A Study About The Impact Of Ellipse Micro-dimple On Hydrodynamic Lubrication Performance

Lubrication is a technical measure used to improve the friction state of friction pair and reduce friction and wear. It's the important research content of tribology. In recent years, the technology of surface texture developed rapidly, providing a new way to improve the tribological properties of friction pairs.It has significant research value.At present, the researchers have done a lot of researches on the surface texture shape and the optimization design of the parameters. However, most of them studied the tribological lubrication properties of the textured surface through the measurement of the frictional force or friction coefficient.Though small part of researches on evaluating lubrication properties of the textured surface have been done by measuring the film thickness, the shape of texture unit was mostly circular or groove. Lubrication film load carrying capacity and film thickness are two important evaluation indexes on hydrodynamic lubrication. Therefore, this paper chose the ellipse dimple as the research object to study its impact on hydrodynamic lubrication performance in both theory and experiment.In theoretical research, the average dimensionless lubrication film pressure is used to judge the lubrication performance of the ellipse dimple. A ellipse dimple model is developed under hydrodynamic lubrication based on Reynolds equation to study the influence of inclination angle of ellipse dimple long axis,slender ratio,depth, area ratio and equivalent radius on the average dimensionless lubrication film pressure. The calculation results showed that ellipse dimple placed parallel to the direction of sliding velocity, with bigger slender ratio and equivalent radius and the area ratio of 5% and the depth close to the film thickness, can get larger lubrication film pressure.In experimental research, the elliptic micro-dimples with different geometric parameters were fabricated on a silicon wafer by using photolithography and wet etching process.The oil film thickness were investigated through the light interference test machine of oil film thickness under different loads and speeds. The effects of dimple parameters including inclination angle of ellipse,slender ratio,depth, area ratio and equivalent radius on the characteristics of oil film thickness were studyed. According to the test data,it can draw the following conclusions: the elliptic dimples with appropriate geometric parameters can increase the oil film thickness, obtain better hydrodynamic lubrication performance. The oil film thickness increased with the increase of rotational speed, and decreased with the increase of load. In all of the samples,the sample with the inclination angle of 0°, the slender ratio of 4, the depth of 5?m, the area ratio of 5.67% and the equivalent radius of 100?m showed the highest oil film thickness and optimal results. Compared to no texture sample, it can increase the oil film thickness obviously, improve the lubrication effect of friction pairs. When the load is 1N, the average oil film thickness increase by 10%. When the load is 4N, the average oil film thickness increased by 10.9%.