Mechanistic driving force for martensite decay in rolling contact fatigue

Martensite decay due to large scale microstructural alterations is the main fatigue process which occurs during extensive rolling contact fatigue in bearing applications. Despite its practical and scientific importance, the full description of the controlling phenomena is still incomplete. Here, we demonstrate that the main mechanistic driving force for martensite decay comes from the positive components of the principal subsurface stress tensor. Such a conclusion is derived using the concept of Continuum Damage Mechanics where the damage rate is controlled by the elastic energy release and plastic strain range. Modeling results are compared with experiments and a good quantitative agreement is obtained. The analysis presented here illuminates the mechanistic reasons on why the fastest material decay occurs at the depth corresponding to the so-called maximum orthogonal shear stress.