2022年毕业设计论文外文文献翻译机械设计制造及其自动化轴承的摩擦与润滑中英文对照 .docx

《2022年毕业设计论文外文文献翻译机械设计制造及其自动化轴承的摩擦与润滑中英文对照 .docx》由会员分享，可在线阅读，更多相关《2022年毕业设计论文外文文献翻译机械设计制造及其自动化轴承的摩擦与润滑中英文对照 .docx（18页珍藏版）》请在淘文阁 - 分享文档赚钱的网站上搜索。

1、精选学习资料 - - - - - - - - - Friction , Lubrication of Bearing In many of the problem thus far , the student has been asked to disregard or neglect friction . friction is present to some degree whenever two parts are in contact and move on each other friction refers to the resistance of two or more part

2、s to movement. Friction is harmful or valuable depending upon where it occurs. friction is necessary for fastening devices such as screws and rivets which depend upon friction to hold the fastener and the parts together drivers, brakes, and tires are additional applications where friction is necessa

3、ry The friction of moving parts in a machine is harmful because it reduces the mechanical advantage of the device. The heat produced by friction is lost energy because no work takes place. required to overcome the increased friction. Heat is destructive in that it causes expansion. Expansion may cau

4、se a bearing or sliding surface to fit tighter . If a great enough pressure builds up because made from low temperature materials may melt. There are three types of friction which must be overcome in moving parts: 1starting, 2sliding, and3rolling. Starting friction is the friction between two solids

5、 that tend to resist movement. When two parts are at a state of rest, the surface irregularities of both parts tend to interlock and form a wedging action. T produce motion in these parts, the wedge-shaped peaks and valleys of the stationary surfaces must be made to slide out and over each other . T

6、he rougher the two surfaces, the greater is starting friction resulting from their movement . Since there is usually no fixed pattern between the peaks and valleys of two mating parts, the irregularities do not interlock once the parts are in motion but slide over each other . The friction of the tw

7、o As shown in figure ,starting friction is always greater than sliding surfaces is known as sliding friction. friction . Rolling friction occurs when roller devces are subjected to tremendous stress which cause the parts to change shape or deform. Under these conditions, the material in front of a r

8、oller tends to pile up and forces the object to roll slightly uphill. This changing of shape , known as deformation, causes a movement of molecules. As a result ,heat is produced from the added energy required to keep the parts turning and overcome friction. The friction caused by the wedging action

9、 of surface irregularities can be overcome partly by the precision machining of the surfaces. However , even these smooth surfaces may require the use of a substance between them to reduce the friction still more. This substance is usually a lubricant which provides a fine, thin oil film. The film k

10、eeps the surfaces apart and prevents the cohesive forces of the surfaces from coming in close contact and producing heat . Another way to reduce friction is to use different materials for the bearing surfaces and rotating parts. This explains why bronze bearings, soft alloy s, and copper and tin iol

11、ite bearings are used with both soft and 1 / 10 名师归纳总结 - - - - - - -第 1 页,共 10 页精选学习资料 - - - - - - - - - hardened steel shaft. The iolite bearing is porous. Thus, when the bearing is dipped in oil, capillary action carries the oil through the spaces of the bearing. This type of bearing carries its o

12、wn lubricant to the points where the pressures are the greatest. Moving parts are lubricated to reduce friction, wear , and heat. The most commonly used lubricants are oils, greases, and graphite compounds. Each lubricant serves a different purpose. The conditions under which two moving surfaces are

13、 to work determine the type of lubricant to be used and the system selected for distributing the lubricant. On slow moving parts with a minimum of pressure, an oil groove is usually sufficient to distribute the required quantity of lubricant to the surfaces moving on each other . A second common met

14、hod of lubrication is the splash system in which parts moving in a reservoir of lubricant pick up sufficient oil which is then distributed to all moving parts during each cycle. This system is used in the crankcase of lawn-mower engines to lubricate the crankshaft, connecting rod ,and parts of the p

15、iston. A lubrication system commonly used in industrial plants is the pressure system. In this system, a pump on a machine carries the lubricant to all of the bearing surfaces at a constant rate and quantity There are numerous other sy stems of lubrication and a considerable number of lubricants ava

16、ilable for any given set of operating conditions. Modern industry pays greater attention to the use of the proper lubricants than at previous time because of the increased speeds, pressures, and operating demands placed on equipment and devices. Although one of the main purposes of lubrication is re

17、duce friction, any substance-liquid , solid , or gaseous-capable of controlling friction and wear between sliding surfaces can be classed as a lubricant. Varieties of lubrication Unlubricated sliding . Metals that have been carefully treated to remove all foreign materials seize and weld to one anot

18、her when slid together . In the absence of such a high degree of cleanliness, adsorbed gases, water vapor ,oxides, and contaminants reduce frictio9n and the tendency to seize but usually result in severe wear；this is called “ unlubricated ” or dry sliding.Fluid-film lubrication . Interposing a fluid

19、 film that completely separates the sliding surfaces results in fluid-film lubrication. The fluid may be introduced intentionally as the oil in the main bearing of an automobile, or unintentionally , as in the case of water between a smooth tuber tire and a wet pavement. a liquid such as oil, water

20、, and a wide range of other materials, it may also be a Although the fluid is usually gas. The gas most commonly employed is airBoundary lubrication . A condition that lies between unlubricated sliding and fluid-film lubrication is 2 / 10 名师归纳总结 - - - - - - -第 2 页,共 10 页精选学习资料 - - - - - - - - - refe

21、rred to as boundary lubrication, also defined as that condition of lubrication in which the friction between surfaces is determined by the properties of the surfaces and properties of the lubricant other than viscosity Boundary lubrication encompasses a significant portion of lubrication phenomena a

22、nd commonly occurs during the starting and stopping off machines. Solid lubrication. Solid such as graphite and molybdenum disulfide are widely used when normal lubricants do not possess sufficient resistance to load or temperature extremes. But lubricants need not take only such familiar forms as f

23、ats, powders, and gases； even some metals commonly serve as sliding surfaces in some sophisticated machines. Function of lubricants Although a lubricant primarily controls friction and ordinarily does perform numerous other functions, which vary with the application and usually are interrelated . Fr

24、iction control . The amount and character of the lubricant made available to sliding surfaces have a profound effect upon the friction that is encountered. For example, disregarding such related factors as heat and wear but considering friction alone between the same surfaces with on lubricant. Unde

25、r fluid-film conditions, friction is encountered. In a great range of viscosities and thus can satisfy a broad spectrum of functional requirements. Under boundary lubrication conditions , the effect of viscosity less significant than the chemical nature of the lubricant. Wear control . wear occurs o

26、n lubricated surfaces by abrasion, corrosion ,and solid-to-solid contact wear by providing a film that increases the distance between the sliding surfaces ,thereby lessening the damage by abrasive contaminants and surface asperities. Temperature control . Lubricants assist in controlling corrosion o

27、f the surfaces themselves is twofold. When machinery is idle, the lubricant acts as a preservative. When machinery is in use, the lubricant controls corrosion by coating lubricated parts with a protective film that may contain additives to neutralize corrosive materials. The ability of a lubricant t

28、o control corrosion is directly relatly to the thickness of the lubricant film remaining on the metal surfaces and the chermical composition of the lubricant. Other functions Lubrication are frequently used for purposes other than the reduction of friction. Some of these applications are described b

29、elowPower transmission . Lubricants are widely employed as hydraulic fluids in fluid transmission devices. Insulation . In specialized applications such as transformers and switchgear , lubricants with high dielectric constants acts as electrical insulators. For maximum insulating properties, a lubr

30、icant must be kept 3 / 10 名师归纳总结 - - - - - - -第 3 页,共 10 页精选学习资料 - - - - - - - - - free of contaminants and waterShock dampening . Lubricants act as shock-dampening fluids in energy transferring devices such as shock absorbers and around machine parts such as gears that are subjected to high intermi

31、ttent loads. Sealing . Lubricating grease frequently performs the special function of forming a seal to retain lubricants or to exclude contaminants. The object of lubrication is to reduce friction ,wear , and heating of machine pars which move relative to each other . A lubricant is any substance w

32、hich, when inserted between the moving surfaces, accomplishes these purposes. Most lubricants are liquidssuch as mineral oil, silicone fluids, and water,but they may be solid for use in dry bearings, greases for use in rolling element bearing, or gasessuch as air for use in gas bearings. The physica

33、l and chemical interaction between the lubricant and lubricating surfaces must be understood in order to provide the machine elements with satisfactory life. The understanding of boundary lubrication is normally attributed to hardy and doubleday , who found the extrememly thin films adhering to surf

34、aces were often sufficient to assist relative sliding. They concluded that under such circumstances the chemical composition of fluid is important, and they introduced the term “ boundary lubrication” . Boundary lubrication is at the opposite end of the spectrum from hydrodynamic lubrication. Five d

35、istinct of forms of lubrication that may be defined : a hydrodynamic； bhydrostatic celastohydrodynamic dboundary； esolid film. Hydrodynamic lubrication means that the load-carrying surfaces of the bearing are separated by a relatively thick film of lubricant, so as to prevent metal contact, and that

36、 the stability thus obtained can be explained by the laws of the lubricant under pressure ,though it may be； but it does require the existence of an adequate supply at all times. The film pressure is created by the moving surfaces itself pulling the lubricant under pressure, though it maybe. The fil

37、m pressure is created by the moving surface to creat the pressure necessary to separate the surfaces against the load on the bearing . hydrodynamic lubrication is also called full film ,or fluid lubrication . Hydrostatic lubrication is obtained by introducing the lubricant ,which is sometime air or

38、water ,into the load-bearing area at a pressure high enough to separate the surface with a relatively So ,unlike hy drodynanmic lubrication, motion of one surface relative to another is not required . Elasohydrodynamic lubrication is the phenomenon that occurs when a lubricant is introduced between

39、surfaces which are in rolling contact, such as mating gears or rolling bearings. The mathematical explanation requires the hertzian theory of contact stress and fluid mechanics. 4 / 10 名师归纳总结 - - - - - - -第 4 页,共 10 页精选学习资料 - - - - - - - - - When bearing must be operated at exetreme temperatures, a

40、solid film lubricant such as graphite or molybdenum disulfide must be use used because the ordinary mineral oils are not satisfactory is currently being carried out in an effort, too, to find composite bearing materials with low wear rates as well as small frictional coefficients. In a journal beari

41、ng, a shaft rotates or oscillates within the bearing , and the relative motion is sliding . in an antifriction bearing, the main relative motion is rolling . a follower may either roll or slide on the cam. Gear teeth mate with each other by a combination of rolling and sliding . pistions slide withi

42、n their cylinders. All these applications require lubrication to reduce friction ,wearThe field of application for journal bearing s is immense. The crankshaft and connecting rod bearings of an automotive engine must poerate for thousands of miles at high temperatures and under varying load conditio

43、ns . the journal bearings used in the steam turbines of power generating station is said to have reliabilities approaching 100 percent. At the other extreme there are thousands of applications in which the loads are light and the service relatively unimportant. a simple ,easily installed bearing is

44、required ,suing little or no lubrication. In such cases an antifriction bearing might be a poor answer because because of the cost, the close ,the radial space required ,or the increased inertial effects. Recent metallurgy developments in bearing materials , combined with increased knowledge of the

45、lubrication process, now make it possible to design journal bearings with satisfactory lives and very good reliabilities. 参考文献：1. Chambers T . L., Parkinson A. R., 1998, “ Knowledge Representation and Conversion of HybridExpert S ystems. ” T ransactions of the ASME, v 120,pp 468-474 2. Koelsch, Jame

46、s R., 1999, “ Software boosts mold design efficiency“ Molding Syst16-23. 3. Lee, Rong-Shean, Chen, Yuh-Min, Lee, Chang-Zou,1997 “ Development of a concurrent molddesign system: A knowledge-based approach ” , Computer Integrated Manufacturing Systems, v 10,n 4, p 287-307 4. Steadman Sally , Pell Kynr

47、ic M, 1995, forinjection molding of plastic parts“ Expert systems in engineering design: “ Journal of Intelligent Manuf名师归纳总结 - - - - - - -5. Fernandez A., Castany J., Serraller F ., Javierre C., 1997, “ CAD/CAE assistant for the design ofmolds and prototypes for injection of thermoplastics echnolog

48、ical, v 8, p 1 17-124. “ Information T6. Douglas M Bryce, 1997, njection molding -Material selection and product design” , v 2,pp 5 / 10 第 5 页,共 10 页精选学习资料 - - - - - - - - - 1-48. 7. Douglas M Bryce, 1997, “ Plastic injection molding-Mold design fundamentals-120 ” , v2, pp 1轴承的摩擦与润滑 现在看来,有很多这种情形,很多同学在被问到关于摩擦的问题时,往往都没 引起足够的重视,甚至是忽视它；实际上,摩擦从某种程度上说,存在于任何两个相 接触并有相对运动趋势的部件之间；而摩擦这个词,本身就意味着,两个或两个以上 部件的阻挡相对运动趋势；在一个机器中,运动部件的摩擦是有害的,由于它降低了机械对能量的充分利 用；由它引起的热能是一种铺张的能量；由于不能用它做任何事情；