Thermodynamically Consistent Void-Based Damage Model*

A thermodynamically consistent model for the nucleation and growth of voids under dynamic loading conditions is presented. Voids are modelled as thick-walled spheres within a representative volume element (RVE). The statistical distribution of dominant material defect void nucleation resistance and local stress state variation within the RVE are given by a probability density function (PDF) informed by molecular dynamics data and polycrystal calculations. The PDF specifies the interaction between the spatially varying stress state and the dominant class of material defect and serves to bridge the microscale problem to the RVE macroscale. Energy is assigned to defect and thermal physical subsystems accounting for free surface creation within the local power balance. The effects of inertia, compressibility, and creation of free surfaces are shown to be non-negligible under weak shock loading and are demonstrated to provide regularization through inherently introduced length scales. The plasticity model is demonstrated to represent simple compression experiments at varying initial temperature and deformation rate conditions for high-purity tantalum. The complete damage model is then used to describe three different plate impact experiments conducted with high-purity tantalum. These three experiments differ in their impact velocity and imposed stress profile via graded flyer plate design and result in significantly different damage fields and free-surface velocity traces. The results are interpreted in the context of energy partitioning and numerical simulations are compared directly with the experimental damage fields and free-surface velocity profiles.