Theoretical and experimental investigations of lubrications at point contacts.

A theoretical and experimental study of hydrodynamic lubrication between surfaces which touch, nominally, at a single point has been carried out. The first theoretical study involves the most general case of two surfaces of any curvature and having any directions of sliding and rolling motions. The theory has been applied to derive the dependence of oil film thickness between hypoid gears upon the design parameters. The second theoretical study is concerned with the hydrodynamic lubrication of a sphere spinning about its point of contact with a cylindrical groove. This motion is a simulation of one element of the kinematic behaviour of a ball in an angular contact bearing and calculations have been made to show the relative effect of this motion in the generation of a hydrodynamic film under these conditions. Experimental investigations have been made, using a crossed cylinders machine, into the nature of the oil film under conditions of elastohydrodynamic lubrication at point contacts. The optical interference technique has been used to derive the dependence of film thickness between cylinders of steel and glass upon speed and load using a medium viscosity mineral oil as a lubricant. The factors which affect the overall shape of the film under these conditions have also been investigated. Finally, results are presented of a direct comparison between the optical and capacitive methods of measuring the film thickness at point contacts.