On the fatigue limit of ductile metals under complex multiaxial loading

The classical strength hypotheses are not applicable for the calculation of the fatigue limit under multiaxial loading with changing directions of the principal stresses. Hitherto, two groups of concepts have been proposed, the critical plane approach and the integral approach. In the present paper it is shown that with the integral approach, in particular the Shear Stress Intensity Hypothesis SIH, a good estimation can be achieved with complex periodical loads. This is verified using the results of 179 test series with ferritic and ferritic perlitic steel with a range of the tensile strength of Rm=400–1600 MPa. References will be given to further hypotheses and developments.