attributes of cuttlebone with respect to different growth directions during quasi-static compression tests were investigated. As the growth direction increased, a discernible decline in both stiffness and energy absorption performance within the cuttlebone structure was observed, thus revealing the anisotropy of the compression behavior of cuttlefish bone. These insights not only deepen the understanding of cuttlebone's mechanical behavior but also offer valuable knowledge that can inform biomimetic and bioinspired engineering designs for a range of applications.
2024, 44(4): 043103.
doi: 10.11883/bzycj-2023-0315
Abstract:
As a novel folded structure, the truncated square pyramid (TSP) structure exhibits excellent impact resistance and energy absorption performance. It also has the merit of simple and modulated fabrication of its unit cell. To further verify the performance of TSP sandwich panels under local impact load, impact tests are carried out in this work by using an air cannon testing system. The unit cells are firstly prepared by multi-stage mold-pressing and then modular arranged to form single and multi-layer sandwich panels. The impact protection performance and energy absorption properties of the back-supported cladding cases and unsupported sandwich structures are investigated under different impact scenarios. Their impact resistance performances are evaluated by measuring and comparing the displacement time histories of the single-layer sandwich structures and their deformation modes after impact. For the back-supported cladding cases, a measuring system with five load cells is placed behind the back plate of the cladding and is rigidly supported to record the time history and distribution of the transmitted force of the claddings under impact. Their impact mitigation performances are evaluated by analyzing the recorded force-time histories under various loading scenarios. It is found that the maximum displacement and residual displacement of the back plate increase with the increase of impact velocity for the unsupported cases. For the rigidly supported claddings, the double-layered cladding shows significantly improved energy absorption and impact mitigation performance than the single-layered one. It shows a better utilization of the core, which leads to a reduced initial peak transmitted force. In addition, it is found that the impact position has a significant effect on the dynamic response of the claddings as it changes the peak transmitted force and its occurrence time because of the change in deformation modes. The research results provide a reference for the engineering design and application of TSP sandwich structures.
As a novel folded structure, the truncated square pyramid (TSP) structure exhibits excellent impact resistance and energy absorption performance. It also has the merit of simple and modulated fabrication of its unit cell. To further verify the performance of TSP sandwich panels under local impact load, impact tests are carried out in this work by using an air cannon testing system. The unit cells are firstly prepared by multi-stage mold-pressing and then modular arranged to form single and multi-layer sandwich panels. The impact protection performance and energy absorption properties of the back-supported cladding cases and unsupported sandwich structures are investigated under different impact scenarios. Their impact resistance performances are evaluated by measuring and comparing the displacement time histories of the single-layer sandwich structures and their deformation modes after impact. For the back-supported cladding cases, a measuring system with five load cells is placed behind the back plate of the cladding and is rigidly supported to record the time history and distribution of the transmitted force of the claddings under impact. Their impact mitigation performances are evaluated by analyzing the recorded force-time histories under various loading scenarios. It is found that the maximum displacement and residual displacement of the back plate increase with the increase of impact velocity for the unsupported cases. For the rigidly supported claddings, the double-layered cladding shows significantly improved energy absorption and impact mitigation performance than the single-layered one. It shows a better utilization of the core, which leads to a reduced initial peak transmitted force. In addition, it is found that the impact position has a significant effect on the dynamic response of the claddings as it changes the peak transmitted force and its occurrence time because of the change in deformation modes. The research results provide a reference for the engineering design and application of TSP sandwich structures.
2024, 44(4): 043104.
doi: 10.11883/bzycj-2023-0243
Abstract:
In order to study the dynamic behaviors and energy dissipation characteristics of marble under cyclic impact loading, a split Hopkinson pressure bar system was first adopted to determine the five representative incident velocities of striking projectile through the trial impact method. Based on this, constant amplitude cyclic impact tests of the marble samples were performed, and stress uniformity of the samples was examined. Then, a systematic analysis is conducted on the test data from the aspects of strain rate time history curve, stress-strain relationship, impact times and energy dissipation properties. Finally, a damage variable is defined based on the energy evolution, and the associated mechanism between energy dissipation and damage development of the rock samples is further explored. The results show that the time-history curves of the strain rate of the samples exhibit a plateau segment with a constant rate of change at low projectile velocities, and the stress-strain curve has a certain rebound at the post-peak stage. The peak stress of the rock samples decreases with the increase of the number of cycles, while the peak strain, average strain rate and cumulative absorption specific energy take on the opposite trend, and their change rates all show a sudden increase phenomenon before sample’s break or fracture. The peak stress has a linear relationship with the average strain rate, while the variation of sample elastic modulus with average strain rate generally follows an exponential decay law. There is a positive linear correlation between the dissipated specific energy and the average strain rate of the marble samples. The damage variable defined based on energy dissipation analysis can better characterize the break or fracture process of the marble samples under dynamic loading. The research results of this study have certain reference value for revealing the evolution mechanism of rock internal damage under cyclic load disturbance.
In order to study the dynamic behaviors and energy dissipation characteristics of marble under cyclic impact loading, a split Hopkinson pressure bar system was first adopted to determine the five representative incident velocities of striking projectile through the trial impact method. Based on this, constant amplitude cyclic impact tests of the marble samples were performed, and stress uniformity of the samples was examined. Then, a systematic analysis is conducted on the test data from the aspects of strain rate time history curve, stress-strain relationship, impact times and energy dissipation properties. Finally, a damage variable is defined based on the energy evolution, and the associated mechanism between energy dissipation and damage development of the rock samples is further explored. The results show that the time-history curves of the strain rate of the samples exhibit a plateau segment with a constant rate of change at low projectile velocities, and the stress-strain curve has a certain rebound at the post-peak stage. The peak stress of the rock samples decreases with the increase of the number of cycles, while the peak strain, average strain rate and cumulative absorption specific energy take on the opposite trend, and their change rates all show a sudden increase phenomenon before sample’s break or fracture. The peak stress has a linear relationship with the average strain rate, while the variation of sample elastic modulus with average strain rate generally follows an exponential decay law. There is a positive linear correlation between the dissipated specific energy and the average strain rate of the marble samples. The damage variable defined based on energy dissipation analysis can better characterize the break or fracture process of the marble samples under dynamic loading. The research results of this study have certain reference value for revealing the evolution mechanism of rock internal damage under cyclic load disturbance.
2024, 44(4): 043201.
doi: 10.11883/bzycj-2023-0197
Abstract:
The existing specifications and studies mainly focus on the scenarios that the spherical charges are ignited at the central point and explosion is in free air, while the studies of the blast loadings of cylindrical charges air explosion, especially the reflected overpressure acting on the structure, are relatively limited. The blast loading calculation formula for spherical charge cannot be applied for cylindrical charge as attributed to the parametric influences such as scaled distance, length-to-diameter ratio, ignition method, azimuth angle, incident angle and relative location of reflected plane. To explore the incident and reflected blast loadings of cylindrical charges air explosion, firstly, three shots of explosion test of the single-end ignited cylindrical TNT charge were conducted. The corresponding numerical simulations are conducted based on the finite element program AUTODYN, and the applicability of the adopted finite element analysis method is verified by comparing with the experimental incident and reflected overpressure-time histories of spherical and cylindrical charges air explosion of tests, as well as the peak incident overpressure-scaled distance relationship of unified facilities criteria (UFC) 3-340-02 of spherical charges air explosion. Furthermore, the numerical simulations of more than 1000 sets of cylindrical charges air explosion scenarios considering the scaled distance, length-to-diameter ratio, ignition method, azimuth angle and rigid reflection are carried out based on validated finite element analysis method. The distribution characteristics of peak overpressure, maximal impulse of the incident blast wave and the corresponding shape factors are examined and discussed. The judging criteria and determination methods for the critical scaled distance of peak overpressure and maximal impulse are proposed by using data fitting, and the variation law of the reflected peak overpressure and the rigid reflection coefficient are revealed. Finally, a calculation method for the incident and reflected blast loadings of cylindrical charges air explosion is proposed and experimentally verified by 360 sets data. The method can rapidly predict the blast loadings on building structures, and provide reference for evaluating the ammunition damage efficiency, analyzing structural dynamic response and failure, as well as for the corresponding blast-resistant design.
The existing specifications and studies mainly focus on the scenarios that the spherical charges are ignited at the central point and explosion is in free air, while the studies of the blast loadings of cylindrical charges air explosion, especially the reflected overpressure acting on the structure, are relatively limited. The blast loading calculation formula for spherical charge cannot be applied for cylindrical charge as attributed to the parametric influences such as scaled distance, length-to-diameter ratio, ignition method, azimuth angle, incident angle and relative location of reflected plane. To explore the incident and reflected blast loadings of cylindrical charges air explosion, firstly, three shots of explosion test of the single-end ignited cylindrical TNT charge were conducted. The corresponding numerical simulations are conducted based on the finite element program AUTODYN, and the applicability of the adopted finite element analysis method is verified by comparing with the experimental incident and reflected overpressure-time histories of spherical and cylindrical charges air explosion of tests, as well as the peak incident overpressure-scaled distance relationship of unified facilities criteria (UFC) 3-340-02 of spherical charges air explosion. Furthermore, the numerical simulations of more than 1000 sets of cylindrical charges air explosion scenarios considering the scaled distance, length-to-diameter ratio, ignition method, azimuth angle and rigid reflection are carried out based on validated finite element analysis method. The distribution characteristics of peak overpressure, maximal impulse of the incident blast wave and the corresponding shape factors are examined and discussed. The judging criteria and determination methods for the critical scaled distance of peak overpressure and maximal impulse are proposed by using data fitting, and the variation law of the reflected peak overpressure and the rigid reflection coefficient are revealed. Finally, a calculation method for the incident and reflected blast loadings of cylindrical charges air explosion is proposed and experimentally verified by 360 sets data. The method can rapidly predict the blast loadings on building structures, and provide reference for evaluating the ammunition damage efficiency, analyzing structural dynamic response and failure, as well as for the corresponding blast-resistant design.
Effect of steel ratio on the impact resistance of GFRP tube concrete-encased steel composite members
2024, 44(4): 043202.
doi: 10.11883/bzycj-2023-0246
Abstract:
To investigate the effect of the steel ratio on the impact resistance of glass fiber reinforced polymer (GFRP) tube concrete-encased steel composite members, 15 numerical models of composite members were established. The whole impact process, the dynamic response and the stress distribution of each composite member at different characteristic moments during the low-velocity impact were analyzed. The bending moment contributions at typical cross sections and the energy dissipation under different impact moments were explored. Meanwhile, the corresponding failure mode was determined, based on the maximum principal plastic strain distribution of concrete, tensile and compression damage of GFRP tube matrix, and equivalent plastic strain distribution of steel. Additionally, the effect of the steel ratio on the impact performance of members with different slenderness ratios was investigated by analyzing the time history curves of the impact force, displacement, energy transformation and energy consumption. The results show that the impact load-bearing capacity of GFRP tube concrete-encased steel members is improved by 7% to 134% and the lateral displacement is reduced by 13% to 68% compared with the GFRP tube concrete members. Furthermore, it can be observed that the failure mode of the members is mainly bending, and the concrete is crushed in the impact region. The bending stiffness has a significant influence on the impact performance of the member under lateral impact loading. The impact force of the member increases with the increase in the steel ratio, whereas the impact force of the member decreases with the increase in the slenderness ratio. Moreover, narrow flange steel with a higher moment of inertia is more favorable for the impact resistance of the member when the difference in steel ratio is 1.5%. The energy consumption of the encased steel is a major contributor to the total energy consumption of the member when the slenderness ratio is greater than or equal to 20. The GFRP tube plays a dual role in bearing the impact force and confining the concrete in a circumferential direction at the oscillation stage during the impact process.
To investigate the effect of the steel ratio on the impact resistance of glass fiber reinforced polymer (GFRP) tube concrete-encased steel composite members, 15 numerical models of composite members were established. The whole impact process, the dynamic response and the stress distribution of each composite member at different characteristic moments during the low-velocity impact were analyzed. The bending moment contributions at typical cross sections and the energy dissipation under different impact moments were explored. Meanwhile, the corresponding failure mode was determined, based on the maximum principal plastic strain distribution of concrete, tensile and compression damage of GFRP tube matrix, and equivalent plastic strain distribution of steel. Additionally, the effect of the steel ratio on the impact performance of members with different slenderness ratios was investigated by analyzing the time history curves of the impact force, displacement, energy transformation and energy consumption. The results show that the impact load-bearing capacity of GFRP tube concrete-encased steel members is improved by 7% to 134% and the lateral displacement is reduced by 13% to 68% compared with the GFRP tube concrete members. Furthermore, it can be observed that the failure mode of the members is mainly bending, and the concrete is crushed in the impact region. The bending stiffness has a significant influence on the impact performance of the member under lateral impact loading. The impact force of the member increases with the increase in the steel ratio, whereas the impact force of the member decreases with the increase in the slenderness ratio. Moreover, narrow flange steel with a higher moment of inertia is more favorable for the impact resistance of the member when the difference in steel ratio is 1.5%. The energy consumption of the encased steel is a major contributor to the total energy consumption of the member when the slenderness ratio is greater than or equal to 20. The GFRP tube plays a dual role in bearing the impact force and confining the concrete in a circumferential direction at the oscillation stage during the impact process.
2024, 44(4): 043301.
doi: 10.11883/bzycj-2023-0388
Abstract:
To investigate the feasibility and characteristics of high-velocity formed projectile formation driven by electromagnetic loading, exploratory experiments of projectile formation by electromagnetically driven the linear liner were conducted using the pulsed power generator CQ-7. Photon Doppler velocimeter (PDV) was employed to measure the velocity of the electromagnetic-driven projectiles and validate their penetration into aluminum targets. A physical model and numerical simulation method for electromagnetic-driven projectile formation were established using fluid dynamics software and corresponding electromagnetic simulation modules. The changes in current density and magnetic pressure during the electromagnetic loading stage were studied and the dynamic processes of projectile formation and penetration into aluminum targets were simulated. The numerical simulation method was verified through the comparison between numerical results and experimental data. Based on this, the influences of liner configuration and loading energy on the projectile formation parameters of equal wall thickness hemispherical liner were explored. The results indicate that the outer curvature radius has a minor impact on the head velocity of the projectile, while the head velocity significantly increases with decreasing wall thickness and increasing loading energy. The aspect ratio of the projectile gradually increases with decreasing outer curvature radius and wall thickness, as well as increasing loading energy. The conversion between quasi-spherical and long rod-shaped projectile modes can be achieved by changing the structural parameters, and for the same structural parameter, the conversion between two modes can be achieved by controlling the loading energy. Finally, the feasibility of obtaining high-velocity and high-mass-formed projectiles using electromagnetic-driven technology was predicted using numerical simulation methods, and it can be figured out from the results that a projectile with a higher velocity and larger mass can be formed by increasing the loading energy and the sizes of the shaped liner, effectively breaking through the velocity limit of a traditional penetrator driven by explosive detonation.
To investigate the feasibility and characteristics of high-velocity formed projectile formation driven by electromagnetic loading, exploratory experiments of projectile formation by electromagnetically driven the linear liner were conducted using the pulsed power generator CQ-7. Photon Doppler velocimeter (PDV) was employed to measure the velocity of the electromagnetic-driven projectiles and validate their penetration into aluminum targets. A physical model and numerical simulation method for electromagnetic-driven projectile formation were established using fluid dynamics software and corresponding electromagnetic simulation modules. The changes in current density and magnetic pressure during the electromagnetic loading stage were studied and the dynamic processes of projectile formation and penetration into aluminum targets were simulated. The numerical simulation method was verified through the comparison between numerical results and experimental data. Based on this, the influences of liner configuration and loading energy on the projectile formation parameters of equal wall thickness hemispherical liner were explored. The results indicate that the outer curvature radius has a minor impact on the head velocity of the projectile, while the head velocity significantly increases with decreasing wall thickness and increasing loading energy. The aspect ratio of the projectile gradually increases with decreasing outer curvature radius and wall thickness, as well as increasing loading energy. The conversion between quasi-spherical and long rod-shaped projectile modes can be achieved by changing the structural parameters, and for the same structural parameter, the conversion between two modes can be achieved by controlling the loading energy. Finally, the feasibility of obtaining high-velocity and high-mass-formed projectiles using electromagnetic-driven technology was predicted using numerical simulation methods, and it can be figured out from the results that a projectile with a higher velocity and larger mass can be formed by increasing the loading energy and the sizes of the shaped liner, effectively breaking through the velocity limit of a traditional penetrator driven by explosive detonation.
2024, 44(4): 043302.
doi: 10.11883/bzycj-2023-0312
Abstract:
In order to compare and analyze the characteristic and mechanism of damaging on 45 steel target plate penetrated by the WF/Zr-MG and 93W rod, a penetration experiment under hypervelocity impact was carried out. The analysis of penetration was performed at both macro and micro levels, in which the macroscopic quantitative characterization quantity was studied by equivalent diameter of reamer, and the microscopic morphology, phase transition and hardness characteristics of the target plate were obtained by scanning electron microscopy, optical microscope, X-ray diffraction and microhardness tester.The experimental results indicate that the WF/Zr-MG rod completely penetrated the target plate, while the 93W rod remained in the target plate. The armor-piercing capacity of WF/Zr-MG rod is higher than that of 93W rod with equivalent reaming diameter of 16.7 mm and 18.4 mm respectively, and the former is 10.18% lower than the latter. From the microscopic perspective, the aspect ratios of the fine grain layer after penetrated by the WF/Zr-MG rod and the 93W rod are 4.5 and 7.3, respectively. In addition, the width of the high-hardness layer are 10.2 mm and 8.9 mm, with Vickers hardness HV peaks at 249 and 287, respectively. The wider high-hardness layer observed in the former case can be attributed to the continuous burning of the Zr-based amorphous alloy during the penetration process, resulting in a larger temperature affected zone and consequently a greater area of hardness enhancement. On the other hand, in the latter case, the strength of the target plate during penetration is significantly higher due to the buckling and backflow of the WF/Zr-MG rod, while the 93W alloy core exhibits a "mushroom head" phenomenon. This reduces extrusion deformation on the target plate, thereby weakening the effect of grain elongation, reducing the increase in hardness peak value, and minimizing energy loss per unit length of the target plate. Ultimately, it enhances the armor-piercing capability of the WF/Zr-MG rod.
In order to compare and analyze the characteristic and mechanism of damaging on 45 steel target plate penetrated by the WF/Zr-MG and 93W rod, a penetration experiment under hypervelocity impact was carried out. The analysis of penetration was performed at both macro and micro levels, in which the macroscopic quantitative characterization quantity was studied by equivalent diameter of reamer, and the microscopic morphology, phase transition and hardness characteristics of the target plate were obtained by scanning electron microscopy, optical microscope, X-ray diffraction and microhardness tester.The experimental results indicate that the WF/Zr-MG rod completely penetrated the target plate, while the 93W rod remained in the target plate. The armor-piercing capacity of WF/Zr-MG rod is higher than that of 93W rod with equivalent reaming diameter of 16.7 mm and 18.4 mm respectively, and the former is 10.18% lower than the latter. From the microscopic perspective, the aspect ratios of the fine grain layer after penetrated by the WF/Zr-MG rod and the 93W rod are 4.5 and 7.3, respectively. In addition, the width of the high-hardness layer are 10.2 mm and 8.9 mm, with Vickers hardness HV peaks at 249 and 287, respectively. The wider high-hardness layer observed in the former case can be attributed to the continuous burning of the Zr-based amorphous alloy during the penetration process, resulting in a larger temperature affected zone and consequently a greater area of hardness enhancement. On the other hand, in the latter case, the strength of the target plate during penetration is significantly higher due to the buckling and backflow of the WF/Zr-MG rod, while the 93W alloy core exhibits a "mushroom head" phenomenon. This reduces extrusion deformation on the target plate, thereby weakening the effect of grain elongation, reducing the increase in hardness peak value, and minimizing energy loss per unit length of the target plate. Ultimately, it enhances the armor-piercing capability of the WF/Zr-MG rod.
2024, 44(4): 045201.
doi: 10.11883/bzycj-2023-0358
Abstract:
Decoupled charge structure is widely used in contour blasting for rock excavation engineering, and its efficacy in rock breaking is tied intricately to both the decoupling ratio and the transfer features of explosion energy. In this study, the analysis delves into the damage degree and failure patterns of cubic red sandstone samples through two groups of lab-scale blasting tests utilizing various charging modes. To precisely quantify the features of rock fragmentation size distribution (FSD) induced by blasting load, a three-parameter generalized extreme value (GEV) function was introduced. In addition, a three-dimensional finite element model was developed in ANSYS software. The numerical model was calibrated based on the tested results of sample R1 by comparing the fracture networks and FSD curves. This validated model was then deployed to model the rock fracture behavior under decoupled charge blasting, and the evolution of blasting cracks and explosion pressure inside the rock sample was reproduced. Moreover, the effects of axial and radial decoupled ratios and the choice of coupling medium on the rock fragmentation and fracture patterns were discussed. The results showed that the three-parameter GEV function can better characterize the rock fragmentation features resulting from blasting. Notably, the average size of the fragment decreases linearly with the decrease of the decoupling ratio, and the degree of fragmentation tends to be uniform. By comparing the energy distribution and damage levels of rock when using different coupling mediums, it was found that water as the coupling medium exhibits the highest efficiency in energy transfer, followed by wet sand and dry sand, and air has the lowest energy transfer efficiency. Furthermore, the theoretical stress transmission coefficient calculated by the equivalent wave impedance method can well reflect the rock fragmentation features and serve as a valuable reference for rock blasting in decoupled charge.
Decoupled charge structure is widely used in contour blasting for rock excavation engineering, and its efficacy in rock breaking is tied intricately to both the decoupling ratio and the transfer features of explosion energy. In this study, the analysis delves into the damage degree and failure patterns of cubic red sandstone samples through two groups of lab-scale blasting tests utilizing various charging modes. To precisely quantify the features of rock fragmentation size distribution (FSD) induced by blasting load, a three-parameter generalized extreme value (GEV) function was introduced. In addition, a three-dimensional finite element model was developed in ANSYS software. The numerical model was calibrated based on the tested results of sample R1 by comparing the fracture networks and FSD curves. This validated model was then deployed to model the rock fracture behavior under decoupled charge blasting, and the evolution of blasting cracks and explosion pressure inside the rock sample was reproduced. Moreover, the effects of axial and radial decoupled ratios and the choice of coupling medium on the rock fragmentation and fracture patterns were discussed. The results showed that the three-parameter GEV function can better characterize the rock fragmentation features resulting from blasting. Notably, the average size of the fragment decreases linearly with the decrease of the decoupling ratio, and the degree of fragmentation tends to be uniform. By comparing the energy distribution and damage levels of rock when using different coupling mediums, it was found that water as the coupling medium exhibits the highest efficiency in energy transfer, followed by wet sand and dry sand, and air has the lowest energy transfer efficiency. Furthermore, the theoretical stress transmission coefficient calculated by the equivalent wave impedance method can well reflect the rock fragmentation features and serve as a valuable reference for rock blasting in decoupled charge.
2024, 44(4): 045301.
doi: 10.11883/bzycj-2023-0367
Abstract:
In recent years, with the rapid development of technology and equipment in the fields of aerospace, defense, and military industries, multilayer lightweight metal composite materials have attracted widespread attention to face complex service environments and reduce equipment weight. Titanium, aluminum, magnesium, and other lightweight metals and their alloys have advantages such as high specific strength, high specific elastic modulus, high damping and shock absorption, high electrostatic shielding, and high machinability, making them the most promising lightweight metal materials for application. In this study, the explosive welding experiments of TA2/AZ31B/2024Al multilayer light metal plate were carried out using a parallel explosive-welding process. Using scanning electron microscopy, electron backscatter diffraction, split Hopkinson pressure bar, and three-dimensional contour scanning, the interfacial microstructure characteristics, material phase changes, dynamic mechanical properties, and impact fracture characteristics of multilayer explosive welded composite plates were studied systematically. The results indicate that the four joining interfaces of the multilayer lightweight metal composite plate after welding present unique waveform structure characteristics of explosive welding, and there are no obvious defects at the joining interfaces. The overall welding quality is good. The grain refinement occurs at the joining interfaces and forms the fine grain region. The grain structure in the 1060Al transition layer exhibits typical elongated layered grain characteristics due to strong plastic deformation, and deformation texture and recrystallization texture characteristics appear at all four joining interfaces. The maximum dynamic compressive strength of the sample along the X-direction is 605 MPa, and the three-dimensional morphology of the fracture interface presents unique structural features similar to the water ripples. The maximum dynamic compressive strength of the sample along the Z-direction is 390 MPa, and the three-dimensional morphology of the fracture interface presents fibrous ductile fracture characteristics. Due to the different wave impedance of the metals, the delamination failure occurs in the X-direction sample, which is caused by the shear stress between the Al/Mg joining interfaces. Since the strength of 1060Al is lower than that of other metals, the Z-direction sample is first destroyed from the 1060Al layer, and slip shear fracture occurs along the 45° direction.
In recent years, with the rapid development of technology and equipment in the fields of aerospace, defense, and military industries, multilayer lightweight metal composite materials have attracted widespread attention to face complex service environments and reduce equipment weight. Titanium, aluminum, magnesium, and other lightweight metals and their alloys have advantages such as high specific strength, high specific elastic modulus, high damping and shock absorption, high electrostatic shielding, and high machinability, making them the most promising lightweight metal materials for application. In this study, the explosive welding experiments of TA2/AZ31B/2024Al multilayer light metal plate were carried out using a parallel explosive-welding process. Using scanning electron microscopy, electron backscatter diffraction, split Hopkinson pressure bar, and three-dimensional contour scanning, the interfacial microstructure characteristics, material phase changes, dynamic mechanical properties, and impact fracture characteristics of multilayer explosive welded composite plates were studied systematically. The results indicate that the four joining interfaces of the multilayer lightweight metal composite plate after welding present unique waveform structure characteristics of explosive welding, and there are no obvious defects at the joining interfaces. The overall welding quality is good. The grain refinement occurs at the joining interfaces and forms the fine grain region. The grain structure in the 1060Al transition layer exhibits typical elongated layered grain characteristics due to strong plastic deformation, and deformation texture and recrystallization texture characteristics appear at all four joining interfaces. The maximum dynamic compressive strength of the sample along the X-direction is 605 MPa, and the three-dimensional morphology of the fracture interface presents unique structural features similar to the water ripples. The maximum dynamic compressive strength of the sample along the Z-direction is 390 MPa, and the three-dimensional morphology of the fracture interface presents fibrous ductile fracture characteristics. Due to the different wave impedance of the metals, the delamination failure occurs in the X-direction sample, which is caused by the shear stress between the Al/Mg joining interfaces. Since the strength of 1060Al is lower than that of other metals, the Z-direction sample is first destroyed from the 1060Al layer, and slip shear fracture occurs along the 45° direction.
2024, 44(4): 045401.
doi: 10.11883/bzycj-2023-0263
Abstract:
In order to find a new, clean and efficient inhibitor of PE dust explosion, the Mg-Al hydrotalcite was used to inhibit PE dust explosion by using standard 20 L spherical explosion test system and minimum ignition temperature test system of dust cloud. The inhibition properties of Mg-Al hydrotalcite for PE dust explosion are analyzed from the aspects of explosion overpressure and minimum ignition temperature, and are compared with aluminum hydroxide and magnesium hydroxide. The results showed that the inhibition effect of Mg-Al hydrotalcite on explosion overpressure and minimum ignition temperature of polyethylene dust is superior to that of aluminum hydroxide and magnesium hydroxide. In terms of explosion overpressure, when the inhibition ratio is 2, Mg-Al hydrotalcite can completely inhibit the explosion of polyethylene dust, while the inhibition ratios required for aluminum hydroxide and magnesium hydroxide to achieve complete explosion suppression of polyethylene are 4 and 5 respectively. With the increase of inhibition ratio, the maximum explosion pressure rise rate of polyethylene dust decreased. The inhibition effect of Mg-Al hydrotalcite on the explosion pressure rise rate of polyethylene dust is also better than that of aluminum hydroxide and magnesium hydroxide. In terms of minimum ignition temperature, when the inhibition ratio was 1, Mg-Al hydrotalcite increased the minimum ignition temperature of polyethylene dust to 710 ℃, which was 290 ℃ higher than that of pure polyethylene dust. Under the same conditions, aluminum hydroxide and magnesium hydroxide can increase the minimum ignition temperature of polyethylene dust by 260 ℃ and 250 ℃ respectively. Therefore, the inhibition effect of Mg-Al hydrotalcite on the minimum ignition temperature of polyethylene is also greater than that of aluminum hydroxide and magnesium hydroxide. In addition, the inhibition mechanism of Mg-Al hydrotalcite on polyethylene dust explosion was analyzed based on its pyrolysis characteristics and infrared spectra.The physical effect is mainly realized by absorbing heat from the reaction system and diluting the oxygen concentration. The chemical action is mainly achieved by the pyrolysis products carbon dioxide and water participating in and blocking the polyethylene explosion chain reaction.
In order to find a new, clean and efficient inhibitor of PE dust explosion, the Mg-Al hydrotalcite was used to inhibit PE dust explosion by using standard 20 L spherical explosion test system and minimum ignition temperature test system of dust cloud. The inhibition properties of Mg-Al hydrotalcite for PE dust explosion are analyzed from the aspects of explosion overpressure and minimum ignition temperature, and are compared with aluminum hydroxide and magnesium hydroxide. The results showed that the inhibition effect of Mg-Al hydrotalcite on explosion overpressure and minimum ignition temperature of polyethylene dust is superior to that of aluminum hydroxide and magnesium hydroxide. In terms of explosion overpressure, when the inhibition ratio is 2, Mg-Al hydrotalcite can completely inhibit the explosion of polyethylene dust, while the inhibition ratios required for aluminum hydroxide and magnesium hydroxide to achieve complete explosion suppression of polyethylene are 4 and 5 respectively. With the increase of inhibition ratio, the maximum explosion pressure rise rate of polyethylene dust decreased. The inhibition effect of Mg-Al hydrotalcite on the explosion pressure rise rate of polyethylene dust is also better than that of aluminum hydroxide and magnesium hydroxide. In terms of minimum ignition temperature, when the inhibition ratio was 1, Mg-Al hydrotalcite increased the minimum ignition temperature of polyethylene dust to 710 ℃, which was 290 ℃ higher than that of pure polyethylene dust. Under the same conditions, aluminum hydroxide and magnesium hydroxide can increase the minimum ignition temperature of polyethylene dust by 260 ℃ and 250 ℃ respectively. Therefore, the inhibition effect of Mg-Al hydrotalcite on the minimum ignition temperature of polyethylene is also greater than that of aluminum hydroxide and magnesium hydroxide. In addition, the inhibition mechanism of Mg-Al hydrotalcite on polyethylene dust explosion was analyzed based on its pyrolysis characteristics and infrared spectra.The physical effect is mainly realized by absorbing heat from the reaction system and diluting the oxygen concentration. The chemical action is mainly achieved by the pyrolysis products carbon dioxide and water participating in and blocking the polyethylene explosion chain reaction.
2024, 44(4): 045402.
doi: 10.11883/bzycj-2023-0295
Abstract:
In order to further reveal the characteristic of metal mesh to inhibit the flame propagation of hydrogen-methane premixed mixture, hydrogen and methane mixed gas with hydrogen mixing ratio of 0%, 10%, 20% and 30% were selected to conduct the experimental investigation of the effect of hydrogen mixing ratio inhibiting the fire processing through wire mesh with varied size in an explosion pipeline with an inner diameter of 60 mm and a total visible length of 1024 mm. Firstly, the flame propagation process was recorded by a high-speed camera, and the effect of hydrogen mixing ratio on fire resistance of wire mesh with different mesh numbers and the change of flame morphology were analyzed. Secondly, the average velocity of flame front movement was calculated according to the interval of 50 mm, and the flame propagation velocity within the visible area of the pipeline was analyzed. The interaction law between the metal wire mesh and the flame was mainly characterized by the flame propagation velocity on both sides of the metal wire mesh. The results show that with the increase of hydrogen content, the difficulty of flame retardancy of metal wire mesh increases, and the flame retardancy effect of metal wire mesh can transition from success to failure, and the impact on flame propagation may shift from inhibition to promotion. When the wire mesh fails to resist the fire, the wire mesh will cause the flame to fold and cause the flame to accelerate, but the first appearance of the tulip flame is delayed. With the increase of hydrogen mixing ratio, the acceleration phenomenon of flame passing through the wire mesh is more obvious. Increasing the mesh number of wire mesh can improve the fire resistance of wire mesh to hydrogen-methane premixed flame. The larger the mesh number, the stronger the fire resistance. More than 60 mesh wire mesh can effectively quench hydrogen and methane premixed flame.
In order to further reveal the characteristic of metal mesh to inhibit the flame propagation of hydrogen-methane premixed mixture, hydrogen and methane mixed gas with hydrogen mixing ratio of 0%, 10%, 20% and 30% were selected to conduct the experimental investigation of the effect of hydrogen mixing ratio inhibiting the fire processing through wire mesh with varied size in an explosion pipeline with an inner diameter of 60 mm and a total visible length of 1024 mm. Firstly, the flame propagation process was recorded by a high-speed camera, and the effect of hydrogen mixing ratio on fire resistance of wire mesh with different mesh numbers and the change of flame morphology were analyzed. Secondly, the average velocity of flame front movement was calculated according to the interval of 50 mm, and the flame propagation velocity within the visible area of the pipeline was analyzed. The interaction law between the metal wire mesh and the flame was mainly characterized by the flame propagation velocity on both sides of the metal wire mesh. The results show that with the increase of hydrogen content, the difficulty of flame retardancy of metal wire mesh increases, and the flame retardancy effect of metal wire mesh can transition from success to failure, and the impact on flame propagation may shift from inhibition to promotion. When the wire mesh fails to resist the fire, the wire mesh will cause the flame to fold and cause the flame to accelerate, but the first appearance of the tulip flame is delayed. With the increase of hydrogen mixing ratio, the acceleration phenomenon of flame passing through the wire mesh is more obvious. Increasing the mesh number of wire mesh can improve the fire resistance of wire mesh to hydrogen-methane premixed flame. The larger the mesh number, the stronger the fire resistance. More than 60 mesh wire mesh can effectively quench hydrogen and methane premixed flame.
