机械设计制造专业英语译文.doc

1，The use of metals has always been a key factor in the development of the social systems of man. Of the roughly 100 basic elements of which all matter is composed, about half are classified as metals. The distinction between a metal and a nonmetal is not always clear-cut. The most basic definition centers around以为中心 the type of bonding existing between the atoms of the element, and around the characteristics of certain of the electrons某种电子 associated with these atoms. In a more practical way, however, a metal can be defined as an element which has a particular package of properties.在人类社会的发展中，金属的应用起着关键性的作用。构成物质的大约100种基本元素中，大约有一半为金属。金属和非金属之间的区别不是特别明显。最基本的定义集中在元素原子间存在的连接形式和与这些原子相关联的电子的某些特性。然而，在实际应用中，可以将具有某些特性集合金属定义为某种元素。Metals are crystallineadj.晶体的 when in the solid state and, with few exceptions极少例外 (e.g. mercury), are solid at ambient周围环境的 temperatures. They are good conductors of heat and electricity and are opaque不透明的 to light. They usually have a comparatively high density. Many metals are ductile柔软的；易延展的-that is, their shape can be changed permanently永久地，长期不变地 by the application of a force without breaking. The forces required to cause this deformation and those required to break or fracture a metal are comparatively high, although, the fracture forces is not nearly =far from,much less than as high as would be expected from simple consideration of the forces required to tear apart the atoms of the metal.除了少数例外金属在常温下是固态的。它们是热和电的良导体，不透光。它们往往具有较高的密度。许多金属具有延展性，也就是说，在不被破坏的情况下它们的形状在外力的作用下可以发生变化。引起永久变形所需的力和最终使金属断裂所需的力相当大，尽管发生断裂所需的力远没有像所预期的撕开金属原子所需的力那么大。One of the more significant of these characteristics from our point of view is that of crystallinitycrystallinity ,kristlinti. A crystalline solid is one in which the constituent atoms are located in a regular three-dimensional array as if they were located at the corners of the squares of a three-dimensional chessboardn. 棋盘. The spacing of the atoms in the array is of the same order as the size of the atoms, the actual spacing being a characteristic of the particular metal. The directions of the axes of the array define the orientation of the crystal in space. The metals commonly used in engineering practice are composed of a large number of such crystals, called grains晶粒. In the most general case一般情况下, the crystals of the various grains are randomly oriented in space. The grains are everywhere in intimate contact with one another and joined together on an atomic scale. The region at which they join is known as a grain boundary.从我们的观点来看，在所有的特性中结晶性是最重要的。结晶体是这样一种结构，组成它的原子定位在规则的三维排列中，仿佛位于三维棋盘的方格的角上。原子间距随着原子大小呈规律性变化，原子间距是金属的一种特性。三维排列的轴线决定了晶体在空间中的方向。在工程实践中应用的金属由大量的晶体组成，这些晶体称之为晶粒。在大多数情况下，晶粒在空间中是自由排列的。在原子范围内，晶粒之间相互接触紧密结合。晶粒之间连接区域被称为晶界。An absolutely pure metal (i.e.也就是 one composed of only one type of atom) has never been produced. Engineers would not be particularly interested in such a metal even if it were to be produced, because it would be soft and weak. The metals used commercially inevitably不可避免地 contain small amounts of one or more foreign elements, either metallicmetallic mitlik, me-adj. 金属的，含金属的 or nonmetallic. These foreign elements may be detrimental有害的, they may be beneficial, or they may have no influence at all on a particular property. If disadvantageous, the foreign elements tend to be known as impurities杂质. If advantageous, they tend to be known as alloying elements合金元素. Alloying elements are commonly added deliberately故意地，蓄意地 in substantialadj. 大量的；实质的；内容充实的substantial evidence:实（质）体证据|实质性证据|实质证据substantial order:大宗订单|大订单 amounts in engineering materials. The result is known as an alloy.绝对纯净的金属从来也没有被生产出来过。即使绝对纯净的金属可以生产出来，工程师们对它们也并不会特别感兴趣，因为它们很柔软、脆弱。实际应用中的金属往往都包含着一定数量的一种或多种外来金属或非金属元素，这些外来元素可能是有害的也可能是有益的或者它们对某种特定的属性没有影响。如果是有害的，这些外来元素被认为是杂质。如果是有益的，它们被认为是合金元素。在工程材料中往往被特意地加入一定数量的合金元素。得到的物质被叫做合金。The distinction between the descriptors “metal” and “alloy” is not clear-cut. The term “metal” may be used to encompass both a commercially pure metal and its alloys. Perhaps it can be said that the more deliberately an alloying addition has been made and the larger the amount of the addition, the more likely it is that the product will specifically be called an alloy. In any event无论如何，不管怎样, the chemical composition of a metal or an alloy must be known and controlled within certain limits if consistent一致的 performance is to be achieved in service. Thus chemical composition has to be taken into account when developing an understanding of the factors which determine the properties of metals and their alloys.金属和合金区别不大。金属这个词可以包括工业用纯金属和它的合金。也许可以这样说，合金元素越故意的被添加，被添加的合金元素的量越大，那么生产出来的产品越倾向于被称之为合金。不管怎样，如果想使一种金属或合金在使用中表现出稳定一致的特性，在其中添加何种化学成分，它的量多大都应该在控制范围之内。因此，当想了解决定金属和合金性质的因素时，应充分考虑它们的化学组成。Of the 50 or so metallic elements, only a few are produced and used in large quantities in engineering practice. The most important by far is iron铁, on which are based the ubiquitous普遍的，无处不在的 steels and cast irons (basically alloys of iron and carbon). They account for about 98% by weight of all metals produced. Next in importance for structural uses (that is, for structures that are expected to carry loads) are aluminum铝, copper, nickel, and titanium taiteinim, ti-n. 化钛（金属元素）. Aluminum accounts for about 0.8% by weight of all metals produced, and copper about 0.7%, leaving only 0.5% for all other metals. As might be expected, the remainders are all used in rather相当 special applications. For example, nickel alloys are used principally主要地 in corrosion-and heat-resistant applications, while titanium is used extensively广泛地 in the aerospace industry because its alloys have good combinations of high strength and low density. Both nickel and titanium are used in high-cost, high-quality applications, and, indeed, it is their high cost that tends to restrict their application.在50种左右的金属元素里，工程实践中只有少数金属被大量生产和使用。到目前为止最重要的是铁，以它为基础构成了处处可见的钢和铸铁。（主要由铁和碳构成的合金）它们的重量占所有生产出来的金属重量的98%。在结构应用（也就是说，可以承受载荷的结构）中居于其次位置的是铝、铜、镍和钛。在所有的金属产量中，铝占0.8，铜占0.7，剩下的占0.5。剩下的金属用于相对特殊的用途。例如，镍合金主要用于抗磨损和耐高温的用途，由于钛合金具有高强度和低密度的综合特性，钛被广泛应用于航空工业中。镍合钛有高成本和高质量的使用特性，事实上，它们高的成本限制了它们的应用。We cannot discuss these more esotericadj. 秘传的；限于圈内人的；难懂的Esoteric Buddhism:密宗|密宗，特别是指西藏的喇嘛教。 properties here. Suffice it to say1. Suffice it to say that you love me.只要说你爱我就够了。2. Suffice it to say that the gun was his.只需说这枪是他的就够了。 that a whole complex of properties in addition to structural strength is required of an alloy before it will be accepted into, and survive in, engineering practice. It may, for example, have to be strong and yet have reasonable corrosion resistance; it may have to be able to be fabricated by a particular process such as deep drawing, machining, or welding; it may have to be readily容易地 recyclable; and its cost and availability may be of critical importance.我们不能在这里讨论这些深奥的特性。在合金材料被采用和应用于工程实际之前，掌握其结构强度和它的综合性质就够了。举例来说，它可以强度很高，并且有好的耐磨性；它可以被例如拉伸加工，机械加工，或焊接等特殊工艺来加工出来；它可以被循环利用；它的成本和实用性是首要的。3,The material properties can be classified into three major headings: (i) Physical, (ii) Chemical, (iii) Mechanical.Physical propertiesDensity or specific gravity, moisture mist n. 水分；湿度；潮湿；降雨量 content, etc., can be classified under this category.材料特性主要分为三类：(i)物理特性，(ii)化学特性，(iii)力学性能。物理特性密度或特定的重力，湿度等都属于此范畴。Chemical propertiesMany chemical properties come under归入 this category. These include acidity sidti n. 酸度；酸性；酸过多；胃酸过多 or alkalinity,lklinti n. 碱度；碱性, reactivity化学反应的活性 and corrosion. The most important of these is corrosion which can be explained in laymans terms as the resistance of the material to decay腐朽，腐烂 while in continuous use in a particular atmosphere.化学特性许多化学特性都归入到这个范畴。其中包括酸性或碱性，活性和耐腐蚀性。而在这其中最重要的是耐腐蚀性，通俗的解释是材料在特定大气中长期使用时，抵抗腐蚀的能力。Mechanical propertiesMechanical properties include the strength properties like tensile, compression, shear, torsion, impact, fatigue and creepn. 爬行；毛骨悚然的感觉；谄媚者vi. 爬行；蔓延；慢慢地移动；起鸡皮疙瘩creep:蠕变|潜变|渐变creep strength:蠕变强度|潜变强度|蠕变弱度creep strain:蠕变变形|蠕动应变|蠕变应变. The tensile strength of a material is obtained by dividing the maximum load, which the specimen bears by the area of cross-section of the specimen.力学特性力学特性包括诸如拉伸，压缩，剪切，扭转，冲击，疲劳和蠕变等强度特性。一种材料的拉伸强度由试件承载的最大载荷除以试件的横截面积得到。This is a curve plotted between the stress along the Y-axis(ordinate) and the strain along the X-axis(abscissabsis n. 数横坐标；横线) in a tensile test. A material tends to change or changes its dimensions when it is loaded, depending upon the magnitude大小 of the load. When the load is removed it can be seen that the deformation disappear s. For many materials this occurs up to一直到；相当于；忙于，在做；由决定的 a certain value of the stress called the elastic limit. This is depicted by the straight line relationship and a small deviation,di:vieinn. 偏差；误差；背离average deviation:平均偏差|平均差|平均偏差，均差 thereafter, in the stress-strain curve.如图所示为在拉伸试验中沿着X轴（横轴）的应变和沿着Y轴（纵轴）的应力之间的关系曲线。材料在加载时，随着载荷大小的变化，尺寸会发生改变。当卸载时，变形消失。对于许多材料来说，上述情况发生的应力极限值称为弹性极限。在应力-应变曲线中，直线关系和随后的小小的弯曲描述了上述的加载和卸载。Within the elastic range, the limiting value of the stress up to which the stress and strain are proportional, is called the limit of proportionality. In this region, the metal obeys Hookes law, which states that the stress is proportional to strain in the elastic range of loading (the material completely regains its original dimensions after the load is removed). In the actual plotting of the curve, the proportionality limit is obtained at a slightly lower value of the load than the elastic limit. This may be attributed to the time-lag in the regaining of the original dimensions of the material. This effect is very frequently noticed in some no-ferrous有色金属铁的，含铁的 metals.在弹性范围内，应力应变成比例的应力极限值称为比例极限。在这个区域中，金属服从胡克定律阐述了在加载的弹性范围内，应力和应变成比例关系（材料在卸载后，能够完全回复它原来的尺寸）。在曲线的实际绘制中，比例极限值要稍微比弹性极限值低。这可能是由于材料回复原尺寸需要的时间延迟。这种现象在一些有色金属中常常出现While iron and nickel exhibitizibitn. 展览品；证据；展示会vt. 展览；显示；提出（证据等）vi. 展出；开展览会 clear ranges of elasticity, copper, zinc（锌）, tin（锡）, etc, are found to be imperfectlyimp:fiktliadv. 有缺点地；不完美地；未完成地 elastic even at relatively（相当地） low values of stresses. Actually the elastic limit is distinguishable（可区分的） from the proportionality（比例性） limit more clearly depending upon the sensitivity（灵敏性） of the measuring instrument.铁和镍存在明显的弹性范围，铜，锌，锡等即使在相当低的应力值下弹性也表现得不是很充分。实际上依靠测试仪器的精确性可以使比例极限和弹性极限区分得更清晰When the load is increased beyond the elastic limit, plastic deformation starts. Simultaneously the specimen gets work-hardened. A point is reached when（这时） the deformation starts to occur more rapidly than the increasing load. This point is called the yield point Q. the metal which was resisting the load till then, starts to deform somewhat rapidly, i. e. , yield. The yield stress is called yield limit.当在弹性极限之上增大载荷时会产生塑性变形。同时，试件发生加工硬化。到达某点后变形的速度快于载荷增加的速度。这一点叫做屈服极限点。一开始一直在抵抗载荷的金属在这一点后开始迅速地发生形变，也就是，屈服。屈服应力叫做屈服极限。The elongation of the specimen continues form Q to S and then to T. the stess-strain relation in this plastic flow period is indicated by the portion QRST of the curve. At T the specimen breaks, and this load is called the breaking load. The value of the maximum load S divided by the original cross-sectional area of the specimen is referred to as the ultimate tensile strength of the metal or simply the tensile strength.试件从Q到S在到T不断地延长。在这个塑性流动期间的应力-应变关系表示为曲线上的QRST段。在T点试件断裂，此时的载荷称为断裂载荷。最大荷载值S除以试件的横截面积为金属的最大拉伸强度或简单地称为拉伸强度Logically speaking, once the elastic limit is exceeded, the metal should starts to yield, and finally break, without any increase in the value of stress. But the curve records an increased stress even after the elastic limit is exceeded. Two reasons can be given for this behavior:1. the strain hardening of the material;2. the diminishingdiminiiadj. 逐渐缩小的；衰减的v. 减少；递减；衰减；削弱的权势 cross-sectional area of the specimen, suffered on account of 1. On account of the weather, we had to cancel the projected outing.the plastic deformation.逻辑上来说，一旦超过弹性极限，金属应该就会屈服直至最后断裂，在应力值上应该没有增加。但是实际的曲线却记录了在超过弹性极限后的增加了的应力。这种现象的发生可能有两种原因：1. 材料的应变强化；由于塑性变形引起的试件横截面积的缩小The more plastic deformation the metal undergoes, the harder it becomes, due to work-hardening. The more the metal gets elongated the more its diameter(and hence, cross-sectional area) is decreased. This continues until the point S is reached.因为基督就是上帝，为我们受苦，他自己身为父，好叫祂也能救赎我们。）由于加工硬化，金属在发生塑性变形时会变得越来越硬。金属拉伸越长它的直径越小。这种现象一直持续到曲线上的S点。After S, the rate at which the redution in area takes place, exceeds the rate at which the stress increases. Strain becomes so high that the redution in area begins to produce a localized effect at some point. This is called neching.Reduction in cross-sectional area takes place very rapidly; so rapidly that the load value actully drops. This is indicated by ST. Failure occurs at this point T.Then percentage elongation and reduction in area indicate the ductility or plasticity of the material:Where and are the original and the final length of the specimen; and are the original and the final cross-sectional area.超过S点后，面积减少的速度超过了应力增加的速度。应变变得很大，面积的减少在某些点产生了局部效应。叫做颈缩。横截面积减小的速度非常快；以至于实际上载荷降低