Evaluation of crack growth direction criteria on mixed-mode fatigue crack growth experiments

The predictive capabilities of different fatigue crack growth direction criteria in finite element simulations are investigated. Crack growth direction criteria based on stress intensity factors, energetic measures and kinematic (displacement) measures are evaluated for mixed-mode fatigue crack growth experiments in the literature. More specifically, the development of the experimentally found crack path is simulated numerically, and the directions from the different criteria are compared to the known crack path along the development of the fracture. The simulated experiments featured proportional and non-proportional loading. Of the evaluated criteria, those based on energetic and displacement measures are able to accurately capture the tensile-mode fatigue crack growth direction for all examined experiments. Furthermore, the displacement-based criterion is able to capture the direction of shear-mode crack growth as well as the transition from shear- to tensile-mode growth and the subsequent tensile-mode growth. Modeling the cyclic elastic plastic material response does not improve the accuracy of the predicted directions for the considered cases.