The Metallography of Fatigue Cracks Initiated at Notches in an Al-0.5% Mg Alloy

Abstract

The metallographic characteristics of fatigue cracks initiated in notched specimens have been studied and compared with those of cracks originating at the surface of smooth electropolished samples. The distribution of fatigue damage at a notch root is similar in general, but not in detail, to that observed on the surfaces of plain specimens. The characteristics of crack growth from a notch are governed in the initial stages by the notch profile, but subsequently become independent of the notch-root radius. The fracture surfaces of notched and plain specimens differ substantially in appearance, a variety of features being observed at crack lengths shorter than those at which optically visible Stage-II ripples appear.