ABSTRACT
The primary function of a lubricant is to prevent wear of the rolling and sliding contacts of a
bearing through hydrodynamic, elastohydrodynamic (EHL), or boundary lubrication; how-
ever, there are many other vital functions, such as:
. Minimizing the frictional power loss of the bearing
. Acting as a heat transfer medium to remove heat from the bearing, or redistributing the
heat energy within the bearing to minimize differential thermal expansions . Protecting the precision surfaces of the bearing components from corrosion . Removing wear debris from the roller contact paths . Minimizing the amount of extraneous dirt entering the roller contact paths . Providing a damping medium for cage dynamic motions
No single lubricant or class of lubricants can satisfy all the requirements for bearing operating
conditions, from cryogenic to ultrahigh temperatures, from very slow to ultrahigh speeds, and
from benign to highly reactive operating environments. As for most engineering tasks, a
compromise is generally exercised between performance and economic constraints. The
economic constraints involve not only the cost of the lubricant and the method of application,
but also its impact on the life cycle cost of the mechanical system.
