Study On Dichromatic Interferometry Of Lubricant Film Measurement

Elastohydrodynamic lubrication (EHL) is a dominating mechanism in lubricationof many machine elements, such as rolling bearings and gears, and the lubricating filmthickness has been one of the most concerns in the study of EHL. For a pretty long time,the EHL film chromatic inteferometry neasurment has been concentrated on theimplementation of the optical technique, and related instrumentation, and less work wasdeveoted to the fundamentals of the measurement principles. In this thesis, a model hasbeen built to describe the measurement of EHL films by dichromatic interferometry, anddetailed analyses were carried out to understand the principles. Furthermore, an novelmeasurement method has also been presented, which is based on the intensity valuses ofR and G components in the interferences.On the basis of the multi-beam interference and the CCD camera spectralresponses, a colorimetric model has been established for the interference measurementof lubricating film thickness. A computation program was built for rendering theinterferograms generated by a dichromatic light source in the lubricating filmmeasurement..For a static ball-glass disc contact, theoretical simulation and lab tests forthe red/green dichromatic interferograms were well correlated.Further analyses showed that the dichromatic interferogram was mainly influencedby the FWHMs of the green/red filter, the thickness of the beam splitter, the spacerthickness and the lubricants. A small FWHM,4-10nm in the beam splitter thickness andlow spacer thuickness can lead to high contrast of interference fringes.Simulations have been carried out for color rendering of dichromaticinterferometric measurement of the film thickness in a process of impacting andentrainment in an ball-on-disc EHL contact, and the properties of interferomgrams wererevelaed. Color simulations have also been carried out for EHL films for iso-thermaland Newtoinian fluids under stable conditions, in which the influence of speeds andloads were investigated.Based on the above analyses, a novel RG method was developed for lubricant filmmeasurement. In this approach, the pseudo-cycle of the interference is determined by comparing a series of fulm thickness values by different R and G compoinents, and thenthe film thickness can be obtained automatically. Theoretical analysis and simulatedmeasurements have proved the applicability of the proposed approach..