A Dichromatic Interference Intensity Modulation Approach to Measurement of Lubricating Film Thickness

The study aims to extend the measurement range of dichromatic interferometry in lubricating film thickness measurement. Subtraction of two sets of interference fringes, which are produced by dichromatic (red and green) lights, gives a modulated signal of intensity against film thickness. The measuring range without wavelength ambiguity is limited to the first half-cycle of the beat wave in the modulated signal. Theoretical and experimental analyses of the modulated interference intensity variation against film thickness were conducted. The differences in the pattern of the modulated interference intensity were obtained in the first three half-cycles of the beat wave. Based on that, a robust dichromatic interference intensity modulation approach for lubricating film measurement was derived and its measuring range without wavelength ambiguity was successfully extended to the magnitude equivalent to three half-cycles of the beat wave. To test the feasibility and credibility of this approach, the film thickness in elastohydrodynamic and hydrodynamic lubricated contacts was measured. The results were well correlated with the classical theory. Using red and green lasers with wavelength of 653 and 532 nm, respectively, the measurement range can be extended to 4 μm.

[1]  Wen,et al.  On thin film lubrication , 1996 .

[2]  Lavern Dale Wedeven.  Optical measurements in elastohydrodynamic rolling-contact bearings , 1970 .

[3]  Olov Marklund,et al.  Measuring Lubricant Film Thickness with Image Analysis , 1994 .

[4]  S. Wen,et al.  Thin film lubrication. Part I. Study on the transition between EHL and thin film lubrication using a relative optical interference intensity technique , 1996 .

[5]  Motohiro Kaneta,et al.  Effects of elastic moduli of contact surfaces in elastohydrodynamic lubrication , 1992 .

[6]  Jérôme Molimard,et al.  Thin Film Colorimetric Interferometry , 2001 .

[7]  Miroslav Liška,et al.  Differential colorimetry: tool for evaluation of chromatic interference patterns , 1997 .

[8]  W. Hardy.  II. Note on static friction and on the lubricating properties of certain chemical substances , 1919 .

[9]  D. Zhu,et al.  Elastohydrodynamic Lubrication With O/W Emulsions , 1994 .

[10]  P. Wong,et al.  A Wide Range Measuring System for Thin Lubricating Film: From Nano to Micro Thickness , 2004 .

[11]  I. Křupka,et al.  Application of Spectroscopic Reflectometry to Elastohydrodynamic Lubrication Films Study , 2011, Tribology Letters.

[12]  Hugh Spikes,et al.  The Measurement and Study of Very Thin Lubricant Films in Concentrated Contacts , 1991 .

[13]  P. Hariharan.  Basics of Interferometry , 2006 .

[14]  P. L. Wong,et al.  Interferometry Measurement of Lubricating Films in Slider-On-Disc Contacts , 2010 .

[15]  E. Palik.  Handbook of Optical Constants of Solids , 1997 .

[16]  James C Wyant,et al.  Computerized interferometric surface measurements [Invited]. , 2013, Applied optics.

[17]  An exploration of the elastohydrodynamic— hydrodynamic transition through film thickness measurements in rolling point contacts , 2009 .

[18]  P. Wong,et al.  Determination of thin hydrodynamic lubricating film thickness using dichromatic interferometry. , 2014, Applied optics.

[19]  J. Molimard,et al.  New tools for the experimental study of EDH and limit lubrications , 1999 .

[20]  M. Kirk.  Hydrodynamic Lubrication of ‘Perspex’ , 1962, Nature.

[21]  Hugh Spikes,et al.  The Development of a Spacer Layer Imaging Method (SLIM) for Mapping Elastohydrodynamic Contacts , 1996 .

[22]  P. L. Wong,et al.  A multi-beam intensity-based approach for lubricant film measurements in non-conformal contacts , 2002 .

[23]  R. Gohar,et al.  Theoretical and experimental studies of the oil film in lubricated point contact , 1966, Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences.

[24]  A. Cameron,et al.  Evaluation of Lubricants Using Optical Elastohydrodynamics , 1968 .

[25]  Hugh Spikes,et al.  Measurement of Sub-Nanometer Lubricant Films Using Ultra-Thin Film Interferometry , 2003 .

[26]  R. Gohar,et al.  The Mapping of Elastohydrodynamic Contacts , 1967 .