The impact of vibration on bearings refers to the impact on the bearing’s own performance and operating performance when vibration occurs in the bearing’s working environment. The vibration discussed is vibration from the working environment, not the vibration of the bearing itself. The existence of vibration in the working environment of the bearing includes vibration during the operation of the bearing and vibration under the static state of the bearing.
Effect of vibration on static bearings
After the bearing is installed on the equipment, it may bear a certain load even when the equipment is not running. For example, for a horizontal motor, when the motor is not running, the bearings at both ends of the motor bear the gravity of the motor’s rotor, and the radial load is almost similar to that when the bearings are running. The impact of the vibration of the working environment of the above motor on the bearing itself is what we call the impact of vibration on static bearings.
In the above examples, common working conditions include: ship motors, motors on platforms with vibration, etc.
Vibration in bearing operating conditions may be axial, radial, or combined (with components in both axial and radial directions). Let’s first look at the impact of radial vibration on the bearing for radial bearings.
When the motor in the above working conditions is not running, only the rolling elements in the contact area of the motor bearing bear the load, and this load is not static, but an impact load. For the bearing rolling elements in the contact area, this impact load is related to the acceleration of the vibration. If this impact load exceeds the rated static load of the bearing, it may cause plastic deformation of the bearing raceway and rolling elements. In this way, noise will occur when the bearing is running. As the operating time increases, fatigue and other phenomena will occur along the plastic deformation edge, and the bearing life will be greatly affected.
When the vibration is relatively small, the impact load between the rolling elements and the raceway of the bearing is not large, but load pulsations continue to occur. It is difficult to form a lubricating film between the rolling elements and the raceway in the non-operating state. In this operating state One type of fretting wear that will directly lead to internal bearing wear—pseudo Brinell indentation. Pseudo Brinell indentation will cause abnormal noise in bearing operation, which will lead to premature failure of the bearing.
For radial bearings, if the direction of vibration is axial (or has an axial component), it will often bring about axial load bearing marks on the bearing, thereby causing bearing failure. If the vibration amplitude is large, it may hit the bearing rib or cage. In severe cases, deformation of the cage and ribs may occur.
The impact of vibration on bearings in operation
When the bearing is running, the rolling elements should run smoothly on the raceway. If there is vibration in the environment, the rolling of the rolling elements will be affected, and the positive pressure on the raceway will also become a pulsating cycle load. This rolling state is very unfavorable for the formation of lubricating oil film. If the vibration amplitude is large, its impact is similar to that of a static bearing under vibration.
Precautions for bearing application under vibration conditions
Changes in the internal load of the bearing under vibration conditions will cause the above problems. On the other hand, special considerations are also required in the application of the bearing:
①Under vibration conditions, the matching force between the bearing and its mating surface will change. For places with excessive fit or loose fit, it may cause unstable positive pressure pulsation, which may create conditions for the bearing to run. Therefore, the fit of the bearings does not need to be loose under general vibration conditions.
② Vibration conditions have a greater impact on bearing lubrication. At this time, it is often difficult to form a lubricating oil film. At this time, you need to use some grease with extreme pressure additives, which will play a good role in lubrication of the bearings under vibration conditions.
③In terms of lubrication life, on the other hand, the vibration of the bearing will also cause the rolling elements to shear the grease soap base more frequently, which will affect the bearing life. Therefore, under vibration conditions, the life of the grease is calculated as 50%.
④ Under vibration conditions, the fatigue life of the bearing deviates greatly from the actual life, so it is often necessary to use the method of checking the safety factor to check the impact of the maximum vibration on the bearing.
⑤The preload of the bearing will also become a pulsating preload under vibration conditions, and general spring washers will fail early due to this pulsating load. The failure of spring washers in the current field of new energy vehicles is all related to this. Therefore, it must be dealt with from the perspective of bearing configuration.
