X-Ray Study of Surface Residual Stress Produced in Fatigue Process of Annealed Metals

Abstract

Changes in surface residual stress during fatigue process of annealed specimen are investigated adopting X-ray stress measurement. It is found that in torsional fatigue a tensile residual stress appears in the early stage of fatigue process, which is insensitive to the alternation of applied stress range. Meanwhile in bending fatigue, the residual stress produced during stress alternations is fairly dependent on the range of applied stress. For instance, in the case of completely reversed bending fatigue, compressive residual stress is produced at the early period of fatigue process. Considerations are made on the mechanism of the changes in residual stresses, in connection with the behavior of microscopic lattice defects during fatigue process. The effect of residual stress on fatigue life is also discussed.