Load and life

The total number of revolutions or the total number of working hours at a certain rotational speed before the contact fatigue wear of any component of the rolling bearing is referred to as the bearing life of the bearing and the life of the bearing is very variable. The bearings of the same batch are operated under the same conditions and their life It can be several times or even dozens of times. 90% of the same batch of bearings is referred to as the rated life L when the total number of revolutions (or working hours) reached or exceeded before fatigue spalling.
The load that can withstand the rated life of 1 million revolutions is the rated dynamic load C. When the sum of the amount of plastic deformation at the contact point between the rolling element and the raceway subjected to the maximum load is one ten-thousandth of the diameter of the rolling element, the load that can withstand is the rated static load C0. The higher the rated load, the stronger the bearing’s load capacity. Radial bearing rated load is pure radial load, thrust bearing rated load is pure axial load. The actual load of the bearing is often different from the rated load and must be converted into equivalent load.
Under the equivalent dynamic load P, the bearing life is the same as the actual load condition. Under the equivalent static load P0, the total plastic deformation at the contact between the rolling element and the raceway with the largest load is the same as the actual load. The relationship between the rated life of the bearing, the rated dynamic load and the equivalent dynamic load is

In the formula, ε is the life index: ball bearing ε=3, roller bearing ε=10/3. When selecting a bearing, it is usually taken as the life expectancy of the bearing during the repair or overhaul period of the machine. For example, the equipment that is not frequently used is 500 to 2000 hours; the machine that is used continuously for 8 hours a day is 2 to 30,000 hours; and the machine that is used continuously for 24 hours a day is 40 to 100 thousand hours. In fact, only a few bearings are damaged when the life expectancy is reached.