Multiaxial fatigue criteria versus experiments for small crack under rolling contact fatigue

Rolling contact fatigue (RCF) is traditionally a very critical loading condition for fatigue and, moreover, material defects (as inclusions and inhomogeneities) play a significant role in determination of the service life of materials exposed to out-of-phase stresses, which typically occur at the interface and below the surface of contacting bodies. In this paper we summarize the results previously obtained for two different hard steels (that is, a bearing and a gear steel), together with a new set of experimental data for a mild railway wheel steel, that have been subjected to out-of-phase multiaxial fatigue loading, simulating RCF conditions in presence of small shallow pre-cracks. Then, the experimental results obtained have been discussed by employing the Dang Van and Liu– Mahadevan criteria, which are criteria extensively applied in the case of RCF problems. The results show that the Liu–Mahadevan criterion is close enough to experimental RCF tests, while the Dang Van criterion needs a substantial modification for the load cases when a negative hydrostatic stress component is present.