When the bearing is working, the roller should do pure rolling motion on the inner and outer ring raceways. If the driving roller cage is required to have enough drag power, it can overcome its resistance, when the roller drag power is not enough to overcome the resistance, then, in addition to rolling, will be accompanied by some sliding, and this relative to the inner ring (or outer ring) speed difference, it is skid.

Roller bearing skid is a necessary condition for rubbing bearings, but the occurrence of skid may not necessarily cause surface scratches.

Some factors that cause roller bearings to slip and rub are, such as vibration and alternating load of the shaft, which produce a force that can tear the lubricating oil film and cause scratches on some areas of the working face (roller and inner ring raceway working face are more common).

Compared with fatigue spalling, the depth of bearing scratches is shallow and banded. Compared with the normal working face, it is rough and uneven. Figure 2 is a picture taken by a high power electron microscope. The bearing skid zone is a large area of small pockmarks, and the edge of the zone is dragging many small “streamline”. The depth of the pit in the center area of bearing scratches is about 30~40 microns. Close examination under an electron microscope showed that the pockmarks were formed by small pieces of metal falling from the surface.

Therefore, it can be imagined that skid scratches are the result of material transfer due to the interaction of the uneven and rough surface of the metal after the lubricating oil film is destroyed. Some materials are “stained” to form pockmarks; The more heavily stained areas protrude above the original surface. In addition, some parts of the working surface are bruised, which is closely related to the extent of alternating load and oil film damage. In serious cases, too much friction heat is generated between the roller and the inner ring, so that the inner ring expands and the radial clearance is reduced, so that the bearing is stuck.

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