Development of a New Life Equation for Ball and Roller Bearings

The conventional rolling bearing life equation ⁽¹⁾, which is based on the theory of Lundberg and Palmgren, has a problem in that it does not match the actual bearing life in all operating conditions. For instance, while the actual life of a bearing under clean lubrication is 20 times longer than the calculated life, actual life under contaminated lubrication is as low as one-tenth of the calculated life.

To solve this problem, the following life equation (Eq. 1: Advanced Bearing Life Equation) was developed with the a_NSK life modification factor:

The new a_NSK factor is based on data from bearing life aNSK tests involving over 450 roller bearings and over 550 ball bearings under a variety of operating conditions. The new life equation with the a_NSK factor showed a satisfactory fit between calculated life and actual life.