An elastic-plastic finite element model for rolling contact fatigue

Abstract

Rolling contact fatigue (RCF) is a dominant source of failure in tribo-machinery. The two most important failure mechanisms in RCF are sub-surface originated spalling and surface originated pitting. In this study, both the fatigue damage mechanisms are investigated using a Voronoi finite element (VFEM) model in conjunction with a continuum damage mechanics approach. The combined methodology allows for evaluating the effects of material microstructure topology on fatigue life. First, by coupling an EHL line contact model with VFEM and effects of surface dents on fatigue life is evaluated. Next, the VFEM is extended to incorporate elastic-plastic material behavior in order to study the effects of material plasticity on RCF. Mises based plasticity model with kinematic hardening is employed to include the effects of material plasticity. The fatigue lives, spall patterns and fatigue life scatter obtained for surface and sub-surface initiated fatigue are found to be in good corroboration with experimental observations. Further, using the elastic-plastic finite element model, the effects of plasticity induced residual stresses on fatigue life is determined. Based on the numerical results, generalized equations are proposed in order to estimate the optimum preload required for achieving maximum enhancement in rolling contact fatigue life. Finally, the current model is combined with Fick\u27s law for stress assisted diffusion in order to capture carbon migration occurring during RCF. Using this approach, the microstructural alterations which are commonly observed in fatigued bearing microstructure are predicted which are found to be consistent with experimental findings