| Friction and wear extensively exist in the kinematic pair of diffierent kinds ofactive machines. According to statistic, there is about 30~50% of energy consumedby friction in the world industry department. 75% of disable machine probablyproduced by wear. As for a developed industrialized country, the economic losscaused by friction and wear costs 1-2% of Gross National Product every year.Thereby it is very meaningful for advancing the work abilities and lifetime ofmachine and gaining huge economic benefit and social benefit to deal with frictionand wear correctly.With the development of internal-combustion engine, people dedicatestheirself to reduce the friction and wear of piston-cylinder system that is mostimportant for engine, due to 60-70% of total friction loss of engine approximatelycome from it, which influence the lifetime and edurability of engine seriously. In thepast, the research of friction and wear mostly concentrated on piston ring-cylindersystem. but turns to piston skirt increasingly in recent years because of its importantfunctions such as guiding direction, bearing lateral pressure, thermal transmissionand so on. If the friction and wear of piston skirt cann't be disposed in a good way,itwill result in serious wear even scratch,cylinder sticking and cylinder score.This thesis adopt model test, mechanism analysis and finite element simulationmethod to discuss and optimize the wear resistance ability of different kinds ofnon-smooth forms, instead of engine bench test for its high cost and long test period,which is important theory reference for applying bionic non-smooth technic topiston.Biology non-smooth concept and biology non-smooth wear resistance theorywere advanced by JiLin University Key Laboratory of Terrain-Machine BionicsEngineering, Ministry of Education, which had been applied successfully to bionicplough, bionic bulldozing plate and roll etc. In this thesis, on the basis of wearresistance theory of soil animals, four kinds of bionic non-smooth forms twelvelmodel samples in all are designed. In addition one kind of flat plate sample whichhas no any non-smooth structure serves as credence of contrast. Base on piston'scomplicated working conditions and lubrication status,four kinds of model tests aredesigned that are dipping lubricant test,dripping lubricant test, cold start test and dryfriction test.Orthogonal test optimization is adopted in dipping lubricant test and drippinglubricant test, which the primary and secondary factor is Non-smooth Sorts,Non-smooth Distribution, Non-smooth Spacing and Non-smooth Dimension for theformer and Non-smooth Sorts, Non-smooth Distribution, Non-smooth Dimensionand Non-smooth Spacing for the latter and both optimal combination is through-holewith dimension of 2mm, spacing of 5mm and interlaced distribution. On the basis ofthe two tests No. 8 sample and flat plate sample are used to contrast in cold start testand dry friction test,The results of model tests indicates that all of non-smooth samples are betterwear resistance and lubrication status than flat plate sample and obviously differenteach other, which little influenced by External conditions. On dipping lubricant testand dripping lubricant test condition the through-hole sample are less 55%~87%wear rate and over 10 times anti-wear distance than flat plate sample.Base on wear pictures and friction coefficient curves,the wear resistacemechanism of bionic non-smooth is as follow: strong storing lubrican ability,distributing lubrican uniformly, small contact area and better heat dissipationpotential.It is educed through three-dimensional friction contact analysis which contactpressure and equivalent stress are gotten that the non-smooth through-hole candistributing stress uniformly and weaken stress concentration, which is very helpfulto improve wear resistance and lubricant status. In order to make calculation moreaccurate and convergence fast, hexahedron map mesh is applied in flat plate sampleand non-smooth sample. |
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