A Method for the Prediction of Fatigue Limits of Notched Members

Abstract

A method for predicting the fatigue thresholds of notched components proposed by Tanaka and Nakai was modified to obtain a simpler formulation. The method requires three material data for prediction : the fatigue limit of smooth specimens, the threshold stress intensity range for long cracks, and the threshold value of the effective stress intensity range. For notched components, the fatigue limit for crack initiation, the fatigue limit for fracture, and the length of non-propagating cracks are predictable as functions of the applied stress and notch geometry. The fatigue tests were conducted with center-notched plates of low-carbon steel with two different grain sizes and the results were compared with the prediction. Good agreement was obtained for the fatigue limit for the nucleation of a Stage II crack. The prediction was slightly conservative for the fatigue limit for fracture. Agreement in the length of non-propagating cracks between prediction and experiment was fairly good. Several simple formulae were derived for easy application for practical purposes.