Method for fatigue life prediction of notched specimen with considered stress relaxation

In order to efficiently and accurately obtain local stress/strain at notch under cyclic loading and predict the notch fatigue life, a stress/strain simplified calculation method was developed based on viscoplastic constitutive equations and the test results of stress/strain for smooth specimens under cyclic loading. The errors between the stress/strain calculated by the developed method and test results are within 5% for smooth specimens. The simplified calculation method combined with life prediction equation was used in the fatigue life prediction of powder metallurgy superalloy FGH97 semi-circular single-edge notched specimens by iteration. The results show that the stress relaxation at notch root is fully considered by the developed method, and the fatigue life prediction of FGH97 unilateral circular notch specimens give good estimation with a scatter band of less than 2.