Possible failures of rolling bearings during operation

• Shanghai Zhio Technology Co.,Ltd 
• 2023-08-29

Rolling bearings may be damaged due to various reasons during operation, such as improper assembly, poor lubrication, moisture and foreign body intrusion, corrosion and overloading, etc., which may lead to premature bearing damage. Even if the installation, lubrication and maintenance are normal, after a period of operation, the bearing will appear fatigue spalling and wear and can not work properly. In short, the failure causes of rolling bearings are very complex. The main failure forms and causes of rolling bearings are as follows.
1. Fatigue peeling
The inner and outer raceways of the rolling bearing and the surfaces of the rolling elements both bear the load and roll relative to each other. Due to the action of the alternating load, a crack is first formed at a certain depth under the surface, and then expands to the contact surface, causing the surface layer to peel off pits and develop into large pieces. This phenomenon is fatigue spalling. Fatigue spalling increases shock loads, vibration and noise during operation. Under normal circumstances, fatigue spalling is often the main reason for the failure of rolling bearings. Generally speaking, the bearing life refers to the fatigue life of the bearing, and the life test of the bearing is the fatigue test. The test regulations stipulate that the bearing life is considered to end when a fatigue spalling pit with an area of 0.5mm2 appears on the raceway or rolling element. The fatigue life of rolling bearings has a large dispersion. In the same batch of bearings, the difference between the high life and the low life can be dozens or even hundreds of times. This shows the importance of rolling bearing fault monitoring from another perspective.
2. Wear
Due to the intrusion of dust and foreign matter, the relative movement of the raceway and the rolling elements will cause surface wear, and poor lubrication will also increase the wear. The motion accuracy of the machine is reduced, and the vibration and noise also increase. For mechanical bearings, it is often the amount of wear that limits the life of the bearing.
In addition, there is a fretting wear. When the bearing does not rotate, due to the action of vibration, there is slight and repeated relative sliding between the rolling elements and the contact surface of the raceway, resulting in wear and tear, and a vibration-like wear scar is formed on the surface of the raceway.
3. Plastic deformation
When the bearing is subjected to excessive shock load or static load, or additional load caused by thermal deformation, or when foreign matter with high hardness invades, dents or scratches will be formed on the raceway surface. This will make the bearing produce severe vibration and noise during operation. And once there is an indentation, the impact load caused by the indentation can further cause spalling of nearby surfaces.
4. Rust
Corrosion is one of the more serious problems of rolling bearings, and high-precision bearings may not continue to work due to loss of accuracy due to surface corrosion. Direct intrusion of water or acid and alkaline substances will cause bearing corrosion. When the bearing stops working, the bearing temperature drops to the dew point, and the moisture in the air condenses into water droplets attached to the bearing surface will also cause rust. In addition, when there is current passing through the bearing, the current may pass through the contact points on the raceway and the rolling elements, and the thin oil film causes electric sparks to cause electrical corrosion, forming washboard-like unevenness on the surface.
5. Fracture
Excessive loads may cause bearing parts to break. Improper grinding, heat treatment and assembly can cause residual stress, and excessive thermal stress during operation can also cause bearing parts to break. In addition, improper assembly method and assembly process may also cause the bearing ring rib and roller chamfer to drop blocks.
6. Gluing
When working under the condition of poor lubrication and high speed and heavy load, the bearing parts can reach a very high temperature in a very short time due to friction and heat, resulting in surface burns and gluing. The so-called gluing refers to the phenomenon that the metal on the surface of one part adheres to the surface of another part.
7. Cage damage
Improper assembly or use may cause the cage to deform, increase the friction between it and the rolling elements, and even cause some rolling elements to be stuck and unable to roll, and may also cause friction between the cage and the inner and outer rings. This damage can further exacerbate vibration, noise and heat, resulting in bearing damage.