Dresden 2006 – scientific programme

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MM: Metall- und Materialphysik

MM 25: Poster Session

MM 25.8: Poster

Wednesday, March 29, 2006, 15:30–17:30, P4

Near- and Sub-Surface Fatigue of Rolling Bearings — •Jürgen Gegner — SKF GmbH, Material Physics, Ernst-Sachs-Str. 5, D-97424 Schweinfurt, Germany

Material response of hardened steel to rolling contact starts with strain strengthening in the plastically deformed edge zone and the build-up of compressive residual stresses in the short shakedown period. The following steady-state stage controls a certain part of bearing lifetime, the duration of which depends on the loading conditions. The depth profiles of the equivalent stresses that are defined by the applied Hertzian pressure determine the positions of maximum residual stress (v. Mises) and material aging (orthogonal shear stress). In the final instability stage, steel softening occurs and is accompanied by decreasing XRD half width: in the classical Voskamp sub-surface rolling contact fatigue mode, high residual stresses can be built up, the magnitude of which correlates to the external load. On the other hand, for instance in case of boundary lubrication with metal-metal contact, the Nierlich (near-) surface failure mechanism is characterized by diminishing stress levels. In order to investigate this practically most important damage mode in more detail, X-ray diffraction based material response analysis of gear roller bearings stemming from rig tests is performed.