Research On Terminal Effect Of The Chisel-Shape Projectile

The research of projectile penetrating/perforating into metallic target plates is usually come down to non-linear problems of three kinds of geometry, material constitutive model and contacting boundary. It is a great challenge in mechanics, material science, and computational mathematics. And widely caught scholars’ s eyes at home and abroad. In this paper, combining with the existed experimental results and theory and numerical method, we have studied the penetration/perforation effect of a rigid projectile penetrating into metallic target plates with different geometric configurations, especially for the terminal effect of the chisel-shape projectile. The following is the main contents of the dissertation,(1) Theoretical analysis on penetration of chisel-shape projectile into metallic target platesThis paper considers the problem of non-steady penetration of a chisel-rigid projectile into an target of finite thickness. Assuming the projectile material are rigid and the target material are elastic-plastic which exactly satisfies the J2 flow theory and the condition of impenetrability. By introducing a reasonably velocity field, the motion of the chisel projectile exactly satisfies in both the continuity equation and the momentum equation. The target region is subdivided into an elastic region ahead of the projectile where the strains are assumed to be small, and a rigid-plastic region near the projectile where the strains can be arbitrarily large. Using the velocity field function, the momentum equation is solved exactly in both the elastic and the rigid-plastic regions to find expressions for the pressure and stress fields. In this model, the effects of the free front and rear surfaces of the target and the separation of the target material from the projectile are approximate, and the force applied to the projectile is calculated analytically. The projectile motion equation is obtained which is solved numerically. Also, for reasonable simplification, a analytical expression for the depth of penetration or the residual velocity is developed, and the influence of the chisel angle for the depth of penetration is researched.(2) The numerical analysis of penetration of different geometric configurations projectileIn this assay, numerical simulations were performed using the LS-DYNA finite element code. The model of different geometric configurations projectile penetrating into metallic target plates have been established to study the penetration effect of various of projectiles such as flat, sphere and cone(thin or thick plate). The constitutive relation is the phenomenological model proposed by John-Cook which is frequently used for impact analysis, and the penetrated energy, the residual velocity or ballistic limit is developed which compared with experiments is good ever though no empirical parameters be used. Finally the reliability of the model have been proved.(3) The analysis and verification of the penetrated model of chisel-shape.The main objective of the present paper is to study the mechanism of penetration. On the basis of experiments researching, combining the approximate flow field analysis model of Yarin and beginning with the fundamental equations of fluid mechanics, the velocity field and the equation of the move of the chisel-shape projectile can be developed. The approximate expressions of penetration depth and the residual velocity with the initial impacting velocity are obtained for the exploration of the penetration mechanisms of the chisel-shape projectile. Meanwhile, LS-DYNA have been used for numerical analysis and model verification. At last, the factor of different chisel-angle or length-diameter ratio is studied to the penetration effect. The chisel-shape projectile has a more high penetration efficiency than other shape projectile. In particular, chisel-shape projectile has an obvious increase to the dynamic failure of the target plate material for higher impact. Under the same initial impact conditions, the chisel-shape can obtain higher penetration depth for reduce the chisel angle appropriate.