Effects of Machining Induced Residual Shear and Normal Stresses on Fatigue Life and Stress Intensity Factor of Inconel 718

Residual shear stresses and normal stresses induced by machining affect the fatigue performance of components. Thus, residual shear and normal stresses should be considered simultaneously when evaluating the influence of residual stress on fatigue performance. In the present paper, the influences of residual shear and normal stresses on the fatigue life and stress intensity factor (SIF) of turned Inconel 718 were investigated. Firstly, the cos alpha measurement method was utilized to calculate the residual shear stress and residual normal stress of turned Inconel 718. Then, the combined effects of residual shear and normal stresses on fatigue life were evaluated through uniaxial tension-tension fatigue tests. Thirdly, a prediction model for the SIF was proposed by taking the residual shear and normal stresses into account. Finally, the predicted SIF was validated by the published experimental data from the literature. The predicted results of the proposed model generally agreed well with the available experimental data.