Effect of notch root radius on fatigue crack initiation

Abstract

The initiation of a fatigue crack terminates the useful life of small components. The initiation process is intimately related to cyclic plastic deformation and thus occurs mostly at notches where stresses are elevated appreciably. The root radius of such notches dictates the severity of stress and strain concentration. Using notched specimens of varying root radii the initiation lives were determined experimentally. Both the fictitious elastic notch root stress and the local strain at the notch root have been used to correlate with the initiation life. The local strain approach, together with Neuber's rule, is observed to give less scatter. The design-oriented nominal mean stress method of Juvinall yields results comparable with the local strain approach.