Microstructure-based fatigue modelling with residual stresses: Prediction of the fatigue life for various inclusion sizes

In this study, the inclusion induced fatigue failure of a high-carbon bearing steel was investigated. The experimental results showed that the size of calcium aluminate inclusions observed near the fatigue crack initiation site ranges from 12.5 mu m to 33.2 mu m and the size has a pronounced impact on the fatigue life. A microstructurebased model that considers the residual stresses between the steel matrix and inclusions induced by the heat treatment of the steel was developed and applied to investigate the effect the inclusion size on fatigue properties. The detailed model parameter calibration strategy and its validation were illustrated. It is concluded that the model considering the residual stress showed very good predictive capability of the S-N curves for different inclusion sizes, while the model without residual stresses failed to reflect the inclusion size effect on the S-N curve. In addition, based on the simulation data with accurate inclusion size control, an analytical relation between fatigue life, fatigue stress, and inclusion size was proposed for the investigated steel.