机械设计及其自动化毕业设计外文翻译中英文轴承的摩擦与润滑

1、机械设计及其自动化毕业设计外文翻译中英文轴承的摩擦与润滑广西大学 毕业设计（论文）外文翻译毕业设计（论文）题目：夕卜文题目:friction , lubrication of bearing译文题目：轴承的摩擦与润滑 系别：机械工程系专业:机械工程制造及其自动化班级：学号：姓名：指导教师：外文文献原文：friction , lubrication of bearingtn many of the problem thus far , the student has been asked to disregard or neglect frictionactually , friction is

2、 present to some degree whenever two parts are in con tact and move on each ot her. the term fric tion refers to the rcsistancc of two or more parts to movcment.friction is harmfu1 or valuable depending upon where it occurs. friction is necessary for fastening devices such as screws and rivets which

3、 depend upon friction to hold the fastener and the parts together. belt drivers, brakes, and tires are additional applications where friction is necessary.the friction of moving parts in a machine is harmful because it reduces the mechcinical advantage of the device- the heat produced by friction is

4、 lost energy because no work takes place. also , greater power is required to overcome the increased friction. heat is destructive in that it causes expansion. expansion may cause a bearing or sliding surface to fit tighter. if a great eno ugh pressure builds up because made from low temperature mat

5、erials may melt.there are three types of friction which must be overcome in moving parts: lstarting, 2sliding， and3rolling. starting friction is the friction between two solids that tend to resist movement. when two parts are at a state of res t, the surface irregular it ies of both parts tend to in

6、tcrlock and form a wedging action. to produce motion in those parts， the wedge-shaped peaks and valleys of the stationary surfaces must be made to slide out and over each other. the rougher the two surfaces, the greater is starting friction resulting from their movement since there is usually no fix

7、ed pa.t tern bet ween the peaks and valleys of two mating parts, the irregularitics do not intorlock once the parts are in motion but slide over each other. the friction of the two surfaces is known as slidingfriction. as shown in figure ,starting friction is always greatct than sliding friction rol

8、ling friction occurs when roller devces are subjected to tremendous stress which cause the parts to change sheipe or deform. under these conditions, the material in front of a roller tends to pile up and forces the object to roll slightly uphill. this changing of shape , known as deformation, causes

9、 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 of surface irregularities can be overcome partly by the precision machining of the surfaces. however, even these smooth su

10、rfaces may require the use of a substanee between them to reduce the friction still mote. this substance is usually a lubricant explains why bronze bearings, soft alloys, and copper and tin iolite bearings are used with both soft and hardened steel shaft. the iolite bearing is porous. thus, when the

11、 bearing is dipped in oil, capillary action carries the oil through the spaces of the bearing. this type of bearing carries its own lubricant to the points where the pressures arc the greatest.which provides a fine, thin oil film, and prevents the cohesive forces of contact and producing heat anothe

12、r different materials for the bearingthe film keeps the surfaces apart the surfaces from coming in close way to reduce friction is to use surfaces and rotating parts. thismoving parts are lubricated to reduce friction, wear, and heat the most commonly used lubricants are oils, greases, and graphite

13、compounds. each lubricant serves a different purpose. the conditions under which two moving surfaces are to work determine the type of lubricant to be used and the system selected for distributing the lubricant.on slow moving pairts with a minimum of pressure, an o订 groove is usually sufficient to d

14、istribute the required quantity of lubricant to the surfaces moving on each other a seco nd comm on method of lubricat i on 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 us

15、ed in the erankcase of lawn-mower engines to lubricate the crankshaft, connecting rod , and parts of the piston.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

16、and quantity.there are numerous other systems of lubrication and a considcrablc number of lubricants available for any given set of operating conditions. moder n in dus try pays greater atte nt ion to the use of the proper lubrica nts than at previous time because of the increased speeds, pressures,

17、 and operating demands placed on equipment and devices.alt hough one of the main purposes of lubrication is reduce fric tion,any substance-liquid , solid , or gaseous-capable of controlling friction and wear between sliding surfaces can be classed as a lubricant.varieties of lubricationuniubricated

18、sliding. metals that have been carefully treated to remove all foreign materials seize and weld to one another when slid together. in the absence of such a high degree of cleanliness, adsorbed gases, water vapor , oxides, and contciminants reduce frictio9n wind the tendency to seize but usually resu

19、lt in severe wear; this is called “imlubricated ” or dry siiding.fluid-film lubrication. interposing a fluid film that completely separates the sliding surfaces results in fluid-film lubrication. the fluid may be int roduced intention ally as the oil in the main bearing of an auto mobile, or uninten

20、tionally, as in the case of water bet ween a smooth tuber tire and a wet pavemen t. alt hough the f lui d is usual ly a liquid such as oil, water, and a wide range of other materials, it may also be a gas. the gas most commonly employed is air.boundary lubrication. a condition that lies between uniu

21、briceited sliding and fluid-film lubrication is referred to as boundary lubrication, al so defined as that con di tion of lubrica tion in wh i ch the fricti on between surfaces is determined by the properties of the surfaces and properties of the lubricant other than viscosity. boundary lubrication

22、cncompasses a significant portion of lubrication phonomcnei and 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 resista nee to load or tempereiture extrem

23、es. but lubricants need not t ake only such familiar forms as fats, powders, and gases; even some metals commonly serve as sliding surfaces in some sophisticated machines.function of lubricantsalthough a lubricant primarily controls friction and ordinarily does perform numerous other functions, whic

24、h vary with the application and usually arc intorrclated friction 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 fricti

25、on alone between the same surfaces with on lubricant. under 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 effeet of viscosity on friction becomes less signi

26、ficant than the chemical nature of the lubricant.wear control. wear occurs on lubricated surfaces by eibrasion, 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 contaminemts and surface

27、 asperities.temperature control. lubricants assist in controlling corrosion of the surfaces thcmsclvcs is twofold. when machinery is idle, the lubricant acts as a preservative. when machinery is in use, the lubricant controls corrosion by coating lubriceited parts with a protective film that may con

28、tain additives to neutralize corrosive materials. the ability of a lubricant to control corrosion is directly relatly to the thickness of the lubricant him remaining on the metal surfaces and the chermical composition of the lubricant.other functionslubrication are frequently used for purposes other

29、 than the reduction of friction. some of these applications are described below.power transmission. lubricants are widely employed as hydraulic fluids in fluid transmission devices.tnsulation. in specialized applications such as transformers and switchgear , lubricants with high dielectric constants

30、 acts as electrical insulators. for imum insulating properties, a lubricant must be kept free of contaminemts and water.shock dampening. lubricants act as shock-dampening fluids in energy transferring devi ces such as shock absorbers and around machine parts such as gears that are subjected to high

31、intermittent loads.sealing. lubricating grease frequently performs the special function of forming a seal to retain lubricants or to exclude con tdininnnts.the object of lubrication is to reduce friction , wear , and hcating of machine pars which move relative to each other. a lubricant is any subst

32、anee which, 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 eiir for use in gas bearings. the

33、 physical and chemical interaction bet ween the lubrica nt 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 f订ms adhering

34、 to surfaces 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 lubricatio

35、n.five distinct of forms of lubrication that may be defined :a hydrodynennic; 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， e

36、md that the stability thus obtained can be explained by the laws of the lubricant under pressure , though it may be; but it docs 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.

37、 the film pressure is created by the moving surface to creat the pressure necessary to separate the surfaces against the load on the bearinghydrodynamic lubrication is also called full film , or fluid lubrication hydrostatic lubrication is obtained by introducing the lubricant , which is sometime ai

38、r or water , into the load-bearing area at a pressure high enough to separate the surface with a relatively thick film of lubricant. so ,unlike hydrodynanmic lubrication, motion of one surface relative to another is not required elasohydrodynamic lubrication is the phenomenon that occurs when a lubr

39、icant is introduced between surfaces which are in rol1ing contact, such as mating gears or rol1ing bearings. the mathematical explanation requires the hertzian theory of contact stress and fluid mechanics.who n bearing mus t be opera ted at exet reme tc mpcra tu res, a solid film lubricant such as g

40、raphite or molybdenum disulfide must be use used because the ordinary min era! oils are not satisfac to ry. must research 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 bearing, a shaft r

41、otates or oscillates within thebearing , and the relative motion is slidingin an antifriction bearing, the main relative motion is rollinga follower may either roll or slide on the cam. gear teeth mate with each other by a combination of rolling and slidingpistions slide within their cylinders. all

42、these applications require lubrication to reduce friction , wear, and heating.the field of application for journal bearing s is immense. the erankshaft and connecting rod bearings of an automotive engine must poerate for thousands of miles at high temperatures and under varying load conditionsthe jo

43、urnal bearings used in the steam turbines of power genera ting st at ion 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 instilled bearing is require

44、d ,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 in creased kno wlcdgc of the lub

45、rica tion process, now make it possible to design journal bearings with satisfactory lives and very good reliabi1ities参考文献：1. chambers t. l., parkinson a. r., 1998, "knowledge representation and convcrsion of hybridexpcrt systems. ” transactions of the asme, v 120,pp 468-4742. koelsch, james r.

46、,1999, usoftware boosts mold designefficiency “ molding systems, v57, n 3, p 16-233. lee, rong-shean, chen, yuh-min, lee, chang-zou, 1997 "development of a concunrent molddesign system: a knowledge-based approach” , computer integrated manufacturing systems, v 10, n 4, p 287-3074. steadman sall

47、y, pell kynric m, 1995, “ expert systems in engineering design: an application forinjcction molding of plastic parts “ journal of intelligent manufacturing, v6, p 347-353.5. fernandez a., cas temy j-, serraller f., javierre c.,1997,“cad/cae assistant for the design ofmolds and prototypes for injecti

48、onof thermoplastics information technological, v 8, p 117-1246. douglas m bryce, 1997,uplastic injection molding -materialselection and product design” , v 2, pp 148.7. douglas m bryce, 1997, "plastic injection molding-mold design fundamentals" , v2, pp 1-120中文译文：轴承的摩擦与润滑现在看来，有很多这种情况，许多学生在

49、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止相对运动趋势。在一个机器中，运动部件的摩擦是有害的，因为它降低了机械对能量的充 分利用。由它引起的热能是一种浪费的能量。因为不能用它做任何事情。还有, 它述需要更大的动力来克服这种不断增大的摩擦。热能是有破坏性的。因为它产 牛了膨胀。而膨胀可以使得轴承或滑 动表面之间的配合更紧密。如果因为膨胀 导致了一个足够大的积压力，那么，这个轴承就可能会卡死或密封死。另外，随着 温度的升高，如果不是耐高温材料制造

50、的轴承，就可能会损坏甚至融化。在运动部件之间会发生很多摩擦，如1 启动摩擦2.滑动摩擦3 转动摩擦。启动摩擦是两个固体之间产生的倾向于组织其相对运动趋势的摩擦。当两 个固体处于静止状态时，这两个零件表面的不平度 倾向于相互嵌入，形成楔入作 用，为了使这些部件“动”起来。这些静止部件的凹谷和尖峰必须整理光滑，而且 能相互抵消。这两个表面之间越不光滑，由运动造成的启动摩擦（最大静摩擦力） 就会越大。因为，通常来说，在两个相互配合的部件之间，其表面不平度没有固定的图 形。一旦运动部件运动起来，便有了规律可循，滑动就可以实现这一点。两个运动 部件之间的摩擦就叫做滑动摩擦。启动摩擦通常都稍大于滑动摩擦。

51、转动摩擦一般发生在转动部件和设备上，这些设备“抵触”极大的外作用 力，当然这种外力会导致部件的变形和性能的改变。在这种情况下,转动件的材料趋向于堆积并且强迫运动部件缓慢运动，这种改变就是通常所说的形变。可以使 分子运动。当然,最终的结果是，这种额外的能量产生了热能,这是必需的。因为 它可以保证运动部件的运动和克服摩擦力。由运动部件的表面不平度的楔入作用引起的摩擦可以被部分的克服，那就 需要靠两表面之间的润滑。但是，即使是非常光滑的两个表面之间也可能需要一 种物质，这种物质就是通常所说的润滑剂，它可以提供一个比较好的、比较薄的油 膜。这个油膜使两个表面分离，并且组织运动部件的两个表面的相互潜入，

52、以免产 生热量使两表面膨胀，又引起更近的接触。减小摩擦的另一种方式是用不同的材料制造轴承和转动零件。可以拿黄铜 轴承、铝合金和含油轴承合金做例子进行解释。也就是说用软的或硬的金属组成 表面。含油轴承合金是软的。这样当轴承在油中浸泡过以后，因为毛细管的作用, 将由带到轴承的各个表面。这种类型的轴承把它的润滑剂带到应力最大的部位。对运动部件润滑以减小摩擦，应力和热量，最常用的是油、脂、还有合成剂。 每一种润滑剂都有其各自不同的功能和用途。两个运动部件之间的运动情况决定 了润滑剂的类型的选择。润滑剂的分布也决定了系统的选择。在低速度运动的部件，一个油沟足以将所需要的数量的润滑剂送到相互运 动的表面。

53、第二种通用的润滑方法是飞溅润滑系统，在每个周期内这个系统内一些零 件经过润滑剂存储的位置，带起足够的润滑油，然后将其散布到所有的运动零件 上。这种系统用于草坪修剪机中发动机的曲轴箱，对曲轴、连杆和活塞等零件进 行润滑。在工业装置屮，常用的有一种润滑系统是压力系统。这种系统屮，一个机器上的一个泵，可以将润滑剂带到所有的轴承表面。并且以一种连续的固定的速度 和数量。关于润滑,还有许多其他的系统，针对各种类型的润滑剂，对不同类型的运 动零件是有效的。由于设备或装置的速度、压力和工作要求的提高，现代工业比 以前任何时候都更注重选用适当的润滑剂。尽管润滑的主要目的之一是为了减小摩擦力,任何可以控制两个滑动表面 z间摩擦和磨损的物质，不管是液体还是固体或气体，都可以归类于润滑剂。润 滑的种类无润滑滑动。经过精心处理的、去除了所有外来物质的金属在相互滑动吋 会粘附或熔接到一起。当达不到这么高的纯净度时，吸附在表而的气体、水蒸气、 氧化物和污染物就会降低摩擦力并减小粘附的趋势，但通常会产