A LOW CYCLE FATIGUE LIFE PREDICTION MODEL OF SINGLE CRYSTAL NICKEL-BASED SUPERALLOYS USING CRITICAL PLANE APPROACH COMBINED WITH CRYSTALLOGRAPHIC SLIP THEORY

The anisotropy is the most remarkable characteristic for single crystal nickel-based superalloys, which makes fatigue behavior and life prediction highly correlate with the crystallographic orientation. Based on critical plane approach and preferred crystallographic slip mechanism, an anisotropic LCF life model is proposed to account for orientation dependent fatigue life in this paper. In addition, the effects of the mean stress and stress-weakening caused by asymmetric loading are also considered. The critical plane is determined by searching for 30 potential slip systems. Moreover, the slip plane with the maximum resolved shear stress amplitude in the crystallographic microstructure of the single crystal nickel based superalloy is chosen as the critical plane. The LCF test data are utilized to obtain the regression equation by multiple linear fitting method. The presented LCF life model is applicable for more complex stress state and has higher prediction accuracy than the CDY model.