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Bearing life rating theory and formula2016-10-13
For modern high quality bearings, the nominal or basic rating life may vary greatly from the actual service life in a particular application. In a particular application, the service life is affected by a variety of factors, including lubrication, contamination, misalignment, installation, correctness, and environmental factors.
Therefore, the ISO 281:1990/Amd 2:2000 contains a modified equation of life to supplement the calculation of the basic rated life. This life calculation method employs a correction factor that calculates the lubrication, contamination, and fatigue limit of the bearings. The ISO 281:1990/Amd 2:2000 also allows the bearing manufacturer to recommend the appropriate method to calculate the available bearing life correction factors according to the operating conditions. The SKF correction factor A, SKF uses the concept of the fatigue load limit Pu, similar to the algorithm used for other machine components. The fatigue load limit is listed on the product list. In addition, SKF aSKF also uses the life factor (viscosity) and lubrication condition of a coefficient of the pollution degree of C to reflect the use of the operating conditions.
The ISO 281:1990/Amd SKF equation and the rating life of uniform Lnm = A1 aSKF L10 2:2000 = A1 aSKF (C/P) p if the speed is constant, life can be used to work the hours equation, Lnmh = A1 aSKF 106/ (60N) L10, where Lnm = SKF rated life (reliability 100-n1)%, million transfer Lnmh = SKF (rated life reliability as 100-n1)%, operating hours L10 = Basic rated life (reliability of 90%), A1 = million life reliability coefficient aSKF = SKF life factor = basic dynamic load rating, KNP = equivalent dynamic load KN
N = rotating speed, r/minp = life expectancy equation, index 3, for ball bearings, 10/3, for roller bearings
1) the coefficient n represents the possibility of failure, for example, the difference between the necessary reliability and the 100%.
In some cases, it is preferable to use a separate unit to indicate the life of the bearings without millions of turns or hours. For example, the bearing life of axle bearings for road and rail vehicles is usually expressed by running kilometers.