Qualitative and quantitative characterizati ons of fracture surfaces of AL6XN super-austen itic stainless steel fatigued at different stress amplitudes

Fracture surfac e featu re s of the AL6X N super-austenitic stainless steel fatigued at different stress amplitudes were observed by SEM and quantitative ly analyzed by a fractal method. It was found that the mor phologies corresponding to three character is ticzones of fracture surface, i. e. , fatigue crack source (or in itia t io n) zone , crack growth zone and final rapid fracture area , are more or less related with the applied stress amplitude D s/2. A quanti tative relationship between the total fatigue life and theaverage fractal d imension of scanning profile of fractures urface was experimentally established . The lower the fractal dimension, the longer the fatigue life is . A similar change of fractal dimension with the applied Ds /2 in the fatigue crack source and groth zones suggests that crack initiation and propagation lives might contribute comparably to the resulting total fatigue life of the AL6XN super-austenitic stainless steel tested under constant stress amplitude control.