Experimental observations and computer simulations of metallic projectile fragmentation and impact crater development in metal targets

The vast majority of the investigations in impact cratering phenomena have involved the understanding of the dynamic response of target material macro- and microstructural issues. There has been little focus on the projectile fragmentation during impact, especially, interaction of projectile fragmentation with the forming crater. As a result, this study intends to further the understanding of the fragmentation phenomena characteristics of metallic projectiles in metal targets. The effect of spherical (dp = 3.175 mm) stainless steel projectiles (rho = 7.86 g/cm3) impacting nickel (rho = 8.9 g/cm3), Oxygen Free High Conductivity (OFHC) copper (rho = 8.96 g/cm3), 70-30 brass (rho = 8.45 g/cm3) and stainless steel targets with velocities ranging from 0.52 to 5.12 km/s were examined by Scanning Electron Microscopy (SEM). AUTODYN-3D computer simulation software was utilized to model the impact and projectile fragmentation process. SPH (Smoothed Particle Hydrodynamics) Processor with a principal stress failure model was used to model the projectile and was coupled with a Lagrangian target.; Computer simulations generated through AUTODYN-3D were validated reasonably well (qualitatively) against laboratory experimental results to characterize the dynamic fracture of the projectile upon impacting a stationary target at normal incidence. The projectile fragmentation onset velocity began at 0.69 km/s or ∼1 km/s and projectile debris fragment size decreased with increasing impact velocity. Fragment measurements showed hypervelocity to occur at 6 km/s corresponding to zero fragment size.