FEM simulation of fatigue crack growth

Fatigue crack growth in various plane specimens made from Al alloys was simulated by the two-dimensional elastic-plastic finite element method. Cyclic plastic deformation and classic low-cycle fatigue criteria for material at the crack tip were used for a direct prediction of the immediate crack rate. Such plane stress calculations give a good estimation of the fatigue crack rate in thin plates under constant amplitude loading and explain the well-known retardation or acceleration of the crack after typical sudden changes of the loading cycle. The overload effect seems to be the most important. However, a similar plane strain model of the fatigue crack in a thick-walled body gives unrealistic low values of the rate.