Ductile fracture crack phase-field model equipped with a novel degrading fracture toughness

Abstract

This study aims to enhance the crack phase-field model for ductile fracture by introducing a novel degrading fracture toughness to reflect damage evolution based on the phenomenological justification for the failure mechanism in elastoplastic materials. The free energy consists of elastic, pseudo-plastic and crack components. The governing equations are derived as stationary conditions for the corresponding local and global optimization problems within the continuum thermodynamics framework. Then, we introduce a degrading fracture toughness to reflect the evolution of micro-defects and their coalescences that are caused by both plastic deformation and negative hydrostatic pressure. Equipped with this implement, the proposed crack phase-field model realizes the reduction of both stiffness and fracture toughness to simulate the failure phenomena of elastoplastic materials. Two numerical examples are presented to demonstrate the capability of the proposed model in reproducing typical ductile fracture behaviors.