1993 Volume 42 Issue 472 Pages 72-77
In order to establish a multiaxial low cycle fatigue criterion which can evaluate the fatigue life of high temperature components, biaxial low cycle fatigue tests of 304 stainless steel have been carried out with the cruciform specimens at 550°C under proportional and nonproportional loading conditions. A multiaxial low cycle fatigue criterion and its application to fatigue damage evaluation in design have been discussed based on the present test results and the previous results which were produced by tension-compression and torsion tests at elevated temperatures with the tubular specimens.
Configuration of iso-fatigue life contours of the Case B loading on the Γ-plane in which the maximum shear planes are on planes inclined 45° from the surface was different from that of the Case A loading in which they are on planes 90° from the surface, because of difference in fracture mechanism. The influence of normal strain in the maximum shear plane, εn, on fatigue life was not observed in the Case B loading, while the fatigue life was strongly affected by εn in the Case A loading. From iso-fatigue contours on the Γ-plane, the equivalent shear strain range, Δγ for the Case B loading was newly defined. It was confirmed that the biaxial fatigue life data of proportional and nonproportional loadings could be correlated well with Δγ and a fatigue damage evaluation procedure by applying Δγ in design was proposed.
