On the application of multiaxial high-cycle fatigue criteria using the theory of critical distances

This paper proposes that the application of multiaxial fatigue criteria in terms of the theory of critical distances requires the use of a distance which may be different from the widely adopted value given by half of the El Haddad’s intrinsic crack length. Three criteria (Modified Wöhler Curve Method, Crossland and Dang Van) are evaluated at the appropriate critical distance and compared with experimental data obtained from specimens containing small and/or sharp notches under proportional loading. The Modified Wöhler Curve Method provided the best estimates. It is also shown that this theory can be extended to the prediction of the loading ratio, R, effect on the threshold stress intensity factor range for propagation of long cracks.