A model for predicting the creep-fatigue life under stepped-isothermal fatigue loading

• A damage-based lifetime model for stepped-isothermal fatigue has been proposed.
• It concerns high frequency mechanical load and low frequency temperature variation.
• Tensile stress per cycle is integrated in the creep damage evolution model.
• Interaction between creep and fatigue damage is considered to be nonlinear.
• Good accuracy of model prediction and application for stepped-isothermal fatigue.

A model is developed herein for predicting the fatigue life of creep-fatigue damage interaction, which is induced by combined high frequency mechanical loading and low frequency temperature variation, i.e. stepped-isothermal fatigue loading. The model is derived from continuum damage mechanics. In the model, the interaction between creep and fatigue damage is considered to be nonlinear. To validate the proposed model, a cast aluminum alloy is fatigue tested at 200–350 °C and 350–400 °C. The results show that good agreement can be achieved between predicted life and experimental data.