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Analysis of the Fitting Surface Condition of the Failed Bearing

by:JNSN     2021-12-28
The condition of the mating surface of the failed bearing can reflect the support of the bearing ring in the shaft and the bearing seat, and we can draw many inferences from this. The rotation of the ferrule relative to the mating surface will cause abnormal noise. They can also cause fretting corrosion and wear, thereby further contaminating the lubricant with corrosive and abrasive particles. In addition, as the supporting condition of the ferrule deteriorates, fretting corrosion will make disassembly difficult. A few examples are given below. Fretting corrosion phenomenon: There are dark brown drag marks on the mating surface, and occasionally brown wear materials can be found near the bearing or in the lubricant. Wearing of the mating surface (inner hole, outer surface of the outer ring) may cause fatigue fracture for rotating parts (usually shafts), and for stationary parts (usually bearing seats), it may damage the function of the floating bearing, see Figure 13. From these fretting corrosion conditions, the location and size of the load-bearing area and the creeping conditions of the ferrule can usually be inferred, as shown in Figure 14. Reason: When the fit is too loose with respect to the force, there will be fretting between the mating parts, which can not achieve synchronous rotation. The processing quality of the mating surface is poor. The deflection of the shaft, the deformation of the bearing seat model and the ring bearing the circumferential load bear the floating bearing Remedial measures for floating function: The ring bearing the point load provides the floating function of the floating bearing. As far as possible, use a tight fit on the bearing mating surface to increase the stiffness of the shaft (bearing seat). (Prevent the ferrule from expanding and loosening due to changes in the material structure) Improve the roundness of the mating surface. If necessary, check and improve the surface quality of the mating surface. 3.2.2 Shaft holding scars or sliding wear. Phenomenon: There is cold welding on the mating surface (inner ring inner hole, outer ring outer surface) and axial mating surface, or it will appear in the bright area with good surface roughness, see Figure 15, 16. The wear of the mating surface and the end face will reduce the preload or increase the clearance, see Figure 17. Reason: The loosely fitted inner ring and shaft/outer ring and the bearing seat rotate under the action of the circumferential load; the same will happen when there is static load and imbalance. The axial support of the ring is insufficient and the floating bearing does not float smoothly. Remedy: As much as possible Use a tight fit on the bearing mating surface to increase the axial contact area to ensure the axial support to ensure the dryness of the mating surface to improve the function of the floating bearing 3.2.3 Uneven support of the bearing ring: the traces of the mating surface are not in the expected load-bearing area. The mating surface is worn out in some areas and not in contact at all in other areas, see Figures 18 and 19. Fatigue damage and fracture caused by uneven load distribution and bending of ferrule. Because the inner ring of the tapered roller bearing has too little support, the ribs are broken (Figure 20), and plastic deformation occurs because the contact surface is too small. Reason: Inappropriate design. Insufficient machining accuracy. Remedy: Replace the mating parts and ensure the rigidity of the bearing seat. If necessary, use other bearings to check the mating parts. 17 Evaluate the running characteristics and damage of the removed bearing. Condition of the mating surface 18: Outer ring Fretting corrosion on the outer surface occurs at the rigid point contact with the bearing seat (for example: ribs) 19: Only half the width of the outer ring outer diameter is supported 3.2.4 End surface scratch phenomenon: circumferential scratches/bearing ring Wear of end face or seal, see Figure 21, 22. Reason: The bearing is not sufficiently positioned in the bearing seat or on the shaft. There are a lot of impurities in the narrow gap between the bearing and the mating parts. The fit is too loose and the axial clearance is too large. Remedy: Correctly adjust the fit to ensure the cleanliness of the lubricant. Axial clearance, as much as possible to make it more suitable.
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