In the process of mechanical design, engineers and technicians pay close attention to the service life of rolling bearings. In fact, what people call bearing life in the field of engineering technology usually refers to bearing fatigue life.
When the bearing operates under load, the load is transferred from one bearing ring to another through the rolling element. There will be corresponding stress distribution in the metal material. The maximum shear stress occurs at a certain depth below the metal material on the contact surface between the rolling element and the raceway.
This shear stress occurs repeatedly every time the rolling body rolls over the raceway. When the number of occurrences reaches a certain amount, the metal will fatigue and begin to fail. No matter what the material is, the reciprocating of this shear stress will always occur, but the time of occurrence is proportional to the number of times the rolling body rolls and the positive pressure.
When the initial fatigue point appears, fatigue will spread to the metal surface along a certain direction, and finally the metal surface of the bearing will peel off. This is a very typical bearing failure mode - surface fatigue spalling. The above description of bearing failure process is bearing fatigue failure. Under a given working condition, the time of bearing fatigue failure (number of turns) is what we call fatigue life.
In fact, every bearing has its fatigue limit. However, even under the same working conditions, due to the uniformity of metal materials in the bearing, it is impossible for a large number of bearings to have exactly the same fatigue life. Therefore, we introduce the concept of reliability coefficient.
