Penetration with instrumented rods

Abstract

The response of long rods during penetration is being examined by strain measurements performed with foil resistance gages. Early experiments in this investigation employed the reverse ballistic approach in which stationary rods were impacted by armor targets launched from a light-gas gun. Although satisfactory results were obtained for both normal and oblique impacts, the reverse ballistic approach strictly limited the target diameter, and the target mass limited the impact velocity to values below the range of current ballistic interest. In order to overcome the major limitations imposed by reverse ballistics a technique for launcing instrumented rods has been developed. With this technique strain gages on the rod are connected to thin metal contacts located on the front surface of the plastic sabot. Prior to impact, the contacts are pierced by stationary probes and a low-resistance electrical path is provided during approximately 100 mm of travel by the sabot. A series of impact tests has been performed at normal incidence with steel rods impacting steel targets at a velocity of 1000 m/s. Strain-time signals from these tests were amenable to a simple wave analysis which provided relationships between stress and strain, and particle velocity and strain, to strain of 15%. Results of the analysis are discussed in the context of their relationship to the experimental technique. Details of the experimental technique and its refinement are presented and problem areas are considered.