A Fatigue Model Incorporating Temperature Effect for Predicting High-Cycle Fatigue Life of Alloys

In this study, a high-cycle fatigue model that incorporates temperature effect has been developed based on the theoretical analysis of fatigue thermal activation energy and fatigue damage rate. The temperature and the fatigue life are integrated into a new combined high-cycle fatigue parameter and a cubic polynomial relationship between this combined parameter and the fatigue stress is established. This model can unify the high-cycle fatigue test data under different temperatures into one multifactorial quantitative equation. To validate the fitting capability of the proposed model, it was applied to fit 18 different alloys: 6 titanium alloy, 8 nickel-based superalloy, 2 carburized steel, and 2 single-crystal superalloy. The experimental data of these alloys were concurrently fitted using both the proposed model and the three-parameter S-N model for comparative analysis. The fitting performance of the two models was evaluated and compared based on the root mean square error (RMSE) and the coefficient of determination (R 2 ). The results of the comparison demonstrated that the proposed model exhibited fitting ability for different alloys. In addition, compared with the three-parameter S-N model recommended in standards, the proposed model incorporates the temperature effect and it enables the prediction of high-cycle fatigue life at untested temperatures based on existing experimental data. The predictive accuracy of the model was verified utilizing experimental data from six different alloys: TC4 titanium alloy, TC11 titanium alloy, K4169 superalloy, DD6 single-crystal superalloy, FGH96 superalloy, GH706 superalloy.