Recent advances in fatigue crack growth modeling

Recent advances in our understanding of fatigue crack growth processes and respective crack growth modeling techniques are reviewed. Much of the observed experimental behavior (such as the effects of notches, maximum applied stress, crack length, in-plane biaxiality, out-of-plane constraint, and transient loadings) can be explained based on crack closure concepts. Both Dugdale based models and finite element techniques have been utilized. However, so far neither approach has accounted for crystallographic slip effects, grain orientation effects, or microstructural barriers. A model for crack closure with two microscopic crystallographic slip directions is used to model microscopic cracks. The model predicts variations in closure levels as the orientations of the two slip directions, with respect to the crack growth direction, are changed. In addition, a solution is proposed for the asperity micro-contact problem through a unique roughness induced closure model using a statistical description of asperity heights, asperity densities, and material flow properties.