Elastohydrodynamic film thickness mapping by computer differential colorimetry

This paper describes a new experimental technique for the study of elastohy drodynamic (EHD) lubricant films. This technique, which is based on the com puter processing of EHD chromatic interferograms, uses a combination of ima ge analysis and differential colorimetry for film thickness evaluation This approach overcomes some major limitations of conventional optical interfer ometry and allows the precise mapping of lubricant plm thickness distributi on in EHD contacts, including transient and quasistatic phenomena. The tech nique has been used for the evaluation of chromatic interference patterns o btained from a conventional optical test rig for rolling point contacts. Th ree-dimensional representations of lubricant film thickness and shape with high accuracy and spatial resolution have been obtained. The technique's ac curacy has been checked and a comparison with conventional monochromatic in terferometry has been done for validation. The technique's resolution has b een confirmed through the observation of local film thickening just before the EHD exit constriction for both pure rolling and sliding conditions.