Microstructural observation of overload effect on the fatigue crack growth of 2024-T3 Al-alloy

Microstructural investigation of fracture surfaces after fatigue crack growth experiments on 2024-T3 centrally cracked specimens was carried out. Variable amplitude loadings were used with periodic overload cycles added to constant amplitude cycles. During fatigue tests when R = 0.1, for every 1000 cycles 1, 2, 3, 4 and 5 overload was applied. The fatigue fracture surfaces were examined in the scanning electron microscopy (SEM) to obtain more detailed information on crack growth contributions of different overload cycles and it was shown that fatigue crack growth retardation occurred when periodic overload cycles were applied after every 1000 cycles.