Projectile shape effects on hypervelocity impact craters in aluminum

Linear high-density polyethylene cylinders, with fineness ratios of 1/6, 1/3, 2/3, 1, and 3, and spheres were launched into thick targets of hard (2024-T35l) aluminum at velocities up to 11.3 km/sec.The effects of projectile shape on the various crater parameters were determined quantitatively from the basic crater dimensions: depth, diameter, and volume.In the hypervelocity regime, the dimensionless penetration, P/d, varied with the projectile fineness ratio, lid, to the 1/4 power for fineness ratios between 1/6 and 1.For fineness ratios greater than 1, the power increased and approached unity, as would be expected from shaped-charge jet theory.For engineering purposes, in the hypervelocity regime, a sphere produces the same crater as a cylinder of equal diameter and lid of 2/3.