Why does the nup bearing ring break?

1. The outer wall of the nup bearing ring has severe pitting corrosion and extrusion deformation.

2. The fractures of nup bearing ferrules include transverse fractures and longitudinal fractures. It can be seen from the fracture morphology that the cracks start from the outer wall and extend to the inner wall to tear, and the cracks are all located at the fatigue pitting or peeling off of the outer wall. At the fatigue spalling of the fragments, large areas of pitting corrosion are also found on the outer wall. It can be seen that fatigue pitting and shedding caused by excessive contact stress may be the source of cracking of nup bearing rings. In addition, due to the axial thrust at the rib and the deep recess, the stress concentration is large and it is easy to break at the rib.

3. A macro crack was found on one fragment. This crack is a surface crack, a fatigue crack caused by contact stress, and a precursor to fatigue shedding. During the test, when we used a metallographic cutting machine to cut and sample the bearing ring fragments, due to vibration and external impact load, some fragments were further broken or cracked. The cracks or cracks were located at the ribs, which shows that the material Hard and brittle, with poor impact resistance, and the ribs are more likely to break due to large structural stress.

4. Many wear grooves and peeling blocks were also found on the inner surface of the nup bearing ring, as well as macroscopic cracks. This shows that there is relative sliding friction between the nup bearing ring and the shaft. According to the working principle of the bearing, the nup bearing ring should have an interference fit with the shaft. When the shaft rotates, the bearing ring rotates with the shaft, and the roller rolls between the bearing ring and the outer ring to reduce the vibration of the shaft. If the gap between the shaft and the bearing ring is too large, relative sliding friction will occur between the shaft and the bearing ring, which will cause the rollers to fail to roll normally, the ring to directly bear large contact stress, and the bearing to work overloaded, leading to fatigue pitting and corrosion. Fatigue falls off.

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