High-temperature LCF life estimation based on stress gradient effect of notched GH4169 alloy specimens

Based on the Neuber's rule and Walker equation, a new measurement method considering the influence of mean stress and stress gradient is proposed. A stress gradient factor is defined to correct the traditional Walker equation; thus, it is easy to estimate the life of the structural components only based on the purely elastic finite element analysis. The low-cycle fatigue experiment was carried out by using the direct aging GH4169 notched specimen with different stress concentration factors under evaluated temperature. The fracture morphology of specimens was analyzed to determine the crack initiation position and the damage mechanism. The data points of the experiment life and the estimation life are correlated well within a three times scatter band. It indicates that the Walker equation corrected by introducing a new kind of measurement of stress gradient is reliable to estimate the notched specimen fatigue life.