A Theoretical And Experimental Study On Surface Texturing Piston Ring

The piston ring/liner rubbing pair is one of the most important rubbing pair in combustion motor and the friction loss between piston ring and cylinder liner is about 19% of the total friction loss in the internal-combustion engine. So, a large amount of works were done by domestic and foreign scholars in controlling the tribological performance of this rubbing pair. By improving the material of piston ring/liner and the coating of surface, they carried on deep and fundamental research. Surface texture technology which is to fabricate the geometrical profile which regularly arranges with certain dimension on the surface of rubbing pair has been proved to be an efficient method to improve the tribological performance. It attracts more attention around the world and has been widely applied to many surfaces of rubbing pair. In this thesis, a theoretical and expeimental study were performed on friction properties of piston ring/liner with surface texture under full lubrication.In theoretical research, a two-dimensional Reynolds equation is developed under hydrodynamic lubrication. The dimensionless hydrodynamic pressure distribution at various micro-pore geometry parameters and arrangement are obtained from a solution of the Reynolds equation by finite difference method. In order to accelerate convergence, multi-grinder method and over-relaxation iterative method are used. In the condition of full texture, the best depth of dimple is the same as the film thickness. The area ratio of texture is depend on the ratio between the depth of dimple and the film thickness. The diameter is in directproportion to the non-dimensional pressure. Partial texture also plays an important part in improving the non-dimensional pressure. The optimum value of partial textured portion is 60% and the pressure is directproportion to area ratio and diameter of texture. When the depth of dimple is seventy percent to the film thickness , computational results show great bearing capacity.In experimental research, the lithography and micro-electrochemical machining technology are used to fabricate texture on the surface of actual segmental barrel-shaped piston ring. Under different speeds, pressures and sufficient lubrication, an optimized reciprocating friction-abrasion testing rig is used to study the influence of dimple diameter, depth, area ratio and partial texture portion on tribological properties of piston ring/liner. From the experimental data obtained in different working conditions, there exists an optimal indentation geometric parameters. In respect of diameter and depth , it is found that an optimum depth-diameter ratio can be found under different pressure and speed. At the same time, there is a close relation between the depth and the film thickness. The trend is the same as the result of theoretical computation. In respect of aera ratio, it appears excellent antifriction properties when the area ratio are 10.4% and 15.5%. In the respect of partial texture, there is no remarkbale antifriction properties compareing with the full texture when the area ratio is lower and the film thickness is thin. With the increasing of area ration and film thickness, partial texture shows great antifriction properties and the optimum ratio is 80%.