Prediction of fatigue crack initiation lives at elongated notch roots using short crack concepts

Re-initiation lives of fatigue cracks departing from stop-holes roots, previously introduced at the tip of deep cracks on modified SE(T) specimens, have been satisfactorily predicted using their properly calculated notch sensitivity factor q, considering the notch tip stress gradient influence on the fatigue behavior of mechanically short cracks. This is an indispensable detail, since traditional q estimates are only applicable to semi-circular notches, whereas elongated slits can have q values which also depend on their shape, not only on their tip radius. Based on this experimental evidence, a criterion for acceptance of short cracks is proposed.