Penetration of a plastically-deforming target by slender projectiles

Abstract
Penetration of a plastically-deforming target by slender projectiles was studied by a combined experimental and numerical approach. Two types of conical-nosed steel projectiles with the same mass but different mass distributions were employed for penetration tests on 6061-T6 aluminium alloy cylindrical blocks at impact velocities ranging from 230 m/s to 460 m/s. Experimental results show that the mass distribution has only negligible influence on penetration effectiveness – the variation of penetration depth with impact velocity is similar for the two projectile types. Predictions of analytical relations based on Spherical Cavity Expansion Theory (SCET) for penetration depth were compared with experimental data, and good agreement was observed. Finite element modelling was performed using ABAQUS Explicit, with the objective of establishing a numerical model that can predict the penetration depth with good accuracy. Friction and thermal softening effects were first examined and shown to be insignificant. Three failure criteria, based on a constant failure strain, the Johnson-Cook model, and Bao-Wierzbicki's theory, were evaluated; the last was found to be the most suitable. Consequently, a numerical model ignoring friction and thermal effects, with target material failure described by the Bao-Wierzbicki criterion, was utilised. Its predictions of penetration depth correlated well with experimental data.