Phase field modelling of fatigue crack growth at constant and variable amplitude loading

The phase field method is a diffuse boundary solution to complex multi-phase problems with temporally evolving boundaries. In this work, through a methodology based on the variational approach to fracture, the phase field method is used to predict fatigue crack growth numerically. Rather than user elements, an analogy between heat transfer and the phase field equation is exploited to allow the use of pre-existing coupled temperature-displacement elements. The influence of material fatigue parameters on the crack propagation path is studied in benchmark cases. Crack propagation paths confirmed by experimental data are achieved. An alteration to existing fatigue damage formulations is proposed, to capture the crack closure phenomenon. This addition is found capable of simulating crack retardation effects due to an overload, allowing the establishment of a phase field fatigue model capable of realistically modeling variable amplitude loading in the tensile region.