A combined high and low cycle fatigue life prediction model for hydraulic turbine runner welded joints considering mean stress effect

To characterize the nonlinear damage evolution, a new coupled damage term is proposed within the framework of the Palmgren-Miner (P-M) rule, explicitly considering the interaction between the maximum load, stress amplitude ratio, and frequency ratio. The robustness and accuracy of the proposed model were validated using experimental results from the welded joints and four additional alloy materials. By effectively mitigating the non-conservative bias and excessive conservatism inherent in existing methods, this study provides a reliable tool for fatigue life prediction of welded structures under CCF loading spectra. By effectively mitigating the non-conservative bias and excessive conservatism inherent in existing methods, this study provides a reliable tool for fatigue life prediction of welded structures under CCF loading spectra.