Fatigue Crack Path and Life Predictions in 2D Structures

A methodology to predict the fatigue crack path in generic 2D structures and its propagation life under variable-amplitude (VA) loading considering crack retardation effects is presented. It uses specially developed self-adaptive finite elements to calculate the generally curved fatigue crack path and the associated mixed-mode stress intensity factors KI and KII at each propagation step, assuming constant-amplitude loading and fixed crack increments. This process requires only a few remeshing steps and is computationally efficient. Then, the calculated KI values are fitted by an analytical expression, which is used in a local-approach fatigue design program to predict crack propagation lives under VA loading, considering load interaction effects such as crack retardation or arrest after overloads. This methodology is experimentally validated by fatigue crack growth tests on special specimens, whose standard geometry was modified with holes positioned to attract or to deflect the cracks