Estimation of Fatigue Life of Notched Specimens of P91 Steel by Analytical Approaches

To understand the effect of multiaxial state of stress at laboratory scale, specimens with different kinds of notches are widely used. In this investigation, the effect of notch root radii on low cycle fatigue life of P91 steel has been studied. Fatigue tests were carried out on notched specimens having notch radius of 1.25, 2.5 and 5.0 mm at net stress amplitudes of 250, 300 and 350 MPa at 823 K. To estimate the fatigue life in the presence of a notch based on local strain at the notch root, different analytical approximation methods such as linear rule, Neuber’s rule and strain energy density approach have been employed. The fatigue life could be predicted within a factor of ±16 on experimental fatigue life. The difference among the predicted fatigue lives by the different analytical methods decreased with increasing notch radii. The strain energy density method and linear rule predicted nearly equal fatigue lives in all the cases.