Measurement of oil film thickness of a connecting-rod big end bearing by using image processing technique

This paper presents an experimental method to measure the thickness of oil film of a connecting-rod big end bearing. A specific experimental device and a connecting-rod model of photo-elastic material are used to determine the load diagram and to measure the oil film thickness. The method consists in taking two images of a solid, before and after deformation. The surface of the connecting rod is painted with dark spots. Reference images, before deformations, and deformed images are recorded by using a CCD camera and imaging software at different angular positions of the crankshaft. We have developed a technique to measure the thickness of the film by the correlation method of digital images. The measurements of oil film thickness according to the crank angle corresponding with the load diagram and are confirmed by electrohydrodynamic lubrication. The thicknesses of film thus measured can then be compared with the thicknesses given by the numerical calculations.