Effect of hardening induced by cold expansion on damage fatigue accumulation and life assessment of aluminium alloy 2024

Hole cold expansion (HCE) is an effective method to prolong the fatigue life of mechanical structures because it introduces residual compressive tangen- tial stresses around the expanded hole. The enhancement method of fatigue life and the crack initiate and growth behavior of a holed specimen was investigated by using the 2024 Aluminum alloy. The purpose of present study is to propose a simple technical method for enhancement of fatigue life in a hole cold expansion of pre-cracked spec- imen. Fatigue damage accumulation of cold expanded hole in aluminum alloys used in land transportation components was investigated. Tests were carried out using pre-cracked SENT specimens. Tests were performed in two and four block loading under constant amplitude. Two sequences were com- pared. The increasing and the decreasing magnitude were compared. The experi- mental results were compared to the damage calculated by the Miner's rule and a new simple fatigue damage indicator. This comparison shows that the ‘model of the mage stress’, which take into account of the loading history, yields a good estimation of the experimental results. Moreover, the error is minimized in comparison to the Miner's model.