A fully numerical life prediction framework for notched structures under different types of creep-fatigue loadings and damage mechanisms

This study investigated the behavior of double-notched specimens under two types of creep-fatigue interaction (CFI) loadings, including conventional strain-controlled creep-fatigue interaction (CCFI) and hybrid stress–strain controlled creep-fatigue interaction (HCFI) loadings. In the experimental part, this work presented the first experimental investigation of damage mechanisms in double-notched specimens subjected to HCFI loadings. Notably, the results revealed that under HCFI loadings with constant dwell stress, damage is driven by progressive microstructural degradation at the specimen core, rather than by stress concentration at the notch root. In contrast, under CCFI loadings, stress concentration at the notch root plays a dominant role in damage development. Furthermore, a full numerical creep-fatigue analysis (FN-CFA) method, independent of multiaxial parameters, was developed to predict the CFI life of notched specimens. This method also accurately captured the transition in maximum damage location. Overall, this study provides critical insights into the damage mechanisms of geometrically discontinuous structures under CFI loadings and introduces advanced damage assessment and life prediction methods essential for the design of high-temperature components.