Subsurface residual stress concentrations during rolling contact fatigue

The accumulation of plastic microdeformation during cyclic stressing under rolling contact loading conditions, as in ball and roller bearings, results in a complex state of residual stress. A tri-axial state of residual stress develops in the subsurface region below the contacting surfaces exhibiting components of macro residual stress, compressive in both the axial and circumferential directions and tensile in the radial direction. In this paper, consequences of the developed residual stress state and of the changes in micro-yield behavior of the hardened bearing steel are discussed, together with a presentation of radial-residual stress depth distributions as measured on cross-sectioned samples. The residual stress-depth map over a cross-sectional plane through the inner ring shows a strong temperature influence on the penetration depth of the developed state of residual stress. Apparently the depth at which micro-yielding will occur, which gives rise to the development of residual stresses, depends strongly on the bearing operating temperature.