A method to estimate fatigue limit using (1/Nf)-S curve

Abstract

This paper describes a unique method for determining fatigue limit from high-cycle fatigue (HCF) data by using (1/Nf)-S curve called 1/Nf method. The method is applicable for testing different alloy-environment systems at any load R-ratios and where the plateau limit is not observed, like in Al-alloys and in environmental fatigue. Due to inherent scatter in the fatigue data approaching fatigue limit, a staircase method is often utilized, but this method requires about 15–30 specimens to be tested just to determine only the fatigue limit. The proposed 1/Nf method for estimating fatigue limits is verified against the data from staircase method for several alloys. The comparison with the staircase method shows a good agreement resulting in a difference of 4 % or less. The implication of the proposed method for very high cycle fatigue (∼109) is also demonstrated.