A unified rule for high-cycle and low-cycle fatigue life prediction in multi-scale framework

This paper develops a unified rule for both low-cycle fatigue and high-cycle fatigue life prediction from macro-scale to micro-scale. In the macro-scale, the unified rule is proposed on the basis of the concept of the effective strain energy density. In the micro-scale, the unified rule represented by a new fatigue indicator parameter is developed by considering the combined effects of the energies in shear and normal directions for individual slip systems. A large number of low-cycle and high-cycle fatigue experimental data of Inconel 718 superalloy at room temperature is used to verify the prediction capacities of the newly unified rule. Compared with the prediction accuracy of the existing fatigue damage models, the unified rule shows more accurately predicted results for both low-cycle and high-cycle fatigue life. Most of the fatigue experimental data falls into a range within a scatter band of +/- 3 on life.