Effects of alloy type and heat treatment on ejecta and crater sizes in aluminum alloys subjected to hypervelocity impacts

The effects of alloy type and heat treatment on crater size, ejecta fragment mass, and ejecta fragment size were examined for polycarbonate spheres striking thick aluminum alloy targets at very high velocities. The diameter and depth of the craters were compared with those obtained through an empirical equation. The size and mass of the ejecta fragments collected from the test chamber were also measured. The ejecta fragment mass was proportional to the impact energy of the projectiles, and the ejecta fragment size was proportional to the cubic root of the impact energy. The calculated characteristic lengths, cross-sectional areas, and mass-to-area ratios were compared with those from the NASA breakup model and Hataʹs model. The ejecta ring diameter obtained from the witness plates decreased with increasing impact velocity.