ELASTOHYDRODYNAMIC LUBRICATION (EHL)

Tribology Group of the University of Pisa

Theoretical/numerical studies began in the 70's.

Experimental work has been made since the 80's.

Experimental Research

Optical interferometry is one of the most used technique to determine the film thickness and shape in typical elastohydrodynamic lubrication (EHL) conditions. Simulations of real machine contacts, such as those between rolling elements and races of bearings, are realized using transparent discs and specimens with proper radii of curvature. White or monochromatic lights are used to obtain interference patterns from which lubricant film thickness and shape can be evaluated. This experimental apparatus is a typical interferometric test rig using both white and monochromatic light. Two motors, one for the specimen and one for the disc, allow to do tests with different rolling and sliding speed conditions.

The Experimental Apparatus

With the use of two gas bearings tests in pure rolling conditions (with the disc disconnected from its motor and only moved by the contact with the specimen) and measure of friction force are also possible.
The interference patterns are recorded using a video camera and a recorder; stored images are then discarded in a computer and elaborated with an image processing program developed in the MATLAB environment.

Monochromatic (546nm) Interference Image
and corresponding 3-D Mesh Surface Plot (ball-plane contact)