Abstract
Small fatigue crack initiation behaviour in a series of specimens containing different sizes of micro-notch has been observed through RepliSet system during interrupted low cycle fatigue tests. From the replicating observations, very initial single crack or multiple cracks near the micro-notch area can be captured. Since then, the crack initiation life for each specimen can be determined. Computationally, a numerical procedure with a combination of crystal plasticity theory and finite element implementation has been constructed for predicting small fatigue crack initiation life as well as identifying the crack initiation sites near the micro-notches. With the help of fatigue indicator parameter represented by accumulated plastic slip, the predicted numbers of cycles for the submodels with various micro-notch sizes agreed with the experimental ones. In addition, the simulation results can successfully reveal the mechanism in crack initiation sites. The stress concentration effect was found to be responsible for corner crack initiation, while the combined effects of stress concentration and grain orientation around micro-notch area showed great influence on edge crack initiation.
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