Analysis of void coalescence accounting for nonuniform void distributions

Abstract

Void growth and coalescence are investigated in a class of non-uniform void populations under load conditions of overall axial symmetry. Fast Fourier transform based finite strain calculations were carried out using three-dimensional periodic cells containing monodispersed equiaxed voids embedded in an elastic–plastic matrix with isotropic linear hardening. Constant stress triaxiality was maintained in a given calculation and a range of triaxialities were explored. Both the overall stress–strain relation of the porous material and the evolution of porosity are natural outcomes to this type of analysis. In particular, circumstances were examined under which a transition to uniaxial straining of the cell occurs, thereby introducing a measure of ductility. The results show that nonuniform void dispersions do not necessarily lower the overall ductility relative to a reference ordered (simple cubic) dispersion. This finding is interpreted in light of the inherent competition between a recently uncovered phenomenon of distribution softening and persistent isotropy in void spacing evolution.