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ROLLING BEARING FAILURE
Lubrication Failures
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Lubrication failures index
5.2 Rolling contacts
There is a need to develop a satisfactory lubricant film at the rolling contacts; in the majority of cases this will be an elastohydrodynamic film, but in very heavily-loaded bearings it can be a film developed by reaction of extreme pressure additives in the oil. Failure to develop a satisfactory lubricant film gives rise to a smearing type of damage that is usually referred to as 'surface distress' (figure 5.2).
| Click on photograph to enlarge | |
 | Figure 5.2 'Surface distress' in deep groove ball bearing caused by breakdown of elastohydrodynamic lubrication film |
| Main Characteristics | A characteristic of both types of lubrication failure is that the temperature rises through increased friction loss in the bearing. This may allow a breakdown in lubrication to be detected before failure occurs, though if a lot of heat is generated sufficient thermal gradient may develop between inner and outer race (for example, on a rotating shaft, the housing usually provides a better heat sink for the outer than the shaft does for the inner race so that the latter reaches a higher temperature) to result in loss of internal bearing clearance, giving rise to a different failure mechanism ('Loss of Internal Clearance'). |
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| Possible Confusion with Other Types of Damage | |
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