The effects of metallic material on the penetration resistances of ceramic-metal hybrid structures against vertical long-rod tungsten projectiles were studied by artillery-launched experiments and numerical simulation...The effects of metallic material on the penetration resistances of ceramic-metal hybrid structures against vertical long-rod tungsten projectiles were studied by artillery-launched experiments and numerical simulation.Hybrid structures with rectangular cores in transverse orthogonal arrangement and slidefitting ceramic inserts of zirconia toughened alumina prisms were fabricated with titanium alloy TC4(Ti6 Al4 V),AISI 4340 steel and 7075 aluminum alloy panels,respectively.The results showed that the hybrid structure of Ti6A14V exhibited the highest penetration resistance,followed by that of 7075 aluminum alloy with the same area density.The penetration resistance of the hybrid structure of AISI4340 steel was the lowest.The underlying mechanisms showed that the metallic material of a ceramicmetal hybrid structure can directly affect its energy absorption from the impact projectile,which further affects its penetration resistance.Different metallic frames exhibited different failure characteristics,resulting in different constraint conditions or support conditions for ceramic prisms.The high penetration resistance of the Ti6Al4V hybrid structure was due to its stronger back support to ceramic prisms as compared with that of AISI 4340 steel hybrid structure,and better constraint condition for ceramic prisms by metallic webs as compared with that of 7075 aluminum alloy hybrid structure.The results of mass efficiency and thickness efficiency showed that the Ti6Al4V hybrid structure has advantages in reducing both the thickness and the mass of protective structure.In addition,because the ceramic-metal hybrid structures in the present work were heterogeneous,impact position has slight influence on their penetration resistances.展开更多
The Alekseevskii–Tate model is the most successful semi-hydrodynamic model applied to long-rod penetration into semi-infinite targets. However, due to the nonlinear nature of the equations, the rod(tail) velocity, pe...The Alekseevskii–Tate model is the most successful semi-hydrodynamic model applied to long-rod penetration into semi-infinite targets. However, due to the nonlinear nature of the equations, the rod(tail) velocity, penetration velocity, rod length, and penetration depth were obtained implicitly as a function of time and solved numerically By employing a linear approximation to the logarithmic relative rod length, we obtain two sets of explicit approximate algebraic solutions based on the implicit theoretica solution deduced from primitive equations. It is very convenient in the theoretical prediction of the Alekseevskii–Tate model to apply these simple algebraic solutions. In particular, approximate solution 1 shows good agreement with the theoretical(exact) solution, and the first-order perturbation solution obtained by Walters et al.(Int. J. Impac Eng. 33:837–846, 2006) can be deemed as a special form of approximate solution 1 in high-speed penetration. Meanwhile, with constant tail velocity and penetration velocity approximate solution 2 has very simple expressions, which is applicable for the qualitative analysis of long-rod penetration. Differences among these two approximate solutions and the theoretical(exact) solution and their respective scopes of application have been discussed, and the inferences with clear physical basis have been drawn. In addition, these two solutions and the first-order perturbation solution are applied to two cases with different initial impact velocity and different penetrator/target combinations to compare with the theoretical(exact) solution. Approximate solution 1 is much closer to the theoretical solution of the Alekseevskii–Tate model than the first-order perturbation solution in both cases, whilst approximate solution 2 brings us a more intuitive understanding of quasi-steady-state penetration.展开更多
The“self-sharpening”effect has been observed experimentally in the penetration of tungsten high-entropy alloy(WHEA)into steel targets in previous study.From the microscopic observation of the residual WHEA long-rod ...The“self-sharpening”effect has been observed experimentally in the penetration of tungsten high-entropy alloy(WHEA)into steel targets in previous study.From the microscopic observation of the residual WHEA long-rod projectile(LRP),the multiphase structure at micro-scale of WHEA is the key effects on self-sharpening penetration process.In order to describe the distinctive penetration behavior,the interaction between micro phases is introduced to modify the hydrodynamic penetration model.The yield strengths of WHEA phases are determined based on the solid solution strengthening methods.Combined with the elbow-streamline model,the self-sharpening mechanism is revealed in view of the multi-phase flow dynamics and the flow field in the deformation area of the LRP nose is characterized to depict the shear layer evolution and the shape of the LRP’s nose as well as the determination of the penetration channel.The self-sharpening coefficient considering the reduction of nose radius is proposed and introduced into the penetration model to calculate the depth of penetration and the penetration channel.Results show that the multi-phase interaction at the microscopic level contributes to the inhomogeneous distribution of the WHEA phases.The shear layer evolution separates part of the LRP material from the nose and makes the nose radius decrease more quickly.It is also the reason that WHEA LRPs have a pointed nose compared with the mushroom nose of WHA heavy alloy(WHA)LRPs.The calculated results agree well with the corresponding experimental data of WHA and WHEA LRPs penetrating into semi-infinite medium carbon steel targets with elevated impact velocities.展开更多
Mass loss should be considered while calculating the penetration depth of concrete by eroding long-rod projectiles of high velocity.The penetration process is divided into two phases：eroding phase and rigid phase.Dur...Mass loss should be considered while calculating the penetration depth of concrete by eroding long-rod projectiles of high velocity.The penetration process is divided into two phases：eroding phase and rigid phase.During eroding phase,a model to predict the penetration depth is established on the assumption that there is a chipping region in the bottom of crater.During rigid phase,Forrestal formula is adopted to calculate the penetration depth.Using this model,the depth of concrete penetration by a tungsten alloy long-rod projectile is calculated.When the critical eroding velocity is between 950 m/s and 1 000 m/s,the result is in good agreement with the experimental data.展开更多
The nose shape effect on long-rod penetration was investigated by establishing numerical 2D models with different original nose shapes.The variations in nose shapes and the mass erosion rate of the rods in the transie...The nose shape effect on long-rod penetration was investigated by establishing numerical 2D models with different original nose shapes.The variations in nose shapes and the mass erosion rate of the rods in the transient phase,primary penetration phase,and secondary penetration phase were adequately analyzed by two dimensionless parameters,i.e.,the nose shape factor N* and the diameter ratio of the rod nose and shank n.In general,N*,η and the mass erosion rate of the rod vary distinctly in different phases,i.e.,unsteady in the initial transient and the secondary penetration phases,and quasi-steady in the primary penetration phase.Furthermore,a relationship between the mass erosion of the rod and the variation in the nose shape was established.A three-phase 2D model of long-rod penetration was further constructed by considering the variations in nose shape.This research may provide a reference to improve the theoretical model of long-rod penetration.展开更多
The relationship between the average penetration velocity,UˉUˉ,and the initial impact velocity, V0V0,in long-rod penetration has been studied recently. Experimental and simulation results all show the linear relatio...The relationship between the average penetration velocity,UˉUˉ,and the initial impact velocity, V0V0,in long-rod penetration has been studied recently. Experimental and simulation results all show the linear relationship between UˉUˉ and V0V0 over a wide range of V0V0 for different combinations of rod and target materials. However, the physical essence has not been fully revealed.In this paper, the Uˉ?V0Uˉ?V0relationship is profoundly analyzed using hydrodynamic model and Alekseevskii-Tate model. Especially, the explicitUˉ?V0Uˉ?V0 relationships are derived fromapproximate solutions of Alekseevskii-Tate model. Besides, the decelerationin long-rod penetration is discussed. The decelerationdegree is quantified by adeceleration index,α=2μˉ/(KΦJp)≈Ypρ?1/2p(ρ?1/2p+ρ?1/2t)V?20α=2μˉ/(KΦJp)≈Ypρp?1/2(ρp?1/2+ρt?1/2)V0?2, which is mostly related to the impact velocity, rod strength and rod/target densities. Thus, the state of penetration process can be identified and designed in experiments.展开更多
基金the support received from the National Natural Science Foundation of China(No.11872121)。
文摘The effects of metallic material on the penetration resistances of ceramic-metal hybrid structures against vertical long-rod tungsten projectiles were studied by artillery-launched experiments and numerical simulation.Hybrid structures with rectangular cores in transverse orthogonal arrangement and slidefitting ceramic inserts of zirconia toughened alumina prisms were fabricated with titanium alloy TC4(Ti6 Al4 V),AISI 4340 steel and 7075 aluminum alloy panels,respectively.The results showed that the hybrid structure of Ti6A14V exhibited the highest penetration resistance,followed by that of 7075 aluminum alloy with the same area density.The penetration resistance of the hybrid structure of AISI4340 steel was the lowest.The underlying mechanisms showed that the metallic material of a ceramicmetal hybrid structure can directly affect its energy absorption from the impact projectile,which further affects its penetration resistance.Different metallic frames exhibited different failure characteristics,resulting in different constraint conditions or support conditions for ceramic prisms.The high penetration resistance of the Ti6Al4V hybrid structure was due to its stronger back support to ceramic prisms as compared with that of AISI 4340 steel hybrid structure,and better constraint condition for ceramic prisms by metallic webs as compared with that of 7075 aluminum alloy hybrid structure.The results of mass efficiency and thickness efficiency showed that the Ti6Al4V hybrid structure has advantages in reducing both the thickness and the mass of protective structure.In addition,because the ceramic-metal hybrid structures in the present work were heterogeneous,impact position has slight influence on their penetration resistances.
基金supported by the National Outstanding Young Scientist Foundation of China (Grant 11225213)the Key Subject "Computational Solid Mechanics" of China Academy of Engineering Physics
文摘The Alekseevskii–Tate model is the most successful semi-hydrodynamic model applied to long-rod penetration into semi-infinite targets. However, due to the nonlinear nature of the equations, the rod(tail) velocity, penetration velocity, rod length, and penetration depth were obtained implicitly as a function of time and solved numerically By employing a linear approximation to the logarithmic relative rod length, we obtain two sets of explicit approximate algebraic solutions based on the implicit theoretica solution deduced from primitive equations. It is very convenient in the theoretical prediction of the Alekseevskii–Tate model to apply these simple algebraic solutions. In particular, approximate solution 1 shows good agreement with the theoretical(exact) solution, and the first-order perturbation solution obtained by Walters et al.(Int. J. Impac Eng. 33:837–846, 2006) can be deemed as a special form of approximate solution 1 in high-speed penetration. Meanwhile, with constant tail velocity and penetration velocity approximate solution 2 has very simple expressions, which is applicable for the qualitative analysis of long-rod penetration. Differences among these two approximate solutions and the theoretical(exact) solution and their respective scopes of application have been discussed, and the inferences with clear physical basis have been drawn. In addition, these two solutions and the first-order perturbation solution are applied to two cases with different initial impact velocity and different penetrator/target combinations to compare with the theoretical(exact) solution. Approximate solution 1 is much closer to the theoretical solution of the Alekseevskii–Tate model than the first-order perturbation solution in both cases, whilst approximate solution 2 brings us a more intuitive understanding of quasi-steady-state penetration.
基金This work was supported by the National Natural Science Foundation of China(Grant 11790292)the NSAF Joint Fund(Grant U1730101).
文摘The“self-sharpening”effect has been observed experimentally in the penetration of tungsten high-entropy alloy(WHEA)into steel targets in previous study.From the microscopic observation of the residual WHEA long-rod projectile(LRP),the multiphase structure at micro-scale of WHEA is the key effects on self-sharpening penetration process.In order to describe the distinctive penetration behavior,the interaction between micro phases is introduced to modify the hydrodynamic penetration model.The yield strengths of WHEA phases are determined based on the solid solution strengthening methods.Combined with the elbow-streamline model,the self-sharpening mechanism is revealed in view of the multi-phase flow dynamics and the flow field in the deformation area of the LRP nose is characterized to depict the shear layer evolution and the shape of the LRP’s nose as well as the determination of the penetration channel.The self-sharpening coefficient considering the reduction of nose radius is proposed and introduced into the penetration model to calculate the depth of penetration and the penetration channel.Results show that the multi-phase interaction at the microscopic level contributes to the inhomogeneous distribution of the WHEA phases.The shear layer evolution separates part of the LRP material from the nose and makes the nose radius decrease more quickly.It is also the reason that WHEA LRPs have a pointed nose compared with the mushroom nose of WHA heavy alloy(WHA)LRPs.The calculated results agree well with the corresponding experimental data of WHA and WHEA LRPs penetrating into semi-infinite medium carbon steel targets with elevated impact velocities.
基金Sponsored by State Key Laboratory of Explosion Science and Technology Foundation(ZDKT08-04,YBKT09-03)
文摘Mass loss should be considered while calculating the penetration depth of concrete by eroding long-rod projectiles of high velocity.The penetration process is divided into two phases：eroding phase and rigid phase.During eroding phase,a model to predict the penetration depth is established on the assumption that there is a chipping region in the bottom of crater.During rigid phase,Forrestal formula is adopted to calculate the penetration depth.Using this model,the depth of concrete penetration by a tungsten alloy long-rod projectile is calculated.When the critical eroding velocity is between 950 m/s and 1 000 m/s,the result is in good agreement with the experimental data.
基金supported by the National Natural Science Foundation of China(Grant Nos.11872118 and 12002293).
文摘The nose shape effect on long-rod penetration was investigated by establishing numerical 2D models with different original nose shapes.The variations in nose shapes and the mass erosion rate of the rods in the transient phase,primary penetration phase,and secondary penetration phase were adequately analyzed by two dimensionless parameters,i.e.,the nose shape factor N* and the diameter ratio of the rod nose and shank n.In general,N*,η and the mass erosion rate of the rod vary distinctly in different phases,i.e.,unsteady in the initial transient and the secondary penetration phases,and quasi-steady in the primary penetration phase.Furthermore,a relationship between the mass erosion of the rod and the variation in the nose shape was established.A three-phase 2D model of long-rod penetration was further constructed by considering the variations in nose shape.This research may provide a reference to improve the theoretical model of long-rod penetration.
基金The work was supported by the National Natural Science Foundation of China (Grant 11872118)The authors want to express deep gratitude to the reviewers for their sound comments and helpful suggestions.
文摘The relationship between the average penetration velocity,UˉUˉ,and the initial impact velocity, V0V0,in long-rod penetration has been studied recently. Experimental and simulation results all show the linear relationship between UˉUˉ and V0V0 over a wide range of V0V0 for different combinations of rod and target materials. However, the physical essence has not been fully revealed.In this paper, the Uˉ?V0Uˉ?V0relationship is profoundly analyzed using hydrodynamic model and Alekseevskii-Tate model. Especially, the explicitUˉ?V0Uˉ?V0 relationships are derived fromapproximate solutions of Alekseevskii-Tate model. Besides, the decelerationin long-rod penetration is discussed. The decelerationdegree is quantified by adeceleration index,α=2μˉ/(KΦJp)≈Ypρ?1/2p(ρ?1/2p+ρ?1/2t)V?20α=2μˉ/(KΦJp)≈Ypρp?1/2(ρp?1/2+ρt?1/2)V0?2, which is mostly related to the impact velocity, rod strength and rod/target densities. Thus, the state of penetration process can be identified and designed in experiments.
