2021 Vol. 41, No. 3
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2021, 41(3): 031101.
doi: 10.11883/bzycj-2020-0114
Abstract:
Aiming at low calculation accuracy of damage effect caused by less data, uneven, discontinuity and narrow distribution of damage experimental data, data mining technology is introduced to calculate damage effect. The database manages damage metadata and the data cleaning technology is used to identify and eliminate dead points’ data in order to control the data quality in database. An algorithm evaluation method is established to select the optimal empirical algorithm. The dimensionality reduction of high-dimensional damage data is achieved through feature selection and the main control parameters are chosen to train neural network model and k-nearest neighbor search. The “three-stage” damage effects calculation model based on data fusion has been established. The model can be used to calculate weapon damage effect based on experimental data, the empirical algorithm and the BP neural network model. The software has been developed to complete the damage calculation, and the results shows that the proposed method can meet the needs of practical application.
Aiming at low calculation accuracy of damage effect caused by less data, uneven, discontinuity and narrow distribution of damage experimental data, data mining technology is introduced to calculate damage effect. The database manages damage metadata and the data cleaning technology is used to identify and eliminate dead points’ data in order to control the data quality in database. An algorithm evaluation method is established to select the optimal empirical algorithm. The dimensionality reduction of high-dimensional damage data is achieved through feature selection and the main control parameters are chosen to train neural network model and k-nearest neighbor search. The “three-stage” damage effects calculation model based on data fusion has been established. The model can be used to calculate weapon damage effect based on experimental data, the empirical algorithm and the BP neural network model. The software has been developed to complete the damage calculation, and the results shows that the proposed method can meet the needs of practical application.
2021, 41(3): 031400.
Abstract:
2021, 41(3): 031401.
doi: 10.11883/bzycj-2020-0328
Abstract:
During the service time of engineering structure, most structural members are under prestress conditions. In order to clarify the effect mechanism of prestress on the response of metal beams subjected to impulsive loading, the plastic deformations of metal beams under different axial prestress conditions and different impact strength were studied. The prestress conditions were controlled by a self-designed prestress loading device while the impact loadings were realized by the drop-hammer method. Numerical models were also established to simulate the related test conditions. The numerical results are in good agreement with the test results. By comparing the residual deflections of the beams, it is found that the middle-point residual deflection under compressive prestress is larger than that without prestress, and there is no regular rule between the deflection and prestress under the condition of tensile prestress. From the perspective of energy, it is found that the plastic deformation energy of the beam comes from the external dynamic energy and the initial internal energy. The higher the external kinetic energy ratio is, the higher the energy absorption rate of the beam will be. At a lower external kinetic energy ratio, the energy absorption rate of the beam is relatively higher under compressive prestress, and relatively lower under tensile prestress. While at a higher external kinetic energy ratio, the prestress has little effect on the energy absorption rate. Under compressive prestress, the limit moment increases while the length decreases, and the increased plastic deformation energy is distributed in the beam with reduced length, which will inevitably lead to larger residual deflection. Under the tensile prestress, the limit moment decreases while the length increases, and the increased plastic deformation energy is distributed in the beam with the increased length, for which the residual deflection has no obvious rule. This explains to a certain extent the effect mechanism of prestress on the deformation of the metal beam subjected to impact loading.
During the service time of engineering structure, most structural members are under prestress conditions. In order to clarify the effect mechanism of prestress on the response of metal beams subjected to impulsive loading, the plastic deformations of metal beams under different axial prestress conditions and different impact strength were studied. The prestress conditions were controlled by a self-designed prestress loading device while the impact loadings were realized by the drop-hammer method. Numerical models were also established to simulate the related test conditions. The numerical results are in good agreement with the test results. By comparing the residual deflections of the beams, it is found that the middle-point residual deflection under compressive prestress is larger than that without prestress, and there is no regular rule between the deflection and prestress under the condition of tensile prestress. From the perspective of energy, it is found that the plastic deformation energy of the beam comes from the external dynamic energy and the initial internal energy. The higher the external kinetic energy ratio is, the higher the energy absorption rate of the beam will be. At a lower external kinetic energy ratio, the energy absorption rate of the beam is relatively higher under compressive prestress, and relatively lower under tensile prestress. While at a higher external kinetic energy ratio, the prestress has little effect on the energy absorption rate. Under compressive prestress, the limit moment increases while the length decreases, and the increased plastic deformation energy is distributed in the beam with reduced length, which will inevitably lead to larger residual deflection. Under the tensile prestress, the limit moment decreases while the length increases, and the increased plastic deformation energy is distributed in the beam with the increased length, for which the residual deflection has no obvious rule. This explains to a certain extent the effect mechanism of prestress on the deformation of the metal beam subjected to impact loading.
2021, 41(3): 031402.
doi: 10.11883/bzycj-2020-0339
Abstract:
YAG (yttrium aluminum garnet) transparent ceramic, with excellent light transmittance and impact resistance, is an excellent protective material for transparent parts of weapons and equipments. It has a good application prospect in military equipment, aerospace and other national defense fields. The loading responses of material under impact loading are essential for understanding the fracture mechanism and can provide a basis for the composite target design. In order to obtain the fracture characteristics of YAG transparent ceramic composite targets under impact loading, a 9-mm-caliber gas-driven launch platform was used to carry out experiments on the impact of tungsten carbide spherical fragments into YAG transparent ceramic composite targets in the velocity range from 20 m/s to 310 m/s. The typical radial and ring crack propagation velocities were calculated by the surface damage evolution process captured by high-speed photography. The relationship between the impact velocity and the damage characteristics of the recovered targets was analyzed by observing the damage characteristics of the YAG fragments under a macroscope and a microscope. The results show that the propagation velocities of both the radial and ring cracks in the YAG ceramic layer decrease linearly with the increase of time and the crack propagation velocities are almost unaffected by the impact velocities. The central crushing area of the ceramic layer increases with the increase of the impact velocity, and the significant damage area of the intermediate glass layer is related to the area of the bottom ceramic cone. The correlation between ceramic cone angle and impact velocity is weak. Meanwhile, the crack crowns in the ceramic layer were found during the impact process. The relationship between the impact velocity of fragments and the number of crowns was obtained. The feature and the generating reason of the crack crowns were also analyzed. The fracture characteristics under a microscope were significantly affected by the crack orientation and stress wave action. The radial, ring and conical cracks produced more intergranular fracture with the increase of crack propagation distance, and more transgranular fracture with the increase of impact velocity.
YAG (yttrium aluminum garnet) transparent ceramic, with excellent light transmittance and impact resistance, is an excellent protective material for transparent parts of weapons and equipments. It has a good application prospect in military equipment, aerospace and other national defense fields. The loading responses of material under impact loading are essential for understanding the fracture mechanism and can provide a basis for the composite target design. In order to obtain the fracture characteristics of YAG transparent ceramic composite targets under impact loading, a 9-mm-caliber gas-driven launch platform was used to carry out experiments on the impact of tungsten carbide spherical fragments into YAG transparent ceramic composite targets in the velocity range from 20 m/s to 310 m/s. The typical radial and ring crack propagation velocities were calculated by the surface damage evolution process captured by high-speed photography. The relationship between the impact velocity and the damage characteristics of the recovered targets was analyzed by observing the damage characteristics of the YAG fragments under a macroscope and a microscope. The results show that the propagation velocities of both the radial and ring cracks in the YAG ceramic layer decrease linearly with the increase of time and the crack propagation velocities are almost unaffected by the impact velocities. The central crushing area of the ceramic layer increases with the increase of the impact velocity, and the significant damage area of the intermediate glass layer is related to the area of the bottom ceramic cone. The correlation between ceramic cone angle and impact velocity is weak. Meanwhile, the crack crowns in the ceramic layer were found during the impact process. The relationship between the impact velocity of fragments and the number of crowns was obtained. The feature and the generating reason of the crack crowns were also analyzed. The fracture characteristics under a microscope were significantly affected by the crack orientation and stress wave action. The radial, ring and conical cracks produced more intergranular fracture with the increase of crack propagation distance, and more transgranular fracture with the increase of impact velocity.
2021, 41(3): 031403.
doi: 10.11883/bzycj-2020-0335
Abstract:
To study the influences of the cross-sectional shapes on the final depths of penetration, a series of experiments were carried out on the penetration of long-rod projectiles with the same cross-sectional area different cross-sectional shapes into semi-infinite metal targets. The cross-sectional shapes were machined to be circular, square and cross, respectively. These experiments were divided into two groups. In one group of experiments, the long-rod projectiles with the aspect ratio of 8 and 93W alloy cores penetrated into armor-steel target plates. In another group of experiments, the long-rod projectiles with the aspect ratio of 15 and 45 steel cores penetrated into the 45 steel target plates. Depths of penetration under different impact velocities were experimentally obtained for different cross-sectional shapes, aspect ratios, and materials of projectiles and targets, respectively. Experimental results display that the penetration abilities of the three kinds of long-rod projectiles with non-circular cross-section are higher than that of the long-rod projectiles with circular cross-section under the same working conditions. And among the four kinds of long-rod projectiles, the penetration ability of the long-rod projectiles with cross section is the highest, followed by that of the long-rod projectiles with square section. With the increase of the impact velocity, the penetration gains of the cross and square cross-section long-rod projectiles to the circular cross-section ones increase. The cross-section shape of craters penetrated by the triangular cross-section long-rod projectiles takes on arc triangle, and the cross-section shape of craters penetrated by the long-rod projectiles with square and cross sections, respectively, takes on approximate circle. After penetration of the three kinds of non-circular cross-section long-rod projectiles, cracks at certain angles with the axial direction appear in the mushroomed heads of the projectile bodies, which leading to less resistance encountered by the projectiles in the process of penetration. The reason, why the penetration abilities of three kinds of non-circular cross-section long-rod projectiles are higher than that of the circular-section long-rod projectiles, is their structural self-sharpening in the process of penetration.
To study the influences of the cross-sectional shapes on the final depths of penetration, a series of experiments were carried out on the penetration of long-rod projectiles with the same cross-sectional area different cross-sectional shapes into semi-infinite metal targets. The cross-sectional shapes were machined to be circular, square and cross, respectively. These experiments were divided into two groups. In one group of experiments, the long-rod projectiles with the aspect ratio of 8 and 93W alloy cores penetrated into armor-steel target plates. In another group of experiments, the long-rod projectiles with the aspect ratio of 15 and 45 steel cores penetrated into the 45 steel target plates. Depths of penetration under different impact velocities were experimentally obtained for different cross-sectional shapes, aspect ratios, and materials of projectiles and targets, respectively. Experimental results display that the penetration abilities of the three kinds of long-rod projectiles with non-circular cross-section are higher than that of the long-rod projectiles with circular cross-section under the same working conditions. And among the four kinds of long-rod projectiles, the penetration ability of the long-rod projectiles with cross section is the highest, followed by that of the long-rod projectiles with square section. With the increase of the impact velocity, the penetration gains of the cross and square cross-section long-rod projectiles to the circular cross-section ones increase. The cross-section shape of craters penetrated by the triangular cross-section long-rod projectiles takes on arc triangle, and the cross-section shape of craters penetrated by the long-rod projectiles with square and cross sections, respectively, takes on approximate circle. After penetration of the three kinds of non-circular cross-section long-rod projectiles, cracks at certain angles with the axial direction appear in the mushroomed heads of the projectile bodies, which leading to less resistance encountered by the projectiles in the process of penetration. The reason, why the penetration abilities of three kinds of non-circular cross-section long-rod projectiles are higher than that of the circular-section long-rod projectiles, is their structural self-sharpening in the process of penetration.
2021, 41(3): 031404.
doi: 10.11883/bzycj-2020-0334
Abstract:
30CrMnSiNi2A steel is a high-strength low-alloy steel and it is widely used in the defense industry. Its ductile fracture properties were investigated by using a combined experimental-numerical approach to address the need for assessment of structural integrity. The parameters of the Johnson-Cook constitutive model were obtained through quasi-static and dynamic tensile tests on round bar specimens at different temperatures and relevant finite element method iterations. The effects of strain rate and temperature on fracture were studied. The tensile tests on notched round bar specimens were performed to calibrate the fracture strain in the range of high positive stress triaxiality. The tensile tests on butterfly plates and compression tests on short cylindrical specimens covered the fracture properties in the range of low and negative stress triaxiality. The finite element models were computed and the fracture loci in the space of the effective plastic strain to fracture and the stress triaxiality in a wide range from −1/3 to 1.5 were constructed. The parameters of the Johnson-Cook fracture model and Bao-Wierzbicki fracture model were calibrated. It is shown that stress triaxiality has a significant effect on the fracture of 30CrMnSiNi2A steel and the monotonicity of the fracture loci varies in different stress triaxiality range. The Bao-Wierzbicki model is capable of predicting the fracture patterns of the 30CrMnSiNi2A steel in different stress states.
30CrMnSiNi2A steel is a high-strength low-alloy steel and it is widely used in the defense industry. Its ductile fracture properties were investigated by using a combined experimental-numerical approach to address the need for assessment of structural integrity. The parameters of the Johnson-Cook constitutive model were obtained through quasi-static and dynamic tensile tests on round bar specimens at different temperatures and relevant finite element method iterations. The effects of strain rate and temperature on fracture were studied. The tensile tests on notched round bar specimens were performed to calibrate the fracture strain in the range of high positive stress triaxiality. The tensile tests on butterfly plates and compression tests on short cylindrical specimens covered the fracture properties in the range of low and negative stress triaxiality. The finite element models were computed and the fracture loci in the space of the effective plastic strain to fracture and the stress triaxiality in a wide range from −1/3 to 1.5 were constructed. The parameters of the Johnson-Cook fracture model and Bao-Wierzbicki fracture model were calibrated. It is shown that stress triaxiality has a significant effect on the fracture of 30CrMnSiNi2A steel and the monotonicity of the fracture loci varies in different stress triaxiality range. The Bao-Wierzbicki model is capable of predicting the fracture patterns of the 30CrMnSiNi2A steel in different stress states.
2021, 41(3): 031405.
doi: 10.11883/bzycj-2020-0346
Abstract:
There are two difficulties in the measurement of underwater explosion bubble jet load: (1) the bubble jet load is a non-uniform surface load, but its radius of action is only 1/10 of the maximum radius of the bubble, the density of sensitive elements which is limited to the size and installation space is low, so it is difficult to accurately obtain the spatial distribution of bubble jet load; (2) the mechanical environment of the sensor is very complex when measuring the bubble jet load, so the sensor is easy to be damaged, which makes it impossible to obtain the complete time history. Therefore, it is difficult to obtain the spatiotemporal distribution characteristics of bubble jet load by existing measurement methods. In view of this, an array sensor was designed. Several small sensitive elements were processed on a piece of PVDF piezoelectric film by special technology. The size of sensitive elements is 5 mm×5 mm, arranged in 8×8 matrix, and the density of sensitive elements is ≥1 cm−2. At the same time, the sensor protection device was designed on the basis of revealing the damage mechanism of the sensor. The underwater explosion test of small equivalent explosive was carried out in a small observation tank, and the spatiotemporal distribution characteristics of bubble jet load were measured by using array sensor. The results show that: (1) the designed protection device can ensure that the sensor will not be damaged in the process of measuring the bubble jet load; (2) the load in the bubble jet center is the highest and decrease to the surrounding gradually. The peak pressure of the bubble jet load is about 35.6 MPa, which is about 1.16 times of the shock wave peak pressure. The array measurement technology can provide technical support for the in-depth study of underwater explosion bubble jet.
There are two difficulties in the measurement of underwater explosion bubble jet load: (1) the bubble jet load is a non-uniform surface load, but its radius of action is only 1/10 of the maximum radius of the bubble, the density of sensitive elements which is limited to the size and installation space is low, so it is difficult to accurately obtain the spatial distribution of bubble jet load; (2) the mechanical environment of the sensor is very complex when measuring the bubble jet load, so the sensor is easy to be damaged, which makes it impossible to obtain the complete time history. Therefore, it is difficult to obtain the spatiotemporal distribution characteristics of bubble jet load by existing measurement methods. In view of this, an array sensor was designed. Several small sensitive elements were processed on a piece of PVDF piezoelectric film by special technology. The size of sensitive elements is 5 mm×5 mm, arranged in 8×8 matrix, and the density of sensitive elements is ≥1 cm−2. At the same time, the sensor protection device was designed on the basis of revealing the damage mechanism of the sensor. The underwater explosion test of small equivalent explosive was carried out in a small observation tank, and the spatiotemporal distribution characteristics of bubble jet load were measured by using array sensor. The results show that: (1) the designed protection device can ensure that the sensor will not be damaged in the process of measuring the bubble jet load; (2) the load in the bubble jet center is the highest and decrease to the surrounding gradually. The peak pressure of the bubble jet load is about 35.6 MPa, which is about 1.16 times of the shock wave peak pressure. The array measurement technology can provide technical support for the in-depth study of underwater explosion bubble jet.
2021, 41(3): 031406.
doi: 10.11883/bzycj-2020-0338
Abstract:
Interface defeat/dwell can effectively improve the anti-penetration performance of a ceramic armor at certain degree, which attracts the attention from researchers all over the world in recent years. Experiments on a ceramic armor subjected to the impact of a long-rod projectile (LRP) were carried out to investigate the characteristics of interface defeat and penetration during the impact in this paper. A theoretical model for the penetration process of a LRP into a ceramic target with semi-finite thickness at different impact velocities was established by considering interface defeat/dwell to study quantitatively the effect of interface defeat/dwell on the penetration. The theoretically calculated results on dwell/penetration transition velocity, dwell time, penetration velocity and depth of penetration agree well with the experimental data, which proves that the established theoretical model is accurate. The influences of the projectile and ceramic materials on the interface defeat/dwell and penetration were analyzed. Both the experimental results and the calculated results by the theoretical model show that the interaction between LRPs and ceramics transfers from interface defeat to penetration when the impact velocity increases. It also indicates that the established theoretical model can depict the interaction modes of ceramics and LRPs under different impact velocities. The yield stress and density of the projectile materials play a coupling role in the interaction between LRPs and ceramics when the interface defeat/dwell occurs. The higher the yield strength and density of the projectile materials, the shorter the dwell time and the higher the penetrating ability of the projectile. The higher the dynamical yield strength of the ceramics, the more markedly the interface defeat/dwell and the higher the anti-penetration ability of the ceramic armors. The established theoretical model in consideration of interface defeat/dwell can partially reveal the mechanism of the interface defeat, and it can provide a reference for the design of ceramic composite targets.
Interface defeat/dwell can effectively improve the anti-penetration performance of a ceramic armor at certain degree, which attracts the attention from researchers all over the world in recent years. Experiments on a ceramic armor subjected to the impact of a long-rod projectile (LRP) were carried out to investigate the characteristics of interface defeat and penetration during the impact in this paper. A theoretical model for the penetration process of a LRP into a ceramic target with semi-finite thickness at different impact velocities was established by considering interface defeat/dwell to study quantitatively the effect of interface defeat/dwell on the penetration. The theoretically calculated results on dwell/penetration transition velocity, dwell time, penetration velocity and depth of penetration agree well with the experimental data, which proves that the established theoretical model is accurate. The influences of the projectile and ceramic materials on the interface defeat/dwell and penetration were analyzed. Both the experimental results and the calculated results by the theoretical model show that the interaction between LRPs and ceramics transfers from interface defeat to penetration when the impact velocity increases. It also indicates that the established theoretical model can depict the interaction modes of ceramics and LRPs under different impact velocities. The yield stress and density of the projectile materials play a coupling role in the interaction between LRPs and ceramics when the interface defeat/dwell occurs. The higher the yield strength and density of the projectile materials, the shorter the dwell time and the higher the penetrating ability of the projectile. The higher the dynamical yield strength of the ceramics, the more markedly the interface defeat/dwell and the higher the anti-penetration ability of the ceramic armors. The established theoretical model in consideration of interface defeat/dwell can partially reveal the mechanism of the interface defeat, and it can provide a reference for the design of ceramic composite targets.
2021, 41(3): 031407.
doi: 10.11883/bzycj-2020-0343
Abstract:
In order to study the mechanical properties of NEPE propellant at low and high strain rates, the quasi-static and impact eperiments of NEPE propellant were carried out by the electronic universal testing machine and split Hopkinson bar, and the stress-strain curves of NEPE propellant under different strain rates (1.667×10−4−4 500 s−1) were obtained by processing the experiment data. By analyzing the stress-strain curve of low and high strain rates experiment, it can be found that NEPE propellant has obvious nonlinear elasticity and strain rate sensitivity. With the increase of strain rate, the strength, yield stress and elastic modulus of the material increase significantly. Compared with low strain rate, the strain rate sensitivity of the material at high strain rate is higher. Under the high speed impact, a large amount of heat is generated inside the material and cannot be released in time, which makes the internal temperature of the material rise, leading to softening effect of the material and reduction of mechanical properties. In this paper, a nonlinear visco-hyperelastic constitutive model is established to describe the mechanical properties of NEPE propellant at low and high strain rates, in which the Rivlin strain energy function is used to describe the static hyperelastic behaviour, and an integral constitutive model is used to characterize the dynamic response of the material. Considering that the relaxation time has strain rate correlation, a rate-dependent relaxation function is adopted in this paper to replace the traditional Prony series. The hyperelastic parameters were obtained by fitting the hyperelastic part of the constitutive model with extremely slow compression experiment data, and then the other parameters were obtained by fitting the constitutive model with quasi-static and dynamic experiment data. It was proved that the model could well describe the mechanical properties of NEPE propellant at low and high strain rates by the good coincidence degree between the prediction curve and the experiment curve under different strain rates.
In order to study the mechanical properties of NEPE propellant at low and high strain rates, the quasi-static and impact eperiments of NEPE propellant were carried out by the electronic universal testing machine and split Hopkinson bar, and the stress-strain curves of NEPE propellant under different strain rates (1.667×10−4−4 500 s−1) were obtained by processing the experiment data. By analyzing the stress-strain curve of low and high strain rates experiment, it can be found that NEPE propellant has obvious nonlinear elasticity and strain rate sensitivity. With the increase of strain rate, the strength, yield stress and elastic modulus of the material increase significantly. Compared with low strain rate, the strain rate sensitivity of the material at high strain rate is higher. Under the high speed impact, a large amount of heat is generated inside the material and cannot be released in time, which makes the internal temperature of the material rise, leading to softening effect of the material and reduction of mechanical properties. In this paper, a nonlinear visco-hyperelastic constitutive model is established to describe the mechanical properties of NEPE propellant at low and high strain rates, in which the Rivlin strain energy function is used to describe the static hyperelastic behaviour, and an integral constitutive model is used to characterize the dynamic response of the material. Considering that the relaxation time has strain rate correlation, a rate-dependent relaxation function is adopted in this paper to replace the traditional Prony series. The hyperelastic parameters were obtained by fitting the hyperelastic part of the constitutive model with extremely slow compression experiment data, and then the other parameters were obtained by fitting the constitutive model with quasi-static and dynamic experiment data. It was proved that the model could well describe the mechanical properties of NEPE propellant at low and high strain rates by the good coincidence degree between the prediction curve and the experiment curve under different strain rates.
2021, 41(3): 031408.
doi: 10.11883/bzycj-2020-0337
Abstract:
Reactive material is a new type of material with energy-releasing characteristics. It can react chemically and release a large amount of chemical energy under the high pressure and high temperature caused by the impact. Therefore, it has a wide range of potential applications in military fields such as fragments and energy-splitting warheads. In order to realize the design and control of the energy release process of reactive material and promote its weaponized application process, it is necessary to solve a series of complicated mechanical-thermal-chemical coupling problems in the impact-induced energy release behaviors of reactive materials. In the past 40 years, domestic and foreign scholars have carried out a lot of research on the impact-induced energy release behavior of reactive materials. Based on this, this paper systematically combs the research status of the impact-induced chemical reaction mechanism, kinetics and related effects of reactive materials, focusing on the research progress in three aspects: the experimental characterization technology of impact-induced energy release of materials, the theoretical model of impact-induced chemical reaction and the numerical simulation method of shock compression considering the mechanical-thermal-chemical coupling effects. Finally, the summaries are carried out and the future research work, challenges and suggestions are proposed. It is concluded that domestic and foreign scholars have accumulated a certain amount of research on the energy release behaviors of reactive materials, but there is still a lack of richer, finer and intuitive characterization and exploration for the real-time diagnosis of ultra-fast chemical reaction behavior in experiments. However, for the related theoretical and numerical simulation studies, the mechanical thermal chemical theoretical model which can fully describe the impact energy release behavior of active materials has not been established, and there is no effective method to describe the impact energy release behaviors from the macro scale. Therefore, the three aspects of research content, ultra-fast chemical reaction experimental characterization technology, macro-level mechanical-thermal-chemical mechanism and model establishment and its numerical simulation application, and preparation of reactive materials with adjustable properties, will be the focus of attention in promoting the future military application of reactive materials.
Reactive material is a new type of material with energy-releasing characteristics. It can react chemically and release a large amount of chemical energy under the high pressure and high temperature caused by the impact. Therefore, it has a wide range of potential applications in military fields such as fragments and energy-splitting warheads. In order to realize the design and control of the energy release process of reactive material and promote its weaponized application process, it is necessary to solve a series of complicated mechanical-thermal-chemical coupling problems in the impact-induced energy release behaviors of reactive materials. In the past 40 years, domestic and foreign scholars have carried out a lot of research on the impact-induced energy release behavior of reactive materials. Based on this, this paper systematically combs the research status of the impact-induced chemical reaction mechanism, kinetics and related effects of reactive materials, focusing on the research progress in three aspects: the experimental characterization technology of impact-induced energy release of materials, the theoretical model of impact-induced chemical reaction and the numerical simulation method of shock compression considering the mechanical-thermal-chemical coupling effects. Finally, the summaries are carried out and the future research work, challenges and suggestions are proposed. It is concluded that domestic and foreign scholars have accumulated a certain amount of research on the energy release behaviors of reactive materials, but there is still a lack of richer, finer and intuitive characterization and exploration for the real-time diagnosis of ultra-fast chemical reaction behavior in experiments. However, for the related theoretical and numerical simulation studies, the mechanical thermal chemical theoretical model which can fully describe the impact energy release behavior of active materials has not been established, and there is no effective method to describe the impact energy release behaviors from the macro scale. Therefore, the three aspects of research content, ultra-fast chemical reaction experimental characterization technology, macro-level mechanical-thermal-chemical mechanism and model establishment and its numerical simulation application, and preparation of reactive materials with adjustable properties, will be the focus of attention in promoting the future military application of reactive materials.
2021, 41(3): 032201.
doi: 10.11883/bzycj-2021-0005
Abstract:
The transition of fracture mode of 7075 aluminum ring was discovered by using electromagnetic expansion rings technique. The experimental results show that the fracture of the aluminum ring is affected by the maximum normal stress criterion at low strain rate, and tensile fracture easily occurs. Under the high strain rate, the fracture of the aluminum ring is affected by the maximum shear stress criterion and is prone to shear fracture. At the normal strain rate, the fracture of the aluminum ring is affected by both the maximum normal stress and the maximum shear stress criterion, resulting in a mixed fracture mode of tensile and shear fractures. And with the increase of strain rate, the number of fragments in the aluminum ring first increases, then decreases, and then increases again. These inflection points are the transition points of the fracture modes.
The transition of fracture mode of 7075 aluminum ring was discovered by using electromagnetic expansion rings technique. The experimental results show that the fracture of the aluminum ring is affected by the maximum normal stress criterion at low strain rate, and tensile fracture easily occurs. Under the high strain rate, the fracture of the aluminum ring is affected by the maximum shear stress criterion and is prone to shear fracture. At the normal strain rate, the fracture of the aluminum ring is affected by both the maximum normal stress and the maximum shear stress criterion, resulting in a mixed fracture mode of tensile and shear fractures. And with the increase of strain rate, the number of fragments in the aluminum ring first increases, then decreases, and then increases again. These inflection points are the transition points of the fracture modes.
2021, 41(3): 032301.
doi: 10.11883/bzycj-2020-0100
Abstract:
To study and simulate the pre-shock desensitization in the TATB-based heterogeneous explosive, the impact temperature and pressure based AWSD reaction flow model was implemented in a 2D structured mesh Lagrangian elastoplastic hydrodynamics program. The reactant and product EOS parameters were calibrated against the Hugoniot experimental data. To calibrate the parameters of the reaction flow model, one-dimensional numerical simulations of the shock initiation experiments were carried out. We simulated the double-shock experiments in which a first weak shock was followed by a second strong shock with a time interval of 0.45 μs. The results indicate the reaction becomes slower in the precompressed region and the run-to-detonation distance is about 1 mm longer than that in the uncompressed region, which is consistent with the desensitization in double-shock experiments. When simulating the corner-turning, the detonation wave passes through the corner and forms a stable non-initiation region near the corner, which is consistent with the dead zone characteristics of the corner-turning experiment of the LX-17 explosive with the same main composition. The numerical simulation results show that the AWSD reaction rate model based on the impact temperature and pressure can well simulate the pre-shock desensitization of heterogeneous explosives.
To study and simulate the pre-shock desensitization in the TATB-based heterogeneous explosive, the impact temperature and pressure based AWSD reaction flow model was implemented in a 2D structured mesh Lagrangian elastoplastic hydrodynamics program. The reactant and product EOS parameters were calibrated against the Hugoniot experimental data. To calibrate the parameters of the reaction flow model, one-dimensional numerical simulations of the shock initiation experiments were carried out. We simulated the double-shock experiments in which a first weak shock was followed by a second strong shock with a time interval of 0.45 μs. The results indicate the reaction becomes slower in the precompressed region and the run-to-detonation distance is about 1 mm longer than that in the uncompressed region, which is consistent with the desensitization in double-shock experiments. When simulating the corner-turning, the detonation wave passes through the corner and forms a stable non-initiation region near the corner, which is consistent with the dead zone characteristics of the corner-turning experiment of the LX-17 explosive with the same main composition. The numerical simulation results show that the AWSD reaction rate model based on the impact temperature and pressure can well simulate the pre-shock desensitization of heterogeneous explosives.
2021, 41(3): 033101.
doi: 10.11883/bzycj-2020-0119
Abstract:
High-speed railway vehicles are subjected to complex stress and environmental conditions in service. Aluminum alloy extrusions are widely used in energy absorption structures of high-speed trains, due to their excellent mechanical and processing properties. The crashworthiness of the aluminum alloy extrusions is critical to the safe and steady operations of the railway vehicles. In this study, a variety of mechanical tests were conducted on a novel aluminum alloy used for vehicles, i.e., aluminum alloy 6008-T4, including quasi-static and dynamic tension/compression tests, quasi-static tension tests at a wide range of temperatures, fracture tests along different stress paths, etc. The results show that the yield stress of the 6008-T4 aluminum alloy increases by about 15% while the fracture strain increases by about 25% when the strain rate varies from 0.001 s−1 to 2500 s−1. The aluminum alloy 6008-T4 exhibits significant temperature softening in strength: the yield stress decreases by about 60% when the temperature rises from 25 ℃ to 300 ℃. However, the fracture strain at 300 ℃ shows an 80% increase compared to the ambient (25 ℃) result. With the increase of stress triaxiality from 0.1 to 0.6, the fracture strain of the aluminum alloy 6008-T4 decreases by about 40%, and the decreasing trend conforms well to the theoretical prediction by the Johnson-Cook (J-C) model. Then the parameters of the J-C constitutive and damage models were calibrated according to the experimental results. In particular, the local fracture strains are critical for deriving the parameters of the damage model parameters. Therefore, the finite element simulations were combined with the force-displacement curves obtained in the tests to calculate the local fracture strains of the specimens. Compared to the direct measurements, the combined method of the experiments and simulation is more simple and accurate. The experimental curves at different strain rates and temperatures were compared with those predicted by the J-C model. The compariosn shows that they agree well at high temperatures. Finally, the impact penetration test was adopted to verify the acquired parameters. The simulation and experimental results, regarding the projectile positions and the fracture patterns of the target, are consistent, indicating that the parameters and calibration methods presented in this paper are reliable and effective.
High-speed railway vehicles are subjected to complex stress and environmental conditions in service. Aluminum alloy extrusions are widely used in energy absorption structures of high-speed trains, due to their excellent mechanical and processing properties. The crashworthiness of the aluminum alloy extrusions is critical to the safe and steady operations of the railway vehicles. In this study, a variety of mechanical tests were conducted on a novel aluminum alloy used for vehicles, i.e., aluminum alloy 6008-T4, including quasi-static and dynamic tension/compression tests, quasi-static tension tests at a wide range of temperatures, fracture tests along different stress paths, etc. The results show that the yield stress of the 6008-T4 aluminum alloy increases by about 15% while the fracture strain increases by about 25% when the strain rate varies from 0.001 s−1 to 2500 s−1. The aluminum alloy 6008-T4 exhibits significant temperature softening in strength: the yield stress decreases by about 60% when the temperature rises from 25 ℃ to 300 ℃. However, the fracture strain at 300 ℃ shows an 80% increase compared to the ambient (25 ℃) result. With the increase of stress triaxiality from 0.1 to 0.6, the fracture strain of the aluminum alloy 6008-T4 decreases by about 40%, and the decreasing trend conforms well to the theoretical prediction by the Johnson-Cook (J-C) model. Then the parameters of the J-C constitutive and damage models were calibrated according to the experimental results. In particular, the local fracture strains are critical for deriving the parameters of the damage model parameters. Therefore, the finite element simulations were combined with the force-displacement curves obtained in the tests to calculate the local fracture strains of the specimens. Compared to the direct measurements, the combined method of the experiments and simulation is more simple and accurate. The experimental curves at different strain rates and temperatures were compared with those predicted by the J-C model. The compariosn shows that they agree well at high temperatures. Finally, the impact penetration test was adopted to verify the acquired parameters. The simulation and experimental results, regarding the projectile positions and the fracture patterns of the target, are consistent, indicating that the parameters and calibration methods presented in this paper are reliable and effective.
2021, 41(3): 033301.
doi: 10.11883/bzycj-2020-0092
Abstract:
At present, there is no theoretical model for the influence of stiffeners on the impact angle and attack angle of a projectile penetrating a ship plate frame. In this paper, the problem of the rigid hemispherical nosed projectile penetrating the stiffener of the ship's plate frame is studied to give theoretical solution of the change of the attack angle. The stiffener is simplified as a rigid-plastic beam, the motion of which is controlled by plasto-dynamic equations of small deformation. By solving the coupled kinetic equations of the projectile and the beam, the deflection of the beam and the motion of the plastic hinges are obtained. The fracture of the beam is assumed to occur when the maximum tensile strain of the beam reaches the fracture strain of the material. By the above methods, the mechanical model of the penetration process is established. The formulas for the residual velocity, the change of impact angle, and the change of attack angle of the projectile are given. The formulas show that the change of impact angle and attack angle is related to the initial velocity, initial impact angle, initial attack angle, and the ultimate moment of the stiffener. By programming the theoretical formula, it is found that the influence of initial impact angle on the change of impact angle and attack angle at the end of penetration is greater than that of the initial attack angle. When the initial impact angle exceeds a certain value, the change of attack angle will increase dramatically. When the initial impact angle exceeds another limit value, the projectile will ricochet. A higher initial velocity corresponds to a smaller change of the impact angle and the attack angle. The ultimate moment of the stiffener has an important influence on the change of the attack angle.
At present, there is no theoretical model for the influence of stiffeners on the impact angle and attack angle of a projectile penetrating a ship plate frame. In this paper, the problem of the rigid hemispherical nosed projectile penetrating the stiffener of the ship's plate frame is studied to give theoretical solution of the change of the attack angle. The stiffener is simplified as a rigid-plastic beam, the motion of which is controlled by plasto-dynamic equations of small deformation. By solving the coupled kinetic equations of the projectile and the beam, the deflection of the beam and the motion of the plastic hinges are obtained. The fracture of the beam is assumed to occur when the maximum tensile strain of the beam reaches the fracture strain of the material. By the above methods, the mechanical model of the penetration process is established. The formulas for the residual velocity, the change of impact angle, and the change of attack angle of the projectile are given. The formulas show that the change of impact angle and attack angle is related to the initial velocity, initial impact angle, initial attack angle, and the ultimate moment of the stiffener. By programming the theoretical formula, it is found that the influence of initial impact angle on the change of impact angle and attack angle at the end of penetration is greater than that of the initial attack angle. When the initial impact angle exceeds a certain value, the change of attack angle will increase dramatically. When the initial impact angle exceeds another limit value, the projectile will ricochet. A higher initial velocity corresponds to a smaller change of the impact angle and the attack angle. The ultimate moment of the stiffener has an important influence on the change of the attack angle.
2021, 41(3): 035101.
doi: 10.11883/bzycj-2020-0126
Abstract:
In order to improve the bottom protection capability of military vehicles, a reliable optimization method was proposed for the design of vehicle protection components. In the traditional optimization process, if the uncertainty of design variables is not considered, the performance of design objectives will fluctuate or even fail. In this paper, multi-objective reliability optimization was introduced into the optimization of explosion protection. The surrogate model with the highest accuracy was constructed and chosen after the design variables were selected through experimental design and sensitivity analysis. The reliability optimization of the protection components was achieved by the multi-objective genetic algorithm. Eventually, through experiment and simulation verification, the optimized protective components met the requirements of protection and lightweight, and the reliability was improved, which can provide reference for the subsequent design and production of protective components.
In order to improve the bottom protection capability of military vehicles, a reliable optimization method was proposed for the design of vehicle protection components. In the traditional optimization process, if the uncertainty of design variables is not considered, the performance of design objectives will fluctuate or even fail. In this paper, multi-objective reliability optimization was introduced into the optimization of explosion protection. The surrogate model with the highest accuracy was constructed and chosen after the design variables were selected through experimental design and sensitivity analysis. The reliability optimization of the protection components was achieved by the multi-objective genetic algorithm. Eventually, through experiment and simulation verification, the optimized protective components met the requirements of protection and lightweight, and the reliability was improved, which can provide reference for the subsequent design and production of protective components.
