Continuum damage mechanics-based approach to the fatigue life prediction for 7050-T7451 aluminum alloy with impact pit

A continuum damage mechanics-based approach is proposed to predict the fatigue life of 7050-T7451 aluminum alloy that has undergone foreign object impact damage. Lemaitre's plasticity damage model is adopted to evaluate the damage field arisen from impact. Then Chaudonneret's damage model is applied to the fatigue damage accumulation caused by cyclic loading. The numerical dynamic analysis simulating the foreign object impact process is conducted to obtain the plastic strain history and the residual stress field. Fatigue damage evolution is implemented by the finite element method via coupling operations on the damage field and the stress field. The fatigue test for specimens with an impact pit is conducted to validate the aforementioned approach. The predicted life and the site of crack initiation are in accordance with the test results. Finally, the effects of impact plastic damage, residual stress, impact pit depth, and radius on the fatigue life are investigated.