The basic relationships between residual stress, white layer, and fatigue life of hard turned and ground surfaces in rolling contact]

The characteristics of residual stress (RS) profiles and their effects on rolling contact fatigue life for precision turned and ground surfaces with a white layer (WL) are very controversial. This study has shown that: (a) Hard turning with a fresh tool generates a ''hook'' shaped RS profile characterized by surface compressive RS and subsurface maximum compressive RS. While gentle grinding only generates maximum compressive RS at the surface and a shallow subsurface zone of compressive RS. The ''hook'' shaped RS profile with surface compressive RS contributes to a longer (similar to 40%) fatigue life of a machined surface. (b) A turned WL surface by a worn tool generates a high tensile stress in the area of the WL, but becomes more highly compressive in the deeper subsurface than the turned one without a WL. The high tensile RS at the surface leads to a much shorter (7.6 times) fatigue life. (c) A ground WL only shifts the RS to tension but hardly affect the basic shape of the profile for a ground fresh surface. The surface tensile RS coupled with near surface peak tensile RS produces the shortest (7.8 times) fatigue life. (C) 2010 CIRP.