Influence of Surface Texture on Tribological Property of Piston Ring/Cylinder Tribopair
|School||Nanjing University of Aeronautics and Astronautics|
|Course||Mechanical Design and Theory|
|Keywords||Surface texture Piston ring Electrochemical machining Tribology Orthogonal Experiment Oil starvation lubrication|
The tribological phenomena generally exists and 1/3～1/2 of the present global energy consumption presents as frictional loss in all kinds of ways. If the frictional loss can be reduced as much as possible, a large amount of energy can be saved. In these developed nations such as America, UK and Germany, the loss caused by friction and wear accounts for 2%～7% of GNP every year. In 2006, the number reaches up to 950 billion RMB. According to some research, only 35% of the energy in the engine is used for acceleration and 17% for cruising, but 48% of the energy presents as frictional loss in which the friction between piston ring and cylinder accounts for 19%. From these datas, the energy loss caused by the friction of piston ring and cylinder is relatively big. As a result, how to control the tribological performance of this tribopair well is the work people devote themselves to. In addition, it plays a crucial role in improving the reliability and durability of the engine. Surface texture technology which is to fabricate the geometrical profile which regularly arranges with certain dimension on the surface of tribopair has been proved to be an efficient method to improve the tribological performance. At present, it has been widely applied to many fields such as cylinder, journal bearing, mechanical seal and magnetic medium.In order to study the influence of surface texture on the tribological performance of piston ring–cylinder tribopair, a reciprocating test rig was developed. Appropriate piston ring segment was chosen to be the specimen on the surface of which surface texture was fabricated through electrochemical machining technology. The parameters of surface texture include the diameter, area ratio, depth and angle of the pit. According to the orthogonal experiment method, the tribological experiment was carried out with four factors mentioned above and four levels under the condition of full lubrication and different speed and load. Then the experimental datas could be achieved, the corresponding analysis was processed and surface texture was optimized. Besides, the tribological performance of the specimens of different surface texture parameters was studied under the condition of oil starvation lubrication. The result shows that the specimen with certain surface texture parameters can improve the tribological performance efficiently under certain conditions compared with the untextured specimen. The result shows that the specimens with appropriate pit parameters can obviously reduce the friction coefficient compared with the untextured specimen under full lubrication. With comprehensive consideration, the factors influencing the observed index are pit diameter, depth, area ratio and angle according primacy sequence. The optimal geometric parameters are diameter 200μm, area ratio 8%, depth 10μm and angle 60°. Under oil starvation lubrication, the specimen with the parameter of diameter 240μm, area ration 16% and depth 10μm can reduce the friction coefficient by 20.9% at the oil flowing rate of 0. 3125ml/min compared with the untextured specimen.