A crystal plasticity and cohesive element model for rolling contact fatigue of bearing steels

Rolling element bearing failures are typically initiated by a two-stage process where a subsurface microcrack formed in the material microstructure subsequently grows to a spall spanning the bearing surface. While the crack propagation phase can be modeled using macroscopic models, the localized initiation phase must account for microstructural inhomogeneity. This paper describes such a two-stage approach that uses two distinct models for the initiation and propagation phases in RCF. Both the initiation and propagation models use Voronoi tessellations to account for the granular topology of bearing steel grains. The RCF initiation phase is simulated using a localized submodel approach, where a crystal plasticity (CP) framework is implemented to characterize plastic strain accumulation at the microscale. CP-based metrics are used to correlate the microplasticity developed under RCF loading with the formation of fatigue micro-cracks and the corresponding initiation life estimations. The subsequent macrocrack growth phase is modeled with an intergranular crack propagation model using cohesive elements. The total fatigue life estimates derived from the two-stage model demonstrate a good correlation with RCF bench test data.