Bearing Life Calculations in Rotating and Oscillating Applications

This article begins by describing standard bearing life models in continuous rotation before going on to explain how the bearing life can be calculated for roller and ball bearings in oscillatory applications. An oscillation factor aosc is introduced, which accounts for the oscillating and stationary ring. This can be calculated numerically as a function of the oscillation angle θ and load zone parameter ɛ as well the parameters γ = D · cos α / dm and the ball-race osculation factors. Critical angles as used by Rumbarger are also employed at low θ values. Appropriate curve-fitted relationships for both roller and ball bearings are then given for a simple calculation of aosc with an accuracy of approximately 10%. Finally, several methods are suggested for estimating the ɛ parameter using a real case with a finite element analysis load distribution accounting for structural ring deformation and ball-race contact angle variations. The results derived in this article allow the lifetime of any arbitrary oscillating ball or roller bearing to be calculated.