Rolling bearings may be damaged during operation due to various reasons, such as improper assembly, poor lubrication, invasion of moisture and foreign objects, corrosion, and overload, which may lead to premature bearing damage. Even under normal installation, lubrication, and maintenance, after a period of operation, the bearing may experience fatigue peeling and wear, making it unable to function properly. In short, the causes of rolling bearing failures are very complex. The main failure forms and causes of rolling bearings are as follows.
1. Fatigue peeling
The inner and outer raceways of rolling bearings and the surface of the rolling element not only bear loads but also relatively roll. Due to the action of alternating loads, cracks first form at a certain depth below the surface, and then expand to the contact surface, causing spalling pits on the surface and developing into large spalling. This phenomenon is fatigue spalling. Fatigue peeling can cause increased impact load, vibration, and noise during operation. Usually, fatigue peeling is the main reason for the failure of rolling bearings. Generally, the bearing life refers to the fatigue life of the bearing, and the bearing life test is the fatigue test. According to the test regulations, the occurrence of fatigue peeling pits with an area of 0.5mm2 on the raceway or rolling element is considered as the end of bearing life. The fatigue life of rolling bearings is highly dispersed, and within the same batch of bearings, their high and low lifespans can differ by tens or even hundreds of times. This demonstrates the importance of fault monitoring for rolling bearings from another perspective.
2. Wear and tear
Due to the invasion of dust and foreign objects, the relative movement of the raceway and rolling element can cause surface wear, and poor lubrication can also exacerbate wear. The result of wear is an increase in bearing clearance, surface roughness, and reduced bearing operating accuracy, thereby reducing the machine's motion accuracy, and increasing vibration and noise. For precision mechanical bearings, the amount of wear often limits the lifespan of the bearings.
In addition, there is also a type of micro vibration wear. When the bearing does not rotate, due to the effect of vibration, there is slight and repeated relative sliding between the rolling element and the contact surface of the raceway, resulting in wear and tear, forming vibration like wear marks on the raceway surface.
3. Plastic deformation
When the shaft is subjected to excessive impact or static loads, additional loads caused by thermal deformation, or foreign objects with high hardness invade, dents or scratches will form on the surface of the raceway. This will cause severe vibration and noise during the operation of the bearing. And once there are indentations, the impact load caused by the indentations will further cause peeling of the nearby surface.
4. Rust
Rust is one of the serious problems of rolling bearings, and high-precision bearings may lose accuracy due to surface rust and cannot continue to work. Direct invasion of water or acidic or alkaline substances can cause bearing corrosion. When the bearing stops working, the temperature of the bearing drops to the dew point, and water in the air condenses into droplets that attach to the surface of the bearing, which can also cause corrosion. In addition, when there is current passing through the inside of the bearing, the current may pass through the contact points on the raceway and rolling element, causing a thin oil film to cause electric sparks and generate electrical corrosion, forming a washboard like unevenness on the surface.
