Nucleation and propagation modeling of short fatigue crack in rolled bi-modal Ti-6Al-4V alloy

A numerical procedure centered around the crystal plasticity finite element method was developed for the simulation of fatigue crack initiation and propagation in metallic materials. Damage indicators were derived from theoretical dislocation-based models for the prediction of the crack initiation, crack path and crack growth rate, taking into account slip transfer across grain boundaries. They were incorporated into a numerical framework in which an explicitly growing crack was considered via remeshing technique to account for the redistribution of the micromechanical fields ahead of the crack tip. In this regard, a non-local averaging scheme was applied to account for both the spatial heterogeneity of the stress-strain fields and the grains morphology. The proposed framework was tested on a rolled bi-modal Ti-6Al-4V alloy subjected to a fully reversed uniaxial loading condition. Statistically representative synthetic microstructures were generated by a multi-scale anisotropic tessellation procedure considering the presence of multiple lamellar variants within a prior beta-phase grain sharing the same orientation relationship. The predictions of crack initiation, crack path and growth rate were statistically compared with experimental data from prior study to emphasize the predictive capabilities and limitations of the proposed approach.