Hydrodynamic Aspects of Fatigue in Plain Journal Bearings

The fatigue resistance of different bearing materials is usually given an “order of merit” in terms of specific load on the bearing. The bearing material cannot directly sense the applied specific load, since it is the hydrodynamic oil film pressures which directly create the stresses in the lining; both pressures and stresses need to be examined to see if a more meaningful criterion for fatigue can be found. As a first step in this study the experimental fatigue work carried out by Gyde at the University of Denmark was examined and compared with trends in peak specific load, hydrodynamic characteristics, and bearing lining stresses. It has been shown that peak specific load and peak hydrodynamic pressure are not in themselves realistic parameters, but that pressure variation on a bearing element, perhaps including some rapidly forming negative pressures, could be a significant term. The study of the more fundamental material stresses has not yet been extended to allow for the influence of any nonpositive film pressures, but results so far follow similar trends to those obtained on the pressure variation criterion.