Hydrodynamic Lubrication

Abstract

This chapter discusses the theory of hydrodynamic lubrication. The chapter demonstrates how a basic property of all liquids, such as viscosity, can be used to produce cheap, reliable bearings that operate with low friction and wear. The mechanisms of hydrodynamic film generation and the effects of operating variables such as velocity, temperature, load, design parameters, etc., on the performance of such films are outlined. This is explained using bearings commonly found in many engineering applications as examples. Secondary effects in hydrodynamic lubrication such as viscous heating, compressible and non-Newtonian lubricants, bearing vibration and deformation is described and their influence on bearing performance is assessed. Like many important scientific principles, chance observation played an important role in the recognition of hydrodynamic action as a basic mechanism of bearing lubrication. The complete separation of sliding surfaces by a liquid film under full hydrodynamic lubrication can allow bearings to operate indefinitely without any wear. Any liquid or gas can be used for this form of lubrication provided that no chemical attack of the bearing occurs. The disadvantage of hydrodynamic lubrication is that a non-zero sliding or “squeeze” velocity is required before load capacity is obtained. © 1993, Elsevier Science & Technology.