The main forms and causes of rolling bearing failure

Rolling bearings may be damaged due to various reasons during operation, such as improper assembly, poor lubrication, moisture and foreign body intrusion, corrosion and overload, etc. may cause premature bearing damage. Even when the installation, lubrication, use and maintenance are normal, after a period of operation, the bearings will peel off and wear out and they will not work properly. In short, the causes of failure of rolling bearings are very complicated. The main failure forms and causes of rolling bearings are as follows.

1.Fatigue spalling

The inner and outer raceways of the rolling bearing and the surface of the rolling body both bear the load and relatively roll. Due to the effect of the alternating load, a crack is formed at a certain depth below the surface, and then it expands to the contact surface, which causes the surface layer to spall, and develops into large spalling. This phenomenon is fatigue peeling. Fatigue spalling can cause increased shock loads, vibration and noise during operation. In general, 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 bearing life test is the fatigue test. The test procedure stipulates that the fatigue life of the bearing is considered to be the end of the bearing if a fatigue spalling pit with an area of 0.5 mm2 is present on the raceway or rolling element. The fatigue life of rolling bearings is highly dispersed. In the same batch of bearings, the high life and low life can differ by dozens or even hundreds of times, which illustrates the importance of rolling bearing fault monitoring from another angle.

2.Wear and tear

Due to the intrusion of dust and foreign materials, the raceways and rolling elements will cause surface wear when they move relative to each other. Poor lubrication will also increase wear. As a result of wear, the bearing clearance will increase, the surface roughness will increase, and the bearing running accuracy will be reduced. The accuracy of the machine is reduced, and the vibration and noise are also increased. For mechanical bearings, it is often the amount of wear that limits the life of the bearing.

In addition, there is a kind of fretting wear. When the bearing is not rotating, due to the action of vibration, there is a slight and repeated relative sliding between the rolling element and the raceway contact surface, which causes wear and tear, and a chatter-like wear mark is formed on the raceway surface.

3. Plastic deformation

When the bearing is subjected to excessive impact load or static load, or additional load due to thermal deformation, or a foreign body with a high hardness is invaded, dents or scratches will be formed on the raceway surface. This will cause the bearing to generate severe vibration and noise during operation. And once there is an indentation, the impact load caused by the indentation will further cause the nearby surface to peel off.

4. Rust

Corrosion is one of the more serious problems of rolling bearings. High-precision bearings may lose accuracy due to surface corrosion and cannot continue to work. Direct intrusion of water or acid and 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 and attaches to the bearing surface, which will also cause corrosion. In addition, when an electric current passes through the bearing, the electric current may pass through the contact points on the raceway and the rolling body, and a thin oil film may cause electric sparks to cause electric erosion, thereby forming a rubbing-like unevenness on the surface.

5. fracture

Excessive load may cause the bearing parts to break. Grinding, heat treatment and improper assembly will cause residual stress. Excessive thermal stress during work will also cause bearing parts to break. In addition, improper assembly methods and assembly processes may also cause the block of the bearing ring flange and roller chamfer.

6.Gluing

When working under poor lubrication and high-speed and heavy-load conditions, due to friction and heating, the bearing parts can reach very high temperatures in a short time, resulting in surface burns and gluing. The so-called gluing refers to the phenomenon that the metal on the surface of one component adheres to the surface of another component.

7. The cage is damaged

Improper assembly or use may cause deformation of the cage, increase friction between it and rolling elements, and even cause some rolling elements to become stuck and unable to roll, which may also cause friction between the cage and the inner and outer rings. This damage will further exacerbate vibration, noise and heat, resulting in bearing damage.