Theoretical And Numerical Study Of Long Rod Penetration Into Metallic Thick Targets Finite In Radial Extent

Due to the frequent local conflicts and terrorist attacks in recent years, which is a menace to the building structures, high speed impact dynamics has been one of the most active research fields in explosion mechanics. In this paper, for the problem of penetrating into metallic thick target finite in radial extent dividing into rigid projectiles penetration and high-speed long rods penetration, an analytical and computational effort is undertaken to examine the effect of the lateral free boundary of the target on the performance of penetration. Some results are achieved, such as the theoretical prediction models, the complete deforming process of materials and the change rule of some physical parameters. Major research work and innovative achievements are listed below:(1) Using the unified strength theory, in the consideration of the intermediate principal stress effect to analyze the elastic-plastic stage and plastic stage of two target materials, analytical solutions of radial pressure on the cavity wall are obtained. Resistance formulas and penetration depth formulas of the rigid projectiles penetrating into metallic thick target finite in radial extent are deduced, not only expanding the scope of application, but also increasing the accuracy. Penetration depth ranges of all kinds of target with equal tension-pressure strength under different impact velocities are presented. Extending the calculation to the conical- nosed projectile and spherical- nosed projectile, the effect of nose shape on the penetration depth are analyzed. Using Simpson method to solve, the effect of the parameter b, impacting velocity of projectile and target radius on the depth of penetration limit are also discussed.(2) Considering the intermediate principal stress effect and mass abrasion, the finite cylindrical cavity expansion model based on the unified strength theory is used to propose the target’s resistance and penetration depth solutions of the problem on high-speed long rods penetrating into metallic thick target finite in radial extent of ideal elastic plastic materials. Then the penetration depth solution is extended to the linear strain- hardening materials. Predicting the penetration depth ranges of all kinds of target with equal tension-pressure strength for different ratio of target to projectile, the anti-penetration strength potentials of target can be played objectively and fully. Solving the formula in this paper by MATLAB, influencing factors of terminal effects are studied.(3) Using explicit dynamic program, ANSYS/LS-DYNA, choosing different constitutive models, the numerical models of rigid steel projectile penetrating into aluminium alloy target and tungsten alloy abrasion long rod penetrating into steel target finite in radial extent are built. Analyzing the history curves of penetration depth, projectile velocity, and acceleration, the change rules of impact process are revealed and the effect for the lateral free boundary of target, projectile initial velocity, and the ratio of length to diameter of rod on penetration behavior are discussed. Condition of ignoring the effect of the lateral free boundary of the target is accurate to a specific value. Numerical calculations of abrasion long rod penetration at different impact velocity are performed, and the curves of interface pressure, penetration depth, rod head velocity and rod tail velocity, length and mass of rod vary with the time are obtained and described. Meanwhile, the different effects of the rod nose shape on low-speed and high-speed penetration are studied. Deformation feature, the time- history change and state change of deforming non-erosive projectile are also analyzed.(4) In order to study the influence of incident angle on trajectory in the instance of oblique penetration, the processes of projectile penetrating plumb and obliquely into metallic target are numerically simulated, whose incident angle varies from 0° to 70°. The movement path, the depth- line curves, velocity- line curves, deceleration- line curves and the track angle-line curves are got through analysis. Based on the models of oblique penetration, changing initial attack angle(13 sets of ?) to study the variation regularity of the projectile deflexion, the trajectory shape and the influence of attack angle on the penetration performance.