Modeling Short-Crack Propagation in 3D Polycrystalline Microstructures through Adaptive Crack Insertion

This manuscript describes a computational framework for modeling short-crack propagation in three-dimensional (3D) polycrystalline microstructures. The proposed framework integrates the adaptive crack-insertion scheme with crystal plasticity finite-element modeling to describe the mechanical state of the microstructure under cyclic loading. Crack propagation directions and growth rates are computed a-posteriori, based on local measures of deformation and stress. Spurious oscillations in the local measures are controlled by applying a distance-based smoothing technique to the local stress and strain fields around the crack front. An adaptive local mesh smoothing technique is utilized during each growth step to avoid unphysical localized kinks that tend to nucleate and accumulate under sustained cyclic loading. The performance and sensitivity of the proposed approach to mesh density, cycle-jump parameters, as well as crack model parameters are assessed based on numerical simulations. The capabilities of the model are demonstrated by comparing model outcomes with an experimentally observed microstructural fatigue crack morphology. The proposed approach demonstrates sufficient computational efficiency that facilitates simulation of crack growth in large microstructures subjected to fatigue loading.