A bi‐parametric Wöhler curve for high cycle multiaxial fatigue assessment

This paper presents a method for estimating high‐cycle fatigue strength under multiaxial loading conditions. The physical interpretation of the fatigue damage is based on the theory of cyclic deformation in single crystals. Such a theory is also used to single out those stress components which can be considered significant for crack nucleation and growth in the so‐called Stage I regime. Fatigue life estimates are carried out by means of a modified Wöhler curve which can be applied to both smooth and blunt notched components, subjected to either in‐phase or out‐of‐phase loads. The modified Wöhler curve plots the fatigue strength in terms of the maximum macroscopic shear stress amplitudes, the reference plane − where such amplitudes have to be evaluated − being thought of as coincident with the fatigue microcrack initiation plane. The position of the fatigue strength curve also depends on the stress component normal to such a plane and the phase angle as well. About 450 experimental data taken from the literature are used to check the accuracy of the method under multiaxial fatigue conditions.