2022 Vol. 42, No. 4
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2022, 42(4): 041101.
doi: 10.11883/bzycj-2021-0053
Abstract:
Blast-induced traumatic brain injury (bTBI) is one of the major injuries sustained by soldiers in armed conflict, which has been widely concerned by domestic and overseas researchers in recent years. The brain injury caused by a direct interaction between the blast wave and the head is called primary bTBI. Currently, the injury mechanism of primary bTBI is still unclear. The primary bTBI may be the combined result of multi-factors, such as stress wave propagation, skull flexural deformation, cerebrospinal fluid cavitation, and trunk compression. Since it is a complex problem involving the interdisciplinary of medical and engineering, multi-physical field coupling, and coexistence of short-term and long-term effects, it is necessary to reveal the injury mechanism of bTBI by combining physical experiments, numerical simulations, and medical diagnosis. There are three strategies to investigate bTBI. One is to establish a high-precision and multi-physical-field numerical model to describe the interaction of the blast wave and the head. The second is to develop a surrogate head model to measure the skull strain, intracranial pressure, acceleration, and other mechanical quantities. The third is to analyze human and animal pathology and physiology. Comparing the results of these three strategies can reveal the injury mechanism of bTBI in medicine and mechanics. The research status and development in this field are introduced in this paper based on the authors’ previous research. The evaluation indexes of bTBI are summarized, including the medical indexes related to behavior and physiology and the critical mechanical indexes, such as skull strain, intracranial pressure, and local stress. Furthermore, the protective structure design based on the injury mechanism and the evaluation indexes is described, including the improvement of the helmet system based on new materials, the design of the helmet buffer system, the increase of the sealing of the head protection system, etc. To figure out the bTBI mechanism, more accurate measurement of the in-situ mechanical properties of the brain tissue, and high fidelity numerical and physical models are needed. For bTBI protection research, it needs to improve the biological matching degree and the accuracy of the experimental platform. Finally, three development trends of the bTBI research are pointed out, including the development of multi-scale head models, accurate measurement and verification of the injury indexes and threshold, comprehensive investigation of injury mechanism, evaluation, and protection.
Blast-induced traumatic brain injury (bTBI) is one of the major injuries sustained by soldiers in armed conflict, which has been widely concerned by domestic and overseas researchers in recent years. The brain injury caused by a direct interaction between the blast wave and the head is called primary bTBI. Currently, the injury mechanism of primary bTBI is still unclear. The primary bTBI may be the combined result of multi-factors, such as stress wave propagation, skull flexural deformation, cerebrospinal fluid cavitation, and trunk compression. Since it is a complex problem involving the interdisciplinary of medical and engineering, multi-physical field coupling, and coexistence of short-term and long-term effects, it is necessary to reveal the injury mechanism of bTBI by combining physical experiments, numerical simulations, and medical diagnosis. There are three strategies to investigate bTBI. One is to establish a high-precision and multi-physical-field numerical model to describe the interaction of the blast wave and the head. The second is to develop a surrogate head model to measure the skull strain, intracranial pressure, acceleration, and other mechanical quantities. The third is to analyze human and animal pathology and physiology. Comparing the results of these three strategies can reveal the injury mechanism of bTBI in medicine and mechanics. The research status and development in this field are introduced in this paper based on the authors’ previous research. The evaluation indexes of bTBI are summarized, including the medical indexes related to behavior and physiology and the critical mechanical indexes, such as skull strain, intracranial pressure, and local stress. Furthermore, the protective structure design based on the injury mechanism and the evaluation indexes is described, including the improvement of the helmet system based on new materials, the design of the helmet buffer system, the increase of the sealing of the head protection system, etc. To figure out the bTBI mechanism, more accurate measurement of the in-situ mechanical properties of the brain tissue, and high fidelity numerical and physical models are needed. For bTBI protection research, it needs to improve the biological matching degree and the accuracy of the experimental platform. Finally, three development trends of the bTBI research are pointed out, including the development of multi-scale head models, accurate measurement and verification of the injury indexes and threshold, comprehensive investigation of injury mechanism, evaluation, and protection.
2022, 42(4): 042201.
doi: 10.11883/bzycj-2021-0174
Abstract:
In order to study the contact explosion resistance of ultra-high performance concrete (UHPC), 24 contact explosion experiments were conducted. The target slabs were cast in UHPC with or without reinforcement, and the compressive strength grades of the UHPCs were C120, C150 and C180. The slabs were laid on supporting ring beams and the back faces of the slabs were free. The TNT was placed on the center of the front face. The size of the target slab was 1.5 m×1.5 m×0.3 m, and the main reinforcements were\begin{document}$\varnothing $\end{document} ![]()
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In order to study the contact explosion resistance of ultra-high performance concrete (UHPC), 24 contact explosion experiments were conducted. The target slabs were cast in UHPC with or without reinforcement, and the compressive strength grades of the UHPCs were C120, C150 and C180. The slabs were laid on supporting ring beams and the back faces of the slabs were free. The TNT was placed on the center of the front face. The size of the target slab was 1.5 m×1.5 m×0.3 m, and the main reinforcements were
2022, 42(4): 042301.
doi: 10.11883/bzycj-2021-0253
Abstract:
In order to study the influence of the venting structure on the ignition time and the internal physical field changes before thermal ignition of melt cast explosives, slow cookoff tests with multi-point temperature measurements were designed for two groups of ammunitions with or without a venting structure. The area of the venting hole was designed to meet the requirements of the pressure balance method for the critical cross-sectional area. The temperature-time curves of the two ammunitions heated at a rate of 3.3 ℃/h were obtained through the tests. The opening time of the venting hole was determined. It was found that venting led to a decrease in the internal temperature of the explosive and delayed the ignition time. A universal cookoff model (UCM), including the buoyancy-driven flow after the explosive melt and the variation of the decomposition rate with pressure and reaction process, was applied to the cookoff simulation of Comp-B. In the simulation, the ammunition without a venting structure was considered to be sealed during the cookoff process. The opening time of the venting hole for the ammunition with a venting structure was determined based on the test. After the venting hole was opened, the ammunition was considered to be fully ventilated, and the decomposition rate of the explosive reduced. The variations of the temperature field and internal pressure of the ammunitions with or without a venting structure during the cookoff process were simulated. The results show that under the slow cookoff condition, the internal pressure of the ammunition increases slowly at first and then sharply. The pressure change trend of the ammunition with a venting structure is the same as that without a venting structure. The action of the venting structure will suddenly reduce the decomposition rate of the explosive, and then the internal temperature decreases. The decrease in the decomposition rate and the product bubbles-driven convection lead to a delay in the ignition time. Due to the convection, the ignition points of the explosives are all in the top area.
In order to study the influence of the venting structure on the ignition time and the internal physical field changes before thermal ignition of melt cast explosives, slow cookoff tests with multi-point temperature measurements were designed for two groups of ammunitions with or without a venting structure. The area of the venting hole was designed to meet the requirements of the pressure balance method for the critical cross-sectional area. The temperature-time curves of the two ammunitions heated at a rate of 3.3 ℃/h were obtained through the tests. The opening time of the venting hole was determined. It was found that venting led to a decrease in the internal temperature of the explosive and delayed the ignition time. A universal cookoff model (UCM), including the buoyancy-driven flow after the explosive melt and the variation of the decomposition rate with pressure and reaction process, was applied to the cookoff simulation of Comp-B. In the simulation, the ammunition without a venting structure was considered to be sealed during the cookoff process. The opening time of the venting hole for the ammunition with a venting structure was determined based on the test. After the venting hole was opened, the ammunition was considered to be fully ventilated, and the decomposition rate of the explosive reduced. The variations of the temperature field and internal pressure of the ammunitions with or without a venting structure during the cookoff process were simulated. The results show that under the slow cookoff condition, the internal pressure of the ammunition increases slowly at first and then sharply. The pressure change trend of the ammunition with a venting structure is the same as that without a venting structure. The action of the venting structure will suddenly reduce the decomposition rate of the explosive, and then the internal temperature decreases. The decrease in the decomposition rate and the product bubbles-driven convection lead to a delay in the ignition time. Due to the convection, the ignition points of the explosives are all in the top area.
2022, 42(4): 042302.
doi: 10.11883/bzycj-2021-0257
Abstract:
In order to study the static compression mechanical properties and damage characteristics of the JH-14C booster explosive, quasi-static compressive experiments were performed on a testing machine equipped with an environmental chamber (INSTRON). According to the GJB 770B–2005 powder test method, dimensions of the cylindrical specimen were set as\begin{document}$\varnothing $\end{document} ![]()
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In order to study the static compression mechanical properties and damage characteristics of the JH-14C booster explosive, quasi-static compressive experiments were performed on a testing machine equipped with an environmental chamber (INSTRON). According to the GJB 770B–2005 powder test method, dimensions of the cylindrical specimen were set as
2022, 42(4): 042303.
doi: 10.11883/bzycj-2021-0376
Abstract:
In modern warfare, shallow-buried explosives, such as landmines and improvised explosive devices, pose serious threats to civil/military vehicles and passengers. To study the explosion morphology and impacting effects of shallow-buried explosives (TNT), a novel set of test facility was proposed in this study and used to perform shallow-buried sand explosion tests. By changing the type of sand and the buried depth of the explosives, the propagation of shock wave, the ejection trajectory of explosion products and sand, the deformation morphology of target plate, and the spatial distribution of explosion load were systematically investigated. It was demonstrated that shallow-buried sand explosion generated a shock wave in air, with a propagation velocity significantly greater than the ejection velocity of explosion products and sand. Upon detonation, the explosion products and sand were rapidly ejected outwards with continuously increasing volume, and spread around after hitting the target plate. The impulse generated by shallow-buried sand explosion was non-uniformly distributed in space, largest in the central explosion area and gradually decreasing outwards. The buried depth of explosives in sand affected the relative position of explosive products and sand when they were ejected. When the buried depth was relatively small, the explosive products would break through the covered sand layer and directly act on the target plate. When the buried depth was sufficiently large, the explosive products were essentially covered by a sand layer, which acted on the target plate together at a delayed instant. The type of sand used significantly affected the deformation morphology of the target plate. The sand purposely prepared in accordance with the NATO standard AEP-55 not only caused overall bending deformation of the target plate, but also formed a large number of pits on the target plate, thus generating a penetration effect. In contrast, the ordinary river sand only caused overall bending deformation of the target plate, with little penetration effect observed. The results obtained in this study are helpful for designing more effective protective structures against intense blast impacting from shallow-buried explosives.
In modern warfare, shallow-buried explosives, such as landmines and improvised explosive devices, pose serious threats to civil/military vehicles and passengers. To study the explosion morphology and impacting effects of shallow-buried explosives (TNT), a novel set of test facility was proposed in this study and used to perform shallow-buried sand explosion tests. By changing the type of sand and the buried depth of the explosives, the propagation of shock wave, the ejection trajectory of explosion products and sand, the deformation morphology of target plate, and the spatial distribution of explosion load were systematically investigated. It was demonstrated that shallow-buried sand explosion generated a shock wave in air, with a propagation velocity significantly greater than the ejection velocity of explosion products and sand. Upon detonation, the explosion products and sand were rapidly ejected outwards with continuously increasing volume, and spread around after hitting the target plate. The impulse generated by shallow-buried sand explosion was non-uniformly distributed in space, largest in the central explosion area and gradually decreasing outwards. The buried depth of explosives in sand affected the relative position of explosive products and sand when they were ejected. When the buried depth was relatively small, the explosive products would break through the covered sand layer and directly act on the target plate. When the buried depth was sufficiently large, the explosive products were essentially covered by a sand layer, which acted on the target plate together at a delayed instant. The type of sand used significantly affected the deformation morphology of the target plate. The sand purposely prepared in accordance with the NATO standard AEP-55 not only caused overall bending deformation of the target plate, but also formed a large number of pits on the target plate, thus generating a penetration effect. In contrast, the ordinary river sand only caused overall bending deformation of the target plate, with little penetration effect observed. The results obtained in this study are helpful for designing more effective protective structures against intense blast impacting from shallow-buried explosives.
2022, 42(4): 043101.
doi: 10.11883/bzycj-2021-0051
Abstract:
In order to promote the application process of an ultrafine grained (UFG) D6A low-alloy medium-carbon steel in semi-armor-piercing warhead shells, mechanical behaviors and microscopic deformation mechanism of the UFG D6A steel under dynamic loading were studied. The UFG D6A steel (d = 510 nm) was prepared by using inter-critical rolling and low temperature annealing process, whose microstructure features show that nanoscale spherical cementite grains are uniformly distributed in the equiaxed ferrite matrix. Dynamic tensile experiments were performed with a rotating Hopkinson bar apparatus at strain rates ranging from 500 s−1 to 1000 s−1. Micromorphology of specimens before and after tensile loading was observed by transmission electron microscopy. Combined with these observations, the dynamic mechanical properties of the UFG steel under high strain rates were extensively studied. The results reveal that the UFG D6A steel achieves both excellent strength and well toughness simultaneously with a dynamic tensile strength of 2 200 MPa and an average dynamic fracture elongation of 13%. The dynamic tensile strength is obviously higher than the quasi-static tensile strength (approximately 2 times), while the toughness is lower than that under quasi-static conditions. It is observed that the cementite content increases dramatically during the dynamic tensile experiment process, which can effectively restrict the movement of dislocations to produce additional plastic deformation resistance. Consequently, grain refinement and the precipitation of nanosized carbides are considered to play key roles for strengthening the steel. The severe plastic deformation reduces the average grain size and increases the density of grain boundaries within the material, which is considered to eventually lead to the decrease of dynamic fracture elongation of the UFG D6A steel. The drops of yield stress were observed apparently during dynamic tensile process, which is mainly due to the increase of the mobile dislocation density. These research results may give deeper insights into the relationship between material microstructure and mechanical behavior of UFG steels, and provide a significantly experimental and theoretical basis for the application of UFG D6A steels in the military equipment field.
In order to promote the application process of an ultrafine grained (UFG) D6A low-alloy medium-carbon steel in semi-armor-piercing warhead shells, mechanical behaviors and microscopic deformation mechanism of the UFG D6A steel under dynamic loading were studied. The UFG D6A steel (d = 510 nm) was prepared by using inter-critical rolling and low temperature annealing process, whose microstructure features show that nanoscale spherical cementite grains are uniformly distributed in the equiaxed ferrite matrix. Dynamic tensile experiments were performed with a rotating Hopkinson bar apparatus at strain rates ranging from 500 s−1 to 1000 s−1. Micromorphology of specimens before and after tensile loading was observed by transmission electron microscopy. Combined with these observations, the dynamic mechanical properties of the UFG steel under high strain rates were extensively studied. The results reveal that the UFG D6A steel achieves both excellent strength and well toughness simultaneously with a dynamic tensile strength of 2 200 MPa and an average dynamic fracture elongation of 13%. The dynamic tensile strength is obviously higher than the quasi-static tensile strength (approximately 2 times), while the toughness is lower than that under quasi-static conditions. It is observed that the cementite content increases dramatically during the dynamic tensile experiment process, which can effectively restrict the movement of dislocations to produce additional plastic deformation resistance. Consequently, grain refinement and the precipitation of nanosized carbides are considered to play key roles for strengthening the steel. The severe plastic deformation reduces the average grain size and increases the density of grain boundaries within the material, which is considered to eventually lead to the decrease of dynamic fracture elongation of the UFG D6A steel. The drops of yield stress were observed apparently during dynamic tensile process, which is mainly due to the increase of the mobile dislocation density. These research results may give deeper insights into the relationship between material microstructure and mechanical behavior of UFG steels, and provide a significantly experimental and theoretical basis for the application of UFG D6A steels in the military equipment field.
2022, 42(4): 043102.
doi: 10.11883/bzycj-2021-0260
Abstract:
Bamboo scrimber is a new type of bamboo-based composite materials with outstanding mechanical properties which is more effective than some wood such as pine. In order to evaluate the impact mechanical properties of the bamboo scrimber along the grain under impact loading, this study made the samples by commercial bamboo scrimber as the research object with the density about 1.06 g/cm3 and the moisture content about 8.52%, manufactured by Moso bamboo with the age of 3−5 years. The quasi-static uniaxial compression, cyclic loading and unloading, and dynamic loading tests were all carried out to explore its loading deformation process, various mechanical performance parameters, and the strain rate effect under different strain rates, as obtained by the MTS universal material testing machine and the split Hopkinson pressure bar (SHPB) testing system, respectively. The results show that the compression process of the bamboo scrimber along the grain can be divided into an elastic deformation stage and an elastic-plastic deformation stage. The failure type of bamboo scrimber under compression load was ductile failure with much better energy absorption capacity than brittle failure. Its various strength indexes, including elastic ultimate strength, yield strength and failure strength showed high strain rate sensibility, all go up with the increase of the strain rate. A linear relationship exists between the dynamic increase factor (DIF) and strain rate, with a slope of about 0.0024. The strain energy density during the compression process of the bamboo scrimber also exhibits a linear relationship with the strain, and it increases with the increase of strain rate, indicating that the energy absorption capacity of bamboo scrimber increases with the increasing strain rate. In summary, as verified by tests, the impact mechanical properties of the bamboo scrimber along the grain are good and its strain rate effect is significant.
Bamboo scrimber is a new type of bamboo-based composite materials with outstanding mechanical properties which is more effective than some wood such as pine. In order to evaluate the impact mechanical properties of the bamboo scrimber along the grain under impact loading, this study made the samples by commercial bamboo scrimber as the research object with the density about 1.06 g/cm3 and the moisture content about 8.52%, manufactured by Moso bamboo with the age of 3−5 years. The quasi-static uniaxial compression, cyclic loading and unloading, and dynamic loading tests were all carried out to explore its loading deformation process, various mechanical performance parameters, and the strain rate effect under different strain rates, as obtained by the MTS universal material testing machine and the split Hopkinson pressure bar (SHPB) testing system, respectively. The results show that the compression process of the bamboo scrimber along the grain can be divided into an elastic deformation stage and an elastic-plastic deformation stage. The failure type of bamboo scrimber under compression load was ductile failure with much better energy absorption capacity than brittle failure. Its various strength indexes, including elastic ultimate strength, yield strength and failure strength showed high strain rate sensibility, all go up with the increase of the strain rate. A linear relationship exists between the dynamic increase factor (DIF) and strain rate, with a slope of about 0.0024. The strain energy density during the compression process of the bamboo scrimber also exhibits a linear relationship with the strain, and it increases with the increase of strain rate, indicating that the energy absorption capacity of bamboo scrimber increases with the increasing strain rate. In summary, as verified by tests, the impact mechanical properties of the bamboo scrimber along the grain are good and its strain rate effect is significant.
2022, 42(4): 043301.
doi: 10.11883/bzycj-2021-0146
Abstract:
Fiber-metal laminates are highly designable due to the characteristics of their constituent materials and laminate structure. They have the characteristics of anisotropy, large interface differences, and flexible design. Optimizing the design of fiber-metal laminates is of great significance to the enhancement of its mechanical properties and weight reduction. In order to improve the ballistic performance of fiber-metal laminates, of which the layer direction and layer thickness are optimized based on the response surface analysis method. For layup direction optimization, several layup directions are designed based on the corresponding principles according to the composite material layup optimization design requirements, and the energy absorptions of the corresponding structures are calculated, respectively, then the design plan for the better layup direction is screened out. For the optimization of ply thickness, the relative thickness ratio of each ply of the fiber-metal laminate is used as the design variable, and the specific energy absorption of the structure is the design goal. The Box-Behnken method is used to design the experiment. According to the test plan, the explicit dynamic calculation program ABAQUS/Explicit is used for parametric modeling to obtain test sample points, and the design test samples are analyzed by using variance analysis and parameter estimation, and the response surface model of structural specific energy absorption (SEA) is established. The errors between the experimental values and the predicted values are compared, and the model can be used for prediction; the genetic algorithm is used to optimize the obtained response surface equation, and the optimization effect is verified by ABAQUS/Explicit. The optimization result shows that the accuracy of the obtained response surface model is high. Under the premise of not increasing the thickness and weight of the laminate, the best layup plan is finally obtained, which improves the energy absorption capacity of the laminate. Finally, the mass of laminates decreases by 11.70% and the energy absorption increases by 19.40% under the optimal lamination scheme.
Fiber-metal laminates are highly designable due to the characteristics of their constituent materials and laminate structure. They have the characteristics of anisotropy, large interface differences, and flexible design. Optimizing the design of fiber-metal laminates is of great significance to the enhancement of its mechanical properties and weight reduction. In order to improve the ballistic performance of fiber-metal laminates, of which the layer direction and layer thickness are optimized based on the response surface analysis method. For layup direction optimization, several layup directions are designed based on the corresponding principles according to the composite material layup optimization design requirements, and the energy absorptions of the corresponding structures are calculated, respectively, then the design plan for the better layup direction is screened out. For the optimization of ply thickness, the relative thickness ratio of each ply of the fiber-metal laminate is used as the design variable, and the specific energy absorption of the structure is the design goal. The Box-Behnken method is used to design the experiment. According to the test plan, the explicit dynamic calculation program ABAQUS/Explicit is used for parametric modeling to obtain test sample points, and the design test samples are analyzed by using variance analysis and parameter estimation, and the response surface model of structural specific energy absorption (SEA) is established. The errors between the experimental values and the predicted values are compared, and the model can be used for prediction; the genetic algorithm is used to optimize the obtained response surface equation, and the optimization effect is verified by ABAQUS/Explicit. The optimization result shows that the accuracy of the obtained response surface model is high. Under the premise of not increasing the thickness and weight of the laminate, the best layup plan is finally obtained, which improves the energy absorption capacity of the laminate. Finally, the mass of laminates decreases by 11.70% and the energy absorption increases by 19.40% under the optimal lamination scheme.
2022, 42(4): 044101.
doi: 10.11883/bzycj-2021-0201
Abstract:
In order to obtain the propagation process of detonation wave by multi-point initiation of explosive, a suitable ultra-high speed photoelectric framing photography technique was studied. A self-developed ultra-high speed photoelectric framing camera with an exposure time of 5 ns, spatial resolution of 40 lp/mm and photographic frequency of 200 MHz combined with plexiglass optical shutter technology was adopted. We obtained eight high-resolution detonation wave images of plastic bonded explosives based on HMX and TATB under the condition of three-point synchronous initiation. The whole process of the detonation wave propagation and interaction was captured successfully, and the details of the coherent interaction and the Mach Rod were observed. The experimental results show that the ultra-high speed photoelectric framing photography based on the independent exposure mode have the advantages of short exposure time, continuous adjustable image interval and high spatial resolution, and the propagation and interaction of the detonation wave can be observed in great detail. The experimental method and results provide a valuable reference for the study of the interaction and Mach reflection of the detonation waves.
In order to obtain the propagation process of detonation wave by multi-point initiation of explosive, a suitable ultra-high speed photoelectric framing photography technique was studied. A self-developed ultra-high speed photoelectric framing camera with an exposure time of 5 ns, spatial resolution of 40 lp/mm and photographic frequency of 200 MHz combined with plexiglass optical shutter technology was adopted. We obtained eight high-resolution detonation wave images of plastic bonded explosives based on HMX and TATB under the condition of three-point synchronous initiation. The whole process of the detonation wave propagation and interaction was captured successfully, and the details of the coherent interaction and the Mach Rod were observed. The experimental results show that the ultra-high speed photoelectric framing photography based on the independent exposure mode have the advantages of short exposure time, continuous adjustable image interval and high spatial resolution, and the propagation and interaction of the detonation wave can be observed in great detail. The experimental method and results provide a valuable reference for the study of the interaction and Mach reflection of the detonation waves.
2022, 42(4): 044102.
doi: 10.11883/bzycj-2021-0242
Abstract:
The dynamic properties of metals are of importance in shock wave physics, and the time-resolved velocity profile measurement at the interface between the sample and the optical window is often used to decrease the waveform aberrations arising from free-surface reflecting and to obtain the in-situ particle velocity profile in the studied sample. In such cases, the yield strength behavior of the optical window should be taken into account for precise data processing. Among kinds of optical window materials, [100] lithium fluoride (LiF) single crystal is the most widely used window, and little work has been done for its yield strength behavior under dynamic loadings, especially planar shock. In this paper, by using the plate impact and Asay self-consistent technique for high-pressure yield strength, in-situ velocity profiles of the [100] LiF single crystal from shock-release and shock-reshock loading at different pressures were carefully measured by a displacement interferometer system for any reflector (DISAR). Then, the yield strengths under shock compression up to about 60 GPa were educed and found to markedly increase with the increasing of shock pressure, showing a notable pressure-hardening effect. Moreover, by comparing with the results from magnetically-driven isentropic loading in literatures which were the scanty public reports for the high-pressure yield strength of LiF, it was also found that the yield strengths of the [100] LiF under shock compression were higher than those obtained from isentropic loading at the same pressures. This indicates that LiF’s yield strength is more sensitive to strain rate than to temperature up to 60 GPa, and the higher strain rate under shock compression and the dominant strain rate hardening effect results in a higher yield strength. At last, the constitutive model parameters for the [100] LiF were determined to fit to our shock experiments well by using the Huang-Asay equation form. The result above shows that the [100] LiF owns an unignorable flow strength under shock pressures at least to 60 GPa. Moreover, it provides important constitutive parameters for educing the in-situ velocity profiles more accurately in experiments where LiF is used as an optical window, which is essential for researches such as flow strength, phase transition, and shock melting of metal materials.
The dynamic properties of metals are of importance in shock wave physics, and the time-resolved velocity profile measurement at the interface between the sample and the optical window is often used to decrease the waveform aberrations arising from free-surface reflecting and to obtain the in-situ particle velocity profile in the studied sample. In such cases, the yield strength behavior of the optical window should be taken into account for precise data processing. Among kinds of optical window materials, [100] lithium fluoride (LiF) single crystal is the most widely used window, and little work has been done for its yield strength behavior under dynamic loadings, especially planar shock. In this paper, by using the plate impact and Asay self-consistent technique for high-pressure yield strength, in-situ velocity profiles of the [100] LiF single crystal from shock-release and shock-reshock loading at different pressures were carefully measured by a displacement interferometer system for any reflector (DISAR). Then, the yield strengths under shock compression up to about 60 GPa were educed and found to markedly increase with the increasing of shock pressure, showing a notable pressure-hardening effect. Moreover, by comparing with the results from magnetically-driven isentropic loading in literatures which were the scanty public reports for the high-pressure yield strength of LiF, it was also found that the yield strengths of the [100] LiF under shock compression were higher than those obtained from isentropic loading at the same pressures. This indicates that LiF’s yield strength is more sensitive to strain rate than to temperature up to 60 GPa, and the higher strain rate under shock compression and the dominant strain rate hardening effect results in a higher yield strength. At last, the constitutive model parameters for the [100] LiF were determined to fit to our shock experiments well by using the Huang-Asay equation form. The result above shows that the [100] LiF owns an unignorable flow strength under shock pressures at least to 60 GPa. Moreover, it provides important constitutive parameters for educing the in-situ velocity profiles more accurately in experiments where LiF is used as an optical window, which is essential for researches such as flow strength, phase transition, and shock melting of metal materials.
2022, 42(4): 044201.
doi: 10.11883/bzycj-2021-0125
Abstract:
Numerical simulation is an important method to study the penetration into targets. Distinct results may be acquired if different kinds of software are adopted. In this paper, three kinds of commonly-used softwares (LS-DYNA, ABAQUS and PAM-CRASH) were adopted to simulate the same series of penetration experiments. The simulation results were analyzed and the advantages and disadvantages of each kind of software were compared. The purpose of this work is to help the researchers and engineers to select the most suitable software. The results in this paper demonstrate that the calculation results of the three kinds of software are basically consistent with the experimental results. The simulation results of the flat-headed projectile are generally better than those of the hemispherical projectile. The residual velocity of the projectile and the plug velocity were simulated well using all of the three kinds of software. The calculated velocities by ABAQUS and PAM-CRASH are closer to the experimental results, and the average relative errors are generally lower than 15%. Moreover, the errors from most calculation results by PAM-CRASH are even less than 10%. However, for the deformation of the projectile, the calculation results of the three kinds of software are quite different from the experimental ones. There are other differences in the performance of the three kinds of software. For example, the ballistic limits calculated by ABAQUS and LS-DYNA are higher than the experimental results, while those by PAM-CRASH are lower. ABAQUS is most likely to report errors but is balanced by calculation time and effects. LS-DYNA has a low error rate and good robustness. The change of model parameters (such as mesh density, friction coefficient, contact stiffness, viscous damping coefficient, etc.) has little effect on its calculation results. PAM-CRASH is greatly affected by model parameters. The conclusion of this paper is based on the following conditions: the target material is Weldox 460E steel, the projectile is ARNE tool steel, and the impact velocity range is 180－450 m/s. However, it is also of guiding significance for the penetration problem simulation of other materials in this velocity range.
Numerical simulation is an important method to study the penetration into targets. Distinct results may be acquired if different kinds of software are adopted. In this paper, three kinds of commonly-used softwares (LS-DYNA, ABAQUS and PAM-CRASH) were adopted to simulate the same series of penetration experiments. The simulation results were analyzed and the advantages and disadvantages of each kind of software were compared. The purpose of this work is to help the researchers and engineers to select the most suitable software. The results in this paper demonstrate that the calculation results of the three kinds of software are basically consistent with the experimental results. The simulation results of the flat-headed projectile are generally better than those of the hemispherical projectile. The residual velocity of the projectile and the plug velocity were simulated well using all of the three kinds of software. The calculated velocities by ABAQUS and PAM-CRASH are closer to the experimental results, and the average relative errors are generally lower than 15%. Moreover, the errors from most calculation results by PAM-CRASH are even less than 10%. However, for the deformation of the projectile, the calculation results of the three kinds of software are quite different from the experimental ones. There are other differences in the performance of the three kinds of software. For example, the ballistic limits calculated by ABAQUS and LS-DYNA are higher than the experimental results, while those by PAM-CRASH are lower. ABAQUS is most likely to report errors but is balanced by calculation time and effects. LS-DYNA has a low error rate and good robustness. The change of model parameters (such as mesh density, friction coefficient, contact stiffness, viscous damping coefficient, etc.) has little effect on its calculation results. PAM-CRASH is greatly affected by model parameters. The conclusion of this paper is based on the following conditions: the target material is Weldox 460E steel, the projectile is ARNE tool steel, and the impact velocity range is 180－450 m/s. However, it is also of guiding significance for the penetration problem simulation of other materials in this velocity range.
2022, 42(4): 045101.
doi: 10.11883/bzycj-2021-0182
Abstract:
Based on the contact explosion experiments, the absorption performance of the polyurethane foam aluminum and concrete composite structure was analyzed, and the relevant numerical simulation was analyzed and compared. First, polyurethane foam aluminum composite material was made through the pressurized equipment homemade. The hole of the aluminum foam was filled with polyurethane foam through pressure. Then the polyurethane foam aluminum composite material plates and concrete plates were fixed on the explosion experiment apparatus with high sensitivity of strain sensors, acceleration sensors and displacement sensors under the structure or surface. The experiments measured 5 groups of contact explosion experiment data under different structure combinations. Based on the change variables to the experiments, the calculation of numerical simulation experiments were supplemented to make up for other explosion experiments not involved due to lack of experiment conditions. The smooth particle hydrodynamic method (SPH) was used in the numerical simulation to avoid using Lagrange algorithm in explosion shock damage under the large deformation problem of mesh distortion problem. This method can more accurately reflect the explosion impact damage effect. Three kinds of calculation models were used to the numerical simulation. The main research was that the whole antiknock and absorption performance was changed with energy absorption layer thickness change and the number of the structure layer change of the composite structure. Results through explosion experiments and numerical analysis show that absorption performance of polyurethane foam aluminum is superior to that of aluminum foam, energy absorption layer thickness has a great influence on energy absorption effect, and the absorption performance of multilayer structure of polyurethane foam aluminum has no obvious improvement contrasting with the absorption performance of single layer structure with the same thickness. The multilayer structure of polyurethane foam aluminum also increases the difficulty of construction. Under certain conditions, with the reasonable energy absorption layer thickness of the protective structure there is one best combination to ensure that the compound layer thickness of excellent antiknock performance. Finally draw the conclusions: the explosion shock wave energy absorption performance can be improved about 25% by polyurethane foam aluminum than by aluminum foam. The thickness of the polyurethane foam aluminum significantly affects on the energy absorption antiknock performance. The energy absorption performance can improve 50% with increasing the 100% thickness of polyurethane foam aluminum. Effect of changing the antiknock structural energy absorption layers combination is not obvious.
Based on the contact explosion experiments, the absorption performance of the polyurethane foam aluminum and concrete composite structure was analyzed, and the relevant numerical simulation was analyzed and compared. First, polyurethane foam aluminum composite material was made through the pressurized equipment homemade. The hole of the aluminum foam was filled with polyurethane foam through pressure. Then the polyurethane foam aluminum composite material plates and concrete plates were fixed on the explosion experiment apparatus with high sensitivity of strain sensors, acceleration sensors and displacement sensors under the structure or surface. The experiments measured 5 groups of contact explosion experiment data under different structure combinations. Based on the change variables to the experiments, the calculation of numerical simulation experiments were supplemented to make up for other explosion experiments not involved due to lack of experiment conditions. The smooth particle hydrodynamic method (SPH) was used in the numerical simulation to avoid using Lagrange algorithm in explosion shock damage under the large deformation problem of mesh distortion problem. This method can more accurately reflect the explosion impact damage effect. Three kinds of calculation models were used to the numerical simulation. The main research was that the whole antiknock and absorption performance was changed with energy absorption layer thickness change and the number of the structure layer change of the composite structure. Results through explosion experiments and numerical analysis show that absorption performance of polyurethane foam aluminum is superior to that of aluminum foam, energy absorption layer thickness has a great influence on energy absorption effect, and the absorption performance of multilayer structure of polyurethane foam aluminum has no obvious improvement contrasting with the absorption performance of single layer structure with the same thickness. The multilayer structure of polyurethane foam aluminum also increases the difficulty of construction. Under certain conditions, with the reasonable energy absorption layer thickness of the protective structure there is one best combination to ensure that the compound layer thickness of excellent antiknock performance. Finally draw the conclusions: the explosion shock wave energy absorption performance can be improved about 25% by polyurethane foam aluminum than by aluminum foam. The thickness of the polyurethane foam aluminum significantly affects on the energy absorption antiknock performance. The energy absorption performance can improve 50% with increasing the 100% thickness of polyurethane foam aluminum. Effect of changing the antiknock structural energy absorption layers combination is not obvious.
2022, 42(4): 045102.
doi: 10.11883/bzycj-2021-0327
Abstract:
To investigate the effects of venting areas on the structural response of the vessel walls to an explosion, a series of vented explosion experiments of a 10% methane-air mixture were carried out in a 1 m3 rectangular vessel with different venting areas. The adjustable area explosion vent was on the top of the rectangular container, and a piece of aluminum membrane bolted with a flange was used as a vent cover. The vibration acceleration rates and internal overpressures were recorded by an acceleration sensor and a pressure sensor, respectively, the flame propagation images were captured by a high-speed camera during deflagration and the frequency-time distributions of signals were obtained by using the short-time fast Fourier transform. The following conclusions could be obtained by analyzing acceleration rates, internal overpressures, flame propagation images and frequency-time distributions of signals. (1) The change trends of vibration acceleration and internal overpressure are similar, and both have obvious double peaks, but the vibration acceleration peak appears slightly later than the overpressure. As the dimensionless coefficient increases, the first peak of internal overpressure and vibration acceleration increases, and the second peak first decreases, then increases, and finally decreases. (2) Two types of structural response with different amplitudes and frequency distributions were observed. The low-amplitude vibrations are triggered by the combined effects of flame initial propagation, Helmholtz-type oscillations, and Taylor instability, while the high-amplitude vibrations are triggered by the coupling of sound waves and flames. (3) Before the flames are ejected from the vent, the average velocities of the upper flames decrease with the increase of the dimensionless coefficient and the flames are ejected from the vent earlier when the dimensionless coefficient is smaller. (4) Under the current experimental conditions, the thermoacoustic coupling phenomenon is the most violent when the dimensionless coefficient is 25.00, as characterized by the maximum amplitude vibration response and maximum energy high-frequency oscillation. As the dimensionless coefficient further increases or decreases, the thermoacoustic coupling phenomenon gradually attenuates.
To investigate the effects of venting areas on the structural response of the vessel walls to an explosion, a series of vented explosion experiments of a 10% methane-air mixture were carried out in a 1 m3 rectangular vessel with different venting areas. The adjustable area explosion vent was on the top of the rectangular container, and a piece of aluminum membrane bolted with a flange was used as a vent cover. The vibration acceleration rates and internal overpressures were recorded by an acceleration sensor and a pressure sensor, respectively, the flame propagation images were captured by a high-speed camera during deflagration and the frequency-time distributions of signals were obtained by using the short-time fast Fourier transform. The following conclusions could be obtained by analyzing acceleration rates, internal overpressures, flame propagation images and frequency-time distributions of signals. (1) The change trends of vibration acceleration and internal overpressure are similar, and both have obvious double peaks, but the vibration acceleration peak appears slightly later than the overpressure. As the dimensionless coefficient increases, the first peak of internal overpressure and vibration acceleration increases, and the second peak first decreases, then increases, and finally decreases. (2) Two types of structural response with different amplitudes and frequency distributions were observed. The low-amplitude vibrations are triggered by the combined effects of flame initial propagation, Helmholtz-type oscillations, and Taylor instability, while the high-amplitude vibrations are triggered by the coupling of sound waves and flames. (3) Before the flames are ejected from the vent, the average velocities of the upper flames decrease with the increase of the dimensionless coefficient and the flames are ejected from the vent earlier when the dimensionless coefficient is smaller. (4) Under the current experimental conditions, the thermoacoustic coupling phenomenon is the most violent when the dimensionless coefficient is 25.00, as characterized by the maximum amplitude vibration response and maximum energy high-frequency oscillation. As the dimensionless coefficient further increases or decreases, the thermoacoustic coupling phenomenon gradually attenuates.
2022, 42(4): 045103.
doi: 10.11883/bzycj-2021-0374
Abstract:
Wheel tread spalling is one of the common forms of wheel out-of-roundness damage of railway vehicles. During the wheel-rail rolling contact process, the wheel tread spalling will circularly impact the rail, inducing an abnormal large dynamic wheel-rail interaction, which has a serious effect on the stability and safety of high-speed trains. In order to reveal the mechanism of dynamic wheel-rail interaction induced by wheel tread spalling of high-speed trains, a three-dimensional finite element model for the wheel-rail rolling contact was built using the commercial software LS-DYNA. The mechanical responses of the wheel-rail impact caused by the wheel tread spalling of high-speed trains were simulated via the implicit-to-explicit sequential solution. The response characteristics of the wheel-rail vertical/longitudinal contact forces, contact pressure, contact patch, adhesion-slip areas, speed distribution of rail surface nodes, and the stress/strain states during the wheel-rail impact process were analyzed. Meanwhile, the effects of key parameters such as train speed, spalling length and spalling depth on the wheel-rail impact responses were discussed. The results indicate that the wheel-rail vertical dynamic contact force caused by the wheel tread spalling first increases with the train speed and then decreases, and the maximum value appears at a train speed of 300 km/h, which can reach 1.35 times the quasi-static wheel-rail vertical contact force. The maximum wheel-rail longitudinal force fluctuates slightly with the increase of the train speed, and is about 1.25 times the steady wheel-rail longitudinal contact force. The maximum wheel-rail vertical contact force, tangential contact force, the maximum von Mises stress, and equivalent plastic strain of the wheel-rail are monotonically increase with the spalling length. The spalling depth has almost no effect on the wheel-rail contact force, the maximum von Mises stress and equivalent plastic strain of the rail, but has a significant effect on the maximum von Mises stress and equivalent plastic strain of the wheel. The obtained results can provide technical support for the optimal design of the wheel-rail system and the safety of the train operation.
Wheel tread spalling is one of the common forms of wheel out-of-roundness damage of railway vehicles. During the wheel-rail rolling contact process, the wheel tread spalling will circularly impact the rail, inducing an abnormal large dynamic wheel-rail interaction, which has a serious effect on the stability and safety of high-speed trains. In order to reveal the mechanism of dynamic wheel-rail interaction induced by wheel tread spalling of high-speed trains, a three-dimensional finite element model for the wheel-rail rolling contact was built using the commercial software LS-DYNA. The mechanical responses of the wheel-rail impact caused by the wheel tread spalling of high-speed trains were simulated via the implicit-to-explicit sequential solution. The response characteristics of the wheel-rail vertical/longitudinal contact forces, contact pressure, contact patch, adhesion-slip areas, speed distribution of rail surface nodes, and the stress/strain states during the wheel-rail impact process were analyzed. Meanwhile, the effects of key parameters such as train speed, spalling length and spalling depth on the wheel-rail impact responses were discussed. The results indicate that the wheel-rail vertical dynamic contact force caused by the wheel tread spalling first increases with the train speed and then decreases, and the maximum value appears at a train speed of 300 km/h, which can reach 1.35 times the quasi-static wheel-rail vertical contact force. The maximum wheel-rail longitudinal force fluctuates slightly with the increase of the train speed, and is about 1.25 times the steady wheel-rail longitudinal contact force. The maximum wheel-rail vertical contact force, tangential contact force, the maximum von Mises stress, and equivalent plastic strain of the wheel-rail are monotonically increase with the spalling length. The spalling depth has almost no effect on the wheel-rail contact force, the maximum von Mises stress and equivalent plastic strain of the rail, but has a significant effect on the maximum von Mises stress and equivalent plastic strain of the wheel. The obtained results can provide technical support for the optimal design of the wheel-rail system and the safety of the train operation.
