Short fatigue cracks in notched/unnotched specimens under non-proportional loading

A short crack growth model for the prediction of constant amplitude fatigue life to technical crack initiation under multiaxial nonproportional loading has been proposed by Döring et. al. [1, 2]. Here, results of further work are presented which are intended to improve the model and extend its applicability to notched components. A satisfying accuracy of calculated fatigue lives is achieved. This is verified by experimental data (Hoffmeyer et. al. [3, 4]) for shouldered shafts and hollow tube specimen made of fine grained steel S460N under a variety of multiaxial non-proportional loading sequences. The correlation between the perception as stated in the model and real damage evolution is shown comparing calculated and experimentally determined short crack growth curves measured with a replica technique. The accuracy of the short crack model is comparable to conventional multiaxial damage parameters. However the short crack model offers the opportunity for further developments, especially for variable amplitude loading