FAQ

FAQ

Linhai Baiai Metal Forgings Co., Ltd.

Reasons for the loss of self-lubricating bearings

Through macroscopic and microscopic inspections and metallographic inspections, it is found that the fracture surface of the bearing inner ring is flat, the extended ridgeline is clear, the source area, the extended area and the instantaneous area are obvious, and there is no macroscopic plastic deformation and no corrosion characteristics. From the above characteristics, it can be judged that the nature of bearing block loss is fatigue fracture.

The fracture crack originates from the inner side of the end face and expands along the inner side of the bearing and radially; the expansion speed on the inner side of the bearing is greater than the radial expansion speed. Crack A originated near the source area of ​​the fracture, and its propagation speed on the inner side of the bearing was also faster than that on the outer side. The above phenomena all indicate that the formation of cracks originates from the impact force of the shaft on the bearing. Due to the existence of cracks, the actual impact force received before the block breaks is relatively small, so the area of ​​the instantaneous fracture zone is small. Although the hardness of the bearing meets the technical requirements, the larger retained austenite and networked carbides in the structure will obviously reduce the impact toughness of the material and reduce its ability to withstand impact loads.

Since the lowering angle of the landing gear is the same when the aircraft is landing, the position where the bearing is subjected to the maximum impact load, that is, the position of the fracture source area is also fixed. This is also the reason why the location of the B crack is approximately symmetrical with the source area of ​​the broken fracture.

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