Phase-field modeling of 3D fracture in elasto-plastic solids based on the modified GTN theory

Abstract

An appropriate failure model of ductile materials needs to consider complex phenomena at the microscopic level, such as the nucleation, growth, and coalescence of microvoids and the final fracture at the macroscopic level. A recent popular continuous phase-field method based on the regularization of sharp crack discontinuities can easily model macroscopic cracks. In this work, we developed a coupled model to predict the crack law when materials undergo ductile fracture. The coupling model combined the ductile phase-field fracture model of the material with the shear-modified GTN model to illustrate the microscopic damage accumulation caused by the growth of voids and the macroscopic crack initiation and propagation. In addition, a modified phase-field degradation function was established, combining phase field, void volume fraction, and shear damage. This paper also considers the crack propagation law when the materials undergo ductile fracture under different stress triaxialities. In this study, we used the subroutines UEL and UMAT in the commercial finite element software Abaqus to give the staggering solution algorithm for ductile phase-field fracture of the materials. The shear-modified GTN model was written by the subroutine UMAT, while the ductile phase-field fracture model was written by the subroutine UEL. The results of the numerical simulations showed good agreement with the experimental damage failure mechanisms and the load–displacement curves.