In-situ experimental investigation and prediction of fatigue crack growth for aluminum alloys under single spike-overloads

Fatigue crack growth behaviors of three aluminum alloys under single overload are investigated by in-situ optical microscopy testing and in-situ SEM testing. The results show that the shape effect of overload-induced plastic zone leads to a larger crack growth retardation range than that assumed in Willenborg model. Besides, the crack closure effect based on general form of Paris law cannot correlate the post-overload crack growth, but a bi-linear form fit the measured effective stress intensity factor behavior well. Moreover, the crack-front plasticity effected range can match the retardation extent. A modified Willenborg model is proposed to predict crack growth retardation.