Prediction of Thermo-Mechanical Fatigue Life of IN738 LC Using the Finite Element Analysis

This paper describes a study we performed on predicting the thermo-mechanical fatigue (TMF) life of the nickel-based superalloy IN738LC, which is the main material of gas turbine blades. Gas turbine blades experience mechanical fatigue and thermal fatigue as a result of centrifugal force and flames. Furthermore, gas turbine blades experience low cycle fatigue due to frequent startups and shutdowns. In the case of low cycle fatigue behavior that a large plastic deformation mainly occurs, the fatigue life can be decided by the plastic strain amplitude. The hysteresis loop of the material should be derived to obtain the plastic strain. However; precise experimental techniques are required to derive the hysteresis loop, which, in turn, require extensive time and effort. Thus, it is necessary to develop a simple method to obtain the hysteresis loop without the TMF test. In this study, we performed the TMF test and obtained the hysteresis loop and fatigue life curves. We also derived the hysteresis loop and predicted the fatigue life through finite element analysis (FEA). The analysis results were verified by comparison with the experimental results. As a result, the fatigue life of the IN738LC can be predicted with FEA.