A Comparison of Void Growth and Ductile Failure in Plane and Axisymmetric States of Strain

Abstract

Finite element studies of the plastic deformation of a model of a periodic array of voids have shown that the deformation before strain concentrates in the inter-void ligament leading to void coalescense, is very much greater in axisymmetric than in plane states of strain. In experimental tests of notched tensile specimens which produce plane and axisymnetric states of strain in a range of stress states with different hydrostatic components the strain to cause ductile failure by void coalescense does not depend on the state of strain. The void growth calculations and the experiments are reconciled by the view that ductile failure initiates in the most favourable statistical irihomogeneity in which the local strain state does not necessarily correspond to that applied remotely.