Comparison between different methods for the prediction of the fatigue limit of a member with a small crack

In the Kitagawa-Takahashi diagram and the corresponding analytical model by El Haddad et al., the fatigue limit of a cracked member is a monotonically decreasing function of the fatigue crack size. Based on data from fatigue tests by Schönbauer on plain and cracked members of 12% Cr steel at R = -1, the present investigation shows that the Kitagawa-Takahashi-El Haddad 'short-crack' model yields predictions in good agreement with those by Frost and Murakami for different ranges of the crack size. The comparison with Frost's model is based on a surface through-crack, that with Murakami's √area model on an embedded elliptical crack.