An Analysis of Notch-Size Effects at the Fatigue Limit

Abstract This investigation examines the variation of the fatigue notch factor with notch size for sharp and blunt notches. Analytical expressions are developed to predict the fatigue notch factor for sharp notches based on short crack fracture mechanics and for blunt notches based on Neuber's rule. Experimental evidence to support these expressions is provided together with fatigue notch factors for circularly center-notched plate specimens of 2024-T351 aluminum and SAE 1045 steel. The notch diameters were varied from 0.24 to 5.0 mm. The specimens were tested in laboratory air under uniaxial constant-amplitude loading at load ratios of R = −1 and R = 0. Further experimental evidence to support the analysis is provided by data from the literature for two low carbon steels and a copper. At the fatigue limit, the fatigue notch factor increases with notch size for sharp notches. However, a notch-size effect does not occur for blunt notches. The observed notch-size effects from this and other investigations are in good agreement with the analytical expressions that are presented.