Perforation of steel and aluminum targets using a modified Johnson-Cook material model

Numerical perforation studies involving finite element method (FEM) suffer from severe mesh distortion problem when subjected to large deformation in high velocity projectile impact cases. Severe element distortion causes negative volume problem and introduces numerical errors in the simulated results. Mesh free methods, such as smoothed particle hydrodynamics (SPH) method is capable of handling large deformation without any numerical problems, but at substantially high computational resources. To mitigate the problem, coupled smoothed particle hydrodynamics-finite element method (SFM) has been implemented to study the high velocity perforations of steel and aluminum target plates, where the SPH method is adopted only in severely distorted regions and the FEM further away. Strain rate and adiabatic heating have a considerable effect on material properties, especially at high velocity impact, and hence, a new material model with high strain rate and adiabatic temperature effects is adopted herein. Material properties for Weldox 460E steel and AA5083-H116 aluminum plates are determined and used to perform perforation of target plates with varying thicknesses and projectile nose geometries, such as blunt, conical and ogival noses. Numerical residual and ballistic limit velocities show good correlation with the published experimental results. The study demonstrates that the new material model is able to emulate failure characteristics of the steel and aluminum plates as observed in various experimental observations.