The Measurement of Forces Resisting Armor Penetration

Abstract

This paper summarizes the experimental and theoretical status of the optical chronograph developed in the course of ballistic research at the Naval Research Laboratory. The instrument, together with a simple procedure for analysis of data, is capable of yielding the position, velocity, and deceleration of a non-plastically deforming small arms projectile during the armor penetration process, which lasts from 30 to 150 microseconds. Decelerations have been observed up to 5×107 ft./sec.2. The longitudinal vibrations induced in projectiles during impact were observed by a shadow-photography technique which yields time-displacement curves from the motion of the trailing face of a projectile during penetration. The precision of the derived decelerations, about 4 percent, is sufficient to permit the evaluation of strain-rate and inertia effects during high speed indentation by means of conical indenters at strain-rates approaching 2×105/sec.