Investigation On Surface Dimple Of Ehl Film Under Zero Entrainment Velocity

This thesis studies the surface dimple as entrainment velocity equals zero. The work is divieded into three parts: the establishment of high precision numerical algorithm for point contact, the effect of fluid rehology on the thermal elastohydrodynamic lubrication under zero entrainment velocity(ZEV) in line contact and the variation of surface dimple in point contact thermal EHL under ZEV condition.Aiming to master multigrid technique and the method to obtain temperature field which are used to solve numercal Thermal EHL problem, the research on high precision numerical algorithm of point contact is presently firstly. The Reynolds equation and energy equations are derived by the second order difference scheme. An impact load problem is employed as a test case. The results of pressure, film thickness and temperature rise generated by first and second order difference schemes are compared.In the investigation of surface dimple for line contact under ZEV condition, the evolution from a big classical dimple to a small centralized dimple for surface velocity changing from high to low values is revealed. The effect of fluid rheology on dimple is considered. And the comparisons of numerical results between Newtonian and Eyring fluid are given. The influence of surface velocity and applied load on film thickness, traction coefficient and the distribution of pressure, temperature, flow velocity, shear stress within flim are analyzed. In order to improve the lubricating property of ZEV with low velocity, the variation of lubricant viscosity and pressure-viscosity coefficient, surface waviness on film and central dimple are investigated. The variation of surface dimple under ultra-high velocity is studied as well.The study on ZEV is extended into point contact subsequently. Eyring fluid is applied in the numerical simulation for experiment interferograms. The formation of tiny centralized dimple in the experiment is explained by “temperature-viscosity wedge”. The small centralized dimple appearing under low velocity is attributed to low temperature rise in contact region. The impact of velocity on Newtonian and Eyring fluid results is discussed. And the pressure, film thickness and its temperature rise of Newtonian andEyring fluid under different loads are analysed.