Life Calculation of Rolling Bearings

Various types of failure modes may occur in rolling bearings during operation, but fatigue pitting corrosion on the surfaces of rings and rolling elements is one of the most basic and common failure modes of rolling bearings, and is usually used as the basis for calculating the life of rolling bearings. After the bearing is damaged by pitting corrosion, there will usually be strong vibration, noise and heat during operation.

The life of a rolling bearing refers to the number of revolutions or the corresponding operating hours of the bearing before pitting corrosion occurs for the first time in the rolling elements or rings of the bearing. The calculation of bearing capacity of rolling bearing mainly refers to the calculation of bearing life.

Like the fatigue life of general structures, the dispersion of fatigue life of rolling bearings is also quite large (see the figure on the right). In engineering, the bearing life with 90% reliability is defined as the basic rating life of the bearing. In engineering practice, the bearing capacity of a bearing is usually measured by the basic dynamic load rating of the bearing. The so-called basic dynamic load rating of the bearing refers to the load value that the bearing can bear when the basic rated life of the bearing is exactly 1 million revolutions, which is represented by the letter C. The basic dynamic load rating of the bearing is based on the combination of experiment and theoretical analysis, and its value can be found in the rolling bearing manual.

The basic rated life (L10) of a rolling bearing is related to the basic dynamic load rating C of the bearing and the applied load (equivalent dynamic load P) on the bearing, which can be determined according to the calculation formula of the rated life.

An important content in the calculation of rolling bearing life is to calculate the equivalent dynamic load and the calculation of the axial force Fa. Since the failure mode of the bearing is not only pitting corrosion, but the bearing life calculation is mainly aimed at the pitting corrosion life of the bearing, so there will be a certain gap between the calculated life of the bearing and the actual life. To reduce this gap, it should be ensured that the bearings are installed correctly, properly lubricated, and maintain a good operating environment for the bearings. For bearings with important uses, online monitoring and fault diagnosis measures can be taken during use to find faults in time and replace failed bearings.