Predicting the fragmentation onset velocity for different metallic projectiles using numerical simulations

For cubes and spheres under high velocity impact there exists for each system of projectile and target, a threshold velocity that is just sufficient to shatter the projectile. This velocity, usually above 2km/s for metallic projectiles, is known as the fragmentation onset velocity. To determine the fragmentation onset velocity experimentally, a number of experiments in which the impact velocity of the projectile is varied in a controlled manner needs to be conducted [1]. In the work described in this paper, the numerical analysis code AUTODYN was used to simulate the impact of stainless steel and tantalum projectiles onto transparent targets in an attempt to simulate the onset of fragmentation. Using the meshfree SPH method for discretizing the spatial domain of the projectile and a simple failure model that allows the critical spall stress of the material to vary with the local material and loading conditions, encouraging results were obtained, with the fragmentation onset velocity for both projectile/target configurations being reasonably well predicted. In addition, further experiments conducted at TNO-PML, to determine the fragmentation onset velocity for tungsten projectiles, will be reported.