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

Stainless steel (3.18 mm diameter) spherical projectiles impacting 2.5 cm thick targets of nickel, copper, 304 stainless steel, and 70/30 brass at velocities ranging from 0.52 to 5.12 km/s were observed by SEM to form decreasing average fragment sizes with increasing impact velocity, beyond a fragmentation onset velocity of 0.7 km/s. Crater observations by optical microscopy and SEM were qualitatively simulated using an AUTODYN numerical analysis code, which also illustrated a decrease in fragmentation density within the target craters with increasing impact velocity. However, extrapolated simulations corresponding to impact velocities as high as 10 km/s showed residual fragmentation within these craters in contrast to extrapolations of the experimental fragment size versus impact velocity data indicative of zero fragment size at 6 km/s.