Effects of grain size on crack aspect ratio and crack initiation limit in notched specimen of austenitic stainless steel(JIS SUS304)

Aspect ratio is a key factor to calculate stress intensity factor (SIF) K using fracture mechanics. Cracks are approximated to be semi-circle or semi-ellipse in simple calculation, however, their empirical shapes are changed by stress concentration. In this study, in order to calculate K simply and precisely, a new method to predict fatigue crack initiation stress, sigma(w1) of austenitic stainless steel with modified aspect ratio is discussed. The new method succeeded to predict sigma(w1) within 20% error from empirical values using average austenite grain sizes.