Rolling Contact Fatigue Life and Spall Propagation of AISI M50, M50NiL, and AISI 52100, Part II: Stress Modeling

This is the second part of a three-part series that investigates the rolling contact fatigue initiation and spall propagation characteristics of three bearing materials, namely, AISI 52100, VIM-VAR M50, and VIM-VAR M50NiL steels. A systematic investigation of the effects of rolling contact fatigue (RCF) on the evolution of material properties and microstructural changes resulting in spall propagation rate has not been conducted. As a first step toward understanding spall propagation, we present stress distribution in the neighborhood of a spall initiated by RCF by an indent on a hybrid 40-mm ball bearing. Elastic and elastic-plastic subsurface stress fields are computed using finite element models that incorporate the full three-dimensional (3D) ball-raceway geometry. The stress fields predicted indicate extensive yielding around the spall edges. The spall is shown to widen first axially across the width of the raceway, causing the ball to unload as it enters the spall. The effect of the potential impact on the spall trailing edge is also considered. The proposed scenario involves repeated application of contact stress resulting from a combination of ball static and the impact loads results in extensive plastic deformation of the spall trailing edge, leading to degradation and release of material resulting in spall propagation.