Residual stress relaxation and re-shot-peening process of wet shot-peened titanium alloy during tensile fatigue load

Abstract

The surface of TC4 titanium alloy was treated by wet shot-peening (SP). The residual stress relaxation during high and low cycle tensile fatigue was studied, and the effect of re-shot-peening (RSP) on fatigue life was discussed. The results show that relaxation of compressive residual stress still occurs under tensile stress. The fatigue load level has an important influence on the relaxation rate, degree and range of compressive residual stress field (CRSF) of shot peened TC4 titanium alloy. Residual stress relaxation during high cycle fatigue (HCF) mainly occurs in the near surface layer of 0-30 μm, and the relaxation rate is slow, while residual stress relaxation in low cycle fatigue (LCF) mainly occurs in the range of 0-80 μm, which is deeper and faster. RSP also has a great influence on the fatigue life of TC4 titanium alloy. It can significantly improve fatigue life at 25% and 50% of initial SP fatigue life, but has little effect on fatigue life at 75% of initial SP fatigue life. In addition, the strengthening effect of RSP is related to the level of fatigue load, which improves the HCF life obviously.

Keywords

• wet shot-peening
• relaxation of residual stress
• re-shot-peening
• fatigue property