On The Characteristics Of Elastohydrodynamic Lubrication Inaconfined Gap

Elastohydrodynamic lubrication (EHL) is an important lubrication mechanism formechanical components in highly stressed non-conformal contact, such as bearings,gears、cams and so on. The service life of these parts depends largely on the lubricationof the contact surfaces. Therefore, this thesis is concentrated mainly on highly stressedcontact pairs. EHL have been studied with a confined gap experimentally andtheoretically. Completed work includes:(1) A simulating system for the thrust-ball bearing lubrication has been builtpurposely. With this system, studies have been carried out to investigate the film shapes,the actual revolution speed of the ball around the bearing center and then related filmthickness when a ball goes into the loading zone from the un-loading zone under anintentionally non-uniform gap. The results show that when the ball enters into the highloading zone of a small gap from the light loading zone of a large gap, the contact areaincreases and the film thickness decreases, and the lubrication regime changes fromhydrodynamic lubrication to elasto-hydrodynamic lubrication. In the heavy loadingzone, the film thickness does not change obviously. At a fixed position, the filmthickness increases with increasing speed.(2) The relative rigid spatial position of lubricated surfaces in mechanical systemsare restricted by others components, such as those in rolling bearings with preload,where the surfaces of the balls, the inner race and the outer race are loaded together,then the film is produced in a confined gap. As a preliminary study, assuming the rigidrelative position between the surfaces of two contact bodies is fixed, full numericalanalyses have been carried out for line-contact isothermal EHL with confined gaps, andthe influences of working parameters such as speed, material and rigid position on thefilm thickness and pressure have been revealed. The results show that with increasingdimensionless entrainment speed and material parameters, the dimensionless filmthickness and pressure increase. With an increase in the gap parameter, the filmthickness is decreased, but pressure increases. Film thickness formulas are obtained from the numerical film thickness with the different parameters.(3) Full numerical analyses have been carried out for point-contact isothermal EHLwith confined gaps and the influences of working parameters such as speed, materialand rigid separation H00on the film thickness and load-carrying capacity have beenrevealed. New loading capacity and film thickness formulas are obtained from thenumerical data, the results from the formula and the numerical calculation are wellcorrelated.(4) Experiments have been carried out to measure lubricant films with confinedgaps, the results were compared with the numerical analyses, showing good agreement.