On the influence of void clusters on void growth and coalescence during ductile fracture

Based on the behavior of a three-void cluster embedded within a representative volume element, this study utilizes three-dimensional finite element analyses to examine the sensitivity of void growth and coalescence to strain hardening, multiaxial stress state and inter-void spacing. The strain-induced growth of voids within the cluster is accelerated when the voids are closely spaced in a low strain-hardening material subject to high levels of stress triaxiality. Far-field deformation causes strain to concentrate within the inter-void ligament, and the resulting behavior induces a load-loss response of the inter-void region. Based on the load-loss criterion for the onset of void coalescence, the results show that coalescence is accelerated by increasing stress triaxiality and decreasing strain hardening and inter-void spacing. A straightforward analysis is then presented that relates void coalescence to (a) the strain-hardening exponent and (b) the dependence of the plastic constraint factor within the inter-void ligament on strain, the latter being sensitive to far-field stress triaxiality and void geometry. (C) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.