Stress state dependent phase field modeling of ductile fracture

The simulation of ductile fracture is commonly performed with uncoupled damage modeling techniques using the finite element method. In this approach, damage evolution is defined by a failure criterion, and the failure itself is simulated by deleting elements. The local nature of this modeling process results in significant mesh dependency in both crack initiation and propagation phases for certain geometries. Non-local methods have been proposed as a solution to such issues in failure simulations through the introduction of a length scale. The phase-field fracture method is used in this work to address mesh dependency problems in the ductile failure simulations of Inconel 718. The Johnson-Cook and modified Mohr-Coulomb damage criteria for Inconel 718 are utilized in both the uncoupled approach and phase field fracture model. Finite element simulations are performed with varying element sizes and orientations in the crack propagation region, and the results are compared with the experimental observations. Uncoupled ductile failure simulations are performed with Abaqus/Explicit solver while the phase field fracture simulations utilize Abaqus/Standard, and the models are implemented through user subroutines for both methods. Results indicate that the phase field fracture method can be an efficient solution to the mesh dependency problem for ductile fracture simulations.