In-situ optical observation of lubricating film in journal bearings

Milan Omasta^a, Petr Šperka^a, Ivan Křupka^a, Martin Hartl^a, Luboš Smolík^b, Michal Hajžman^b and Pavel Polach^b

^a Brno University of Technology, Technická 2896/2, 616 69, Brno, Czech Republic

^b University of West Bohemia, Faculty of Applied Sciences, Technická 8, 301 00, Plzeň, Czech Republic

Development of a bearing technology has been accompanied by an effort of a direct insight into the fluid film. Since the pioneering experiments of Tower, optical method has proved to be a powerful technique for revealing the complex nature of fluid film bearings. Nowadays, the need for a deeper understanding of phenomena related to e.g. fluid-induced instabilities, surface texturing and non-Newtonian lubricant behaviour represent a potential for other development and application of the technique.

The aim of this work is to demonstrate various techniques for in-situ optical observation of fluid film behaviour in journal bearings. Those techniques are implemented on a journal bearing test rig. Optical investigation is allowed from the outside using a Sapphire ring and from the inside using a hollow shaft with a glass window. The first approach is suitable for application of a particle tracking for the study of fluid-film speed profile and for application of fluorescence technique for the study of fluid-film thickness and cavitation. The inside view allows in-situ observation of bearing wear and behaviour of textured surface. Some preliminary results demonstrate possibilities of those methods for a detailed fluid film investigation.