Study of Film Thickness in Elastohydrodynamic Contacts using a Novel Technique Based on Electrical Capacitance

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This project will provide a new tool for measuring very thin films, characteristic of boundary lubrication conditions, in real, metal-on-metal contacts.One limitation of the current technique for measuring very thin lubricating films is that it uses a fragile, silica spacer layer, which makes it difficult to use under sliding conditions. The other is that the chemistry of lubricant additives, commonly used in lubricating oils, is strongly dependant on the nature of the surfaces in contact. The first stage of the project will thus be aimed at the development of an optical interferometry method without a silica spacer layer, but a thicker than usual, chromium layer. The second stage of the project is dedicated to the adaptation of electrical capacitance for measuring very thin films characteristic to elastohydrodynamic lubrication. The modified optical interferometry technique, developed in the first stage, will be employed to calibrate capacitance measurements. Once the capacitance method is calibrated, it will be used to study film forming properties of two common additive systems, in sliding, metal-on-metal contacts.This study will enable fundamental scientific information to be gained on lubricant behaviour in rolling/sliding, metal-on-metal contacts and it will be of considerable value to lubricants and machine component producers. The research is essential to enable a future study on the rheology of the lubricating films using dielectric spectroscopy.