Optical characterization of elastohydrodynamic lubricated (EHL) contacts using surface plasmon resonance (SPR) effect

In this paper we report a novel optical technique based on the surface plasmon resonance (SPR) phenomenon for studying elastohydrodynamic lubricated (EHL) dimple. While it is well known that the refractive index (RI) variation in the lubricant may provide direct information on the pressure distribution inside a highly pressurized EHL dimple, one can obtain the pressure in the spectral SPR absorption curve, which corresponds to a unique color complexion in the SPR image.We have performed experiments to compare our SPR imaging technique with the one based on conventional optical interferometry. The new SPR technique provides an improvement of over 180 times in measurement accuracy. More importantly, SPR measures the RI directly and does not require any information on the lubricant film thickness. In light of these advantages, the SPR detection approach reported herein should be an attractive technique for studying EHL contacts.