Development and application of a micromechanical model for description of the growth and coalescence of spheroidal voids

In this paper a constitutive model for porous ductile metals with spheroidal voids is investigated. The constitutive model used to describe void growth prior to void coalescence is the Gologanu-Leblond model which is a Gurson like model taking into account not only the void volume fraction but also the void shape. To describe ductile rupture, coalescence criteria have been added to this model. It has been shown that a critical porosity used in the Gurson model for the void coalescence stage is limited to a restricted range of triaxiality. In this work we describe the onset of coalescence using both the Thomason and the Brown and Embury criteria. The first one is a plastic limit load criterion, based on the mechanism of plastic localisation in the intervoid ligament. The second one is based on a simple geometric consideration to predict the fracture of the ligament between two voids. This model is implemented into a User Subroutine for Abaqus/Explicit. Some applications of the improved damaged model are shown.