Including the Method of Lubricant Film Thickness Measurement with the Use of the Monochromatic Interferometry to the Education of Tribology

Abstract

Measuring of distance as presented at the universities is usually limited to dimension down to microns. This orders of distance are sufficient for common engineer’s application. However dimension are a lot smaller when engineers deal with the tribology research. One of the most important progresses in the field of tribology in last century is without doubts the elastohydrodynamic lubrication (EHL). This lubrication regime can be found for example in rolling bearings or gears. Common thickness of the lubricant film in the EHD contact is in order of tens or hundreds of nanometers. Optical method which enables measurements of such distances was developed by Gohar and Cameron in 1960s. This method is based on interference of monochromatic light and provides possibility of obtaining lubricant film thickness from known wavelength of used light and its intensity in the lubricated contact. Students can create central film thickness prediction with use of the analytical formulae of the Hamrock and Dowson. This prediction is then confirmed by hands-on experiment in laboratory. Contact simulator with microscope and red light is used to record sequence of the interferograms. These interferograms are then processed in Matlab® software in order to obtain film thickness.