Bearings can be damaged due to various reasons during equipment operation, such as wear, corrosion, galling, fracture, fatigue spalling, plastic deformation, and cage damage. These can all lead to premature bearing failure. Even under proper installation, lubrication, and normal maintenance, wear and fatigue spalling can occur after a period of time, affecting normal operation. Therefore, the causes of bearing failure are complex. The main forms of rolling bearing failure are as follows:
1. Gluing
When operating under poor lubrication, high speed, and heavy load conditions, frictional heat can cause bearing components to reach very high temperatures in a very short time, leading to surface burns and galling. Galling refers to the phenomenon where metal from one component adheres to the surface of another component.
2. Wear and tear
The intrusion of dust and foreign objects causes surface wear during the relative movement of the raceway and rolling elements. Poor lubrication exacerbates wear, resulting in increased bearing clearance, increased surface roughness, and reduced bearing operating accuracy. Consequently, this also reduces the machine's motion accuracy, and increases vibration and noise. For precision mechanical bearings, wear often limits their lifespan.
3. Rust
Corrosion is one of the most serious problems of rolling bearings. High-precision bearings may lose precision and cease operation due to surface corrosion. Direct intrusion of moisture or acidic/alkaline substances can cause bearing corrosion. When a bearing stops working, the bearing temperature drops to the dew point, and moisture in the air condenses into water droplets that adhere to the bearing surface, also causing corrosion. In addition, when current flows through the bearing, it may pass through the contact points between the raceway and the rolling elements. A very thin oil film can cause electrical sparks, resulting in electrolytic corrosion and forming a corrugated, washboard-like unevenness on the surface.
4. Fatigue spalling
In rolling bearings, the inner and outer raceways and rolling element surfaces bear loads and roll relative to each other. Due to alternating loads, cracks first form at a certain depth below the surface (where the maximum shear stress is), then extend to the contact surface causing spalling pits, and finally develop into large-scale spalling. This phenomenon is called fatigue spalling. Fatigue spalling will cause increased impact loads, vibration, and noise during operation.
5. Plastic deformation
When a bearing is subjected to excessive impact or static loads, or when additional loads are caused by thermal deformation, or when a foreign object with high hardness intrudes, indentations or scratches will form on the raceway surface. This will cause the bearing to generate severe vibration and noise during operation. Moreover, once indentations are formed, the impact load caused by the indentations will further cause spalling of nearby surfaces.
6. Fracture
Excessive loads can cause bearing components to fracture. Improper grinding, heat treatment, and assembly can all cause residual stress, and excessive thermal stress during operation can also lead to bearing component fracture. In addition, improper assembly methods and processes can also cause pieces to chip off at the bearing race flanges and roller chamfers.
7. Cage damage
Improper assembly or use can cause cage deformation, increasing friction between it and the rolling elements, and may even cause some rolling elements to seize and become unable to roll. It may also cause friction between the cage and the inner and outer rings. This damage will further aggravate vibration, noise, and heat generation, leading to bearing failure.
