Modeling void nucleation and growth within periodic clusters of particles

The effect of particle clustering on void damage rates in a ductile materia l under triaxial loading conditions is examined using three-dimensional fin ite element analysis. An infinite material containing a regular distributio n of clustered particles is modeled using a unit cell approach. Deformation strain states characteristic of sheet metal forming are considered; that i s, deep drawing, plane strain and biaxial stretching. Uniaxial tensile stre ss states with varying levels of superimposed hydrostatic tension are also examined. The orientation of a particle cluster with respect to the directi on of major principal loading is shown to significantly influence void dama ge rates. Early in the bulk deformation process, a particle cluster that is aligned with the direction of major principal strain experiences a more ra pid accumulation of plastic strain, resulting in premature void nucleation. After void nucleation, however, the plastic strains within a cluster orien ted transverse to the major principal strain quickly overcome those of the aligned case, leading to higher overall void damage rates. (C) 1998 Elsevie r Science Ltd. All rights reserved.