Film Thickness Analysis for EHL Contacts under Steady-State and Transient Conditions by Automatic Digital Image Processing

[摘要] The knowledge of the film thickness values is very important in lubricated contacts to verify thelubrication conditions. Optical interferometry is one of the most used methodologies for film thicknessand shape determination of Elastohydrodynamic-lubricated contacts.An image processing programme has been developed for the analysis of white light interferograms.The programme, based on the analysis of the hue channel, has been developed in order to process bigamounts of images, as often generated under transient conditions. The measurement range is currentlylimited to a maximum film thickness of 0.7 μm.The programme has been used for analysing several images recorded in tests carried out with a ballon disc contact under steady-state as well as transient conditions for different velocities and slide-to-rollratios. Under transient conditions, the entraining velocity is varied with a sinusoidal law for twodifferent frequencies.The results obtained evidenced an asymmetric reduction of the film thickness when increasing thepercentage of sliding, both for stationary and transient conditions. Under transient conditions withincreasing test frequency, film thickness loops of increasing amplitude have been found that reducetheir amplitude more when the ball is running faster than the disc. Squeeze and thermal effects canexplain the results obtained.

[学科分类] 力学，机械学