An Analysis of the Fatigue Strength of Metals Containing Small Defects

摘要

A modified linear-elastic fracture mechanics approach proposed by McEvily has been applied to predict the effects of small defects on the fatigue limit and the threshold level. In the analysis, three modifications were taken into account (1) the effect of elastic-plastic behavior of small cracks, (2) the Kitagawa effect where in the very small crack regime the required stress for propagation is controlled by the fatigue limit of a smooth specimen rather than by the long-crack threshold condition, and (3) the effect of crack closure development from zero up to the macroscopic level as a newly formed crack extends. Three steels, a brass and an Al alloy were investigated. Good agreement between predicted and experimental results has been obtained and a rational basis for the area~(1/2) parameter model was shown.