Influence Of The Mixed Surface Texture On The Tribological Performance Of Cylinder Liner

In the engine, the combustion chamber provides power for other work like human heart. There isthe system of cylinder liner, piston and piston ring in the combustion chamber and there are two pairsof rubbing pair under rigorous conditions in the system. The friction loss of the system accounts for44percent of the total friction loss in the engine. As the public part of the two pairs of rubbing pair,the tribological performance of cylinder liner have been studied by domestic and overseas scholars inthe choice of materials and surface treatments. Surface texture technology which is a surfacetreatment technology has been proved to be an efficient method to improve the tribologicalperformance. It attracts more attention around the world and has been applied to the system ofcylinder liner, piston and piston ring.In this thesis, an experimental study was employed to research the tribological performance ofthe mixed surface texturing cylinder liner by choosing the cylinder/piston ring rubbing pair. Therewere three forms of mixed surface texture which divided by the distribution of the area ratio: evendensity texture, variable density texture and composite density texture. The even density texture wasthe single area coverage texture, the diameter and area coverage of the dimples were considered inthis paper. The variable density texture was composed of different even density texture in the directionof the velocity, there were two forms of variable density: high-low-high type and low-high-low typein this paper. The composite density texture was that the even density texture was distributed in theform of partial texturing type in the direction of the velocity.In this paper, the cylinder and piston ring specimen were selected from the actual engine. Themicro-pit array was regularly distributed on the inner wall of cylinder liner with mechanical stripes byusing the method of movable mask electrochemical machining technology, the reciprocating frictiontests were carried out on the inner surface of cylinder liner with piston ring specimen. Three forms ofmixed surface texture were investigated by testing the average of friction coefficient in whole strokeunder sufficient lubrication conditions, including even density, variable density and composite density.According to the test results, the action mechanism of the mixed surface texture was briefly analyzed.The experimental research and the test results analysis could draw the following conclusions.1. In the case of the even density, the diameter and area coverage of dimples were the importantfactors which influenced the effect of the mixed surface texture, and the effect of the two factorsinfluenced each other. The geometrical parameter which reduced the friction mostly was the diameter, followed by the area coverage. Compared with the single mechanical honing stripes, the friction–reducing capacity of the mixed surface texture was bigger in the condition of hydrodynamiclubrication. In the condition of boundary lubrication, the mixed surface texture had no obviousadvantage in comparison with the single mechanical honing stripes.2. In the case of the variable density, it was easy to decrease friction using the variable densitytexture which included the density combination of10%-5%-10%and5%-15%-5%under certainconditions in comparison with the even density texture. The tribological performance of the variabledensity texture was determined by squeeze effect of the entire combination and the tribologicalperformance of the even density texture in the combination, and both of them had a role at certainspeed. So the velocity was also the important factor which influenced the tribological performance ofthe variable density texture.3. In the case of the composite density, the friction-reducing capacity of the most optimalcomposite density texture was bigger than the single mechanical honing stripes, and smaller than themost optimal even density texture. The tribological performance of the composite density texture wasdetermined by the positive effects of additional hydrodynamic pressure and the negative effects ofpressure relief of oil flow.