Re-recognition of deep spalling damage mechanism of rolling contact fatigue under heavy load

This paper presents a detailed analysis of the nucleation and propagation of surface-initiated crack in rolling contact fatigue (RCF) of bearing steel under heavy load. The cracks initiated from the junction of machining marks and trailing edge of dents formed by the plastic deformation. Crack propagation and spalling were mainly composed of three stages: (1) cracks initiating from surface defects propagate downward to form small spalling pits; (2) due to the surface stress and the maximum Hertz stress form a stress bridge, the cracks continue to expand towards the Hertz stress peak forming big spall; (3) the trailing edge of the spalling pit is used as the stress raiser to initiate next subsurface cracks and spalling expansion in successive. Different from previous understanding on the formation of subsurface-initiated spalling, the results indicate that under heavy load the spalling at depth of the maximum shear stress zone in the subsurface can initiate from surface cracks.