Estimating the effect of cold forming and post processing on fatigue of high strength steels under component-related loading conditions

Stamping and shot peening of chassis components such as wheels and cross beams introduce residual stresses that affect the fatigue life. The tensile residual stresses from stamping are often found in the most critical areas for fatigue. These areas are commonly subject to bending stress states while smooth material fatigue data for steel sheets more commonly is obtained by uniaxial testing. Both the sensitivity to residual stresses and change in load condition are material dependent posing a challenge in fatigue life estimation of formed and shot-peened specimens. This paper aims to provide a convenient tool for high cycle fatigue life estimations in these conditions solely dependent on uniaxial tensile properties without parameter fitting. The underlying causes for the material dependency is discussed and reflected in the methodology. Uniaxial fatigue testing and fatigue testing of formed specimens with and without subsequent shot peening are performed for validation. • A method for estimating the reduced fatigue life due to cold forming. • A method for estimating the increased fatigue life due to shot peening. • Discussing the relation between fatigue, stress gradients, and monotonic tensile properties. • Exploring the effect of shot peening on fatigue of different steel grades. • Validated through fatigue testing of bent specimens.