Rolling bearing failure index

8.0 Fretting damage

Click on photograph to enlarge
	Figure 8a Fretting on a bearing outer race due to inadequate interference fit and local distortion of housing
	Figure 8b Fretting of a bearing inner race due to inadequate interference fit, leading to fracture of the race.
Main Characteristics	Fretting damage can occur at the contact between the bearing and its seating / housing, particularly where a sliding fit is used, because of small oscillating movements that take place there as the rolling elements pass through the loaded zone (figure 8a). This does not normally give rise to failures, though if it is very severe it can form stress raisers that will initiate fatigue fracture of the race (figure 8b); this differs from the cracking shown in figure 4c by the absence of fretting marks where the cracking has been caused by excessive interference fit. Fretting can also cause sticking of a 'free mounted' bearing as discussed in section 7.
Cause
Note
Possible Confusion with Other Types of Damage
Comment	Where fretting is a problem it can be prevented by applying a thin electro-deposited coating of indium to the surface or the bore or outer diameter before fitting.

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