Estimation of endurance limit under multiaxial loading. Pt. 3

Miltiaxial criteria for endurance limit prediction of metallic materials will be discussed in this paper. The Shear Stress Intensity Hypothesis SIH is improved under consideration of the variable fatigue limit ratio τW/σW and mean stress effects. Fatigue behaviour under synchronous and nonsynchronous stresses and influences such as mean stresses, out-of-phase stresses, different frequencies, nonsinusoidal stress time function are analysed theoretically and verified with test results. The prediction according to SIH shows good agreement with the test results. Based on an extensive statistical investigation it can be recommended to use the SIH for 'crack free materials' and the normal stress hyptohesis NSH for 'materials with cracks'. For components the hypothesis SIH and NSH are developed under consideration of the notch effect. In this study a concept for the prediction of endurance limit under multiaxial loads has been developed. (orig.)