Analysis of Multiaxial Low Cycle Fatigue Life for Single Crystal Ni-Based Superalloy Based on Two-Phase Unit Cell Model

Abstract

Based on micro structure of Ni-based single crystal superalloy, a γ/γ’ two-phase unit cell finite element model was established, and its cyclic stress-strain was simulated under tension/torsion cyclic loading. A low cycle fatigue (LCF) life prediction model of single crystal superalloy was proposed by using cyclic plasticity strain energy as a parameter based on energy dissipation theory. Calculation results of macro finite element model and γ/γ’ two-phase unit cell micro finite element model, and multiaxial LCF test data of CMSX-2 Ni-based single crystal superalloy along [001] orientation were applied to fit the LCF life model by multiple linear regression. The results show that the unit cell model not only reflects the microstructure characteristics of single crystal Ni-based superalloy, but also is better than the macro model in accuracy of analysis, and greatly improve the accuracy of fatigue life prediction. Almost test data fall into the factor of 2.0 scatter band.