Fatigue crack initiation at a notch

A short crack approach has been developed to determine the fatigue crack initiation life at a notch tip, in which the initiation life is assumed to correspond to the period during which an initial crack, equivalent to a microscopic defect, grows to attain a detectable size. This approach is compared to conventional local strain approach and it is shown that the short crack approach gives acceptable predictions as compared to experiments, in the 2024 T351 alloy. In the 7449 alloy, a different approach, using marker-band technique has been applied to determine the short crack growth kinetics at a notch. The advantages and disadvantages of the conventional strain based approach and the short crack model are discussed.