Modeling of dynamic failure by nucleation and growth processes

Abstract
It is well established that high rate failure of structural materials takes place by rate processes occurring at the micro level and involving nucleation, growth, and coalescence of voids or cracks. At the submicroscopic level, the mechanism of failure in materials is dislocation controlled. The process of deformation and failure can be described by plastic glide that involves the mechanism of dislocation pile-ups. A new physically based model describing these processes is proposed. The effects of inertia and rate sensitivity on the growth process, and porosity are examined. The model formulation is three-dimensional and is suitable for a general state of stress and strain. The model constants are calibrated through numerical simulations of one dimensional strain based plate impact experiments. To demonstrate the generality of model to predict spall under multiaxial loading conditions, an experimental configuration in which a flyer plate impacts the base of a solid right circular cone has been simulated. The computational modeling has been performed with thermomechanical coupling. The mechanical threshold stress plasticity model, the new proposed failure model, and the equation of heat conduction have been implemented in the finite element code Abaqus. Results from these simulations are presented and discussed in comparison with the experimental results. This shows the capability of the model in matching the experimentally observed spall patterns in the solid cone.