Mechanisms and modelling of fatigue crack growth under combined low and high cycle fatigue loading

In this paper a mechanism-based model is presented, which is able to describe the evolution of microcracks under pure low cycle fatigue (LCF) and combined LCF and high cycle fatigue (HCF) loading conditions. In order to verify the model and to calibrate the model parameters, the crack length evolution of microcracks is followed at room temperature for pure LCF and combined LCF/HCF loading in a 10%-chromium steel. These studies reveal accelerated crack growth rates under LCF/HCF interaction as soon as a critical crack length is reached. The model is capable of accounting for this effect and needs only few parameters, including the threshold for fatigue crack growth, whose knowledge is crucial for the accuracy of the model.