ANALYZING DUCTILE FRACTURE USING DUAL DILATIONAL CONSTITUTIVE-EQUATIONS

By adopting a suggestion made by Thomason, a new failure criterion for the Gurson-Tvergaard model has been recently introduced by the author s. In this study, a method based on the Gurson-Tvergaard constitutive model and the new failure criterion is applied to the analysis of duct ile fracture. The main features of the method are that the material fa ilure is a natural process of the development of Thomason's dual dilat ional constitutive responses, and the void volume fraction correspondi ng to the failure by void coalescence is not necessarily a material co nstant and is not needed to be fitted beforehand. Furthermore, void nu cleation parameter(s) can be numerically fitted from experimental tens ion results. This method has been implemented into the ABAQUS finite e lement program via a user material subroutine and is applied to the pr ediction of tension problems conducted by the authors. In the analyses , two strain-controlled void nucleation models have been studied and c ompared. The void nucleation parameters corresponding to the two model s have been calibrated. The crack initiation of both smooth and notche d axisymmetric tensile specimens are well predicted by the method. Fin ally, several critical issues in the analysis of ductile fracture are discussed.