Perforation of AA6061-T651 plates by 4340 steel ogive-nose rods with normal impacts

In this study, the perforation of 6061-T651 aluminum alloy (AA) plates by 4340 steel ogive-nose projectiles with normal impacts is considered. The perforation process is assumed to be entirely due to ductile hole growth. Therefore, the cylindrical cavity expansion (CCE) approximation is employed to determine the ballistic limit and residual velocities for 26.3 mm-thick AA6061-T651 target plates. The target plates are considered to be fully elastically compressible, ductile, von Mises solids with the power-law strain hardening, strain rate hardening, and thermal softening due to thermo-mechanical coupling under adiabatic loading conditions. The dynamic CCE simulations based on the finite element method (FEM) provide solutions at various constant expansion velocities utilizing the transient solid-dynamics commercial software Abaqus. At each constant CCE velocity, a minute pre-existing cavity is expanded until the radial cavity-surface displacement reaches the characteristic length identified herein with the projectile shank radius. The corresponding radial stress at the cavity surface coincides with a nearly steady-state value. Subsequently, radial stress versus radial CCE velocity data are fitted with a full quadratic function that is then employed with Newton’s second law to define the axial force acting on the projectile’s nose due to the resistance of the target plate. The corresponding ballistic limit and residual velocities are obtained and demonstrated to be in fairly good agreement with both experimental perforation data and closed-form analytical solutions. The small disparity in results is discussed in detail.