Bearings and Lubricants
Load Rating for Bearings
Bearings - Basic dynamic load rating is the load at which
90% of a group of bearings can survive 1 million inner-race revolutions.
However, some bearing manufacturers use 90 million inner-race revolutions
as the rating basis. In either case, the bearing's basic load rating is the figure
of merit used to evaluate bearing life in applications where fatigue
-- rather than inadequate lubrication, excessive temperature, overloading,
or overspeeding -- is the primary failure mechanism. Relationships
for predicting bearing fatigue life under both constant and sinusoidally
varying radial loads are given elsewhere in this chapter.
Relations for calculating basic dynamic load rating for conventional bearings are given in Sections 9 and 11 of the AFBMA Standards. The calculated ratings tend to be low because of recent advances in bearing technology.
Bearings - Basic static-load rating is the maximum radial
or thrust load a bearing can endure without excessive permanent
deformation. Maximum deformation of rolling element or race that
does not significantly degrade bearing performance is 0.0001 times
the diameter of rolling element bearings. Equations for basic static
load for standard bearings are given in Sections 9 and 11 of the