1997-09-08

A New Method for Studying Surface-Initiated Bearing Failure 972712

:This paper describes method which experimentally reproduces the most prevalent bearing fatigue failure modes experienced in ball and roller bearing applications.Generally, bearing fatigue life is divided into two groups. One is a surface-originating type of fatigue. The other is a subsurface-originating type of fatigue. The mechanism of each type of fatigue has been studied. Bearing materials were developed for long-life based on the study of the mechanism of fatigue. However, the condition of the evaluation method, or life test, may be different from the actual application conditions. For instance, the subsurface-originating type of fatigue is tested under extremely heavy loads. The surface-originating type of fatigue is tested with severely contaminated lubrication. There is the possibility that the evaluation methods do not simulate the failure modes that are actually present in the field. In this study, the failure modes of various ball and roller bearings used in the field have been classified by using X-ray diffraction and by observing the surface conditions. The results show that the damage traces of subsurface fatigue or severely debris-dented surface conditions experienced in the conventional bearing life tests were rare in actual practice. The most prevalent failure mode originated from the minute surface defects, due only to surface damage.A new life test method, a surface damage type life test, was developed to better reproduce the more common fatigue modes seen in practice.

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