A fatigue life model for 5% chrome work roll steel under multiaxial loading

The fatigue behavior of 5% chrome steel heat-treated for wear resistance has been investigated under axial–torsional loading. This material exhibits brittle fracture under monotonic and cyclic loading. The preferred site for crack initiation appears to be carbide clusters on or near the surface. Crack propagation initially progressed in a transgranular mode followed by a mixed transgranular–intergranular mode at a later stage. A parameter given in terms of the maximum normal stress range and the hydrostatic stress range is found to correlate fatigue lives reasonably well. This parameter correctly predicts the experimental trend that in-phase loading is more damaging than out-of-phase loading under a given ratio of axial/shear stress amplitudes. Models for tensile and compressive mean stress effects have also been proposed based on the uniaxial test results.