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Plain Bearing Failure
2.0 Wear
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2.1 Scoring damage of white metal thrust pad by dirt
2.2 Scoring of white metal journal bearing
2.3 Scoring of lead-bronze journal bearing
2.4 Erosion damage of white metal journal bearing
2.5 Erosion damage to axial oil groove in journal bearing
2.6 Summary
Bearing materials are chosen to be soft, not only does this allow them to conform to the journal or thrust collar to accommodate slight misalignment (conformability), but also to allow hard contaminant particles to embed so that they do not score the counterface (embeddability). There is, however, a limit to the latter and with severely contaminated lubricants particles small enough to enter the oil film at the supply groove, but larger than the minimum oil-film thickness can remain proud in the soft bearing metal and score the shaft or thrust collar - scoring.
Scoring results in an increase in clearance that eventually requires the bearing to be replaced. More seriously, however, wear in non-cylindrical profile bearings (e.g. lemon, multi-lobe), used to give enhanced stability, tends to produce a more cylindrical bore that can result in the bearing developing instability. Hydrodynamically-lubricated bearings can operate satisfactorily with a certain amount of scoring; however, a stage is eventually reached when it is no longer possible to generate an oil film at start-up and wiping failure occurs (see Lubrication breakdown).
Particles in high concentration, but small enough to pass through the oil film can erode the soft bearing material in the direction of oil flow in the bearing - erosion. Larger particles trapped in the oil grooves can also cause erosion damage.
Other wear mechanisms such as fatigue, cavitation erosion, fretting, chemical attack and electric erosion are dealt with separately.