Systematic methodology for high temperature LCF life prediction of smooth and notched Ni-based superalloy with and without dwells

This study investigates the computational methodology of estimating the high temperature low cycle fatigue (LCF) strength of smooth and notched directionally solidified (DS) Ni-based superalloy with and without dwells. For the anisotropic LCF of smooth specimens with different strain ratios, a slip system based critical plane concept with modified Smith-Watson-Topper (SWT) parameter is adopted, whose physical basis is discussed. The theory of critical distance is then combined to consider the notch effect. Furthermore, for the strain and stress controlled LCF with dwells in both smooth and notched specimens, the Miner's linear cumulative damage theory is adopted, in which the fatigue damage Df is obtained using above-mentioned methods and the creep damage Dc is calculated by Larson-Miller plots. In spite of the multiple load conditions, all the predicted lives agree remarkably well with experimental results.