Influence of Residual Stress on Fatigue Life of Hot Forged and Shot Blasted Steel Components

Hot forging is a common manufacturing process for the production of large quantities of engineering components. Residual stresses are developed in forged components as a result of various aspects of the manufacturing process, including subsequent cooling, and heat treatment. Residual stresses can significantly affect the deformation and fatigue failure of materials. Hot forged EN15R steel bars were studied. Four batches of specimens representing different stages of the forging process were employed. Residual stresses introduced by the process were measured by X-ray diffraction technique. Fatigue tests were carried out on fourteen specimens from each batch. Weibull distribution for fatigue data was considered. It was found that compressive residual stress had no benefit under low cycle fatigue (LCF) because the residual stresses were completely relaxed due to the large plastic deformation but had a beneficial effect on high cycle fatigue (HCF).