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Surface-initiated fatigue caused by surface defects is one of the most dominant failure modes for bearing contacts. In this study, a damage mechanics-based Voronoi finite-element model (VFEM) is developed and used to investigate the effects of surface defects (such as dents and fretting wear) in elastohydrodynamic lubricated line contacts. A line contact elastohydrodynamic lubricated model is used to calculate the pressure distributions acting over the surface defects, which are then employed by Voronoi finite-element model to determine subsurface stresses. Continuum damage mechanics-based approach is used to incorporate cyclic damage accumulation and progressive degradation of material properties with rolling contact cycling. The model also takes into account the effects of residual stresses generated during the debris denting process. Using this methodology, the model is used to simulate microcrack initiation, coalescence, and propagation stages, finally a fatigue spall. The locations and patterns of dentinitiated spalls are found to be consistent with experimental observations. The fatigue model is used to study the effects of the topology of the material microstructure, dent sharpness, and material properties on rolling contact fatigue (RCF) life and Weibull slopes.

The current study presents the results and effects of fretting wear on rolling contact fatigue (RCF) life of M50 bearing steel. A fretting wear test rig was designed and developed to induce fretting scars on the surface of standard M50 rods commonly used in a three ball and rod RCF testing machine. The fretting machine was used to induce fretting scars at a Hertzian contact pressure of 1.1 GPa, in the presence of MIL-L-23699 lubricant at a frequency of 10 Hz, slip amplitude of 21 µm for different number of cycles. The fretted rods were then evaluated at a contact pressure of 1.7 and 3.4 GPa in the three ball and rod RCF tester to determine the effect of fretted scar on fatigue life. The results indicate that a fretting scar can reduce the fatigue life at 3.4 GPa by an average of 30 per cent and fretted rods operating at 1.7 GPa behave very similar to an unfretted rod operating at 3.4 GPa.