A Novel Viscosity-Based Model for Low Cycle Fatigue-Creep Life Prediction of High-Temperature Structures

Damage evolution during low cycle fatigue, creep, and their interaction behavior is actually a ductility exhaustion process in response to cyclic and static creep. In this article, a novel viscosity-based model for low cycle fatigue-creep life prediction is presented in an attempt to condition viscosity-based approaches for general use in isothermal and thermo-mechanical loading. In this model, it was assumed that only plastic and creep strains caused by tensile stress lead to ductility consumption under stress-controlled loading. Moreover, with its simple expression, the mechanisms of the loading waveform, temperature, and mean stress effects are taken into account within a low cycle fatigue-creep regime. Predicted fatigue lives using the proposed model were found to be in good agreement with reported experimental data from literature. Compared with the generalized strain energy damage function method, the mean strain rate, Smith-Watson-Topper and Goswami's ductility models, the proposed model is widely applicable and more precise in the prediction of low cycle fatigue-creep life.