Fatigue life prediction of turbine blades based on a modified equivalent strain model

Mean stress is known to exert significant effects on fatigue life prediction. Although numerous adjustments have been developed to explain the influence of mean stress, only a few of such adjustments account for mean stress sensitivity. The Smith-Watson-Topper (SWT) model is one of the most widely used models that can provide satisfactory predictions. It is regarded as a case of a Walker model when the material parameter gamma = 0.5. The Walker equation considers the mean stress effect and sensitivity, and it can generate accurate predictions in many fatigue programs. In this work, a modified model that accounts for the mean stress effect and sensitivity is proposed to estimate fatigue life. Several sets of experimental data are used to validate the applicability of the proposed model. The proposed model is also compared with the SWT model and the Morrow model. Results show that the proposed model yields more accurate predictions than the other models. The proposed model is applied to predict the fatigue life of a low-pressure turbine blade.