机械工程英语(刘镇昌)翻译11

1、翻译原文Lesson11 Designs of Machine Components-BearingsA bearing is a support system for rotating, oscillating, or translating machine elements, in which friction has been greatly reduced. Since it has been estimated in various studies that on the average about 30% of all mechanically transmitted energy

2、 are lost to friction, an understanding of friction phenomena in bearings is essential to the machine designer.轴承是一个用于旋转，摆动，或移动机构中大大降低摩擦的支持系统。据各项研究中估计，摩擦所造成的能量损失平均大约占全部机械传递能量的30%，机械设计者对轴承中摩擦现象的了解是必不可少的。Plain bearings provide sliding support, and friction is usually reduced by a liquid, solid, or gas

3、eous lubricant. The following types of plain bearings are in use:滑动轴承提供滑动支承，摩擦通常由液体、固体或气体的润滑剂减少。滑动轴承有以下类型的使用：1 Journal bearings or sleeve bearings support a rotating or oscillating shaft. The bearing usually has a cylindrical shape, while the journal is most often physically a portion of the shaft.

4、When the bearing completely surrounds the journal, we speak of a full bearing; when the bearing only partly surrounds the journal, it is called a partial bearing.轴颈轴承或套筒轴承支撑旋转或摆动轴。轴承通常具有圆柱形状，而轴颈是物理轴最多的一部分。当轴承完全包围轴颈时，我们称之为一个完整的轴承;当轴承仅部分地围绕轴颈时，它被称为一个局部轴承。2 Thrust bearings support an axial load on a ro

5、tating or oscillating shaft.旋转或摆动轴上的推力轴承支撑轴向负荷。3 Line or guide bearings guide and support translating motion.线或导轨轴承引导和支持平移运动。The lubricant in journal bearings is most often oil, in special cases water, and sometimes grease or gas such as air. Some bearing materials provide self-lubrication. Idealy,

6、a film of lubricant separates the surfaces in relative motion. If the lubricant is a fluid, the layer touching the journal moves along with it, while the layer adjacent to the bearing remains stationary. The closer intermediate layers are to the journal, the motion is that of the shear forces betwee

7、n adjacent lubricant layers. To avoid metal-to-metal contact, the minimum film thickness must exceed the combined height of the surface irregularities in journal and bearing. To provide space for the bearing diameter.轴颈轴承的润滑剂，最常用的是油，在特殊情况下可用水，有时是润滑脂或空气等气体。一些轴承材料提供自润滑。理想的情况下，润滑油膜分离在相对运动的表面。如果润滑剂是一种流体

8、，接触轴颈层与它一起移动，而邻近于轴承的层保持静止。越靠近中间层的轴颈，相邻的润滑层之间的剪切力使其运动。为了避免金属与金属接触，最小膜厚必须超过在轴颈和轴承的表面凹凸的组合高度。为轴承内径提供空间。Bearing Materials轴承材料Journal bearing materials should preferably have the following characteristics:滑动轴承材料最好应具有以下特征：1 Good compressive and fatigue strength.良好的压缩性能和疲劳强度。2 Good heat conductivity.良好的导热性

9、。3 Chemical inertness to shaft and housing materials, as well as lubricants.轴，外壳材料以及润滑剂的化学惰性。4 Ductility, to conform to the shape of housing and journal, and to permit the embedment of foreign particles which would otherwise scour the shaft.延展性，以符合壳体和轴颈的形状，并允许外部颗粒的嵌入否则将会冲刷轴。5 Reasonable price.合理的价格。

10、The most commonly used, general-purpose bearing materials are bronze alloys, such as copper-tin-lead, copper-tin, and copper-aluminum bronze, which meet these requirements well.最常用的，一般用途的轴承的材料是铜的合金，如铜 - 锡 - 铅，铜 - 锡，铜和铝青铜，能较好地满足这些要求。Babbits (alloys consisting mainly of either tin or lead), which have

11、 mostly poor fatigue characteristics, and silver, are often used in thin layers with cast iron or steel backing. Silver is used for heavy-duty applications, such as reciprocating aircraft engines.轴承合金（以锡或铅为主的合金），它具有很差的疲劳特性，银，通常以薄层镀在铸铁或钢表面。银是用于高强度应用，如往复式飞机发动机。Cast iron bearings are low in cost and ar

12、e sometimes made integrally with a frame or structure. They operate well with hardened steel journals; however, they have low embeddability and poor heat conductivity.铸铁轴承成本低，有时用整体框架或结构。它们因具有淬硬钢的轴颈而运作良好;然而，它们可嵌入性低、导热性差。Rubber bearings are used for underwater applications, such as hydraulic turbines,

13、 pumps, and propeller shafts. The water serves as both lubricant and coolant. Shaft must of course be made from non-corroding materials such as monel, stainless steel or bronze.橡胶轴承用于水下应用，如液压涡轮机，泵，和螺旋桨轴。水充当润滑剂和冷却剂。当然轴必须由非腐蚀材料制成，如蒙乃尔合金，不锈钢或青铜。Phenolic compounds are often used for structures with inte

14、gral bearings, such as docks, instruments, and switch gear, or for bearings used in locations similar to those in which rubber bearings are used. The material has low heat conductivity, and some swelling and warping may occur in larger sizes, requiring greater than average clearance values.酚类化合物通常用于

15、整体结构轴承，如码头，仪器，和开关装置，或用于那些使用橡胶轴承的结构和位置。该材料具有低的导热性，一些胀大和变形可能会发生在较大尺寸的地方，需要大于平均间隙值。Sintered bearings are made by compressing mainly metallic powder mixtures in a die and subsequently sintering the compacts in an oven. The powders used are mostly copper and tin mixtures, sometimes iron, with the possibl

16、e admixture of other powdered materials imparting some desirable property. A small amount of graphite is sometimes added to the powder mixture for bearings used in oscillating and reciprocating motion applications to provide a certain amount of lubricity. Such bearings are more or less porous, depen

17、ding upon the pressure under which they were manufactured, and may be charged with oil. They thus become self-lubricating and suitable for places where regular maintenance is difficult or impossible. They are often used in small appliances and fractional hp-motors. 烧结轴承通过在模具内压缩主要金属粉末的混合物，并随后烧结在烘箱压块制

18、成。所用的粉末是主要的铜和锡的混合物，有时是铁，与其它某些期望属性粉末材料混合。有时加入少量石墨到粉末混合物中，给应用于摆动和往复运动的轴承提供一定量的润滑。这种轴承都是或多或少多孔的，这取决于下它们被制造的压力，并且可以被装入油。因此它们成为自润滑部分，它的常规维护很困难甚至不可能。它们经常用于小型电器和分数马力电机。Recent Developments in Bearing Technology轴承技术的最新发展Electromagnetic Bearings 电磁轴承In these bearings, the journal floats on a repulsing magneti

19、c field and is kept in a central position between the magnets by corrective signals from sensors between the magnet poles. An application of these bearings usually comprises two radial and one axial (thrust) bearing. Since there is no physical contact between journal and magnets during rotation, the

20、re is no wear. Other advantages are:在这些轴承中，该轴颈漂浮在一个排斥磁场上，并通过来自磁铁两极传感器的纠正信号保持在磁体的中央位置。这些轴承的应用通常包括两个径向和一个轴向（推力）轴承。由于在旋转期间轴颈和磁体之间没有物理接触，所以没有磨损。其他的优点是：1 Absence of noise没有噪音2 No seals or lubricants required无需密封或润滑剂3 Insensitivity to ambient temperatures (operating range is -150 to 450 F)不敏感的环境温度（工作范围为-1

21、50至450°F）4 Operation possible in a vacuum or in corrosive atmospheres在真空或在腐蚀性环境中操作成为可能5 Small losses( from hysteresis and eddy currents ) ，hence small temperature rise损失小（磁滞和涡流），因此，升温小6 High potential circumferential velocities (up to 600 fms)高电位圆周速度（高达600 FMS）Magnetic bearings were originally

22、developed for light loads in earth-orbiting satellites but are beginning to be used in industrial equipment. Journal materials are limited to ferromagnetic types. 最初开发的磁性轴承用于轻负载地球轨道卫星，但也开始在工业设备中使用。轴颈材料限于铁磁类型。Foil Bearings 箔片轴承 Foil bearings are a type of gas bearing with improved properties. They we

23、re developed to overcome operation instabilities inherent with gas bearings ( half- and full-frequency whirl ) and seizing at high temperatures, at which the clearance may become zero. Half- and full-frequency whirl are unstable conditions of journal vibration with a frequency equal to the rpm or ha

24、lf the rpm. The phenomenon occurs mainly in lightly loaded bearings.箔片轴承是提高性能的一种气体轴承。它们被开发以克服在高温下间隙可以变为零时出现的气体轴承（半桥和全频涡动）操作不稳定或卡住。半频和全涡动频率是频率等于所述rpm或半rpm的轴颈振动不稳定条件。这种现象主要发生在轻载轴承。Foil bearings also have improved load capacities. In the 1-2 in. diameter range, bearing pressures may be as high as 30 ps

25、i.箔片轴承还具有良好的承载能力。在1-2英寸的直径范围，轴承压力可以高达30磅。In these bearings, thin, flexible surfaces made from metal foils, which may be as thin as 0.001 in., replace the rigid surface of conventional gas bearings. The flexible foil adapts itself to changing load conditions and maintains a constant gas film thicknes

26、s, thus damping out load variations and reducing the tendency to whirl. Foil bearings are also less sensitive to minor misalignment and journal irregularities, and unlike plain gas bearings, permit the passage of dust or dirt particles. Also, during starts and stops, the load is distributed over a l

27、arger area than in plain gas bearings, where there is essentially line contact between journal and bearing surfaces. Wear is thus reduced.在这些轴承中，薄的，柔性的表面由薄于0.001的金属箔制成，取代的常规气体轴承的刚性表面。柔性箔调整自身适应变化的负载条件和保持恒定的气体膜的厚度，从而阻尼出负荷的变化和减少旋转的倾向。箔轴承对轻微错位和轴颈不规则规较不敏感，而不像普通的气体轴承，可以使灰尘或污物颗粒通过。此外，在启动和停止时，负载被分布的区域比普通气体轴

28、承更大，轴颈与轴承面之间基本上是线接触。从而减少磨损。There are two basic types of foil bearings, tension-dominated and bending dominated. Since metal-to-metal contact exists during start-up and stopping, foils or journals must have special coatings to reduce friction and wear. Foil bearings are often used in high-temperature

29、 applications, such as gas turbines(-65 to 1200 F),so that that materials selected for this type must be able to withstand these conditions.有两种基本类型的箔轴承，张力为主和弯曲为主。由于在启动时和停止存在金属对金属的接触，箔片或轴颈必须有特殊的涂层，以减少摩擦和磨损。箔轴承通常用于高温应用，例如燃气轮机（-65到1200 F）中，因此，选择的这种类型的材料必须能满足这些条件。Bearings with rolling contact滚动轴承In bear

30、ings with rolling contact, the shaft are directly or indirectly supported by rolling elements, such as balls, cylindrical or conical rollers, or needles(i.e., cylindrical rollers with a high L/D ration). The occasionally encountered name 'anti-friction bearings' suggests that this type has l

31、ittle or no friction. This is erroneous, since the friction is merely of another nature than in journal bearings. In bearings with rolling contact, friction losses are caused by the elastic deformation of the surfaces in rolling contact, sliding friction of rolling elements with cages, retaining rin

32、gs and seals, or with one another, and also by some shear of lubricant.在轴承滚动中，轴直接或间接地通过滚动元件，诸如滚珠，圆柱或圆锥滚子，或针（即，圆柱滚子具有高的L / D比）的支持。偶尔遇到'防摩擦轴承'，就认为这种类型具有很少或没有摩擦。这是错误的，因为这仅仅是另一种性质相对于轴颈轴承的摩擦。在轴承的滚动接触，导致摩擦损耗的因素有：滚动接触表面的弹性变形，滚动元件和保持架间、保持环和密封件、或者与另一个的滑动，或者润滑剂的一些剪切摩擦。 The following types of bearings

33、with rolling contact are in use:以下类型的滚动接触轴承正在使用中:1 Ball bearings have rolling elements in the form of balls, which in all but the most inexpensive types are held in cages, separators, or retainers, and inner and outer grooved races.球轴承的球沟槽里有滚动体，这在所有但最便宜的类型隔离环里，分离器，保持件，以及内和外座圈开槽保持滚动元件。2 Roller bearings have mainly cylindrical, conical, or barrel-shaped rollers instead of balls, but are otherwise quite similar to ball bearings.滚子轴承主要是圆柱形，圆锥形，或酒桶形辊，而不是球，但在其他方面非常类似于球轴承。3 Needle