Constitutive modeling and simulation of perforation of targets by projectiles

The effective use of existing finite element codes in the direct simulation of hypervelocity impacts by projectiles is limited by the dependence of the size of localized failure regions on the mesh size and alignment This gives rise to a nonphysical description of the penetration and perforation processes. A micromechanical constitutive model that couples the anisotropic thermoviscodamage mechanism with the thermohypoelastoviscoplastic deformation is presented here as a remedy to this situation. Explicit and implicit microstructural length-scale measures, which preserve the well-posed nature of the differential equations, are introduced through the use of the viscosity and gradient localization limiters. Simple and robust numerical algorithms for the integration of the constitutive equations are also presented. The proposed unified integration algorithms are extensions of the classical rate-independent return-mapping algorithms to the rate-dependent problems. A simple and direct computational algorithm is also used for implementing the gradient-dependent equations. This algorithm can be implemented in the existing finite element codes without numerous modifications, compared with the current numerical approaches for integrating gradient-dependent models. Model capabilities are preliminarily illustrated for the dynamic localization of inelastic flow in adiabatic shear bands and the perforation of a 12-mm-thick Weldox 460E steel plate by a deformable blunt projectile at various impact speeds.