Effects of crystal elasticity on rolling contact fatigue

Rolling contact fatigue (RCF) is one of the primary damage modes for properly installed and lubricated rolling element bearings. Historically, because RCF is a stochastic process, extensive testing with subsequent statistical analysis is required to calibrate models that enable confident prediction of expected bearing service life. Recent research has focused on using computational models of microstructure topology to simulate the scatter in bearing life results. In this study, the anisotropy of the grain crystals and the grain texture of the microstructure are taken into account in addition to the explicit representation of the microstructure topology. Starting with a topological microstructure of Voronoi elements representing the material grains, each grain is assigned a cubic material definition and a set of random Euler angles to define the orientation. This microstructure is then converted into a 2D finite element model and a Hertzian contact is passed over the surface of the polycrystalline microstructure to simulate a roller bearing loading cycle. The maximum shear stress reversal and its location are calculated. Due to mismatch in the orientations of grains, stress concentrations develop on the grain boundaries leading to higher shear stress ranges than those calculated for an isotropic material. Depths of the maximum shear stress range show good agreement with experimental observations of crack initiation locations. The shear stress range and location are used to calculate the relative life of the bearing; evaluating many microstructural domains demonstrates that the life scatter produced by various microstructures relates well to the experimentally observed scatter in bearing life.