A Study On The Pure Squeeze Thermal Elastohydrodynamic Lubrication In Elliptic Contacts

Great efforts have been made by researchers over the world to study the pure squeeze process of a free-dropping ball impacting an oily surface and the following normal bouncing problem. However, thermal effect was ignored in all the previous works regarding the pure squeeze action, and the surfaces were usually assumed to be completely smooth. In this thesis, therefore, the famous experiment carried out by Safa and Gohar in 1986 for the dropping-ball pure squeeze problem was simulated numerically under isothermal conditions. The thermal effect and the influence of surface texture were then added into the analysis consequently.First of all, in order to start the analysis of a bouncing ball in a quarter of the computational domain with Cartesian coordinates under both isothermal and thermal conditions, multi-level techniques for solvng pressures and evaluating elastic deformations were developed together with the column-by-column relaxation scheme for solving temperatures.Secondly, the numerical simulation of the curve of the central pressure against time achieved by Safa and Gohar in their experiment was performed under isothermal conditions, while the influence of some representatively physical and geometric parameters was discussed.Then, the Safa and Gohar's curve was simulated again under thermal conditions. And, the isothermal, thermal, and experimental results were intercompared as well. Furthermore, a thermal EHL solution of the elliptic contact dropping-ball pure squeeze problem was achived the first time in the world. Finally, the analyses of the normal bouncing of a ball on an oily plate with a single bump or dent were made, indicating that the existence of a single bump or dent can change only the local pressure and film thickness in the process, if the height of the roughness is not large enough.