Studies On The Lubricant Film Transportation Within Elastohydrodynamic Lubrication Contacts

This study is mainly concerned with the transportation characteristics of entrapped lubricant film within an EHL contact.For accurate control of experimental parameters and credible experimental results, the mean accelerating time of the driving system of the optical test rig was measured and set to desired value to avoid dynamic effect when entraining lubricants. In addition, the transportation process of the entrapped lubricant within contact zone was directly visualized by incorporation of the image acquisition system—a non-linear editing and acquisition system—"Canopus EDIUS".Using the custom-made optical EHL test rig, experimental studies on the transportation characteristics of the entrapped lubricant within a steel ball-glass plate contact zone were carried out under pure rolling conditions. The results show that the entrapped lubricant induced by impact moves towards the outlet region with moving surfaces. Furthermore, the moving speed of the entrapped lubricant is equal to the entrainment speed when the displacement of the entrapped lubricant center is smaller than a critical value. And when the center displacement travlels more, its speed is lower than the entrainment speed and the central film thickness of the entrapped lubricant goes down. In the inlet region, the entrapped lubricant moves at entrainment speed and its minimum film thickness almost keeps constant. However, the minimum film thickness in the outlet region first increases and then decreases. In addition, the above critical displacement remarkably depends on the entrainment speed, initial dimple depth as well as the applied load.Experimental investigations on the transportation characteristics of the entrapped lubricant under spinning-sliding conditions were also performed by the spinning optical EHL test rig. The central film thickness and the inlet and outlet minimum film thickness of the entrapped lubricant as well as their locations were discussed. At the same time, the effect of the spin-slide ratio on the transportation characteristics of the entrapped lubricant was revealed as well.A mathematical model has been presented to decribe the experiments of lubricant impact entrapment and entrainment under pure rolling conditions. Different from the compulsory load fixing shceme by previous researchers, the present model presents a reasonable physical process to determine the relative rigid location of the solids through the Newton's law. Based on the model built, a computation program has been written to simulate the transportation of the entrapped lubricant. The numerical results were qualitatively correlated to those obtained from the foregoing experiments.