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, Available online , doi: 10.11883/bzycj-2024-0211
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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-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 falling impact of water falling vehicle with boost floatation aids in wave environment was established by coupling 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 falling impact of water falling vehicle with boost floatation aids in wave environment was established by coupling 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.
, 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-2024-0204
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 half and the device length can be reduced from X/L>22.4 to X/L>8 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 half and the device length can be reduced from X/L>22.4 to X/L>8 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-2024-0256
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 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 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-2024-0216
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-2024-0099
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-2024-0239
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 steel fiber reinforced cellular concrete protective layer with different fiber ratios and reinforced concrete slabs under the influence of different explosive mass were studied, and the damage grade prediction curve 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 action of underwater contact explosion, the addition of steel fiber reinforced cellular concrete protective layer can effectively reduce the damage degree of protected reinforced concrete slab (RC), 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 SAP10S15 ratio protective layer is the best. When the amount of explosive increases within a certain range, the SAP10S15 ratio protective layer 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 0.25kg, the damage index of RC slabs strengthened with SAP10S15 protective layer is 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 constructed damage grade prediction curve can directly evaluate the influence of steel fiber volume fraction / explosive amount on the damage grade of RC plate. 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 steel fiber reinforced cellular concrete protective layer with different fiber ratios and reinforced concrete slabs under the influence of different explosive mass were studied, and the damage grade prediction curve 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 action of underwater contact explosion, the addition of steel fiber reinforced cellular concrete protective layer can effectively reduce the damage degree of protected reinforced concrete slab (RC), 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 SAP10S15 ratio protective layer is the best. When the amount of explosive increases within a certain range, the SAP10S15 ratio protective layer 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 0.25kg, the damage index of RC slabs strengthened with SAP10S15 protective layer is 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 constructed damage grade prediction curve can directly evaluate the influence of steel fiber volume fraction / explosive amount on the damage grade of RC plate. The above research results can provide reference for the anti-explosion protection design of wading concrete structures.
, 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-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.
, 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-2024-0318
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-2024-0222
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-2024-0108
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-2024-0179
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-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 simulation results. 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 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 simulation results. 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 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.
, Available online , 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.
, Available online , doi: 10.11883/bzycj-2023-0342
Abstract:
The warhead of conventional weapons is usually composed of a cylindrical charge and a metal case, in which the metal case can affect the attenuation law of peak stress induced by explosion. Therefore, it is important for the blast-resistant design to clarify the attenuation law of stress waves in CF120 concrete 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 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 reference for blast-resistant design to estimate the peak stress induced by cylindrical cased charge explosion.
The warhead of conventional weapons is usually composed of a cylindrical charge and a metal case, in which the metal case can affect the attenuation law of peak stress induced by explosion. Therefore, it is important for the blast-resistant design to clarify the attenuation law of stress waves in CF120 concrete 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 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 reference for blast-resistant design to estimate the peak stress induced by cylindrical cased charge explosion.
, 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-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.
, 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-2024-0063
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.
, Available online , doi: 10.11883/bzycj-2023-0208
Abstract:
In order to solve the problem of high-performance lightweight bulletproof inserts being protected by the penetration of light weapon killing element, this paper carried out penetration experiments on ultra-high molecular weight polyethylene (UHMWPE) laminated sheet, analysed 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 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 fibre plate, 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 being protected by the penetration of light weapon killing element, this paper carried out penetration experiments on ultra-high molecular weight polyethylene (UHMWPE) laminated sheet, analysed 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 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 fibre plate, 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.
, 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-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.
, 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-2023-0404
Abstract:
To study the explosion process of carbon-iron nanomaterials synthesized by gaseous detonation, the effects of different molar ratios of hydrogen-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-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.
, Available online , 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 speeds: 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, SEM (Scanning Electron Microscope) 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 samples are significantly improved, with a maximum dynamic tensile strength increase rate of 66.03%. At the same strain rate, the dynamic tensile strength of the samples 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 samples. 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 samples 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 speeds: 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, SEM (Scanning Electron Microscope) 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 samples are significantly improved, with a maximum dynamic tensile strength increase rate of 66.03%. At the same strain rate, the dynamic tensile strength of the samples 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 samples. 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 samples positively correlate with the strain rate, and samples with higher fiber dosages require more energy to dissipate during failure.
, Available online , doi: 10.11883/bzycj-2023-0459
Abstract:
The layered protective structure composed of 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 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 distribution layer from the frequently-used medium/coarse sand to foam concrete. To investigate the blast resistance of layered protective structure sandwiched by foam concrete (named composite protective structure), the blast test on the layered composite target composed of CF120 concrete (a fiber reinforced high-strength concrete) bursting layer, C5 foam concrete distribution layer and C40 reinforced concrete structure layer was firstly conducted in the present study, in which the damage and failure in the layered composite target and blast waves at specific locations were the 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 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 important reference for the design of protective structure against EPWs.
The layered protective structure composed of 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 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 distribution layer from the frequently-used medium/coarse sand to foam concrete. To investigate the blast resistance of layered protective structure sandwiched by foam concrete (named composite protective structure), the blast test on the layered composite target composed of CF120 concrete (a fiber reinforced high-strength concrete) bursting layer, C5 foam concrete distribution layer and C40 reinforced concrete structure layer was firstly conducted in the present study, in which the damage and failure in the layered composite target and blast waves at specific locations were the 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 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 important reference for the design of protective structure against EPWs.
, 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.
, Available online , 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.
