The industry generally uses L10 life as the basic bearing life evaluation principle, and L10 is the basic rated life. A group of bearings of the same model, under the action of equivalent dynamic load, the total number of revolutions that 90% of the bearings can achieve without material fatigue spalling (pitting corrosion) (millions of revolutions or the number of hours converted according to the speed).
90% bearing is not damaged, which means the reliability is 90%. For very important occasions, it is not enough. The reliability coefficient of the bearing a1 should be considered. a1 is a discount factor based on L10.
When the reliability requirement is 95%, a1=0.62;
When the reliability requirement is 99%, a1=0.25;
When the reliability requirement is 99.9%, a1=0.10.
For example, when the reliability requirement is 95% and other conditions are the same and all are 1, the bearing life is 0.63×L10.
During the initial selection, the P/C values under different reliability levels can be evaluated by referring to the table below.
95% reliability
99% reliability
99.9% reliability
The pursuit of high reliability and long life is always the user's ideal, but it will bring great difficulties to the selection of rolling bearings. For example, the bearing size is too large, the bearing temperature cannot be controlled, and even the appropriate bearing cannot be selected. For example, the minimum load limit, SKF bearings usually require: ball bearing 0.01C, column bearing 0.02C. The specific ratio can be calculated according to the corresponding product table in the bearing sample.
Therefore, the industry generally uses L10 life as the calculation criterion for bearing life to comprehensively consider reliability and economy.
(Source: Electric drive industry)