Surface Residual Stress in Automotive Components: Measurement and Effects on Fatigue Life

The effect of surface processing of automotive components was studied by X-ray diffraction (XRD) to investigate the relationship to component fatigue life. A new methodology was introduced to determine residual stress magnitudes and depth profiles of the residual stress distribution. Surface microstructural characteristics and weighted depths of penetration were taken into account to obtain accurate residual stress measurements and profiles. Residual stress profiles were used in AFGROW software to evaluate the effects of surface conditions on fatigue life and on the initial critical flaw size that can be tolerated in a component with given life requirements, subjected to various loading conditions. The method presented in this paper can be applied to measure residual stresses and evaluate numbers of cycles to failure and critical flaw sizes for components with various size/geometry/material, surface grain structure, degree of surface residual stress, and dynamic loading conditions.