A simulation of growth and coalescence of voids during ductile fracture

During tensile fracture of ductile metals, damage usually percolates from small clusters of microvoids. Experimental observations suggest that a cluster geometry of three closely spaced voids appears especially susceptible to accelerated void growth and coalescence from which fracture propagates. In this study, a three-dimensional finite element model has been developed to simulate the growth and coalescence within a cluster of three equal sized, initially spherical voids, spaced one void diameter apart, and embedded in a tensile specimen. The results show that, while void growth initially occurs at a rate close to that predicted for an isolated void, the growth rate accelerates with strain in a manner that depends on strain hardening and specimen necking. Significantly, a load limit develops within the inter-void ligament at strain levels that are close to the strain hardening exponent, suggesting a void coalescence criterion that depends on strain hardening in a sensitive manner.