Inferring the ballistic resistance of thick targets from static deep indentation tests

Abstract

The aim of this work is to demonstrate that one can derive the value of the dynamic resistive stress, which a given target exerts on a rigid projectile, by following the force needed to push a rigid indenter into the target in a static deep indentation test. In this study, we used a relatively soft target made of a lead-antimony alloy and a concrete target, representing ductile metals and brittle solids, respectively. For both targets, we followed the force-distance curves obtained by the deep indentations of hard punches, as they were slowly pushed in the targets by a loading frame. The effect of friction during these tests was taken into account in order to obtain the net axial resisting stresses, which were applied by the targets on these indenters. These static resisting stresses, at deep penetrations, were compared with the dynamic resisting stresses, which were inferred from the impacts of armor-piercing projectiles on these targets. The good agreement between the two sets of values strongly enhances the claim that one can use static indentation tests in order to estimate the ballistic resistance of various targets to rigid projectile penetration. The effect of strain rate sensitivity is highlighted by the test results for both the metallic and concrete targets. In addition, important insights concerning the cavitation phenomenon in the penetration of rigid projectiles are also highlighted in this work.

A note on the cavitation phenomenon in metallic plates perforated by sharp-nosed rigid projectiles

“…In order to check our simulation results for cases where V 0 > V cav we performed a few perforation tests with 0.5″ APM2 projectiles, with D 0 = 12.7 mm, impacting plates of a lead-antimony alloy. These plates were cut-off the thick targets which were used in Rosenberg et al (2018b), having a density of 10.6 g/cm 3 and a dynamic compressive strength of Y = 0.087 GPa, through a high-rate Kolsky bar test. The stress-strain curves from this test and from a quasi-static test, are given in Rosenberg et al (2018b).…”

“…These plates were cut-off the thick targets which were used in Rosenberg et al (2018b), having a density of 10.6 g/cm 3 and a dynamic compressive strength of Y = 0.087 GPa, through a high-rate Kolsky bar test. The stress-strain curves from this test and from a quasi-static test, are given in Rosenberg et al (2018b). For the 10 mm thick plates which we used in these tests, we have σ r = 2Y = 0.174 GPa and from equation ( 5) we find that V cav = 330 m/s for this projectile/ plate pair.…”