Penetration and perforation processes in metal targets at and above ballistic velocities

Abstract

A study was made of the penetration, perforation and fragmentation of 0·05- to 0·25-in. thick 2024 aluminum and SAE 1020 and 4130 steel alloy plates impacted normally by 0·125- to 0·5-in. dia. AISI 52- 100 hard steel spheres at velocities from 500 to 8800 ft/sec. Data included initial and terminal projectile velocity, radial and transverse strain histories at various positions from the impact point, crater and fragment dimensions and high-speed Kerr cell photographs of collisions at predetermined framing intervals. Quasistatic mechanical properties and target hardnesses were also obtained. The drop in projectile velocity was found to decrease just above the ballistic limit, then steadily rise with increasing initial bullet speed in all target-projectile configurations. The first trend was predicted by a relation based on a simple momentum balance, whereas a more precise analysis provided reasonable correspondence with the data over the entire velocity range. Strain-gage results showed a decrease of dishing relative to radial target motion with increasing impact velocity. Displacement-time curves were constructed using measured initial and terminal projectile velocities, fragment dimensions and Kerr cell records. Force histories of the projectiles were then computed from these data using an empirical relation developed previously. Peak forces obtained were in agreement with calculations from a triangular impulse of the proper duration and of magnitude equal to the measured change in projectile momentum.