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

Purpose 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. Design/methodology/approach The robustness and accuracy of the proposed model were validated using experimental results from the welded joints and four additional alloy materials. Findings 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. Originality/value 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.