A model for penetration by very low aspect ratio projectiles

As the aspect ratio (L/D) of a projectile decreases and the projectile beco mes more disk like, the penetration mode changes. A model for the penetrati on of low L/D projectiles has been developed to explain and predict the low VD penetration event. The model divides the penetration into two phases: f irst a flyer plate type impact, and second, a crater growth phase. Calculat ions provided insight into the physical mechanism involved. Shortly after i mpact, the projectile enters a long period of constant velocity penetration . This behavior leads to the depth of penetration scaling with projectile d iameter. A large crater grows in the target, and the projectile travels int o a debris filled crater as a free body. The velocity is "frozen" in when r elease waves arrive from the free surface. In the model, the crater in the target is analyzed by assuming plastic constitutive response, with the moti on caused by an impulsive load due to the impact. The final depth of penetr ation 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. (C) 1999 Elsevier Scien ce Ltd. All rights reserved.