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Failure And Analysis Of SKF Bearings

Source:  skf bearing  Time:  2020-09-25

1. SKF bearing temperature is too high: When the mechanism is running, the part where the bearing is installed is allowed to have a certain temperature. When touching the housing of the mechanism with your hands, it is normal to not feel hot, otherwise it indicates that the bearing temperature is too high.

The reasons for the high temperature of SKF bearings are: the quality of the lubricant does not meet the requirements or deterioration, the viscosity of the lubricant is too high; the mechanism assembly is too tight (insufficient clearance); the bearing assembly is too tight; the bearing race rotates on the shaft or in the housing; load Too large; the bearing cage or rolling elements are broken, etc.


2. SKF bearing noise: Rolling bearings are allowed to have a slight running noise during operation. If the noise is too loud or there is abnormal noise or impact, it indicates that the bearing is faulty. The cause of noise produced by rolling bearings is more complicated, 1) the mating surfaces of the inner and outer rings of the bearing wear. Due to this kind of wear, it destroys the matching relationship between the SKF bearing and the housing, the bearing and the shaft, causing the axis to deviate from the correct position, and abnormal noise occurs when the shaft moves at high speed. When the bearing is fatigued, the metal on its surface will peel off, which will also increase the radial clearance of the bearing and produce abnormal noise. 2) Insufficient bearing lubrication, formation of dry friction, and bearing breakage will cause abnormal noise. 3) After the bearing is worn and loosened, the cage is loosened and damaged, which will also cause abnormal noise bearing damage. When the rolling bearing is disassembled and inspected, the fault and the cause of the damage can be judged according to the damage of the bearing.


3. Metal peeling off the raceway surface: INA bearing rolling elements and inner and outer ring raceway surfaces are subjected to periodic pulsating loads, resulting in periodic contact stress. When the number of stress cycles reaches a certain value, it will be produced on the working surface of the rolling element or inner and outer ring raceways.

Fatigue and peeling. If the load of SKF bearings is too large, this fatigue will increase. In addition, if the bearing is installed incorrectly and the shaft is bent, the raceway may peel off. Fatigue spalling of the bearing raceway will reduce the running accuracy of the shaft and cause vibration and noise to the mechanism.


4. SKF bearing burn: burnt bearing has tempered color on raceways and rolling elements. The causes of burns are generally insufficient lubrication, the quality of the lubricating oil does not meet the requirements or deterioration, and the SKF bearing assembly is too tight.


5. Plastic deformation: uneven pits appear on the contact surface between the raceway and the roller of SKF bearings, indicating that the bearing has plastic deformation. The reason is that the local stress on the working surface of the bearing exceeds the yield limit of the material under a large static load or impact load. This situation generally occurs on low-speed rotating SKF bearings.


6. SKF bearing race cracks: The reason for the cracks in the bearing race may be that the bearing is too tight, the bearing is loose or the inner ring is loose, the containing parts of the SKF bearing are deformed, and the surface of the SKF bearing is installed poorly.


7. The cage is broken: the reason is insufficient lubrication, broken rolling elements, skewed seat ring, etc.


8. The metal of the cage adheres to the rolling elements. The possible cause is that the rolling elements are stuck in the cage or insufficient lubrication.


9. The raceway of the seat ring is severely worn: it may be caused by foreign matter falling into the seat ring, insufficient lubricating oil or improper lubricating oil grade.
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Several manifestations of SKF bearing fatigue wear:


1). The length of the period when the first material fatigue phenomenon occurs in SKF bearings from the beginning of use is related to the speed of the bearing, the size of the load, and the cleanliness of lubrication.


2). Fatigue is the result of the periodic appearance of shear stresses under the load surface. After a period of time, these shear stresses cause small cracks and then gradually extend to the surface. When the rolling elements pass through these cracks, there will be some The cracks fall off, forming the so-called "skinning phenomenon", and then as the peeling situation continues to expand, the bearing is damaged and cannot be used.


3). The above is the description of SKF imported bearing fatigue. It originally occurred below the surface. Although the initial peeling condition is usually very slight, as the stress increases and the cracks increase, the peeling area spreads. The destruction situation usually lasts for a long period of time, and the obvious stage is when noise and vibration increase.


4). At the initial stage of damage to the bicycle bearing, it may only be difficult to feel when rotating, and later, it is found that there is a pitting sensation when rotating, and the pitting sensation appears in the first stage, the bearing is not unusable, but every time the beads are advanced Both the axle bowl and the axle gear have greater wear and more serious damage. Because the bicycle is a low-speed and high-extreme-pressure type of bearing, even if the surface peeling phenomenon is serious, it is not unusable, but invisible and silent. It consumes your power, and you may just feel that the car does not know why it is not riding smoothly.


5). Therefore, before the SKF imported bearing is completely destroyed, it provides users with enough time to find out. Don't ignore the existence of this kind of friction. It will reduce the riding speed and make the long-distance physical strength consumption greater and slower.

If the roughness of the surface is fine, if the lubricating oil film has an appropriate thickness, the probability of surface stress generation is quite low, which is why it is necessary to select a suitable oil for lubrication. However, if the pressure load exceeds If the pu value of the oil film (fatigue load limit value, such as too high speed, too high pressure impact), the fatigue of the material will come sooner or later.