Semi-Infinite Target Penetration by Ogive-Nose Penetrators: ALEGRA/SHISM Code Predictions for Ideal and Nonideal Impacts

The physics of ballistic penetration mechanics is of great interest in penetrator and countermeasure design. The phenomenology associated with these events can be quite complex, and a significant number of studies have been conducted ranging from purely experimental to “engineering” models based on empirical and/or analytical descriptions to fully coupled penetrator/target, thermomechanical numerical simulations. Until recently, however, there appears to be a paucity of numerical studies considering “nonideal” impacts (Goldsmith, 1999, “Non-Ideal Projectile Impact on Targets,” Int. J. Impact Eng., 22, pp. 95–395). The goal of this work is to demonstrate the SHISM algorithm implemented in the ALEGRA multimaterial arbitrary Lagrangian Eulerian code (Boucheron, et al., 2002, ALEGRA: User Input and Physics Descriptions, Version 4.2, SAND2002-2775, Sandia National Laboratories, Albuquerque, NM). The SHISM algorithm models the three-dimensional continuum solid mechanics response of the target and penetrator in a fully coupled manner. This capability allows for the study of nonideal impacts (e.g., pitch, yaw, and/or obliquity of the target/penetrator pair). In this work predictions using the SHISM algorithm are compared with previously published experimental results for selected ideal and nonideal impacts of metal penetrator-target pairs. These results show good agreement between predicted and measured maximum depths-of-penetration (DOPs), for ogive-nose penetrators with striking velocities in the 0.5–1.5 km/s range. Ideal impact simulations demonstrate convergence in predicted DOP for the velocity range considered. A theory is advanced to explain disagreement between predicted and measured DOPs at higher striking velocities. This theory postulates uncertainties in angle-of-attack for the observed discrepancies. It is noted that material models and associated parameters used here were unmodified from those in literature. Hence, no tuning of models was performed to match experimental data.