The effects of positive and negative overloads to fatigue crack growth rate in 2024-T3 aluminium alloy

11 ABSTRACT Master of Science Thesis THE EFFECTS OF POSITIVE AND NEGATIVE OVERLOADS TO FATIGUE CRACK GROWTH RATE IN 2024-T3 ALUMINIUM ALLOY RAMAZAN KALE Anadolu University Graduate School of Sciences Civil Aviation Program Supervisor: Assist. Prof. Dr. Dilek TURAN 2005, 94 pages In this study realized with 2024-T3 Aluminium alloy, the effect of positive and negative overload on fatigue crack growth rate was investigated. The constant amplitude fatigue experiment was done at 0.11 stress ratio. In variable amplitude experiment overloads were superposed on top of constant amplitude fatigue experiment Positive single overload, negative single overload, negative single overload following positive single overload, and positive single overload following negative single overload experiments were performed in the order given. Positive and negative overload ratios were applied as 1.4, 1.7, and 2. At the end of the experiments, by calculating the number of cycles between specified lengths, retardations and accelerations in variable amplitude fatigue experiments with respect to constant amplitude fatigue experiments were determined. While in the case of negative single overload acceleration was observed; in other experiments, retardations of different ratios were realized depending on overload ratio and the sequence of overloads. Keywords: Fatigue, crack growth, aluminium, constant amplitude loading, positive and negative overloading