Mean stress sensitivity of sintered iron and steel

There is a well-based correlation between the pulsating amplitude sigma(A)(R = 0) and the alternating amplitude sigma(A)(R = -1) in fatigue testing of sintered iron and steel which permits to predict the mean stress sensitivity and the pulsating amplitude if the alternating endurance limit sigmaA(R = -1) has been measured. Without loss of precision the relationship can be extended from smooth unnotched specimen geometries to notched geometries if only the stress concentration factor is known. The coefficients of the predictive equation depend on the brittleness of the material, a systematic approach to take the brittleness into account is still missing. In Haigh diagrams, the slope of the sigma(A)-sigma(m) diagram with tensile mean stresses can be linearly extrapolated also into the compressive mean stress range sigma(m) < 0.