Projectile And Target Penetration Dynamic Response Theory And Numerical Analysis

In this dissertation, we discuss dynamic response of the projectile and target involved in developing earth penetrator and building safeguard in national defense engineering research. Penetration is dynamic process of a projectile impacting and getting into a target. And it is usually come down to three kinds of non-linear problems of large strain geometry, material constitutive model and contacting boundary. It is a great challenge in mechanics, material science, and computational mathematics. And many problems in touch with practice engineering can not be entirely solved.The following is the main contents of the dissertation.1 Theoretical and applied analysis on penetration of long rod projectile.Long rod projectiles are usually used to penetrate thick targets. The mostly used theoretical models of analyzing the long rod projectile penetrating into thick targets are cavity-expansion model and Tate model. Both of these two models need to adjust the material parameters in engineering research.Based on a theoretical model of determination of the velocity potential and the velocity field in the targets, the problems of rigid long rod projectile penetrating or perforating thick targets are studied. The method of calculation is presented, and a code according to it has been written to calculate varied penetration problems of long rod projectile with different nose shape, such as ogive, cone and sphere. Compared with the results of the tests and FEM code, the creditability and applicability of the theory model are studied. The theoretical model has stable analytical foundation and well describes kinetic mechanics of penetrating process. It may get consistent results without modifying material parameters not as other models. And it use less time than other numerical code.The comparability problems on penetrating into aluminum targets are also analyzed. The results showed that the dimensionless residual velocity and penetration depth is equal and the deceleration is in reverse to dimension. At last, the code is tried to calculate penetration problems on concrete targets. And numerical results agreed with the tests are obtained with adjust value of concrete strength. The theoretical model may be abroad used in research of correlative engineering problems.2 Computation and analysis on dynamical responses of the projectile whennormal penetrating into concrete targets with LTZ-2D code.LTZ-2D code is a two dimensional FEM programme to study elastic-plastic hydrodynamics problems. It may be used to analyze dynamic response of projectiles and targets under high velocity impacting. There is error in the computated penetration depth of the code while simulating the problem of penetrating into a thick target. We revise the code to resolve this problem in this dissertation.A shorcoming in the JH-1 constitutive model of concrete in the code that damage has little influence on strength is mended. Then the study presents a careful analysis of the factors such as element dimension and erosion threshold which have influence on the computational results when using LTZ-2D code and confirms some principles of making a computational model. Some reasonable results such as penetration depth, the change of velocity and deceleration of the projectile with change of time are obtained and analyzed in detail, as well as the distribution of pressure, equivalent stress and equivalent strain of the projectile. On the base of those results, the optimized problems of the explosive projectile models are studied by numrical simulation.3 Analysis and construction of constitutive model of concrete under impact loading.The simulation of problems of safety engineering research or tandem projectile penetration into concrete targets require exact describing the damage and fracture of concrete. So we develop a constitutive model that may be used to describe dynamic behavior of concrete under impact loading.Making conclusion on dynamical tests and varied dynamical constitutive models of concrete, a constitutive model is made up for numerical simulation of kinetic energy projectile penetrating into a concrete target. Several factors such as the second and third invariant of stress, strain rate, tension or shear damage are taken into account in this model and it can be used to describe the full mechanical process of linear elastic, hardening plastic and damage softening of geological material. This study gave new model of describing the relation between eccentricity and pressure, the variation between three strength surfaces and tension damage of concrete. The constitutive model is put into LTZ-2D code. The computed results of residual velocity are well consistent with the tests data. And the reasonable figure of fractured concrete target is also obtained. The results show that the constitutive model can well describe the main characters of concrete under impact loading and be better thanJH-1 concrete model mostly used in analysis of impact problems.4 Numerical simulations and analysis on problems of oblique penetrating into concrete targets with 3D code.The process of warheads moving into targets usually be taken as oblique penetration problems. In such situation the projectile impact the target at a oblique angle, the angle between projectile axis and normal surface of the target, as well as a attack angle that between axis and velocity of projectile. Simulation of the problem need three dimesional code. The LS-DYNA software is one of them.The calculated results of LS-DYNA is verified and analysized with tests data. Presenting a numrical computation and analysis on explosive peojectile penetrating into concrete targets, it shows that the explosive is crushed at the begaining of the penetration process and there is interspace between explosive and the tail case of the projectile. The oblique angle and attack angle will decreased the penetrating capability of the projectile as the deflected projectile and incresing stress of the case. Attack angle such as 5° will have a great influence on penetration process.