A large number of rolling bearings are used in the support of gearboxes, which are characterized by very small static and dynamic friction torques, even when the load and velocity vary over a wide range. It is convenient to install and use rolling bearings. However, when the speed of the shaft is close to the limit speed, bearing capacity and life of the bearing drops sharply, and the noise and vibration during high-speed operation are relatively large. The deformation of the shaft and bearing during gear transmission causes deflection of the axis of the inner and outer ring of the gear and bearing, which makes the load distribution on the gear teeth not uniform and reduces the bearing capacity of the transmission parts. Gear teeth often break due to load inhomogeneity and in many cases due to mass of bearings and other factors, such as severe overloading. When choosing bearings, they should be determined not only according to the nature of the load, but also according to the structural requirements of the components. Relevant technical standards, such as DIN281, or bearing manufacturer samples, are available with a complete set of calculation procedures and methods for reference.

The calculated service life should not be less than 30,000 hours. Under normal conditions of installation, lubrication and maintenance, the contact surface of the ring and the rolling body is subjected to repeated action of alternating loads during the operation of the bearing, resulting in fatigue spalling. If fatigue spalling occurs beyond the life span, it is normal damage of rolling bearings. Therefore, generally speaking, bearing life refers to the fatigue life of bearing. The fatigue life of a batch of bearings is always dispersed, but always subject to a certain statistical law, so the bearing life is always associated with the probability of damage or reliability.