A model for penetration by very low aspect ratio projectiles

Abstract

Summary As the aspect ratio (L/D) of a projectile decreases and the projectile becomes more disk like, the penetration mode changes. A model for the penetration of low L/D projectiles has been developed to explain and predict the low L/D penetration event. The model divides the penetration into two phases: first a flyer plate type impact, and second, a crater growth phase. Calculations provided insight into the physical mechanism involved. Shortly after impact, the projectile enters a long period of constant velocity penetration. This behavior leads to the depth of penetration scaling with projectile diameter. A large crater grows in the target, and the projectile travels into a debris filled crater as a free body. The velocity is “frozen” in when release waves arrive from the free surface. In the model, the crater in the target is analyzed by assuming plastic constitutive response, with the motion caused by an impulsive load due to the impact. The final depth of penetration is obtained by combining a one-dimensional depth of penetration and a plastic target cratering response. The model compares well with both large scale numerical simulations and experimental data.