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Rolling bearings may cause damage due to various reasons during operation. Improper assembly, poor lubrication, moisture and foreign matter intrusion, corrosion and overload may cause premature bearing damage. Even after installation, lubrication, and maintenance are normal, after a period of operation, the bearing may experience fatigue peeling and wear and may not work properly. In short, the cause of the failure of the rolling bearing is very complicated. The main fault forms and causes of rolling bearings are as follows.
Fatigue spalling
The inner and outer races of the rolling bearing and the surface of the rolling element are subjected to both load and relative rolling. Due to the alternating load, the crack should be formed at a certain depth below the surface, and then spread to the contact surface to cause the surface layer to peel off and develop to a large piece of peeling. This phenomenon is fatigue peeling. Fatigue spalling can cause increased shock loads, vibrations, and noise during operation. Under normal circumstances, fatigue spalling is often the main cause of rolling bearing failure. Generally speaking, bearing life refers to the fatigue life of the bearing, and the life test of the bearing is the fatigue test. The test procedure stipulates that a fatigue peeling crater with an area of 0.5 mm2 on the raceway or rolling element is considered to be the end of bearing life. The fatigue life of rolling bearings is highly dispersible. In the same batch of bearings, the high life and low life can be several tens of times or even hundreds of times. This explains the importance of rolling bearing fault monitoring from another angle.
2. wear
Due to the intrusion of dust and foreign matter, the surface of the raceway and the rolling element will cause surface wear. The poor lubrication will also aggravate the wear. As a result of the wear, the bearing clearance will increase, the surface roughness will increase, and the bearing running accuracy will be reduced. The motion accuracy of the machine is reduced, and the vibration and noise are also increased. For precision mechanical bearings, the amount of wear often limits the life of the bearing.
In addition, there is a kind of fretting wear. When the bearing does not rotate, due to the action of the vibration, there is a slight, repeated relative sliding between the rolling element and the raceway contact surface to cause wear, and a flared wear scar is formed on the raceway surface.
3. Plastic deformation
When the bearing is subjected to an excessive impact load or static load, or an additional load due to thermal deformation, or a foreign matter having a high hardness intrusion, a dent or scratch is formed on the surface of the raceway. This will cause the bearings to produce severe vibration and noise during operation. Moreover, once the indentation is present, the impact load caused by the indentation further causes the peeling of the nearby surface.
4. Corrosion
Corrosion is one of the serious problems of rolling bearings. High-precision bearings may lose their precision due to surface rust and cannot continue to work. Direct intrusion of moisture or acid or alkaline substances can cause bearing corrosion. When the bearing stops working, the bearing temperature drops to the dew point, and moisture in the air condenses into water droplets attached to the bearing surface, which can also cause rust. In addition, when there is current flowing inside the bearing, current may pass through the contact points on the raceway and the rolling element, and a very thin oil film causes electric spark to cause electric erosion, and a seesaw-like irregularity is formed on the surface.
5. Break
Excessive loads can cause the bearing parts to break. Improper grinding, heat treatment and assembly can cause residual stresses. Excessive thermal stress during operation can also cause bearing parts to break. In addition, improper assembly methods and assembly processes may also cause the bearing ring ribs and the roller chamfers to fall off.
6. Gluing
When working under poor lubrication and high speed and heavy load, due to frictional heat, the bearing parts can reach a very high temperature in a very short time, resulting in surface burns and gluing. Gluing refers to the phenomenon that metal on the surface of one component adheres to the surface of another component.
7. Cage damage
Improper assembly or use may cause deformation of the cage, increase friction between it and the rolling elements, and even cause some rolling elements to become stuck and not roll, which may cause friction between the cage and the inner and outer rings. This damage will further aggravate vibration, noise and heat, resulting in bearing damage.