A dilatational plasticity theory for viscoplastic materials

The dilatational plasticity theory of [J. Engng. Mater. Tech. 99 (1977) 2] is generalized in this paper for viscoplastic materials. A unit-cell model of a viscoplastic matrix containing a microvoid is adopted to establish the viscoplastic constitutive relations for voided, dilating materials. Approximate analytic constitutive relations are proposed, which not only have the correct asymptotic limits but also agree well with the unit-cell model.