Fatigue life estimation under complex loading

The cyclic property of aluminum alloy sheet LY12-CZ is quantitatively reported using accumulated plastic hysteresis energy under cyclic loading as the damage criterion. Nonlinearity of damage accumulation with cycle number under cyclic loading is demonstrated. The formula used to calculate instantaneous plastic strain energy is derived. The total dissipated plastic strain energy for the whole life period is calculated and its variation with stress range is shown. Fatigue damage is separated into static tension damage and cyclic damage. The above analysis is used to develop a fatigue life estimation model. Comparisons of the model predictions and corresponding experimental data show satisfactory agreement.