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 (∼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.