Impact Crater Formation at Intermediate Velocities

The influence of projectile strength on cratering was investigated for projectiles of aluminum alloys impacting semi-infinite aluminum targets over the velocity range of 1 km/sec to 5.0 km/sec. The experimental results showed that crater diameters were not significantly influenced by varying projectile strength. The crater depths were found to vary appreciably with strength at lower velocities but to become virtually the same at 3.5 km/sec for the series of projectile alloys investigated. A simple dynamic model for cratering was developed and compared with the experimental results of this study and other experimental results at higher velocities. These comparisons showed that the model provided predictions of crater diameter which were within 8 percent for the experimental results of this study and within 13 percent for the hypervelocity data. Crater depth predictions showed good agreement with the experimental results of this study for projectiles having greater yield strength than the target material. The predictions of depth as a function of velocity showed qualitative agreement with the hypervelocity data.