机械毕业英语论文翻译

机械毕业英语论文翻译（精选6篇）

机械毕业英语论文翻译 第1篇

Lathe basic technology

Lathes are machine tools designed primarily to do turning, facing and boring, Very little turning is done on other types of machine tools, and none can do it with equal facility.Because lathes also can do drilling and reaming, their versatility permits several operations to be done with a single setup of the work piece.Consequently, more lathes of various types are used in manufacturing than any other machine tool.The essential components of a lathe are the bed, headstock assembly, tailstock assembly, and the leads crew and feed rod.The bed is the backbone of a lathe.It usually is made of well normalized or aged gray or nodular cast iron and provides s heavy, rigid frame on which all the other basic components are mounted.Two sets of parallel, longitudinal ways, inner and outer, are contained on the bed, usually on the upper side.Some makers use an inverted V-shape for all four ways, whereas others utilize one inverted V and one flat way in one or both sets, They are precision-machined to assure accuracy of alignment.On most modern lathes the way are surface-hardened to resist wear and abrasion, but precaution should be taken in operating a lathe to assure that the ways are not damaged.Any inaccuracy in them usually means that the accuracy of the entire lathe is destroyed.The headstock is mounted in a foxed position on the inner ways, usually at the left end of the bed.It provides a powered means of rotating the word at various speeds.Essentially, it consists of a hollow spindle, mounted in accurate bearings, and a set of transmission gears-similar to a truck transmission—through which the spindle can be rotated at a number of speeds.Most lathes provide from 8 to 18 speeds, usually in a geometric ratio, and on modern lathes all the speeds can be obtained merely by moving from two to four levers.An increasing trend is to provide a continuously variable speed range through electrical or mechanical drives.Because the accuracy of a lathe is greatly dependent on the spindle, it is of heavy construction and mounted in heavy bearings, usually preloaded tapered roller or ball types.The spindle has a hole extending through its length, through which long bar stock can be fed.The size of maximum size of bar stock that can be machined when the material must be fed through spindle.The tailsticd assembly consists, essentially, of three parts.A lower casting fits on the inner ways of the bed and can slide longitudinally thereon, with a means for clamping the entire assembly in any desired location, An upper casting fits on the lower one and can be moved transversely upon it, on some type of keyed ways, to permit aligning the assembly is the tailstock quill.This is a hollow steel cylinder, usually about 51 to 76mm(2to 3 inches)in diameter, that can be moved several inches longitudinally in and out of the upper casting by means of a hand wheel and screw.The size of a lathe is designated by two dimensions.The first is known as the swing.This is the maximum diameter of work that can be rotated on a lathe.It is approximately twice the distance between the line connecting the lathe centers and the nearest point on the ways, The second size dimension is the maximum distance between centers.The swing thus indicates the maximum work piece diameter that can be turned in the lathe, while the distance between centers indicates the maximum length of work piece that can be mounted between centers.Engine lathes are the type most frequently used in manufacturing.They are heavy-duty machine tools with all the components described previously and have power drive for all tool movements except on the compound rest.They commonly range in size from 305 to 610 mm(12 to 24 inches)swing and from 610 to 1219 mm(24 to 48 inches)center distances, but swings up to 1270 mm(50 inches)and center distances up to 3658mm(12 feet)are not uncommon.Most have chip pans and a built-in coolant circulating system.Smaller engine lathes-with swings usually not over 330 mm(13 inches)–also are available in bench type, designed for the bed to be mounted on a bench on a bench or cabinet.Although engine lathes are versatile and very useful, because of the time required for changing and setting tools and for making measurements on the work piece, thy are not suitable for quantity production.Often the actual chip-production tine is less than 30% of the total cycle time.In addition, a skilled machinist is required for all the operations, and such persons are costly and often in short supply.However, much of the operator’s time is consumed by simple, repetitious adjustments and in watching chips being made.Consequently, to reduce or eliminate the amount of skilled labor that is required, turret lathes, screw machines, and other types of semiautomatic and automatic lathes have been highly developed and are widely used in manufacturing.2 Numerical Control

One of the most fundamental concepts in the area of advanced manufacturing technologies is numerical control(NC).Prior to the advent of NC, all machine tools ere manually operated and controlled.Among the many limitations associated with manual control machine tools, perhaps none is more prominent than the limitation of operator skills.With manual control, the quality of the product is directly related to and limited to the skills of the operator.Numerical control represents the first major step away from human control of machine tools.Numerical control means the control of machine tools and other manufacturing systems through the use of prerecorded, written symbolic instructions.Rather than operating a machine tool, an NC technician writes a program that issues operational instructions to the machine tool.For a machine tool to be numerically controlled, it must be interfaced with a device for accepting and decoding the programmed instructions, known as a reader.Numerical control was developed to overcome the limitation of human operators, and it has done so.Numerical control machines are more accurate than manually operated machines, they can produce parts more uniformly, they are faster, and the long-run tooling costs are lower.The development of NC led to the development of several other innovations in manufacturing technology: Electrical discharge machining,Laser cutting,Electron beam welding.Numerical control has also made machine tools more versatile than their manually operated predecessors.An NC machine tool can automatically produce a wide of parts, each involving an assortment of widely varied and complex machining processes.Numerical control has allowed manufacturers to undertake the production of products that would not have been feasible from an economic perspective using manually controlled machine tolls and processes.Like so many advanced technologies, NC was born in the laboratories of the Massachusetts Institute of Technology.The concept of NC was developed in the early 1950s with funding provided by the U.S.Air Force.In its earliest stages, NC machines were able to made straight cuts efficiently and effectively.However, curved paths were a problem because the machine tool had to be programmed to undertake a series of horizontal and vertical steps to produce a curve.The shorter the straight lines making up the steps, the smoother is the curve, Each line segment in the steps had to be calculated.This problem led to the development in 1959 of the Automatically Programmed Tools(APT)language.This is a special programming language for NC that uses statements similar to English language to define the part geometry, describe the cutting tool configuration, and specify the necessary motions.The development of the APT language was a major step forward in the fur ther development from those used today.The machines had hardwired logic circuits.The instructional programs were written on punched paper, which was later to be replaced by magnetic plastic tape.A tape reader was used to interpret the instructions written on the tape for the machine.Together, all of this represented a giant step forward in the control of machine tools.However, there were a number of problems with NC at this point in its development.A major problem was the fragility of the punched paper tape medium.It was common for the paper tape containing the programmed instructions to break or tear during a machining process.This problem was exacerbated by the fact that each successive time a part was produced on a machine tool, the paper tape carrying the programmed instructions had to be rerun through the reader.If it was necessary to produce 100 copies of a given part, it was also necessary to run the paper tape through the reader 100 separate tines.Fragile paper tapes simply could not withstand the rigors of a shop floor environment and this kind of repeated use.This led to the development of a special magnetic plastic tape.Whereas the paper carried the programmed instructions as a series of holes punched in the tape, the plastic tape carried the instructions as a series of magnetic dots.The plastic tape was much stronger than the paper tape, which solved the problem of frequent tearing and breakage.However, it still left two other problems.The most important of these was that it was difficult or impossible to change the instructions entered on the tape.To made even the most minor adjustments in a program of instructions, it was necessary to interrupt machining operations and make a new tape.It was also still necessary to run the tape through the reader as many times as there were parts to be produced.Fortunately, computer technology became a reality and soon solved the problems of NC associated with punched paper and plastic tape.The development of a concept known as direct numerical control(DNC)solved the paper and plastic tape problems associated with numerical control by simply eliminating tape as the medium for carrying the programmed instructions.In direct numerical control, machine tools are tied, via a data transmission link, to a host computer.Programs for operating the machine tools are stored in the host computer and fed to the machine tool an needed via the data transmission linkage.Direct numerical control represented a major step forward over punched tape and plastic tape.However, it is subject to the same limitations as all technologies that depend on a host computer.When the host computer goes down, the machine tools also experience downtime.This problem led to the development of computer numerical control.3 Turning The engine lathe, one of the oldest metal removal machines, has a number of useful and highly desirable attributes.Today these lathes are used primarily in small shops where smaller quantities rather than large production runs are encountered.The engine lathe has been replaced in today’s production shops by a wide variety of automatic lathes such as automatic of single-point tooling for maximum metal removal, and the use of form tools for finish on a par with the fastest processing equipment on the scene today.Tolerances for the engine lathe depend primarily on the skill of the operator.The design engineer must be careful in using tolerances of an experimental part that has been produced on the engine lathe by a skilled operator.In redesigning an experimental part for production, economical tolerances should be used.Turret Lathes Production machining equipment must be evaluated now, more than ever before, this criterion for establishing the production qualification of a specific method, the turret lathe merits a high rating.In designing for low quantities such as 100 or 200 parts, it is most economical to use the turret lathe.In achieving the optimum tolerances possible on the turrets lathe, the designer should strive for a minimum of operations.Automatic Screw Machines

Generally, automatic screw machines fall into several categories;single-spindle automatics, multiple-spindle automatics and automatic chucking machines.Originally designed for rapid, automatic production of screws and similar threaded parts, the automatic screw machine has long since exceeded

the confines of this narrow field, and today plays a vital role in the mass production of a variety of precision parts.Quantities play an important part in the economy of the parts machined on the automatic screw machine.Quantities less than on the automatic screw machine.The cost of the parts machined can be reduced if the minimum economical lot size is calculated and the proper machine is selected for these quantities.Automatic Tracer Lathes

Since surface roughness depends greatly on material turned, tooling , and feeds and speeds employed, minimum tolerances that can be held on automatic tracer lathes are not necessarily the most economical tolerances.In some cases, tolerances of 0.05mm are held in continuous production using but one cut.groove width can be held to 0.125mm on some parts.Bores and single-point finishes can be held to 0.0125mm.On high-production runs where maximum output is desirable, a minimum tolerance of 0.125mm is economical on both diameter and length of turn.FromLathe basic technology 中文译文：

车床基础技术

译者：胡谦 学号0803020113 1.车床

车床主要是为了进行车外圆、车端面和镗孔等项工作而设计的机床。车削很少在其他种类的机床上进行，而且任何一种其他机床都不能像车床那样方便地进行车削加工。由于车床还可以用来钻孔和铰孔，车床的多功能性可以使工件在一次安装中完成几种加工。因此，在生产中使用的各种车床比任何其他种类的机床都多。

车床的基本部件有：床身、主轴箱组件、尾座组件、溜板组件、丝杠和光杠。

床身是车床的基础件。它能常是由经过充分正火或时效处理的灰铸铁或者球墨铁制成。它是一个坚固的刚性框架，所有其他基本部件都安装在床身上。通常在床身上有内外两组平行的导轨。有些制造厂对全部四条导轨都采用导轨尖朝上的三角形导轨（即山形导轨），而有的制造厂则在一组中或者两组中都采用一个三角形导轨和一个矩形导轨。导轨要经过精密加工以保证其直线度精度。为了抵抗磨损和擦伤，大多数现代机床的导轨是经过表面淬硬的，但是在操作时还应该小心，以避免损伤导轨。导轨上的任何误差，常常意味着整个机床的精度遭到破坏。

主轴箱安装在内侧导轨的固定位置上，一般在床身的左端。它提供动力，并可使工件在各种速度下回转。它基本上由一个安装在精密轴承中的空心主轴和一系列变速齿轮(类似于卡车变速箱)所组成。通过变速齿轮，主轴可以在许多种转速下旋转。大多数车床有8~12种转速，一般按等比级数排列。而且在现代机床上只需扳动2~4个手柄，就能得到全部转速。一种正在不断增长的趋势是通过电气的或者机械的装置进行无级变速。

由于机床的精度在很大程度上取决于主轴，因此，主轴的结构尺寸较大，通常安装在预紧后的重型圆锥滚子轴承或球轴承中。主轴中有一个贯穿全长的通孔，长棒料可以通过该孔送料。主轴孔的大小是车床的一个重要尺寸，因此当工件必须通过主轴孔供料时，它确定了能够加工的棒料毛坯的最大尺寸。

尾座组件主要由三部分组成。底板与床身的内侧导轨配合，并可以在导轨上作纵向移动。底板上有一个可以使整个尾座组件夹紧在任意位置上的装置。尾座体安装在底板上，可以沿某种类型的键槽在底板上横向移动，使尾座能与主轴箱中的主轴对正。尾座的第三个组成部分是尾座套筒。它是一个直径通常大约在51~76mm（2~3英寸）之间的钢制空心圆柱体。通过手轮和螺杆，尾座套筒可以在尾座体中纵向移入和移出几个英寸。

车床的规格用两个尺寸表示。第一个称为车床的床面上最大加工直径。这是在车床上能够旋转的工件的最大直径。它大约是两顶尖连线与导轨上最近点之间距离的两倍。第二个规格尺寸是两顶尖之间的最大距离。车床床面上最大加工直径表示在车床上能够车削的最大工件直径，而两顶尖之间的最大距离则表示在两个顶尖之间能够安装的工件的最大长度。

普通车床是生产中最经常使用的车床种类。它们是具有前面所叙的所有那些部件的重载机床，并且除了小刀架之外，全部刀具的运动都有机动进给。它们的规格通常是：车床床面上最大加工直径为305~610mm（12~24英寸）；但是，床面上最大加工直径达到1270mm（50英寸）和两顶尖之间距离达到3658mm的车床也并不少见。这些车床大部分都有切屑盘和一个安装在内部的冷却液循环系统。小型的普通车床—车床床面最大加工直径一般不超过330mm（13英寸）--被设计成台式车床，其床身安装在工作台或柜子上。

虽然普通车床有很多用途，是很有用的机床，但是更换和调整刀具以及测量工件花费很多时间，所以它们不适合在大量生产中应用。通常，它们的实际加工时间少于其总加工时间的30%。此外，需要技术熟练的工人来操作普通车床，这种工人的工资高而且很难雇到。然而，操作工人的大部分时间却花费在简单的重复调整和观察切屑过程上。因此，为了减少或者完全不雇用这类熟练工人，六角车床、螺纹加工车床和其他类型的半自动和自动车床已经很好地研制出来，并已经在生产中得到广泛应用。2.数字控制

先进制造技术中的一个基本的概念是数字控制（NC）。在数控技术出现之前，所有的机床都是由人工操纵和控制的。在与人工控制的机床有关的很多局限性中，操作者的技能大概是最突出的问题。采用人工控制是，产品的质量直接与操作者的技能有关。数字控制代表了从人工控制机床走出来的第一步。

数字控制意味着采用预先录制的、存储的符号指令来控制机床和其他制造系统。一个数控技师的工作不是去操纵机床，而是编写能够发出机床操纵指令的程序。对于一台数控机床，其上必须安有一个被称为阅读机的界面装置，用来接受和解译出编程指令。

发展数控技术是为了克服人类操作者的局限性，而且它确实完成了这项工作。数字控制的机器比人工操纵的机器精度更高、生产出零件的一致性更好、生产速度更快、而且长期的工艺装备成本更低。数控技术的发展导致了制造工艺中其他几项新发明的产生：

电火花加工技术、激光切割、电子束焊接

数字控制还使得机床比它们采用有人工操的前辈们的用途更为广泛。一台数控机床可以自动生产很多类的零件，每一个零件都可以有不同的和复杂的加工过程。数控可以使生产厂家承担那些对于采用人工控制的机床和工艺来说，在经济上是不划算的产品生产任务。

同许多先进技术一样，数控诞生于麻省理工学院的实验室中。数控这个概念是50年代初在美国空军的资助下提出来的。在其最初的价段，数控机床可以经济和有效地进行直线切割。

然而，曲线轨迹成为机床加工的一个问题，在编程时应该采用一系列的水平与竖直的台阶来生成曲线。构成台阶的每一个线段越短，曲线就越光滑。台阶中的每一个线段都必须经过计算。

在这个问题促使下，于1959年诞生了自动编程工具（APT）语言。这是一个专门适用于数控的编程语言，使用类似于英语的语句来定义零件的几何形状，描述切削刀具的形状和规定必要的运动。APT语言的研究和发展是在数控技术进一步发展过程中的一大进步。最初的数控系统下今天应用的数控系统是有很大差别的。在那时的机床中，只有硬线逻辑电路。指令程序写在穿孔纸带上（它后来被塑料带所取代），采用带阅读机将写在纸带或磁带上的指令给机器翻译出来。所有这些共同构成了机床数字控制方面的巨大进步。然而，在数控发展的这个阶段中还存在着许多问题。一个主要问题是穿孔纸带的易损坏性。在机械加工过程中，载有编程指令信息的纸带断裂和被撕坏是常见的事情。在机床上每加工一个零件，都需要将载有编程指令的纸带放入阅读机中重新运行一次。因此，这个问题变得很严重。如果需要制造100个某种零件，则应该将纸带分别通过阅读机100次。易损坏的纸带显然不能承受严配的车间环境和这种重复使用。

这就导致了一种专门的塑料磁带的研制。在纸带上通过采用一系列的小孔来载有编程指令，而在塑料带上通过采用一系列的磁点眯载有编程指令。塑料带的强度比纸带的强度要高很多，这就可以解决常见的撕坏和断裂问题。然而，它仍然存在着两个问题。

其中最重要的一个问题是，对输入到带中指令进行修改是非常困难的，或者是根本不可能的。即使对指令程序进行最微小的调整，也必须中断加工，制作一条新带。而且带通过阅读机的次数还必须与需要加工的零件的个数相同。幸运的是，计算机技术的实际应用很快解决了数控技术中与穿孔纸带和塑料带有关的问题。

在形成了直接数字控制（DNC）这个概念之后，可以不再采用纸带或塑料带作为编程指令的载体，这样就解决了与之有关的问题。在直接数字控制中，几台机床通过数据传输线路联接到一台主计算机上。操纵这些机床所需要的程序都存储在这台主计算机中。当需要时，通过数据传输线路提供给每台机床。直接数字控制是在穿孔纸带和塑料带基础上的一大进步。然而，它敢有着同其他信赖于主计算机技术一样的局限性。当主计算机出现故障时，由其控制的所有机床都将停止工作。这个问题促使了计算机数字控制技术的产生。

微处理器的发展为可编程逻辑控制器和微型计算机的发展做好了准备。这两种技术为计算机数控（CNC）的发打下了基础。采用CNC技术后，每台机床上都有一个可编程逻辑控制器或者微机对其进行数字控制。这可以使得程序被输入和存储在每台机床内部。它还可以在机床以外编制程序，并将其下载到每台机床中。计算机数控解决了主计算机发生故障所带来的问题，但是它产生了另一个被称为数据管理的问题。同一个程序可能要分别装入十个相互之间没有通讯联系的微机中。这个问题目前正在解决之中，它是通过采用局部区域网络将各个微机联接起来，以得于更好地进行数据管理。3.车削加工

普通车床作为最早的金属切削机床的一种，目前仍然有许多有用的和为人要的特性和为人们所需的特性。现在，这些机床主要用在规模较小的工厂中，进行小批量的生产，而不是进行大批量的和产。

在现代的生产车间中，普通车床已经被种类繁多的自动车床所取代，诸如自动仿形车床，六角车床和自动螺丝车床。现在，设计人员已经熟知先利用单刃刀具去除大量的金属余量，然后利用成型刀具获得表面光洁度和精度这种加工方法的优点。这种加工方法的生产速度与现在工厂中使用的最快的加工设备的速度相等。

普通车床的加偏差主要信赖于操作者的技术熟练程度。设计工程师应该认真地确定由熟练工人在普通车床上加工的试验件的公差。在把试验伯重新设计为生产零件时，应该选用经济的公差。

六角车床 对生产加工设备来说，目前比过去更注重评价其是否具有精确的和快速的重复加工能力。应用这个标准来评价具体的加工方法，六角车床可以获得较高的质量评定。在为小批量的零件（100~200件）设计加工方法时，采用六角车床是最经济的。为了在六角车床上获得尽可能小的公差值，设计人员应该尽量将加工工序的数目减至最少。

自动螺丝车床 自动螺丝车床通被分为以下几种类型：单轴自动、多轴自动和自动夹紧车床。自动螺丝车床最初是被用来对螺钉和类似的带有螺纹的零件进行自动化和快速加工的。但是，这种车床的用途早就超过了这个狭窄的范围。现在，它在许多种类的精密零件的大批量生产中起着重要的作用。工件的数量对采用自动螺丝车床所加工的零件的经济性有较大的影响。如果工件的数量少于1000件，在六角车床上进行加工比在自动螺丝车床上加工要经济得多。如果计算出最小经济批量，并且针对工件批量正确地选择机床，就会降低零件的加工成本。

自动仿形车床 因为零件的表面粗糙度在很大程度上取决于工件材料、刀具、进给量和切削速度，采用自动仿形车床加工所得到的最小公差一定是最经济的公差。

在某些情况下，在连续生产过程中，只进行一次切削加工时的公差可以达到0.05mm。对于某些零件，槽宽的公差可以达到0.125mm。镗孔和休用单刃刀具进行精加工时，公差可达到0.0125mm。在希望获得最大主量的大批量生产中，进行直径和长度的车削时的最小公差值为0.125mm是经济的。

来源：车床基本技术

机械毕业英语论文翻译 第2篇

Materials may be grouped in several ways.Scientists often classify materials by their state: solid, liquid, or gas.They also separate them into organic(once living)and inorganic(never living)materials.材料可以按多种方法分类。科学家常根据状态将材料分为：固体、液体或气体。他们也把材料分为有机材料(曾经有生命的)和无机材料(从未有生命的)。

For industrial purposes, materials are divided into engineering materials or nonengineering materials.Engineering materials are those used in manufacture and become parts of products.就工业效用而言，材料被分为工程材料和非工程材料。那些用于加工制造并成为产品组成部分的就是工程材料。

Nonengineering materials are the chemicals, fuels, lubricants, and other materials used in the manufacturing process, which do not become part of the product.非工程材料则是化学品、燃料、润滑剂以及其它用于加工制造过程但不成为产品组成部分的材料。

Engineering materials may be further subdivided into: ①Metal ②Ceramics ③Composite ④Polymers, etc.工程材料还能进一步细分为：①金属材料②陶瓷材料③复合材料 ④聚合材料，等等。? Metals and Metal Alloys 金属和金属合金

Metals are elements that generally have good electrical and thermal conductivity.Many metals have high strength, high stiffness, and have good ductility.金属就是通常具有良好导电性和导热性的元素。许多金属具有高强度、高硬度以及良好的延展性。

Some metals, such as iron, cobalt and nickel, are magnetic.At low temperatures, some metals and intermetallic compounds become superconductors.某些金属能被磁化，例如铁、钴和镍。在极低的温度下，某些金属和金属化合物能转变成超导体。

What is the difference between an alloy and a pure metal? Pure metals are elements which come from a particular area of the periodic table.Examples of pure metals include copper in electrical wires and aluminum in cooking foil and beverage cans.合金与纯金属的区别是什么？纯金属是在元素周期表中占据特定位置的元素。例如电线中的铜和制造烹饪箔及饮料罐的铝。

Alloys contain more than one metallic element.Their properties can be changed by changing the elements present in the alloy.Examples of metal alloys include stainless steel which is an alloy of iron, nickel, and chromium;and gold jewelry which usually contains an alloy of gold and nickel.合金包含不止一种金属元素。合金的性质能通过改变其中存在的元素而改变。金属合金的例子有：不锈钢是一种铁、镍、铬的合金，以及金饰品通常含有金镍合金。Why are metals and alloys used? Many metals and alloys have high densities and are used in applications which require a high mass-to-volume ratio.为什么要使用金属和合金？许多金属和合金具有高密度，因此被用在需要较高质量体积比的场合。

Some metal alloys, such as those based on aluminum, have low densities and are used in aerospace applications for fuel economy.Many alloys also have high fracture toughness, which means they can withstand impact and are durable.某些金属合金，例如铝基合金，其密度低，可用于航空航天以节约燃料。许多合金还具有高断裂韧性，这意味着它们能经得起冲击并且是耐用的。

What are some important properties of metals? Density is defined as a material’s mass divided by its volume.Most metals have relatively high densities, especially compared to polymers.金属有哪些重要特性？

密度定义为材料的质量与其体积之比。大多数金属密度相对较高，尤其是和聚合物相比较而言。

Materials with high densities often contain atoms with high atomic numbers, such as gold or lead.However, some metals such as aluminum or magnesium have low densities, and are used in applications that require other metallic properties but also require low weight.高密度材料通常由较大原子序数原子构成，例如金和铅。然而，诸如铝和镁之类的一些金属则具有低密度，并被用于既需要金属特性又要求重量轻的场合。Fracture toughness can be described as a material’s ability to avoid fracture, especially when a flaw is introduced.Metals can generally contain nicks and dents without weakening very much, and are impact resistant.A football player counts on this when he trusts that his facemask won’t shatter.断裂韧性可以描述为材料防止断裂特别是出现缺陷时不断裂的能力。金属一般能在有缺口和凹痕的情况下不显著削弱，并且能抵抗冲击。橄榄球运动员据此相信他的面罩不会裂成碎片。

Plastic deformation is the ability of bend or deform before breaking.As engineers, we usually design materials so that they don’t deform under normal conditions.You don’t want your car to lean to the east after a strong west wind.塑性变形就是在断裂前弯曲或变形的能力。作为工程师，设计时通常要使材料在正常条件下不变形。没有人愿意一阵强烈的西风过后自己的汽车向东倾斜。

However, sometimes we can take advantage of plastic deformation.The crumple zones in a car absorb energy by undergoing plastic deformation before they break.然而，有时我们也能利用塑性变形。汽车上压皱的区域在它们断裂前通过经历塑性变形来吸收能量。

The atomic bonding of metals also affects their properties.In metals, the outer valence electrons are shared among all atoms, and are free to travel everywhere.Since electrons conduct heat and electricity, metals make good cooking pans and electrical wires.金属的原子连结对它们的特性也有影响。在金属内部，原子的外层阶电子由所有原子共享并能到处自由移动。由于电子能导热和导电，所以用金属可以制造好的烹饪锅和电线。It is impossible to see through metals, since these valence electrons absorb any photons of light which reach the metal.No photons pass through.因为这些阶电子吸收到达金属的光子，所以透过金属不可能看得见。没有光子能通过金属。Alloys are compounds consisting of more than one metal.Adding other metals can affect the density, strength, fracture toughness, plastic deformation, electrical conductivity and environmental degradation.合金是由一种以上金属组成的混合物。加一些其它金属能影响密度、强度、断裂韧性、塑性变形、导电性以及环境侵蚀。

For example, adding a small amount of iron to aluminum will make it stronger.Also, adding some chromium to steel will slow the rusting process, but will make it more brittle.例如，往铝里加少量铁可使其更强。同样，在钢里加一些铬能减缓它的生锈过程，但也将使它更脆。

? Ceramics and Glasses 陶瓷和玻璃 A ceramic is often broadly defined as any inorganic nonmetallic material． By this definition, ceramic materials would also include glasses;however, many materials scientists add the stipulation that “ceramic” must also be crystalline.陶瓷通常被概括地定义为无机的非金属材料。照此定义，陶瓷材料也应包括玻璃；然而许多材料科学家添加了“陶瓷”必须同时是晶体物组成的约定。

A glass is an inorganic nonmetallic material that does not have a crystalline structure.Such materials are said to be amorphous.玻璃是没有晶体状结构的无机非金属材料。这种材料被称为非结晶质材料。Properties of Ceramics and Glasses Some of the useful properties of ceramics and glasses include high melting temperature, low density, high strength, stiffness, hardness, wear resistance, and corrosion resistance.陶瓷和玻璃的特性

高熔点、低密度、高强度、高刚度、高硬度、高耐磨性和抗腐蚀性是陶瓷和玻璃的一些有用特性。

Many ceramics are good electrical and thermal insulators.Some ceramics have special properties: some ceramics are magnetic materials;some are piezoelectric materials;and a few special ceramics are superconductors at very low temperatures.Ceramics and glasses have one major drawback: they are brittle.许多陶瓷都是电和热的良绝缘体。某些陶瓷还具有一些特殊性能：有些是磁性材料，有些是压电材料，还有些特殊陶瓷在极低温度下是超导体。陶瓷和玻璃都有一个主要的缺点：它们容易破碎。

Ceramics are not typically formed from the melt.This is because most ceramics will crack extensively(i.e.form a powder)upon cooling from the liquid state.陶瓷一般不是由熔化形成的。因为大多数陶瓷在从液态冷却时将会完全破碎(即形成粉末)。

Hence, all the simple and efficient manufacturing techniques used for glass production such as casting and blowing, which involve the molten state, cannot be used for the production of crystalline ceramics.Instead, “sintering” or “firing” is the process typically used.因此，所有用于玻璃生产的简单有效的—诸如浇铸和吹制这些涉及熔化的技术都不能用于由晶体物组成的陶瓷的生产。作为替代，一般采用“烧结”或“焙烧”工艺。

In sintering, ceramic powders are processed into compacted shapes and then heated to temperatures just below the melting point.At such temperatures, the powders react internally to remove porosity and fully dense articles can be obtained.在烧结过程中，陶瓷粉末先挤压成型然后加热到略低于熔点温度。在这样的温度下，粉末内部起反应去除孔隙并得到十分致密的物品。

An optical fiber contains three layers: a core made of highly pure glass with a high refractive index for the light to travel, a middle layer of glass with a lower refractive index known as the cladding which protects the core glass from scratches and other surface imperfections, and an out polymer jacket to protect the fiber from damage.光导纤维有三层：核心由高折射指数高纯光传输玻璃制成，中间层为低折射指数玻璃，是保护核心玻璃表面不被擦伤和完整性不被破坏的所谓覆层，外层是聚合物护套，用于保护光导纤维不受损。

In order for the core glass to have a higher refractive index than the cladding, the core glass is doped with a small, controlled amount of an impurity, or dopant, which causes light to travel slower, but does not absorb the light.为了使核心玻璃有比覆层大的折射指数，在其中掺入微小的、可控数量的能减缓光速而不会吸收光线的杂质或搀杂剂。

Because the refractive index of the core glass is greater than that of the cladding, light traveling in the core glass will remain in the core glass due to total internal reflection as long as the light strikes the core/cladding interface at an angle greater than the critical angle.由于核心玻璃的折射指数比覆层大，只要在全内反射过程中光线照射核心/覆层分界面的角度比临界角大，在核心玻璃中传送的光线将仍保留在核心玻璃中。

The total internal reflection phenomenon, as well as the high purity of the core glass, enables light to travel long distances with little loss of intensity.全内反射现象与核心玻璃的高纯度一样，使光线几乎无强度损耗传递长距离成为可能。? Composites 复合材料

Composites are formed from two or more types of materials.Examples include polymer/ceramic and metal/ceramic composites.Composites are used because overall properties of the composites are superior to those of the individual components.复合材料由两种或更多材料构成。例子有聚合物/陶瓷和金属/陶瓷复合材料。之所以使用复合材料是因为其全面性能优于组成部分单独的性能。

For example: polymer/ceramic composites have a greater modulus than the polymer component, but aren’t as brittle as ceramics.Two types of composites are: fiber-reinforced composites and particle-reinforced composites.例如：聚合物/陶瓷复合材料具有比聚合物成分更大的模量，但又不像陶瓷那样易碎。

复合材料有两种：纤维加强型复合材料和微粒加强型复合材料。Fiber-reinforced Composites Reinforcing fibers can be made of metals, ceramics, glasses, or polymers that have been turned into graphite and known as carbon fibers.Fibers increase the modulus of the matrix material.纤维加强型复合材料

加强纤维可以是金属、陶瓷、玻璃或是已变成石墨的被称为碳纤维的聚合物。纤维能加强基材的模量。

The strong covalent bonds along the fiber’s length give them a very high modulus in this direction because to break or extend the fiber the bonds must also be broken or moved.沿着纤维长度有很强结合力的共价结合在这个方向上给予复合材料很高的模量，因为要损坏或拉伸纤维就必须破坏或移除这种结合。

Fibers are difficult to process into composites, making fiber-reinforced composites relatively expensive.把纤维放入复合材料较困难，这使得制造纤维加强型复合材料相对昂贵。Fiber-reinforced composites are used in some of the most advanced, and therefore most expensive sports equipment, such as a time-trial racing bicycle frame which consists of carbon fibers in a thermoset polymer matrix.纤维加强型复合材料用于某些最先进也是最昂贵的运动设备，例如计时赛竞赛用自行车骨架就是用含碳纤维的热固塑料基材制成的。

Body parts of race cars and some automobiles are composites made of glass fibers(or fiberglass)in a thermoset matrix.竞赛用汽车和某些机动车的车体部件是由含玻璃纤维(或玻璃丝)的热固塑料基材制成的。Fibers have a very high modulus along their axis, but have a low modulus perpendicular to their axis.Fiber composite manufacturers often rotate layers of fibers to avoid directional variations in the modulus.纤维在沿着其轴向有很高的模量，但垂直于其轴向的模量却较低。纤维复合材料的制造者往往旋转纤维层以防模量产生方向变化。Particle-reinforced composites Particles used for reinforcing include ceramics and glasses such as small mineral particles, metal particles such as aluminum, and amorphous materials, including polymers and carbon black.微粒加强型复合材料

用于加强的微粒包含了陶瓷和玻璃之类的矿物微粒，铝之类的金属微粒以及包括聚合物和碳黑的非结晶质微粒。

Particles are used to increase the modulus of the matrix, to decrease the permeability of the matrix, to decrease the ductility of the matrix.An example of particle-reinforced composites is an automobile tire which has carbon black particles in a matrix of polyisobutylene elastomeric polymer.微粒用于增加基材的模量、减少基材的渗透性和延展性。微粒加强型复合材料的一个例子是机动车胎，它就是在聚异丁烯人造橡胶聚合物基材中加入了碳黑微粒。? Polymers 聚合材料

A polymer has a repeating structure, usually based on a carbon backbone.The repeating structure results in large chainlike molecules.Polymers are useful because they are lightweight, corrosion resistant, easy to process at low temperatures and generally inexpensive.聚合物具有一般是基于碳链的重复结构。这种重复结构产生链状大分子。由于重量轻、耐腐蚀、容易在较低温度下加工并且通常较便宜，聚合物是很有用的。

Some important characteristics of polymers include their size(or molecular weight), softening and melting points, crystallinity, and structure.The mechanical properties of polymers generally include low strength and high toughness.Their strength is often improved using reinforced composite structures.聚合材料具有一些重要特性，包括尺寸(或分子量)、软化及熔化点、结晶度和结构。聚合材料的机械性能一般表现为低强度和高韧性。它们的强度通常可采用加强复合结构来改善。

Important Characteristics of Polymers Size.Single polymer molecules typically have molecular weights between 10,000 and 1,000,000g/mol—that can be more than 2,000 repeating units depending on the polymer structure!聚合材料的重要特性

尺寸：单个聚合物分子一般分子量为10,000到1,000,000g/mol之间，具体取决于聚合物的结构—这可以比2,000个重复单元还多。The mechanical properties of a polymer are significantly affected by the molecular weight, with better engineering properties at higher molecular weights.聚合物的分子量极大地影响其机械性能，分子量越大，工程性能也越好。Thermal transitions.The softening point(glass transition temperature)and the melting point of a polymer will determine which it will be suitable for applications.These temperatures usually determine the upper limit for which a polymer can be used.热转换性：聚合物的软化点(玻璃状转化温度)和熔化点决定了它是否适合应用。这些温度通常决定聚合物能否使用的上限。For example, many industrially important polymers have glass transition temperatures near the boiling point of water(100℃, 212℉), and they are most useful for room temperature applications.Some specially engineered polymers can withstand temperatures as high as 300℃(572℉).例如，许多工业上的重要聚合物其玻璃状转化温度接近水的沸点(100℃, 212℉)，它们被广泛用于室温下。而某些特别制造的聚合物能经受住高达300℃(572℉)的温度。

Crystallinity.Polymers can be crystalline or amorphous, but they usually have a combination of crystalline and amorphous structures(semi-crystalline).结晶度：聚合物可以是晶体状的或非结晶质的，但它们通常是晶体状和非结晶质结构的结合物(半晶体)。

Interchain interactions.The polymer chains can be free to slide past one another(thermo-plastic)or they can be connected to each other with crosslinks(thermoset or elastomer).Thermo-plastics can be reformed and recycled, while thermosets and elastomers are not reworkable.原子链间的相互作用：聚合物的原子链可以自由地彼此滑动(热可塑性)或通过交键互相连接(热固性或弹性)。热可塑性材料可以重新形成和循环使用，而热固性与弹性材料则是不能再使用的。

Intrachain structure.The chemical structure of the chains also has a tremendous effect on the properties.Depending on the structure the polymer may be hydrophilic or hydrophobic(likes or hates water), stiff or flexible, crystalline or amorphous, reactive or unreactive.链内结构：原子链的化学结构对性能也有很大影响。根据各自的结构不同，聚合物可以是亲水的或憎水的(喜欢或讨厌水)、硬的或软的、晶体状的或非结晶质的、易起反应的或不易起反应的。

第二单元

The understanding of heat treatment is embraced by the broader study of metallurgy.Metallurgy is the physics, chemistry, and engineering related to metals from ore extraction to the final product.对热处理的理解包含于对冶金学较广泛的研究。冶金学是物理学、化学和涉及金属从矿石提炼到最后产物的工程学。

Heat treatment is the operation of heating and cooling a metal in its solid state to change its physical properties.According to the procedure used, steel can be hardened to resist cutting action and abrasion, or it can be softened to permit machining.热处理是将金属在固态加热和冷却以改变其物理性能的操作。按所采用的步骤，钢可以通过硬化来抵抗切削和磨损，也可以通过软化来允许机加工。

With the proper heat treatment internal stresses may be removed, grain size reduced, toughness increased, or a hard surface produced on a ductile interior.The analysis of the steel must be known because small percentages of certain elements, notably carbon, greatly affect the physical properties.使用合适的热处理可以去除内应力、细化晶粒、增加韧性或在柔软材料上覆盖坚硬的表面。因为某些元素(尤其是碳)的微小百分比极大地影响物理性能，所以必须知道对钢的分析。Alloy steel owe their properties to the presence of one or more elements other than carbon, namely nickel, chromium, manganese, molybdenum, tungsten, silicon, vanadium, and copper.Because of their improved physical properties they are used commercially in many ways not possible with carbon steels.合金钢的性质取决于其所含有的除碳以外的一种或多种元素，如镍、铬、锰、钼、钨、硅、钒和铜。由于合金钢改善的物理性能，它们被大量使用在许多碳钢不适用的地方。The following discussion applies principally to the heat treatment of ordinary commercial steels known as plain carbon steels.With this process the rate of cooling is the controlling factor, rapid cooling from above the critical range results in hard structure, whereas very slow cooling produces the opposite effect.下列讨论主要针对被称为普通碳钢的工业用钢而言。热处理时冷却速率是控制要素，从高于临界温度快速冷却导致坚硬的组织结构，而缓慢冷却则产生相反效果。? A Simplified Iron-carbon Diagram 简化铁碳状态图

If we focus only on the materials normally known as steels, a simplified diagram is often used.如果只把注意力集中于一般所说的钢上，经常要用到简化铁碳状态图。

Those portions of the iron-carbon diagram near the delta region and those above 2% carbon content are of little importance to the engineer and are deleted.A simplified diagram, such as the one in Fig.2.1, focuses on the eutectoid region and is quite useful in understanding the properties and processing of steel.铁碳状态图中靠近三角区和含碳量高于2%的那些部分对工程师而言不重要，因此将它们删除。如图2.1所示的简化铁碳状态图将焦点集中在共析区，这对理解钢的性能和处理是十分有用的。

The key transition described in this diagram is the decomposition of single-phase austenite(γ)to the two-phase ferrite plus carbide structure as temperature drops.在此图中描述的关键转变是单相奥氏体(γ)随着温度下降分解成两相铁素体加渗碳体组织结构。

Control of this reaction, which arises due to the drastically different carbon solubility of austenite and ferrite, enables a wide range of properties to be achieved through heat treatment.控制这一由于奥氏体和铁素体的碳溶解性完全不同而产生的反应，使得通过热处理能获得很大范围的特性。To begin to understand these processes, consider a steel of the eutectoid composition, 0.77% carbon, being slow cooled along line x-x’ in Fig.2.1.At the upper temperatures, only austenite is present, the 0.77% carbon being dissolved in solid solution with the iron.When the steel cools to 727℃(1341℉), several changes occur simultaneously.为了理解这些过程，考虑含碳量为0.77%的共析钢，沿着图2.1的x-x’线慢慢冷却。在较高温度时，只存在奥氏体，0.77%的碳溶解在铁里形成固溶体。当钢冷却到727℃(1341℉)时，将同时发生若干变化。

The iron wants to change from the FCC austenite structure to the BCC ferrite structure, but the ferrite can only contain 0.02% carbon in solid solution.铁需要从面心立方体奥氏体结构转变为体心立方体铁素体结构，但是铁素体只能容纳固溶体状态的0.02%的碳。

The rejected carbon forms the carbon-rich cementite intermetallic with composition Fe3C.In essence, the net reaction at the eutectoid is austenite 0.77%C→ferrite 0.02%C+cementite 6.67%C.被析出的碳与金属化合物Fe3C形成富碳的渗碳体。本质上，共析体的基本反应是奥氏体0.77%的碳→铁素体0.02%的碳+渗碳体6.67%的碳。

Since this chemical separation of the carbon component occurs entirely in the solid state, the resulting structure is a fine mechanical mixture of ferrite and cementite.Specimens prepared by polishing and etching in a weak solution of nitric acid and alcohol reveal the lamellar structure of alternating plates that forms on slow cooling.由于这种碳成分的化学分离完全发生在固态中，产生的组织结构是一种细致的铁素体与渗碳体的机械混合物。通过打磨并在弱硝酸酒精溶液中蚀刻制备的样本显示出由缓慢冷却形成的交互层状的薄片结构。

This structure is composed of two distinct phases, but has its own set of characteristic properties and goes by the name pearlite, because of its resemblance to mother-of-pearl at low magnification.这种结构由两种截然不同的状态组成，但它本身具有一系列特性，且因与低倍数放大时的珠母层有类同之处而被称为珠光体。Steels having less than the eutectoid amount of carbon(less than 0.77%)are known as hypo-eutectoid steels.Consider now the transformation of such a material represented by cooling along line y-y’ in Fig.2.1.含碳量少于共析体(低于0.77%)的钢称为亚共析钢。现在来看这种材料沿着图2.1中y-y’ 线冷却的转变情况。

At high temperatures, the material is entirely austenite, but upon cooling enters a region where the stable phases are ferrite and austenite.Tie-line and level-law calculations show that low-carbon ferrite nucleates and grows, leaving the remaining austenite richer in carbon.在较高温度时，这种材料全部是奥氏体，但随着冷却就进入到铁素体和奥氏体稳定状态的区域。由截线及杠杆定律分析可知，低碳铁素体成核并长大，剩下含碳量高的奥氏体。

At 727℃(1341℉), the austenite is of eutectoid composition(0.77% carbon)and further cooling transforms the remaining austenite to pearlite.The resulting structure is a mixture of primary or pro-eutectoid ferrite(ferrite that formed above the eutectoid reaction)and regions of pearlite.在727℃(1341℉)时，奥氏体为共析组成(含碳量0.77%)，再冷却剩余的奥氏体就转化为珠光体。作为结果的组织结构是初步的共析铁素体(在共析反应前的铁素体)和部分珠光体的混合物。

Hypereutectoid steels are steels that contain greater than the eutectoid amount of carbon.When such steel cools, as shown in z-z’ of Fig.2.1 the process is similar to the hypo-eutectoid case, except that the primary or pro-eutectoid phase is now cementite instead of ferrite.过共析钢是含碳量大于共析量的钢。当这种钢冷却时，就像图2.1的z-z’线所示，除了初步的共析状态用渗碳体取代铁素体外，其余类似亚共析钢的情况。

As the carbon-rich phase forms, the remaining austenite decreases in carbon content, reaching the eutectoid composition at 727℃(1341℉).As before, any remaining austenite transforms to pearlite upon slow cooling through this temperature.随着富碳部分的形成，剩余奥氏体含碳量减少，在727℃(1341℉)时达到共析组织。就像以前说的一样，当缓慢冷却到这温度时所有剩余奥氏体转化为珠光体。

It should be remembered that the transitions that have been described by the phase diagrams are for equilibrium conditions, which can be approximated by slow cooling.With slow heating, these transitions occur in the reverse manner.应该记住由状态图描述的这种转化只适合于通过缓慢冷却的近似平衡条件。如果缓慢加热，则以相反的方式发生这种转化。However, when alloys are cooled rapidly, entirely different results may be obtained, because sufficient time is not provided for the normal phase reactions to occur, in such cases, the phase diagram is no longer a useful tool for engineering analysis.然而，当快速冷却合金时，可能得到完全不同的结果。因为没有足够的时间让正常的状态反应发生，在这种情况下对工程分析而言状态图不再是有用的工具。? Hardening 淬火

Hardening is the process of heating a piece of steel to a temperature within or above its critical range and then cooling it rapidly.淬火就是把钢件加热到或超过它的临界温度范围，然后使其快速冷却的过程。If the carbon content of the steel is known, the proper temperature to which the steel should be heated may be obtained by reference to the iron-iron carbide phase diagram.However, if the composition of the steel is unknown, a little preliminary experimentation may be necessary to determine the range.如果钢的含碳量已知，钢件合适的加热温度可参考铁碳合金状态图得到。然而当钢的成分不知道时，则需做一些预备试验来确定其温度范围。

A good procedure to follow is to heat-quench a number of small specimens of the steel at various temperatures and observe the result, either by hardness testing or by microscopic examination.When the correct temperature is obtained, there will be a marked change in hardness and other properties.要遵循的合适步骤是将这种钢的一些小试件加热到不同的温度后淬火，再通过硬度试验或显微镜检查观测结果。一旦获得正确的温度，硬度和其它性能都将有明显的变化。

In any heat-treating operation the rate of heating is important.Heat flows from the exterior to the interior of steel at a definite rate.If the steel is heated too fast, the outside becomes hotter than the interior and uniform structure cannot be obtained.在任何热处理作业中，加热的速率都是重要的。热量以一定的速率从钢的外部传导到内部。如果钢被加热得太快，其外部比内部热就不能得到均匀的组织结构。

If a piece is irregular in shape, a slow rate is all the more essential to eliminate warping and cracking.The heavier the section, the longer must be the heating time to achieve uniform results.如果工件形状不规则，为了消除翘曲和开裂最根本的是加热速率要缓慢。截面越厚，加热的时间就要越长才能达到均匀的结果。

Even after the correct temperature has been reached, the piece should be held at that temperature for a sufficient period of time to permit its thickest section to attain a uniform temperature.即使加热到正确的温度后，工件也应在此温度下保持足够时间以让其最厚截面达到相同温度。The hardness obtained from a given treatment depends on the quenching rate, the carbon content, and the work size.In alloy steels the kind and amount of alloying element influences only the hardenability(the ability of the workpiece to be hardened to depths)of the steel and does not affect the hardness except in unhardened or partially hardened steels.通过给定的热处理所得到的硬度取决于淬火速率、含碳量和工件尺寸。除了非淬硬钢或部分淬硬钢外，合金钢中合金元素的种类及含量仅影响钢的淬透性(工件被硬化到深层的能力)而不影响硬度。

Steel with low carbon content will not respond appreciably to hardening treatment.As the carbon content in steel increases up to around 0.60%, the possible hardness obtainable also increases.含碳量低的钢对淬火处理没有明显的反应。随着钢的含碳量增加到大约0.60%，可能得到的硬度也增加。

Above this point the hardness can be increased only slightly, because steels above the eutectoid point are made up entirely of pearlite and cementite in the annealed state.Pearlite responds best to heat-treating operations;and steel composed mostly of pearlite can be transformed into a hard steel.高于此点，由于超过共析点钢完全由珠光体和退火状态的渗碳体组成，硬度增加并不多。珠光体对热处理作业响应最好；基本由珠光体组成的钢能转化成硬质钢。As the size of parts to be hardened increases, the surface hardness decreases somewhat even though all other conditions have remained the same.There is a limit to the rate of heat flow through steel.即使所有其它条件保持不变，随着要淬火的零件尺寸的增加其表面硬度也会有所下降。热量在钢中的传导速率是有限的。No matter how cool the quenching medium may be, if the heat inside a large piece cannot escape faster than a certain critical rate, there is a definite limit to the inside hardness.However, brine or water quenching is capable of rapidly bringing the surface of the quenched part to its own temperature and maintaining it at or close to this temperature.无论淬火介质怎么冷，如果在大工件中的热量不能比特定的临界速率更快散发，那它内部硬度就会受到明确限制。然而盐水或水淬火能够将被淬零件的表面迅速冷却至本身温度并将其保持或接近此温度。Under these circumstances there would always be some finite depth of surface hardening regardless of size.This is not true in oil quenching, when the surface temperature may be high during the critical stages of quenching.在这种情况下不管零件尺寸如何，其表面总归有一定深度被硬化。但油淬情况就不是如此，因为油淬时在淬火临界阶段零件表面的温度可能仍然很高。? Tempering 回火

Steel that has been hardened by rapid quenching is brittle and not suitable for most uses.By tempering or drawing, the hardness and brittleness may be reduced to the desired point for service conditions．

快速淬火硬化的钢是硬而易碎的，不适合大多数场合使用。通过回火，硬度和脆性可以降低到使用条件所需要的程度。

As these properties are reduced there is also a decrease in tensile strength and an increase in the ductility and toughness of the steel.The operation consists of reheating quench-hardened steel to some temperature below the critical range followed by any rate of cooling.随着这些性能的降低，拉伸强度也降低而钢的延展性和韧性则会提高。回火作业包括将淬硬钢重新加热到低于临界范围的某一温度然后以任意速率冷却。

Although this process softens steel, it differs considerably from annealing in that the process lends itself to close control of the physical properties and in most cases does not soften the steel to the extent that annealing would.The final structure obtained from tempering a fully hardened steel is called tempered martensite.虽然这过程使钢软化，但它与退火是大不相同的，因为回火适合于严格控制物理性能并在大多数情况下不会把钢软化到退火那种程度。回火完全淬硬钢得到的最终组织结构被称为回火马氏体。

Tempering is possible because of the instability of the martensite, the principal constituent of hardened steel.Low-temperature draws, from 300℉ to 400℉(150℃~205℃), do not cause much decrease in hardness and are used principally to relieve internal strains.由于马氏体这一淬硬钢主要成分的不稳定性，使得回火成为可能。低温回火，300℉到400℉(150℃~205℃)，不会引起硬度下降很多，主要用于减少内部应变。As the tempering temperatures are increased, the breakdown of the martensite takes place at a faster rate, and at about 600℉(315℃)the change to a structure called tempered martensite is very rapid.The tempering operation may be described as one of precipitation and agglomeration or coalescence of cementite.随着回火温度的提高，马氏体以较快的速率分解，并在大约600℉(315℃)迅速转变为被称为回火马氏体的结构。回火作业可以描述为渗碳体析出和凝聚或聚结的过程。

A substantial precipitation of cementite begins at 600℉(315℃), which produces a decrease in hardness.Increasing the temperature causes coalescence of the carbides with continued decrease in hardness.渗碳体的大量析出开始于600℉(315℃)，这使硬度下降。温度的上升会使碳化物聚结而硬度继续降低。

In the process of tempering, some consideration should be given to time as well as to temperature.Although most of the softening action occurs in the first few minutes after the temperature is reached, there is some additional reduction in hardness if the temperature is maintained for a prolonged time.在回火过程中，不但要考虑温度而且要考虑时间。虽然大多数软化作用发生在达到所需温度后的最初几分钟，但如果此温度维持一段延长时间，仍会有些额外的硬度下降。Usual practice is to heat the steel to the desired temperature and hold it there only long enough to have it uniformly heated.通常的做法是将钢加热到所需温度并且仅保温到正好使其均匀受热。

Two special processes using interrupted quenching are a form of tempering.In both, the hardened steel is quenched in a salt bath held at a selected lower temperature before being allowed to cool.These processes, known as austempering and martempering, result in products having certain desirable physical properties.两种采用中断淬火的特殊工艺也是回火的形式。这两种工艺中，淬硬钢在其被允许冷却前先在一选定的较低温度盐浴淬火。这两种分别被称为奥氏体回火和马氏体回火的工艺，能使产品具有特定所需的物理性能。? Annealing 退火

The primary purpose of annealing is to soften hard steel so that it may be machined or cold worked.退火的主要目的是使坚硬的钢软化以便机加工或冷作。

This is usually accomplished by heating the steel too slightly above the critical temperature, holding it there until the temperature of the piece is uniform throughout, and then cooling at a slowly controlled rate so that the temperature of the surface and that of the center of the piece are approximately the same.通常是非常缓慢地将钢加热到临界温度以上，并将其在此温度下保持到工件全部均匀受热，然后以受控的速率慢慢地冷却，这样使得工件表面和内部的温度近似相同。

This process is known as full annealing because it wipes out all trace of previous structure, refines the crystalline structure, and softens the metal.Annealing also relieves internal stresses previously set up in the metal.这过程被称为完全退火，因为它去除了以前组织结构的所有痕迹、细化晶粒并软化金属。退火也释放了先前在金属中的内应力。

The temperature to which a given steel should be heated in annealing depends on its composition;for carbon steels it can be obtained readily from the partial iron-iron carbide equilibrium diagram.When the annealing temperature has been reached, the steel should be held there until it is uniform throughout.给定的钢其退火温度取决于它的成分；对碳钢而言可容易地从局部的铁碳合金平衡图得到。达到退火温度后，钢应当保持在此温度等到全部均匀受热。This usually takes about 45min for each inch(25mm)of thickness of the largest section.For maximum softness and ductility the cooling rate should be very slow, such as allowing the parts to cool down with the furnace.The higher the carbon content, the slower this rate must be.加热时间一般以工件的最大截面厚度计每英寸(25mm)大约需45min。为了得到最大柔软性和延展性冷却速率应该很慢，比如让零件与炉子一起冷下来。含碳量越高，冷却的速率必须越慢。

The heating rate should be consistent with the size and uniformity of sections, so that the entire part is brought up to temperature as uniformly as possible.加热的速率也应与截面的尺寸及均匀程度相协调，这样才能使整个零件尽可能均匀地加热。? Normalizing and Spheroidizing 正火和球化

The process of normalizing consists of heating the steel about 50℉ to 100℉(10℃~40℃)above the upper critical range and cooling in still air to room temperature.正火处理包括先将钢加热到高于上临界区50℉到100℉(10℃~40℃)然后在静止的空气中冷却到室温。

This process is principally used with low-and medium-carbon steels as well as alloy steels to make the grain structure more uniform, to relieve internal stresses, or to achieve desired results in physical properties.Most commercial steels are normalized after being rolled or cast.退火主要用于低碳钢、中碳钢及合金钢，使晶粒结构更均匀、释放内应力或获得所需的物理特性。大多数商业钢材在轧制或铸造后都要退火。

Spheroidizing is the process of producing a structure in which the cementite is in a spheroidal distribution.If steel is heated slowly to a temperature just below the critical range and held there for a prolonged period of time, this structure will be obtained.球化是使渗碳体产生成类似球状分布结构的工艺。如果把钢缓慢加热到恰好低于临界温度并且保持较长一段时间，就能得到这种组织结构。

The globular structure obtained gives improved machinability to the steel.This treatment is particularly useful for hypereutectoid steels that must be machined.所获得的球状结构改善了钢的可切削性。此处理方法对必须机加工的过共析钢特别有用。? Surface Hardening 表面硬化 Carburizing The oldest known method of producing a hard surface on steel is case hardening or carburizing.Iron at temperatures close to and above its critical temperature has an affinity for carbon.渗碳

最早的硬化钢表面的方法是表面淬火或渗碳。铁在靠近并高于其临界温度时对碳具有亲合力。

The carbon is absorbed into the metal to form a solid solution with iron and converts the outer surface into high-carbon steel.The carbon is gradually diffused to the interior of the part.The depth of the case depends on the time and temperature of the treatment.碳被吸收进金属与铁形成固溶体使外表面转变成高碳钢。碳逐渐扩散到零件内部。渗碳层的深度取决于热处理的时间和温度。

Pack carburizing consists of placing the parts to be treated in a closed container with some carbonaceous material such as charcoal or coke.It is a long process and used to produce fairly thick cases of from 0.03 to 0.16 in.(0.76~4.06mm)in depth.固体渗碳的方法是将要处理的零件与木炭或焦炭这些含碳的材料一起放入密闭容器。这是一个较长的过程，用于产生深度为0.03到0.16 英寸(0.76~4.06mm)这么厚的硬化层。Steel for carburizing is usually a low-carbon steel of about 0.15% carbon that would not in itself responds appreciably to heat treatment.In the course of the process the outer layer is converted into high-carbon steel with a content ranging from 0.9% to 1.2% carbon.用于渗碳的一般是含碳量约为0.15%、本身不太适合热处理的低碳钢。在处理过程中外层转化为含碳量从0.9%到1.2%的高碳钢。

A steel with varying carbon content and, consequently, different critical temperatures requires a special heat treatment.含碳量变化的钢具有不同的临界温度，因此需要特殊的热处理。

Because there is some grain growth in the steel during the prolonged carburizing treatment, the work should be heated to the critical temperature of the core and then cooled, thus refining the core structure.The steel should then be reheated to a point above the transformation range of the case and quenched to produce a hard, fine structure.由于在较长的渗碳过程中钢内部会有些晶粒生长，所以工件应该加热到核心部分的临界温度再冷却以细化核心部分的组织结构。然后重新加热到高于外层转变温度再淬火以生成坚硬、细致的组织结构。

The lower heat-treating temperature of the case results from the fact that hypereutectoid steels are normally austenitized for hardening just above the lower critical point.A third tempering treatment may be used to reduce strains.由于恰好高于低临界温度通常使过共析钢奥氏体化而硬化，所以对外层采用较低的热处理温度。第三次回火处理可用于减少应变。Carbonitriding Carbonitriding, sometimes known as dry cyaniding or nicarbing, is a case-hardening process in which the steel is held at a temperature above the critical range in a gaseous atmosphere from which it absorbs carbon and nitrogen.碳氮共渗

碳氮共渗，有时也称为干法氰化或渗碳氮化，是一种表面硬化工艺。通过把钢放在高于临界温度的气体中，让它吸收碳和氮。

Any carbon-rich gas with ammonia can be used.The wear-resistant case produced ranges from 0.003 to 0.030 inch(0.08~ 0.76mm)in thickness.An advantage of carbonitriding is that the hardenability of the case is significantly increased when nitrogen is added, permitting the use of low-cost steels.可以使用任何富碳气体加氨气，能生成厚度从0.003到0.030英寸(0.08~ 0.76mm)的耐磨外层。碳氮共渗的优点之一是加入氮后外层的淬透性极大增加，为使用低价钢提供条件。Cyaniding Cyaniding, or liquid carbonitriding as it is sometimes called, is also a process that combines the absorption of carbon and nitrogen to obtain surface hardness in low-carbon steels that do not respond to ordinary heat treatment.氰化

氰化，有时称为液体碳氮共渗，也是一种结合了吸收碳和氮来获得表面硬度的工艺，它主要用于不适合通常热处理的低碳钢。

The part to be case hardened is immersed in a bath of fused sodium cyanide salts at a temperature slightly above the Ac1 range, the duration of soaking depending on the depth of the case.The part is then quenched in water or oil to obtain a hard surface.需表面硬化的零件浸没在略高于Ac1温度熔化的氰化钠盐溶液中，浸泡的持续时间取决于硬化层的深度。然后将零件在水或油中淬火。Case depths of 0.005 to 0.015in.(0.13~0.38mm)may be readily obtained by this process.Cyaniding is used principally for the treatment of small parts.通过这样处理可以容易地获得0.005到0.015英寸(0.13~0.38mm)的硬化深度。氰化主要用于处理小零件。Nitriding Nitriding is somewhat similar to ordinary case hardening, but it uses a different material and treatment to create the hard surface constituents.渗氮

渗氮有些类似普通表面硬化，但它采用不同的材料和处理方法来产生坚硬表面成分。In this process the metal is heated to a temperature of around 950℉(510℃)and held there for a period of time in contact with ammonia gas.Nitrogen from the gas is introduced into the steel, forming very hard nitrides that are finely dispersed through the surface metal.这种工艺中金属加热到约950℉(510℃)，然后与氨气接触一段时间。氨气中的氮进入钢内，形成细微分布于金属表面又十分坚固的氮化物。Nitrogen has greater hardening ability with certain elements than with others, hence, special nitriding alloy steels have been developed.氮与某些元素的硬化能力比其它元素大，因此开发了专用的渗氮合金钢。

Aluminum in the range of 1% to 1.5% has proved to be especially suitable in steel, in that it combines with the gas to form a very stable and hard constituent.The temperature of heating ranges from 925℉ to 1,050℉(495℃~565℃).在钢中含铝1%到1.5%被证明特别合适，它能与氨气结合形成很稳定坚固的成分。其加热温度范围为925℉到1,050℉(495℃~565℃)。

Liquid nitriding utilizes molten cyanide salts and, as in gas nitriding, the temperature is held below the transformation range.Liquid nitriding adds more nitrogen and less carbon than either cyaniding or carburizing in cyanide baths.液体渗氮利用熔化的氰化物盐，就像气体渗氮，温度保持在低于转化范围内。液体渗氮时在氰化物溶液中加入比氰化及渗碳都较多的氮和较少的碳。

Case thickness of 0.001 to 0.012in.(0.03~0.30mm)is obtained, whereas for gas nitriding the case may be as thick as 0.025 in.(0.64mm).In general the uses of the two-nitriding processes are similar.液体渗氮可以获得厚度为0.001到0.012英寸(0.03~0.30mm)的硬化层，然而气体渗氮则能获得厚0.025英寸(0.64mm)的硬化层。一般而言两种渗氮方法的用途是类似的。

Nitriding develops extreme hardness in the surface of steel.This hardness ranges from 900 to 1,100 Brinell, which is considerably higher than that obtained by ordinary case hardening.渗氮在钢表面获得远远超出正常标准的硬度。其硬度范围为900到1,100布氏硬度，这远高于普通表面硬化所获得的硬度。

Nitriding steels, by virtue of their alloying content, are stronger than ordinary steels and respond readily to heat treatment.It is recommended that these steels be machined and heat-treated before nitriding, because there is no scale or further work necessary after this process.由于渗氮钢的合金比例，它们比普通钢更强，也容易热处理。建议对这种钢在渗氮前先机加工和热处理，因为渗氮后没有剥落并不需要更多的加工。

Fortunately, the interior structure and properties are not affected appreciably by the nitriding treatment and, because no quenching is necessary, there is little tendency to warp, develop cracks, or change condition in any way.The surface effectively resists corrosive action of water, saltwater spray, alkalies, crude oil, and natural gas.值得庆幸的是由于渗氮处理一点都不影响内部结构和性能，也无需淬火，所以几乎没有任何产生翘曲、裂缝及变化条件的趋势。这种表面能有效地抵御水、盐雾、碱、原油和天然气的腐蚀反应。

第八单元

Grinding is a manufacturing process that involves the removal of metal by employing a rotating abrasive wheel.The latter simulates a milling cutter with an extremely large number of miniature cutting edges.磨削是通过采用旋转磨轮去除金属的制造工艺。磨轮用非常大量的微型切削刃模仿铣刀进行切削。

Generally, grinding is considered to be a finishing process that is usually used for obtaining high-dimensional accuracy and better surface finish.Grinding can be performed on flat, cylindrical, or even internal surfaces by employing specialized machine tools, which are referred to as grinding machines.一般而言，磨削被认为是一种通常用于获得高尺寸精度和较好表面光洁度的精加工作业。磨削通过采用被称为磨床的特殊机床能在平面、圆柱面甚至内表面上进行。

Obviously, grinding machines differ in construction as well as capabilities, and the type to be employed is determined mainly by the geometrical shape and nature of the surface to be ground, e.g., cylindrical surfaces are ground on cylindrical grinding machines.显然，磨床根据结构和功能的不同有所区别，使用何种形式的磨床主要取决于被磨削表面的几何形状和物理性质。例如，圆柱面在外圆磨床上磨削。? Type of Grinding Operations 磨削作业的类型

1.Surface grinding.As the name surface grinding suggests, this operation involves grinding of flat or plane surfaces.Fig.8.1 indicates the two possible variations, either a horizontal or vertical machine spindle.1.表面磨削：就像其名称暗示的那样，表面磨削和平面磨削直接有关。图8.1表示了两种可能的变化：卧式磨床主轴或立式磨床主轴。

In the first case(horizontal spindle), the machine usually has a planer-type reciprocating table on which the workpiece is held.However, grinding machines with vertical spindles can have either a planer type table like that of the horizontal-spindle machine or a rotating worktable.在第一种情况(卧式主轴)，卧式磨床通常具有安装工件的刨床式往复工作台。而立式主轴磨床既可以像卧式主轴磨床那样具有刨床式工作台也可以具有旋转工作台。

Also, the grinding action in this case is achieved by the end face of the grinding wheel(Fig.8.1b), contrary to the case of horizontal-spindle machines, where the workpieces ground by the periphery of the grinding wheel.而且在这种情况下，磨削动作是通过砂轮端面完成的(图8.1b)，这与通过砂轮周边磨削工件的卧式主轴磨床正好相反。

Fig.8.1a and b also indicate the equations to be used for estimating the different parameters of the grinding operation, such as the machining time and the rate of metal removal.图8.1a和b同时简述了用于估计诸如加工时间和金属去除率之类的磨削作业不同参数的方程式。During the surface-grinding operations, heavy workpieces are either held in fixtures or clamped on the machine table by strap clamps and the like, whereas smaller workpieces are usually held by magnetic chucks.在平面磨削时，重的工件用夹具固定或用压板等夹紧在磨床工作台上，而小的工件则通常是用电磁卡盘固定的。

2.Cylindrical grinding.In cylindrical grinding, the workpiece is held between centers during the grinding operation, and the wheel rotation is the source and cause for the rotary cutting motion, as shown in Fig.8.2.In fact, cylindrical grinding can be carried out by employing any of the following methods: 2.圆柱面磨削：在圆柱面磨削中，作业时工件支撑在两顶尖之间，砂轮转动是导致回转切削运动的动力源，如图8.2所示。实际上，圆柱面磨削能通过采用下列任意方法来实现：(1)The transverse method, in which both the grinding wheel and the workpiece rotate and longitudinal linear feed is applied to enable grinding of the whole length.The depth of cut is adjusted by the cross feed of the grinding wheel into the workpiece.(1)横向方法：这种方法中砂轮与工件均旋转且采用线性纵向进给以保证能磨削整个长度。切削深度通过改变砂轮对工件的横向进给来进行调整。

(2)The plunge-cut method, in which grinding is achieved through the cross feed of the grinding wheel and no axial feed is applied.As you can see, this method can be applied only when the surface to be ground is shorter than the width of the grinding wheel used.(2)插入-切削方法：这种方法通过砂轮的横向进给完成磨削而不采用轴向进给。正如料想的那样，这种方法只在要磨削表面比所用砂轮宽度短时才使用。(3)The full-depth method, which is similar to the transverse method except that the grinding allowance is removed in a single pass.This method is usually recommended when grinding short rigid shafts.(3)全深度方法：这种方法除了一次加工就能去除磨削余量外其它与横向方法相同。这种方法通常在磨削较短刚性轴时推荐使用。

Internal grinding.Internal grinding is employed for grinding relatively short holes, as shown in Fig.8.3.The workpiece is held in a chuck or a special fixture.Both the grinding wheel and the workpiece rotate during the operation and feed is applied in the longitudinal direction.内表面磨削：内表面磨削用于相对较短的孔，如图8.3所示。工件安装在卡盘或特殊夹具上。作业时砂轮和工件都回转并且采用纵向进给。

Any desired depth of cut can be obtained by the cross feed of the grinding wheel.A variation from this type is planetary internal grinding, which is recommended for heavy workpieces that cannot be held in chucks.通过砂轮的横向进给能得到任意所需的切削深度。这种方法的一个变体是行星式内表面磨削，当工件较重不能用卡盘固定时推荐使用。

In that case, the grinding wheel not only spins around its own axis but also rotates around the centerline of the hole that is being ground.在这种情况下，砂轮不但绕自身轴线回转，同时还绕被磨削孔的中心线旋转。

Centerless grinding.Centerless grinding involves passing a cylindrical workpiece, which is supported by a rest blade, between two wheels, i.e., the grinding wheel and the regulating or feed wheel.无心磨削：无心磨削用于加工圆柱形工件，工件由托板支撑，在两轮即砂轮和调节或进给轮之间通过去。The grinding wheel does the actual grinding, while the regulating wheel is responsible for rotating the workpiece as well as generating the longitudinal feed.This is possible because of the frictional characteristics of that wheel, which is usually made of rubber-bonded abrasive.砂轮完成实际磨削，而调节轮负责旋转工件和产生纵向进给。由于调节轮通常用橡胶粘结的磨料制成，其摩擦特性使这成为可能。

As can be seen in Fig.8.4, the axis of the regulating wheel is tilted at a slight angle with the axis of the grinding wheel.Consequently, the peripheral velocity of the regulating wheel can be resolved into two components, namely, workpiece rotational speed and longitudinal feed.正如在图8.4中所看到的那样，调节轮的轴与砂轮轴倾斜一个微小角度。因此调节轮的圆周速度可以分解为两个分量，即工件回转速度和纵向进给。These can be given by the following equations: Vworkpiece＝Vregulating wheel×cosα Axial feed＝Vregulating wheel×c×sinα

Where c is a constant coefficient to account for the slip between the workpiece and the regulating wheel(c=0.94~0.98).其值可由下列公式给出：

V工件＝V调节轮×cosα

轴向进给＝V调节轮×c×sinα 式中c是考虑工件和调节轮之间滑动的恒定系数(c=0.94~0.98)。

The velocity of the regulating wheel is controllable and is used to achieve any desired rotational speed of the workpiece.The angleαis usually taken from 1°to 5°and the larger the angle, the larger the longitudinal feed would be.调节轮的速度是可控的并被用于实现工件任意所需的转动速度。α角通常取1到 5°，这角度越大则纵向进给也将越大。

Whenαis taken as 0°, i.e., the two axes of the grinding and regulating wheels are parallel, there is no longitudinal feed of the workpiece.当α取0°时，即砂轮和调节轮轴线平行时，则工件没有纵向进给。? Grinding Wheels 砂轮

Grinding wheels are composed of abrasive grains having similar size and a binder.The actual grinding process is performed by the abrasive grains.Pores between the grains within the binder enable the grains to act as separate single-point cutting tools.砂轮由具有相近尺寸的磨料颗粒和粘合剂组成。实际磨削作业由磨粒完成。在粘合剂中磨粒之间的孔隙使磨粒能象独立的单刃切削刀具一样工作。

These pores also provide space for the generated chips, thus preventing the wheel from clogging.In addition, pores assist the easy flow of coolants to enable efficient and prompt removal of the heat generated during the grinding process.这些孔隙同时还为产生的切屑提供空间以防砂轮堵塞。另外孔隙帮助冷却液容易流动，从而使在磨削作业中产生的热量能有效而迅速地散发。Grinding wheels are identified based on their shape and size, kind of abrasive, grain size, binder, grade(hardness), and structure.砂轮根据它们的形状和尺寸、磨料的类型、磨粒的大小、粘合剂、等级(硬度)和结构组织来分类。

Shape and size of grinding wheels.Grinding wheels differ in shape and size, depending upon the purpose for which they are to be used.Various shapes are shown in Fig.8.5 and include the following types: 砂轮的形状和尺寸：根据砂轮的用途，它们的形状和尺寸是不同的。各种形状如图8.5所示，其中包括：

1)Straight wheels used for surface, cylindrical, internal, and centerless grinding.2)Bevelled-face or tapered wheels used for grinding threads, gear teeth, and the like.3)Straight recessed wheels for cylindrical grinding and facing.1)用于表面、圆柱面、内部和无心磨削的直轮。2)用于磨削螺纹、齿轮轮齿之类的斜面或锥形轮。3)用于圆柱面和端面磨削的直凹轮。

4)Abrasive disks for cutoff and slotting operations.(thickness 0.02 up to 0.2in.(0.5 to 5mm)).5)Cylinders, straight cups, and flaring cups are used for surface grinding with the end face of the wheel.4)用于切断和开槽作业的砂轮片(其厚度从0.02到0.2英寸(0.5到5毫米))。5)用其端面进行表面磨削的圆柱、直杯及外展杯状砂轮。

The main dimensions of a grinding wheel are the outside diameter D, the bore diameter d, and the height H.These dimensions vary widely, depending upon the grinding process for which the wheel is to be used.砂轮的主要尺寸有外径D、孔径d和厚度H。根据采用砂轮的磨削工艺，这些尺寸变化很大。

Kind of abrasive.Grinding wheels can be made of natural abrasives such as quartz, emery, and corundum or of industrially prepared chemical compounds such as aluminum oxide or silicon carbide(known as carborundum).磨料的类型：砂轮可以由象石英、金刚砂、刚玉之类的自然磨料制成，或者由象氧化铝或碳化硅(也称人造金刚砂)之类的工业制备的化学化合物制成。

Generally, silicon carbide grinding wheels are used when grinding low-tensile-strength materials like cast iron, whereas aluminum oxide wheels are employed for grinding high-strength metals such as alloy steel, hardened steel, and the like.当磨削象铸铁类低拉伸强度材料时，一般采用碳化硅砂轮，而磨削合金钢、淬火钢等高强度金属则要用氧化铝砂轮。

Grain size of abrasive used.As you may expect, the grain size of the abrasive particles of the wheel plays a fundamental role in determining the quality of ground surface obtained.所用磨粒的尺寸：正如料想的那样，砂轮磨粒的尺寸对决定所得磨削表面的质量起着根本的作用。

The finer the grains, the smoother the ground surface is.Therefore, coarse-grained grinding wheels are used for roughing operations, whereas fine-grained wheels are employed in final finishing operations.磨粒越细，磨削表面越光滑。所以，粗粒砂轮用于粗加工，而细粒砂轮则用于最后精加工。The grade of the bond.The grade of the bond is actually an indication of the resistance of the bond to pulling off the abrasive grains from the grinding wheel.Generally, wheels having hard grades are used for grinding soft materials and vice versa.粘结体的等级：粘结体的等级实际上是其抵抗将磨粒从砂轮上拉脱的指标。一般而言，具有较硬等级的砂轮用于磨削较软材料，反之亦然。

If a hard-grade wheel were to be used for grinding a hard material, the dull grains would not be pulled off from the bond quickly enough, thus impeding the self-dressing process of the surface of the wheel and finally resulting in clogging of the wheel and burns on the ground surface.如果较硬等级的砂轮用于磨削较硬材料，磨钝的磨粒将不能足够快地脱离粘结体，这会妨碍砂轮表面的自修复，最终导致砂轮的堵塞并在被磨表面留下灼斑。

In fact, the cutting properties of all grinding wheels must be restored periodically by dressing with a cemented carbide roller or a diamond tool to give the wheel the exact desired shape and remove all worn abrasive grains.实际上，所有砂轮的磨削性能都必须定期地通过使用硬质合金滚轮或金刚石修整器修整而被恢复，以求很准确地把砂轮加工成要求的形状，并去除已磨钝的磨粒。

Structure.Structure refers to the amount of void space between the abrasive grains.When grinding softer metals, larger void space are needed to facilitate the flow of the removed chips.结构组织：结构组织与磨粒间的空隙量有关。当磨削较软金属时，需要较大的空隙以便去除切屑的流动。

The binder.Abrasive particles are bonded together in many different ways.These include bond, silicate, rubber, resinoid, shellac, and oxychloride.Nevertheless, the bond is the most commonly used one.粘合剂：磨粒可用多种不同方法粘结在一起。其中包括粘合剂、硅酸盐、橡胶、树脂、虫胶和氯氧化物。然而，粘合剂是最常用的。

In fact, the standard marking system is employed for distinguishing grinding wheels, by providing all the preceding parameters in a specific sequence.在实际生产中，为了区分砂轮采用标准标注系统，通过用一特定顺序将所有上述参数都表示出来。

第十一单元

? The Lathe and Its Construction 车床及其结构

A lathe is a machine tool used primarily for producing surfaces of revolution and flat edges.车床是主要用于生成旋转表面和平整边缘的机床。

Based on their purpose, construction, number of tools that can simultaneously be mounted, and degree of automation, lathes-or, more accurately, lathe-type machine tools can be classified as follows: 根据它们的使用目的、结构、能同时被安装刀具的数量和自动化的程度，车床—或更确切地说是车床类的机床，可以被分成以下几类：

(1)Engine lathes(2)Toolroom lathes(3)Turret lathes(4)Vertical turning and boring mills(5)Automatic lathes(6)Special-purpose lathes(1)普通车床(2)万能车床(3)转塔车床(4)立式车床(5)自动车床(6)特殊车床

In spite of that diversity of lathe-type machine tools, they all have common features with respect to construction and principle of operation.These features can best be illustrated by considering the commonly used representative type, the engine lathe.Following is a description of each of the main elements of an engine lathe, which is shown in Fig.11.1.虽然车床类的机床多种多样，但它们在结构和操作原理上具有共同特性。这些特性可以通过普通车床这一最常用的代表性类型来最好地说明。下面是关于图11.1所示普通车床的主要部分的描述。

Lathe bed.The lathe bed is the main frame, involving a horizontal beam on two vertical supports.It is usually made of grey or nodular cast iron to damp vibrations and is made by casting.车床床身：车床床身是包含了在两个垂直支柱上水平横梁的主骨架。为减振它一般由灰铸铁或球墨铸铁铸造而成。

It has guideways to allow the carriage to slide easily lengthwise.The height of the lathe bed should be appropriate to enable the technician to do his or her job easily and comfortably.它上面有能让大拖板轻易纵向滑动的导轨。车床床身的高度应适当以让技师容易而舒适地工作。

Headstock.The headstock is fixed at the left hand side of the lathe bed and includes the spindle whose axis is parallel to the guideways(the slide surface of the bed).The spindle is driven through the gearbox, which is housed within the headstock.主轴箱：主轴箱固定在车床床身的左侧，它包括轴线平行于导轨的主轴。主轴通过装在主轴箱内的齿轮箱驱动。The function of the gearbox is to provide a number of different spindle speeds(usually 6 up to 18 speeds).Some modern lathes have headstocks with infinitely variable spindle speeds, which employ frictional ,electrical ,or hydraulic drives.齿轮箱的功能是给主轴提供若干不同的速度(通常是6到18速)。有些现代车床具有采用摩擦、电力或液压驱动的无级调速主轴箱。The spindle is always hollow, i.e., it has a through hole extending lengthwise.Bar stocks can be fed through that hole if continuous production is adopted.主轴往往是中空的，即纵向有一通孔。如果采取连续生产，棒料能通过此孔进给。Also, that hole has a tapered surface to allow mounting a plain lathe center.The outer surface of the spindle is threaded to allow mounting of a chuck, a face plate, or the like.同时，此孔为锥形表面可以安装普通车床顶尖。主轴外表面是螺纹可以安装卡盘、花盘或类似的装置。

Tailstock.The tailstock assembly consists basically of three parts, its lower base, an intermediate part, and the quill.The lower base is a casting that can slide on the lathe bed along the guideways, and it has a clamping device to enable locking the entire tailstock at any desired location, depending upon the length of the workpiece.尾架：尾架总成基本包括三部分，底座、尾架体和套筒轴。底座是能在车床床身上沿导轨滑动的铸件，它有一定位装置能让整个尾架根据工件长度锁定在任何需要位置。The intermediate part is a casting that can be moved transversely to enable alignment of the axis of the tailstock with that of the headstock.The third part, the quill, is a hardened steel tube, which can be moved longitudinally in and out of the intermediate part as required.尾架体为一能横向运动的铸件，它可以调整尾架轴线与主轴箱轴线成一直线。第三部分，套筒轴是一淬硬钢管，它能根据需要在尾架体中纵向进出移动。

This is achieved through the use of a handwheel and a screw, around which a nut fixed to the quill is engaged.The hole in the open side of the quill is tapered to enable mounting of lathe centers or other tools like twist drills or boring bars.The quill can be locked at any point along its travel path by means of a clamping device.这通过使用手轮和螺杆来达到，与螺杆啮合的是一固接在套筒轴上的螺母。套筒轴开口端的孔是锥形的，能安装车床顶尖或诸如麻花钻和镗杆之类的工具。套筒轴通过定位装置能沿着它的移动路径被锁定在任何点。The carriage.The main function of the carriage is mounting of the cutting tools and generating longitudinal and/or cross feeds.It is actually an H-shaped block that slides on the lathe bed between the headstock and tailstock while being guided by the V-shaped guideways of the bed.大拖板：大拖板的主要功能是安装刀具和产生纵向和/或横向进给。它实际上是一由车床床身V形导轨引导的、能在车床床身主轴箱和尾架之间滑动的H形滑块。

The carriage can be moved either manually or mechanically by means of the apron and either the feed rod or the lead screw.大拖板能手动或者通过溜板箱和光杆(进给杆)或丝杆(引导螺杆)机动。

When cutting screw threads, power is provided to the gearbox of the apron by the lead screw.In all other turning operations, it is the feed rod that drives the carriage.The lead screw goes through a pair of half nuts, which are fixed to the rear of the apron.在切削螺旋时，动力通过丝杆提供给溜板箱上的齿轮箱。在其余车削作业中，都由光杆驱动大拖板。丝杆穿过一对固定在溜板箱后部的剖分螺母。

When actuating a certain lever, the half nuts are clamped together and engage with the rotating lead screw as a single nut, which is fed, together with the carriage, along the bed.When the lever is disengaged, the half nuts are released and the carriage stops.当开动特定操作杆时，剖分螺母夹在一起作为单个螺母与旋转的丝杆啮合，并带动拖板沿着床身提供进给。当操作杆脱离时，剖分螺母释放同时大拖板停止运动。

On the other hand, when the feed rod is used, it supplies power to the apron through a worm gear.The latter is keyed to the feed rod and travels with the apron along the feed rod, which has a keyway extending to cover its whole length.另一方面，当使用光杆时则通过蜗轮给溜板箱提供动力。蜗轮用键连接在光杆上，并与溜板箱一起沿光杆运动，光杆全长范围开有键槽。

A modern lathe usually has a quick-change gearbox located under the headstock and driven from the spindle through a train of gears.It is connected to both the feed rod and the lead screw and enables selecting a variety of feeds easily and rapidly by simply shifting the appropriate levers.现代车床一般在主轴箱下装备快速变换齿轮箱，通过一系列齿轮由主轴驱动。它与光杆和丝杆连接，能容易并快速地通过简单转换适当的操作杆选择各种进给。

The quick-change gearbox is employed in plain turning, facing and thread cutting operations.Since that gearbox is linked to the spindle, the distance that the apron(and the cuttingtool)travels for each revolution of the spindle can be controlled and is referred to as the feed.快速变换齿轮箱可用于普通车削、端面切削和螺旋切削作业中。由于这种齿轮箱与主轴相连，主轴每转一圈溜板箱(和切削刀具)运动的距离能被控制，这距离就可以被认为是进给。? Lathe Cutting Tools 车床切削刀具

The shape and geometry of the lathe tools depend upon the purpose for which they are employed.车床刀具的形状和几何参数取决于它们的使用目的。

Turning tools can be classified into two main groups, namely, external cutting tools and internal cutting tools.Each of these two groups include the following types of tools: 车削刀具可以分为两个主要组别，即外部切削刀具和内部切削刀具。这两组中的每一组都包括以下类型刀具： Turning tools.Turning tools can be either finishing or rough turning tools.Rough turning tools have small nose radii and are employed when deep cuts are made.车削刀具：车削刀具可以是精车刀具或粗车刀具。粗车刀具刀尖半径较小，用于深切削。

On the other hand, finishing tools have larger nose radii and are used for obtaining the final required dimensions with good surface finish by making slight depths of cut.Rough turning tools can be right-hand or left-hand types, depending upon the direction of feed.They can have straight, bent, or offset shanks.而精车刀具刀尖半径较大，用于通过微量进刀深度来获得具有较好表面光洁度的最终所需尺寸。粗车刀具按其进给方向可以是右手型的或是左手型的。它们可以有直的、弯的或偏置的刀杆。

Facing tools.Facing tools are employed in facing operations for machining plane side or end surfaces.There are tools for machining left-hand-side surfaces and tools for right-hand-side surfaces.Those side surfaces are generated through the use of the cross feed, contrary to turning operations, where the usual longitudinal feed is used.端面刀具：端面刀具用在端面作业中加工平板侧面或端部表面，也有加工左右侧表面之分。与一般采用纵向进给的车削作业相反，那些侧表面通过采用横向进给产生。

Cutoff tools.Cutoff tools, which are sometimes called parting tools, serve to separate the workpiece into parts and/or machine external annular grooves.切断刀具：切断刀具，有时也称为分割刀具，用于将工件分割成若干部分和/或加工外部环形槽。

Thread-cutting tools.Thread-cutting tools have either triangular, square, or trapezoidal cutting edges, depending upon the cross section of the desired thread.Also, the plane angles of these tools must always be identical to those of the thread forms.螺纹切削刀具：螺纹切削刀具根据所需螺纹的横截面，有三角形的、矩形的或梯形的切削刃。同时，这些刀具的平面角必须始终与螺纹形状的平面角保持一致。

Thread-cutting tools have straight shanks for external thread cutting and are of the bent-shank type when cutting internal threads.车外螺纹的螺纹切削刀具为直刀杆，而车内螺纹的螺纹切削刀具则是弯刀杆。

Form tools.Form tools have edges especially manufactured to take a certain form, which is opposite to the desired shape of the machined workpiece.成形刀具：成形刀具有专门制成特定形状的刀刃，这种刀刃形状与被加工工件所需外形正好相反。An HSS tool is usually made in the form of a single piece, contrary to cemented carbides or ceramic, which are made in the form of tips.The latter are brazed or mechanically fastened to steel shanks．

高速钢刀具通常以单件形式制造，而硬质合金或陶瓷刀具则以刀尖形式制造。后者用铜焊或机械方法固定于钢质刀杆上。

Fig.11.2 indicates an arrangement of this latter type, which includes the carbide tip, the chip breaker, the pad, the clamping screw(with a washer and a nut), and the shank.图11.2所示为机械式固定布置方式，它包括了硬质合金刀尖、断屑槽、衬垫、卡装螺杆(带有垫圈和螺母)及刀杆。

As the name suggests, the function of the chip breaker is to break long chips every now and then, thus preventing the formation of very long twisted ribbons that may cause problems during the machining operation.顾名思义，断屑槽的功能就是不时地折断长切屑，以防形成很长的可能会在机加工操作中引起问题的缠绕切屑条。

The carbide tips(or ceramic tips)can have different shapes, depending upon the machining operations for which they are to be employed.The tips can either be solid or with a central through hole, depending on whether brazing or mechanical clamping is employed for mounting the tip on the shank.硬质合金刀尖(或陶瓷刀尖)根据采用它们的机加工操作，可以有不同的形状。根据将刀尖装配在刀杆上是通过用铜焊还是机械卡装，刀尖可以是实心的或是带有中心通孔的。? Lathe Operations 车床操作

In the following section, we discuss the various machining operations that can be performed on a conventional engine lathe.在下面这节中，要讨论的是能在传统普通车床上进行的各种机加工作业。

It must be borne in mind, however, that modern computerized numerically controlled lathes have more capabilities and can do other operations, such as contouring, for example.Following are conventional lathe operations.然而，必须记住现代计算机数控车床具有更多的功能并且可以进行其它操作，例如仿型。下面是传统车床的操作。

Cylindrical turning.Cylindrical turning is the simplest and the most common of all lathe operations.A single full turn of the workpiece generates a circle whose center falls on the lathe axis;this motion is then reproduced numerous times as a result of the axial feed motion of the tool.圆柱面车削：圆柱面车削是所有车床操作中最简单也是最普通的。工件旋转一整圈产生一个圆心落在车床主轴上的圆；由于刀具的轴向进给运动这种动作重复许多次。The resulting machining marks are, therefore, a helix having a very small pitch, which is equal to the feed.Consequently, the machined surface is always cylindrical.所以，由此产生的机加工痕迹是一条具有很小节距的螺旋线，该节距等于进给。因此机加工表面始终是圆柱形的。

The axial feed is provided by the carriage or the compound rest, either manually or automatically, whereas the depth of cut is controlled by the cross slide.轴向进给通过大拖板或复式刀架手动或自动提供，然而切削深度则由横向滑板控制。In roughing cuts, it is recommended that large depths of cuts(up to 0.25in.or 6mm, depending upon the workpiece material)and smaller feeds would be used.On the other hand, very fine feeds, smaller depths of cut(less than 0.05in, or 0.4mm), and high cutting speeds are preferred for finishing cuts.粗车中，推荐使用较大切削深度(根据工件材料可达0.25英寸或6毫米)和较小进给。另一方面，精车则最好采用很小的进给、较小的切削深度(小于0.05英寸或0.4毫米)和较高的切削速度。

Facing.The result of a facing operation is a flat surface that is either the whole end surface of the workpiece or an annular intermediate surface like a shoulder.During a facing operation, feed is provided by the cross slide, whereas the depth of cut is controlled by the carriage or compound rest.端面车削：端面车削操作的结果是将工件整个端部表面或者像轴肩之类的中间环形表面加工平整。在端面车削操作中，进给由横向滑板提供，而切削深度则通过大拖板或复式刀架控制。

Facing can be carried out either from the periphery inward or from the center of the workpiece outward.It is obvious that the machining marks in both cases take the form of a spiral.端面车削既可以从外表面向内切削也可以从工件中心往外切削。很明显在这两种情况下机加工痕迹都是螺线形式。

Usually, it is preferred to clamp the carriage during a facing operation, since the cutting force tends to push the tool(and, of course, the whole carriage)away from the workpiece.In most facing operations, the workpiece is held in a chuck or on a face plate.通常在端面车削作业时习惯于采用夹住大拖板，这是因为切削力倾向于将刀具(当然包括整个大拖板)推离工件。在大多数端面车削作业中，工件被支撑在卡盘或花盘上。

Groove cutting.In cut-off and groove-cutting operations, only cross feed of the tool is employed.The cut-off and grooving tools, which were previously discussed, are employed.开槽：在切断和开槽操作中，刀具只有横向进给。要采用前面已经讨论过的切断和开槽刀具。

Boring and internal turning.Boring and internal turning are performed on the internal surfaces by a boring bar or suitable internal cutting tools.If the initial workpiece is solid, a drilling operation must be performed first.The drilling tool is held in the tailstock, and the latter is then fed against the workpiece.镗孔和内部车削：镗孔和内部车削通过镗杆或合适的内部切削刀具在内表面进行。如果初始工件是实心的，则必须首先进行钻孔作业。钻孔刀具安装在尾架上，然后对着工件进给。

Taper turning.Taper turning is achieved by driving the tool in a direction that is not parallel to the lathe axis but inclined to it with an angle that is equal to the desired angle of the taper.Following are the different methods used in taper-turning practice: 锥面车削：锥面车削通过沿着与车床主轴不平行而倾斜成一个等于锥面所需角度的方向进刀来实现。下面是在实际锥面车削中采用的不同方法：

(1)Rotating the disc of the compound rest with an angle equal to half the apex angle of the cone.Feed is manually provided by cranking the handle of the compound rest.This method is recommended for taper turning of external and internal surfaces when the taper angle is relatively large.(1)将复式刀架盘旋转一个等于圆锥体顶角一半的角度。通过摇动复式刀架操纵柄手动提供进给。当锥角相对较大时切削外锥面和内锥面推荐使用这种方法。(2)Employing special form tools for external, very short, conical surfaces.The width of the workpiece must be slightly smaller than that of the tool, and the workpiece is usually held in a chuck or clamped on a face plate.In this case, only the cross feed is used during the machining process and the carriage is clamped to the machine bed.(2)对很短的外锥面采用特殊的成型刀具。工件的宽度必须略小于刀具的宽度，并且工件通常由卡盘支撑或夹紧在花盘上。在这种情况下，机加工作业时只有横向进给而大拖板则夹紧在床身上。

(3)Offsetting the tailstock center.This method is employed for external taper turning of long workpieces that are required to have small taper angles(less than 8°).The workpiece is mounted between the two centers;then the tailstock center is shifted a distance S in the direction normal to the lathe axis.(3)偏移尾架顶尖。对需要较小锥角(小于8°)的较长工件外锥面车削采用这种方法。工件安装于两顶尖之间；然后将尾架顶尖朝垂直于车床主轴方向移动一距离S。

(4)Using the taper-turning attachment.This method is used for turning very long workpieces, when the length is larger than the whole stroke of the compound rest.The procedure followed in such cases involves complete disengagement of the cross slide from the carriage, which is then guided by the taper-turning attachment.(4)采用锥面车削附加装置。这种方法用于车削很长的工件，其长度大于复式刀架的整个行程。在这种场合下要遵循的步骤是将横向滑板完全脱离大拖板，然后通过锥面车削附加装置进行引导。

During this process, the automatic axial feed can be used as usual.This method is recommended for very long workpieces with a small cone angle, i.e., 8°through 10°.在此作业中，能照常使用自动轴向进给。对具有较小锥角(即8°到10°)的很长工件推荐采用这种方法。

Thread cutting.When performing thread cutting, the axial feed must be kept at a constant rate, which is dependent upon the rotational speed(rpm)of the workpiece.The relationship between both is determined primarily by the desired pitch of the thread to be cut.螺纹切削：在螺纹切削作业时，轴向进给必须保持恒定速率，这取决于工件的转速(rpm)。两者之间的关系基本上由被切削螺纹所需的节距决定。

As previously mentioned, the axial feed is automatically generated when cutting a thread by means of the lead screw, which drives the carriage.When the lead screw rotates a single revolution, the carriage travels a distance equal to the pitch of the lead screw.如前所述，当依靠驱动大拖板的丝杆切削螺纹时轴向进给是自动产生的。丝杆旋转一圈，大拖板就行进等于丝杆节距的一段距离。Consequently, if the rotational speed of the lead screw is equal to that of the spindle(i.e., that of the workpiece), the pitch of the resulting cut thread is exactly equal to that of the lead screw.因此如果丝杆的旋转速度等于心轴的转速(即工件的转速)，生成切削螺纹的节距就正好等于丝杆的节距。

The pitch of the resulting thread being cut therefore always depends upon the ratio of the rotational speeds of the lead screw and the spindle: Pitch of the lead screw/ Desired pitch of workpiece=rpm of the workpiece/rpm of lead screw=spindle-to-carriage gearing ratio.所以被切削生成螺纹的节距总是取决于丝杆和心轴的转速比：丝杆的节距/工件所需节距=工件转速/丝杆转速=心轴到大拖板的传动比。This equation is useful in determining the kinematic linkage between the lathe spindle and the lead screw and enables proper selection of the gear train between them.这公式在决定车床心轴和丝杆之间的运动学关系时很有用，并且提供了正确挑选它们之间轮系的方法。

In thread cutting operations, the workpiece can either be held in the chuck or mounted between the two lathe centers for relatively long workpieces.The form of the tool used must exactly coincide with the profile of the thread to be cut, i.e., triangular tools must be used for triangular threads, and so on.在螺纹切削作业中，工件既能支撑于卡盘中，对相对较长的工件也能安装在两个车床顶尖之间。使用的刀具外形必须正好与要切削螺纹的轮廓一致，即三角形刀具必须用于三角形螺纹等等。

Knurling.Knurling is mainly a forming operation in which no chips are produced.It involves pressing two hardened rolls with rough filelike surfaces against the rotating workpiece to cause plastic deformation of the workpiece metal.滚花：滚花主要是一种不产生切屑的成型操作。它使用两个带有粗锉式表面的淬火滚轮压在旋转的工件上使工件金属产生塑性变形。

Knurling is carried out to produce rough, cylindrical(or conical)surfaces, which are usually used as handles.Sometimes, surfaces are knurled just for the sake of decoration;there are different types of patterns of knurls from which to choose.滚花用于生成粗糙的圆柱(或圆锥)面，通常用来作手柄。有时表面滚花只为装饰之故；有不同的滚花图案类型可供选择。? Cutting Speeds and Feed 切削速度和进给

The cutting speed, which is usually given in surface feet per minute(SFM), is the number of feet traveled in the circumferential direction by a given point on the surface(being cut)of the workpiece in 1 minute.切削速度，通常用每分钟表面英尺给出，就是一分钟内工件(被切削)表面给定点在圆周方向上行进的英尺数。

The relationship between the surface speed and rpm can be given by the following equation: SFM=πDN Where D=the diameter of the workpiece in feet N=the rpm 表面速度与转速之间的关系可以用下式给出： SFM=πDN 式中

D=用英尺表示的工件直径 N=转速

The surface cutting speed is dependant primarily upon the material being machined as well as the material of the cutting tool and can be obtained from handbooks, information provided by cutting tool manufacturers, and the like.表面切削速度主要由被切削材料和切削刀具材料决定，可以从手册、切削刀具生产商提供的资料及类似的东西上查取。Generally, the SFM is taken as 100 when machining cold-rolled or mild steel, as 50 when machining tougher metals, and as 200 when machining softer materials.For aluminum, the SFM is usually taken as 400 or above.There are also other variables that affect the optimal value of the surface cutting speed.一般而言，SFM当机加工冷轧或低碳钢时取100，机加工较坚韧的金属时取50，而机加工较软材料时取200。对铝而言，SFM通常可取400以上。也还存在其它一些变量影响表面切削速度的最佳值。

These include the tool geometry, the type of lubricant or coolant, the feed, and the depth of cut.As soon as the cutting speed is decided upon, the rotational speed(rpm)of the spindle can be obtained as follows: N=SFM/(πD)其中包括刀具形状、润滑剂或冷却液的类型、进给和切削深度。切削速度一旦确定，心轴转速(rpm)就能按下式得到： N=SFM/(πD)The selection of a suitable feed depends upon many factors, such as the required surface finish, the depth of cut, and the geometry of the tool used.Finer feeds produce better surface finish, whereas higher feeds reduce the machining time during which the tool is in direct contact with the workpiece.合适进给的选择取决于许多因素，例如所需表面光洁度、切削深度和所用刀具的几何形状。进给越小生成的光洁度越好，而在刀具与工件直接接触时进给越大则可以减少机加工时间。

机械英语的特点和翻译方法研究 第3篇

关键词：机械英语,特点,翻译方法

0 引言

随着机械制造业的飞速发展, 国际市场的不断开拓, 国际间的技术交流合作日益频繁, 而技术交流合作相关技术资料的翻译必须忠实于原文, 行文简练, 语言流畅。这对从事机械技术翻译的人员提出了更高的要求, 除了掌握英语的基本知识和深厚的语言功底外, 还要具备一些机械专业知识, 了解机械英语的特点, 熟练掌握它的翻译方法和技巧, 这样才能翻译得专业、准确和规范。本文从机械英语的语言特点出发, 探讨了机械领域中专业英语的基本翻译方法。

1 机械英语的特点

1.1 词汇特点

1.1.1 专业词汇、术语多

机械英语所涉及的大多是机械工程领域的专业知识, 许多普通词汇用在机械专业技术中表达的含义与通常概念有所不同。翻译时应译成准确的技术用语, 不能望文生义。如:cylinder (油缸) 、nut (螺母) 、washer (垫圈) 等。

1.1.2 派生词的使用

派生词在机械英语中得到广泛应用。

(1) 由前缀semi- (半) 、non- (否定) 、dis- (分离) 等构成的派生词有:semi-automatic (半自动的) 、nonflammable (不易燃的) 、disassembly (拆卸) 等。

(2) 由后缀-ity、-ness、-tion等派生的名词有:durability (耐久性) 、toughness (韧度) 、tension (张力) 等;

(3) 由后缀-ize、-en、-ify等派生的动词有:pressurize (加压) 、tighten (紧固) 、amplify (放大) 等;

(4) 由后缀-al、-ive、-ous等派生的形容词有:technical (技术的) 、adhesive (带粘性的) 、ferrous (含铁的) 等。

1.1.3 缩略词的广泛使用

机械英语的翻译行文须简练、直观, 术语要规范, 常使用一些缩略词, 缩略形式如下:

(1) 使用词组中每一个词的首字母组成一个缩略词, 如:OEM (Original Equipment Manufacture) 原设备制造、ECU (Engine Control Unit) 发动机控制装置、ROPS (Roll Over Protective Structure) 防滚翻保护装置等。

(2) 半缩略词。将词组的前2个词缩略为首字母, 后面的词保持不变。如:IC forklift=internal combustion forklift (内燃叉车) 、KD key=Kick Down key (换低档键) 、CI engine=compressing ignition engine (压燃式内燃机) 。

(3) 缩略词汇的开头、结尾、中间或两端部分。如:Cab (Cabin) 驾驶室、auto (automatic) 自动、Lab (Laboratory) 实验室等。

1.1.4 复合词占多数

复合词就是由一个以上的词汇组合起来构成的合成词, 这类词在机械英语中屡见不鲜。由连字符连接的复合词有:turbo-charger (涡轮增压器) 、open-loop (开环) 、air-cooling (风冷) 等。不带连字符的复合词有:parking brake (停车制动) 、slotted nut (有槽螺母) 、check valve (单向阀) 、shift control lever (变速操纵杆) 、hydraulic pressure (液压) 等。

1.2 句法特点

1.2.1 句型复杂、长句多

机械英语中从句和长句使用较多。长句逻辑严谨、结构紧凑, 适合表述复杂的观点和理论, 而简单句很难做到这点。如:Do not start an engine by way of traction from another machine, as the engine starting may have forward impact, which will cause possible collision with the traction machine.严禁使用另一台机器以牵引的方式启动发动机, 因发动机经启动后, 会产生前进的动力, 这就有可能引起追尾。

1.2.2 被动语态多

机械英语中被动语态使用也较多。被动语态具有突出动作承受者, 不说明执行者, 使句子结构更紧凑的特点, 有利于强调各种问题、概念、事实或结论等内容。如:The waste oil must be collected with suitable containers during disassembly of any hydraulic line and disposed of according to local laws and regulations.在拆卸液压油路时, 必须用适当的容器来收集废油, 并根据地方法律法规处置所有废油。

1.2.3 常用第三人称作主语

机械英语重在叙事推理, 突出所阐述的客观事物本身。使用第三人称作主语既可以比较客观地陈述事实, 又可避免给人以主观臆断的感觉。所以机械英语常用第三人称作主语, 很少使用第一人称和第二人称作主语。

1.2.4 少用情态动词

机械英语通常不用或少用情态动词。如果使用情态动词, 也只用表示推测的情态动词, 如:may、might、can、could, 其中can表示理论上存在的可能性, 使用频率最高。

如:Motor grader can be used for large area flattening, scraping, earth moving and snow plowing, etc.It can be wildly used for flattening high-grade road, industrial land and farmland.平地机可用于大面积的地面平整、修坡、推土、除雪作业等, 广泛用于高级公路、工业用地和农田的地面平整作业。

1.2.5 广泛使用名词化结构

机械英语要求表达客观、准确、简洁明了, 所以广泛使用名词化结构。如:用“An increase in the thickness of the steel plate”代替“If the thickness of the steel plate is increased”将复合句简化成简单句, 使表达的意思更清晰、准确。

2 常用翻译方法

机械英语翻译既要保证译文与原文信息的等价转化, 同时还要保证译文的读者能够准确而完整地获取原文信息。必须做到忠实于原文, 内容准确, 语言简洁紧凑, 通俗易懂。因此, 笔者将机械英语常用的一些翻译方法和技巧总结如下。

2.1 词汇翻译

2.1.1 专业词汇、术语的翻译

专业词汇、术语有以下几种译法:意译、音译、零译等。意译就是直接将原词的含义译成汉语, 这种译法在机械术语翻译中最为普遍。如:gear (齿轮) 、axle (车轴) 、frame (车架) 等。音译就是根据英语单词的发音翻译成读音相近的汉字。该译法主要用于计量单位、人名、地名、公司名以及某些新生的材料或产品名称的翻译。如:watt (瓦特) 、motor (马达) 、radar (雷达) 、valve (阀) 、Vaseline (凡士林) 等。零译就是把英语专业术语直接引用到汉语文体中。如:PDS (产品设计规格) 、CAE (计算机辅助工程) 等。

2.1.2 词性转换活用

(1) 名词的转译。由于汉语句子中动词用得多, 名词用得少, 因此机械英语中表示动作的动名词、含有动作意思的名词、由动词派生的名词等通常都需要根据情况转译成汉语动词。如:Periodical lubrication of bearing pins is necessary for the maintenance of construction machinery.保养工程机械, 销轴的定期润滑是必要的。此句中的名词“maintenance”转译成了汉语动词。同时, 汉语名词也可转译成英语动词、副词或代词等。如:超低硫燃油在西方发达国家得到了广泛的应用。Ultra-low sulfur diesel fuel is widely used in western developed countries.此处名词“应用”转译成了英语动词。

(2) 动词的转译。机械英语中很多名词派生的动词或由名词转用的动词, 应根据汉语习惯转译为汉语名词。如:This manufacturer sells a great deal of excavators.该厂家挖掘机的销量十分可观。此处动词“sell”转译成了名词。此外, 因汉语句子中名词少, 动词多, 可以几个动词或动词性结构连用, 而英语句子中通常只用一个谓语动词, 名词较多。所以翻译时经常需将汉语动词转译成英语名词。如:使用未经许可的属具可能导致意外事故或机器损坏。The use of unauthorized attachments may result in accidents or machine damage.此处动词“使用”转译成了名词。

2.2 句子翻译的基本方法

2.2.1 采用增译和省略方法

机械英语翻译常采用增译和省略的方法。在英译汉时, 对于没有主语的祈使句和被动句, 应根据汉语习惯增译出主语。如:When carrying out welding or cutting operation with a welding torch, wear special safety helmet and goggles. (当您) 在用焊枪焊接或切割时, 请带上专用安全帽或者护目镜。

英语注重形合, 通常用连词来连接句子;而汉语注重意合, 句子间通常用内在的意义来关联。机械英语中常见“when”开头的从句, 若时间先后次序明显, 在翻译时通常可以将汉语意思“当……时”省略不译。如:When the gear is shifted into reverse, the machine moves backward.把档位换成倒档, 机器就会向后倒车。

2.2.2 词组与分句转换法

由于英语句子修饰性成分多, 而汉语句子则以分句并列为主, 因此翻译时需要用词组与分句转换法, 将英语词组转译成汉语的分句, 或将汉语分句转译成英语词组, 使得译文更符合目的语的语言习惯。如:The radiator group consists of an inter-cooler followed by hydraulic oil radiator and water radiator which are connected in parallel with hydraulic motor drive fan at the end, and torque converter oil radiator underneath.散热器组分三层布置:前部是空空中冷器, 中间并联液压油散和水散热器, 后部是液压马达驱动风扇, 下方为变矩器油散热器。

2.2.3 被动句的翻译

在机械英语中, 被动语态几乎随处可见。被动句可以翻译为汉语的被动语态, 常用“被”“使”“由……”“受到”“为……所”等表示。

如:The welding operation may be realized by spot welding.这种焊接操作可由点焊来实现。

This operating method was accepted by customers.这种操作方法为用户所接受。

根据汉语的表达习惯, 英语被动语态常翻译为汉语主动语态。如:If ultra-low sulfur diesel fuel is not used, the engine could possibly not meet emission standard and the after-treatment system could possibly be damaged.如果不使用超低硫燃油, 发动机不可能符合排放标准, 而且可能损坏后处理系统。

2.2.4 长句的翻译

仔细阅读原文, 弄清长句的基本结构, 找出句子主干、中心内容及其各层含义, 然后分析几层含义之间的相互逻辑关系, 最后按汉语的语言特点和表达方式正确地译出原文, 不必拘泥于原文的形式。长句的翻译方法有:顺序译法、变序译法、分句译法和综合法等。

如:Turn on the hazard warning switch, which is located on the right control panel, machine alarm will sound, and the front and rear turning signal lights will flash at the same time.打开右侧控制面板上的危险警告开关, 机器报警, 同时前后转向信号灯也将开始闪烁。

3 结语

在机械英语翻译实践中, 要做到既忠实于原文又符合译文的语言规范, 不能机械地按原文逐字翻译, 而需要从语法分析入手, 弄清句子的逻辑关系, 摆脱原文的束缚, 结合目的语的语言特点, 灵活运用翻译方法和技巧, 尽可能准确、完整而忠实地传达原文的含义。译者应当不断加强自身的双语素养, 补充学习相关机械专业知识, 善于总结积累翻译经验, 才能翻译出高质量的译文。

参考文献

[1]丁迎.浅谈科技英语长句翻译[J].宁波广播电视大学学报, 2006 (2) .

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[3]韩琴.科技英语特点及其翻译[J].中国科技翻译, 2007 (3) .

[4]卜玉坤.机械英语[M].北京:外语教学与研究出版社, 2004.

机械毕业英语论文翻译 第4篇

【摘要】本文以阀门机械为例，分析了机械工程英语的语言特点。研究表明，采用直译、句群拆分与整合、转译的策略，可使译文更加准确、通顺和规范。

【关键词】机械工程英语 阀门 语言特点 翻译策略

引言

近年来，我国机械制造业取得了迅猛的发展，面对国外的大量机械英语资料，如何将其准确、通顺地传达出来，十分重要。

一、语言特点

1.机械专业词汇的大量使用。在机械英语中，会有大量的专业词汇出现。比如，floating ball valve 浮动球阀，one-piece body ball valve 一片式球阀。

另外，在同一文本中，同一种部件名称有着不同的表达方式。如，valve grid， valve guard， valve stop 均表示“阀挡”。

2.缩略词出现频率高。在阀门行业中，缩略词广泛运用。比如，BC螺栓连接阀帽，BI-ECC 双偏心，PL板式平焊。缩略词专业性较强，译者要有一定的背景知识，才能准确理解。

3.结构复杂的长难句较多。在机械英语中，会有很多长难句。译者在处理长难句时，首先要理清层次，将长句子进行拆分再整合。如：

（1）【原文】From the valve serial number which is clearly identified on the nameplate， all the materials of construction are fully certified in addition to which the body material of the valve is marked by cast lettering.

【译文】标示牌上的阀门编号须能清晰辨认。所有的材质均须充分验证，另外，会将阀体材质说明标记出来。

原文中from引导一个从句，其中由which引导的定语从句，先行词是serial number，译者可将句子结构拆分，再按句子的逻辑关系将句子成分整合，然后准确译出。

二、翻译策略

1.直译。机械工程英语有很强的科学性、严谨性，译文需把握好四个标准：准确、通顺、规范、简练。

在这类文本中，大多数名词均可灵活地采用直译。比如：

（2）【原文】This is due to the flow in the pipeline forcing open the plates and when it stops the plates close.

【译文】由于管道中的流量迫使阀盘打开，当流量中断时，阀盘关闭。

原文的due to直译为“由于”，动名词forcing直译为“迫使”，而open和close分别直译为“打开”和“关闭”即可。

2.句子的拆分和整合。在机械专业英语中，通常会有介词短语、分词结构等，构成一些长难句。因此，译者要将各个句群进行拆分整合。比如：

（3）【原文】By having the whole manufacturing process， it is possible to manufacture virtually anything we make as standard on a very fast timescale to assist with project shutdowns or shorts.

【译文】通过公司集团内整个生产过程，关闭或削减一些项目，这样使我们能够依据标准在短时间内生产任何所需产品。

原文句首是By +doing引导的一个从句，后面的it is possible中it是形式主语。译者可将拆分的从句译出，再按原文的逻辑顺序，重新整合。

3.转译。在阀门机械英语中，常会出现一些含有动作概念的动名词、形容词，译者需将其转译为汉语里的动词。比如：

（4）【原文】Dependent on the materials of construction specified， they can operate over a wide range of temperatures in chemically aggressive duties.

【译文】依赖于指定的材质，可以在具有化学侵蚀性工况及广泛的温度范围内使用。

文中的“dependent”是一个形容词，但具有动作概念，译者可将其转译为动词。为符合汉语的表达习惯，转译也是一个重要的策略。

三、结语

本文结合实例，分析了机械工程英语的特点，并提出相应的翻译策略。鉴于这类文本的专业性较强，译者需扩充专业背景知识，才能使译文更加通顺、规范。

参考文献：

[1]王玲玲，马晶晶.轧制机械英语的特点与翻译技巧探讨[J].机械管理开发，2012（3）.

[2]方敏.机械工程英语的翻译方法[M].北京：机械工业出版社，1989.

[3]廖福妹.机械专业英语语言特点及翻译策略[J].长沙大学学报，2010（1）.

作者简介：

姚瑶（1990-），女，土家族，湖北恩施人，成都理工大学外国语学院硕士研究生，专业为英语笔译。

机械英语专业论文及翻译 第5篇

FIELD OF THE INVENTION 发明的领域

The invention relates to an engine control strategy for a hydraulic camshaft adjuster with mechanical central locking, in particular a vane-type hydraulic camshaft adjuster, having the features of the preamble of claim 1.本发明涉及发动机控制策略与机械液压凸轮轴调节器中央锁定,尤其是叶片式液压凸轮轴调节器,在权利要求1的序言的特点。Camshafts of internal combustion engines are usually driven by crankshafts via a chain or a toothed belt, and here, are continuously adjusted in a closed control loop, with typical adjustment ranges being 40° to 60° crank angle.Crank angles to be set are stored in characteristic maps.Adjustments take place for example hydraulically, fed from the engine oil circuit by means of an electrically actuated control valve, and permit optimized valve control times by means of the parameters of engine load and rotational speed.Depending on the engine concept and number of adjusters, it is thus possible to obtain a considerable reduction in fuel consumption and exhaust-gas emissions and an increase in power and torque.凸轮轴的内燃机通常是由曲轴通过链或齿形带,在这里,不断调整在一个封闭的控制回路,典型的调整范围是40°60°曲柄角度。曲柄角度设置存储在特征地图。例如液压调整发生,美联储从发动机油路通过一个电驱动控制阀,并允许通过优化阀控制倍发动机负载和转速的参数。根据发动机概念和数量的调节器,因此可以获得相当大的减少燃料消耗和废气排放,提高功率和扭矩。

In the state in which they are not hydraulically braced, camshafts and, fixedly connected thereto, rotors of a hydraulic camshaft adjuster tend to perform acoustically noticeable oscillations on account of alternating torques on the camshaft.Said oscillations can be prevented by means of a mechanical connection of the rotor to the stator and therefore to the crankshaft.A known mechanical connection of said type is the camshaft adjuster locked in the center, that is to say between the LATE and EARLY end stops.Two locking pistons which are axially movable in the rotor, and which are also referred to as pins, can be pressed by means of spring force into a locking slot which is positioned opposite in an axially arranged locking cover which is fixedly screwed to the stator, and thereby lock the rotor and stator to one another in a rotationally fixed manner.Unlocking takes place hydraulically by means of oil pressure from the lubricating oil circuit of the engine, which oil pressure is deflected to the locking pistons by means of a controlled supply of current to a solenoid valve and moves said locking pistons axially out of the locking slot into the rotor such that the rotor and stator are rotatable relative to one another.的状态,他们不是液压支撑,凸轮轴,固定连接,转子的液压凸轮轴调节器倾向于执行听觉上明显的振荡的凸轮轴上的交变扭矩。说振荡可以预防通过机械连接的转子定子,因此曲轴。一个已知的机械连接的类型是凸轮轴调节器锁在中心,也就是说之间初末结束停止。两个活塞锁定在转子轴向移动,也被称为别针,可以通过弹力压成相反的锁槽定位在一个轴向锁定封面安排固定螺纹定子,从而锁定转子和定子旋转固定的方式。解锁发生液压通过油压润滑油电路的引擎,这油压偏转到锁定活塞通过一个电磁阀控制的电流供应和行动表示活塞轴向锁定的锁槽的转子,转子和定子旋转相对于另一个。

机械专业英语翻译 第6篇

几何精度设计是在机械制图上使用的一个三维国际工程设计语言。这个语言主要由符号组成，这些符号是清楚地定义在由美国机械工程协会出版的ASME Y14.5M-1994中。这个制图标准在北美使用和全世界都认同。它代替了更早的ANSI Y14.5M-1982标准和已经发展到几乎等同于它的ISO副本。这个标准在确定使用各种几何符号的方式和在清楚地展示设计者的意图的其他方法上是完善的。

几何精度设计的合理使用保证了工程设计想要的形状、配合和功能，没有在车间的假想或每个人都诠释不同的精细制作的笔记。几何精度设计将通过在整个工程设计、制造和品质功能中提供相同的解释，增加制造公差，提升效率和品质来节约公司花销。我们的经验表明许多设计者、车间和品质控制人员，尽管在几何精度设计工作了许多年，但还是没有完全了解要求和没有利用到几何精度设计的所有优点。

设计和生产系统，复杂性，电算化，和全球制造对准确的工程图纸提出了强制性要求。功能测量，刀具，零件尺寸和制造受益于几何精度设计。几何精度设计的学习是重要的，因为它是设计、制造过程和质量三者沟通的粘合剂。

制造，设计系统需要一个易懂的语言，否则，它是不一致的和不可用的。一门技术语言被定义为一个标准，这个被广泛使用的标准是ASME Y14.5M-1994。我们的目的是让几何精度设计和制造过程协调一致。你可以已经在计算机辅助设计课或制图课上接触到几何精度设计。

第二单元

力学概论

力学的基本概念：

力学是用来处理运动，时间和力的科学分析的分支，它由静力学和动力学组成。静力学研究静态系统的分析，这时，时间不是一个考虑的因素;动力学则是随时间变化的系统。力是通过相配合的表面传递到机器各个构件的。例如，从齿轮到轴或一个齿轮通过啮合齿传动到另一个齿轮或连杆通过轴承传到杠杆，从V带到滚轮或从凸轮到传动件。有许多理由都必须知道力的大小。力在边界及配合表面的分布必须要合理，其强度必须在构成表面的材料的工作极限内。例如，如果作用在套筒轴承上的力太大，将会把油膜挤出，并导致金属表面的胶合，过热和轴承过快失效，动力学的研究主要是确定李的大小、时间和位置。

下面将说明一下我们这方面的研究

力：我们最早的关于力的想法是源于我们对推、举和拉河中物体的需要。因此力是一个物体对另一个物体的作用。自觉对力的联系包括力作用的位置，方向和大小，这些称为力的特性。

物质：物质是一种材料或实物，如果它完全封闭则称为物体。

质量：牛顿吧质量定义为物体的数量，由体积和密度来衡量。这定义并不是很多人满意的，因为密度是单位体积的质量。通过猜想我们可以谅解牛顿，可能他并不认为那是个定义。然而，他已经认识到了一个事实，那就是所有的物体都具有不同于重量的内在性质。所以，尽管月球重量不同于地球重量，但一块月球上的岩石仍有特定不变的本质数量。这个恒定的本质数量或物质食粮就是岩石的质量。

国际单位制最大的有点事它对任何物体有且仅有一个单位。长度的单位为米，质量的单位为千克，力的单位为牛顿，时间的单位为秒等等。为了和这种特性保持一致，就要求一个给定的单位或词不能仅一个被认可的技术名称在二个物理量中使用。然而，习惯叫做“重量”的这个词已经在技术和非技术领域广泛使用，表示着物体所受的引力和其本身质量。

粒子：粒子就是指尺寸小到可以忽略的物体。

刚体：物体要么是弹性的，要么是塑性的，只要作用上力都会产生变形。当物体形变量很小时，通常将其假想为刚体，即没有变形的能力，作此假想以便简化分析。

可变形的物体，作为应力和应变是由将要分析的作用力所提供的，则刚体假说将不再适用。因此我们认为物体时可变形的。这种分析常称为弹性物体分析，兵并应用这附加的假说，即在力作用范围内，物体仍保持弹性。

牛顿定律，牛顿三大定律是：

牛顿第一定律：如果一对平衡力作用在一个质点上，那么这个质点仍将保持静止或匀速直线运动。

牛顿第二定律：如果作用在质点上的力不是平衡的，则该质点将经历一个加速度且加速度与合理大小成比例，沿合力方向。

牛顿第三定律：当一对质点相互作用，作用力与反作用力其大小相同，方向相反，作用在过二个质点的直线上。

2，力和力矩：

当一个物体从一个组成系统中聚集到一起，任意两物体间相互作用的力称为约束力。约束力使物体以特定的方式运动。作用在系统上的力称为作用力。

有的力在作用中并没有实际的物理接触。例如，电力磁力和引力。有许多，但不是大多数的力我们会涉及到。这些力是通过物理的或机械上的接触相互作用的。

力是个矢量，力的要素是：力的大小，方向和作用点。力的方向包括那条沿力的指向为方向的直线。因此力可能沿直线正向，也可能沿直线反向。二个大小相等，方向相反，作用不共线的合力。任意二个这种力作用在物体上将会形成一个力偶，力臂是作用线的垂直距离，作用和面是通过二个作用力的平面。

第三单元

简单机械

图3-1给出了直杠的三种布置情况，每个例子中Ｆ是支点；Ｐ是作用力，作用在ｂ点上；Ｗ是载荷，作用在ｃ点上，当杠杆处于平衡时，为Ｐ使杠杆绕ｆ转动的趋势必须与载荷ｗ使杠杆往反方向旋转的趋势相平衡。忽略在支点上的摩擦力，以上关系可用数学式表达为：Ｐ＊ＢＦ＝ＷＸ从上式可以看出，施加的作用力乘以支点到一作用点应等于另一侧的乘积，从这可以导出“机械效率”这个量，它等于载荷除以作用力：

机械效率＝Ｗ／Ｐ＝ｂｆ／ｃｆ

图３－１Ａ中如果ｂｆ／ｃｆ＝３，就意味着３０磅的载荷能被１０磅的为所平衡。如果力稍超过这个数值，杠杆将会随着为Ｐ的增大而绕点ｆ旋转，为Ｐ比载荷Ｗ增加得更快更大，这也是机械效率，但应忽略摩擦力的作用，显然，ｆ、ｃ间的距离越短，杠杆的力放大八月入越大。

图３－１Ａ的布置情况可在钳子和剪刀上找到，而图３－１Ｂ的情况可在手推车中找到，ｆ相相当是车轮，Ｗ为载荷，力Ｐ由操作者施加在手柄上。图３－１Ｃ中，杠杆的作用于是作为一种运动放大装置，它用在脚踏板上来驱动一些小机械。脚踏板上ｂ的小运动可在ｃ产生大运动。

图３－１Ｄ中所示的差动滑轮就是基于杠杆原理。半径为Ｒ的轮Ａ和半径为ｒ的轮Ｂ固定在轴上，并可以转动。力Ｐ是由一条位于轮边缘一个槽中的绳子所提供的，载荷 W由绕在驱动轴上的绳子来提升。当驱动轴静止时，力P促使轴的转动趋势与W促使轴的转动趋势相等，且方向相反。忽略轴承摩擦力的话，力P和大轮半径R的乘积将等于载荷W与驱动轴半径的乘积：P*R=w*r 机械效率还是等于W/P，也等于轮R与驱动轴R的比值。

这种情况和杠杆类似。然而杠杆只能移动载荷很短的距离。而差动滑轮能移动开荷 的距离，只限制于线强长度。

当轮A和绳由装辐条的轮代替时，差动涔轮就仅适于从井里提升一桶桶的水。然而更重要的是差动滑轮的原理在许多工具和机械中是很显而易见的。例如，螺刀，由手提供的力作用在大半径上就能在小半径上转化出很大的力作用在螺钉上。

滑轮是一种最基本的简单机械之一。它从根本上说是由一个轮子和一个支承组成，轮子的轮边带有槽，槽上绕着柔软的绳子，而支承有如固定的或可动的轴承组，一个往下的拉力会产生一个大小相同的向上的力。图3-1E中滑轮和可动组B结合时，如果饭略摩察力的话，绳中所有点的张力P是一样的，因此在绳松开的这边给定一个向下的拉力，将可以提起这个拉力两倍的重物W，而重物W的上升速度交为绳移动速度的一半。因此机械效率为2倍，若使用种种带有固定的和可动的轴承组的滑轮组合，那机械效率将比2倍还要大。例如熟知的轴承级和滑车组合就是一种基本的力放大装置。

现在来考虑一下图3-2中楔的运动。它由力P向左边击打。当角度Q越小，摩擦力F也越小时，以r表示的分力N将会越大。对于任一楔表面的粗糙度以及对奕的摩托车擦力，如果角Q大于一个给定值，即使力P撤掉后，楔仍会保持原位或像粘住了。

可楔紧的锥度在机床主轴中常用来夹抚持切削刀具，如钻头铰刀。其它应用楔原理的机械装置有木刨，子，刀，金属世削刀具和凸轮

丝杠可以认为是楔锥在一个圆柱体上。丝杠是由在实心圆柱上切削出连续不断的槽所形成的，这些被实心材料分开的，连续的，圆周的槽称为螺纹。螺纹和槽都是螺旋形的。

如果将图3-3右侧所示的图ACC`A`H上线段AB`和BD 在左侧直径为d的圆柱上，将会形成1。5图的螺旋。其对应的轴向距离l称为导程。导程角λ是用来度量螺旋的倾斜角。

一些早期的螺钉，其切削方法类似于用展开的如图3-3左边的螺旋一条柔软的金属薄板，以右螺角形式，缠绕在圆柱形毛坯上，以便右角的一臂能平行于轴线，斜边用在圆柱上形成螺旋，用作切削螺旋槽的导向。

如果滑动无件被约束为沿平行圆柱轴线运动，如图3-3中的F，沿着轴线00`运动，它就能被圆柱体的旋转、螺旋或是拉直螺旋的平移所驱动。另一种情况，楔的运动是很明显的。如果螺帽的一部分构件F，它限制了旋转运动但轴向运动是自由的，丝杆螺帽组合将会把螺旋运动转化成

第四单元

机构

基本类型

机构的目的是为了传递运动，而不管机构有没有变更。虽然机构有许多中组成形式，但总的来说只有三种分类，如图4-1所示

图中的每种机构，杆2和杆4都是通过O点和Q点联接到杆1的。这两种机构的运动传递方式如图4-1所示：（A）通过柔性的包裹联接器传递，如皮带，绳子，缆和链条等；（B）通过直接接触传递，如用凸轮，齿轮或是摩擦轮；（C）用刚性的联接杆或联轴器传递。在各种情况中杆2都是驱动件，它以每分钟n2转的转速转动，而杆4是从动件，以每分钟n4的转速转动，对于这三种情况，杆2和杆4的转速比是由Of的长度与Qf的长度比值所决定的。图4-1A中由于点f固定与OQ的中心，所以它的速率是一个常量，在图4-1B和4-1C中，由于点f将会随着物体的转动而移动，故其速率是变化的。直接接触的物体能设计成只会摆动，如图4-1B，或只会持续转动。在所有的情况中，点f都是位于有公法线和中心线的交点上。

直接接触机构

在大多数的情况中，直接接触的表面互相之间是滑动的，并仅仅只有滑动运动。这样表面情况是很容易恶化的。而在特定的条件下，表面磨损不厉害的纯滚动接触具有更高的效率。如果其他条件满足了，物体将会以匀速传递运动。这些特定的情况在齿轮联接和凸轮联接中是很有用的。纯滚动的条件是接触点位于中心线上。

共有三种纯滚动接触的情况，当两物体是圆柱体时，公法线和中心线是重合的，所能传递的载荷是由其表面摩擦所决定的，这就是所谓的基于摩擦的滚动。对于不依赖于摩擦的驱动，其公法线一定不能穿过驱动件或从动件的中心。忽略摩擦，且两相互接触物体间的力沿着法线作用时，当力的作用线没有穿过从动件的转动枢轴线时，从动件将被主动驱动。图4-1B中的物体，接触点在P，提供主动驱动。

任一直接接触物体，其速率比的公式中唯一的变量就是图4-1B中点f的位置。因此，保持匀速或恒定速率比的条件是公法线在一些固定点上通过中心线。尽管法线可能会转动，但只要它在相同点通过中心线，速率比将会保持恒定。

对于大多数给定的物体形状或轮廓，另一物体的，轮廓都能被构造出来，用于以匀速速率传递运动。这就是共轭轮廓。其本身就是存在能传递共轭运动的数学曲线；摆线和渐进线就是其中的两种；用于齿轮轮齿中。摆线就是跟踪空间中滚动轮边缘的一点所形成的轨迹。轮齿的轮廓是跟踪小圆边缘的一点在大圆内外侧滚动所形成的轨迹。渐开线就是处于大圆的内外侧，渐开线就是跟踪小圆边缘一点沿大圆内外侧滚动所形成的轨迹。渐开线也是跟踪从圆柱体上展开的线上的一点所形成的轨迹。通过研究一对渐开线的接触能很好地理解两渐开线轮齿表面的相互作用方式。图4-2中，由基圆1和基圆2产生的两条渐开线通过点m、f和n想联接，且应注意到由于基圆2比基圆1大，渐开线便有不同的形状。

第五单元

连杆机构

连杆机构也许可以定义为实体物体或连杆的载体，其中每根杆件通过销联接（铰链）或滑动接头至少和其他两个杆件相联接。为了满足这个定义，连杆机构必须形成一个无限的封闭的链或一系列封闭的链。很明显，由很多杆联接的链与只有一个杆相比，其性能是不同的。这在机械上就提出了一个非常重要的问题，那就是为传递运动而给定机构的适应性问题。其适应性取决于杆件和街头的数量。

自由度，三杆机构（包括三杆联接在一起的）很明显是一个刚性框架；连杆之间不可能有相对运动，为了表达四杆机构中连杆的相对位置，只需知道任意两杆间的夹角。（算上固定连杆OQ，图5-1C所示机构有4个连杆，因此是四杆机构。）这个连杆机构有一个自由度。要确定五杆机构中连杆的相对位置需要两个角度，也就是它有两个自由度。

带有一个自由度的连杆机构，其运动是有约束的。例如，连杆所有点在其它连杆上的轨迹是固定而又确定的。通过假定连杆上所求轨迹是固定的，并移动与约束相协调的连杆，轨迹是很容易得到的或很容易可视化观察到。

四杆机构。当所受约束的连杆机构中的一个构件固定时，这个连杆机构将变成一个在机械中能够完成有用的机械功能的机构，在销连接的连杆机构中，输入杆（主动杆）和输出杆（从动杆）通常是以枢轴的连接方式连接到固定杆上的；这个连接杆（连接件）通常既不是输入杆，也不是输出杆。由于任意连杆都能固定。如果四种机构中，连杆都不等长，并且都有不同的输入-输出关系，那么就能得到四杆机构。这四种机构也就是所谓的基本连杆机构的转换。

当图5-1左边中最短杆a固定时，杆b和杆d就能完成整圈的旋转运动。这就是双曲柄机构。若曲柄b以恒定的速度转动，则曲柄d将以变化的速度作同向转动。双曲柄机构本身，或者和别机构联接起来时，其曲柄都能提供有用的运动效果，图中，曲柄b是主动杆，它以匀速率逆时针旋转；曲柄d为从动件；三者都能同时完成整圈的旋转运动。但当b转过150°的角度是，从动杆d只能转动50°的角度。这就是意味着从B运动到B’时，曲柄d将比b转得慢，而从B’运动到B时，d比b转得快。如果将同样比例的曲柄d联接到包装机械的主轴上，例如联接运动较慢的轴上，那它将会暂停运动或者停顿。这在必须慢速的地方将派上用场。

通过将最短杆a作为主动杆能得到四杆机构的第二种转换。如图5-1右所示，在杆a做整圈旋转运动的同时；其相对的杆，可能在杆b，c，或杆d，却只能在φ角的范围内摆动。这称为曲柄摇杆机构。它是产生带有急回动作的摆动运动的有用装置。产生急回运动的原因是：当杆a逆时针旋转时，会带动杆 c从B摆动到B’，其摆过角度为θ1，而杆c从B’摆动到B时，其摆过的角度为θ2。由于曲柄a的转速是恒定的，且θ1大于θ2，因此摇杆从右摆动到左的时间将长于其它摆动途径。只有当活动杆件沿一个方向移动，急回装置快速将杆件送回初始位置时，机械才是做有用功。

图5-1右所示的极端位置，曲柄a与连接杆b共线，且假定摇杆c为主动杆时，就必须提供方法使从动杆a通过死点。在用脚踏式操作的磨刀机上，脚踏板连接着杆c，磨刀机主轴连接着杆a，就是靠着磨刀机的角动量使杆通过死点。

在四杆机构的第三种转换中，最短杆a为连接杆，其它的杆件只能摆动，这就是双摇杆机构。

连杆机构的综合，在连杆机构中，用图形法和分析法很容易测定出杆件的位移，速度和加速度。设计或综合连杆来满足特定要求就难得多了。还没有可用的方法来设计双曲柄机构以满足给定的输入-输出的关系谱。能做的就是调查一些选定的特定结构的性能特性。并挑选出其中最佳的

在曲柄摇杆机构中，设计者能控制摇杆的摆动角度，并在一定的程度上控制急回。而曲柄和要干的位移，速度和加速度却无法关联起来。

若四杆机构中的连杆总是以相同或相反的方向转动，并且他们的转动范围远小于180°，那么就有可能将曲柄转动在3点，4点，5点或者甚至更多的位置关联起来。图形法和分析法都能建立这种关联。

第六单元 飞轮

飞轮是一个连接到机械主轴上的重的轮子，它的目的是为了抵消和减轻在机械速度上由所提供的或所需要的动力的造成的速度不均匀性引起的任何波动。飞轮也被用来测试制动器和储存可以在紧急情况下使用的能量，或者可以在快速释放时提供大的力。

抵抗一个旋转物体使其速度发生变化的办法是改变它的惯性矩。这个性质取决于对旋转轴的材料的处置上。惯性矩是与物体的每个构件的重量和它们到旋转轴的距离的平方获得的乘积成正比。普通几何形状物体的惯性矩可以在手册中得到；对于非普通的形状，它们可以由整体的积分或者通过经验来确定。从惯性矩的性质可知，一个飞轮的材质在尽可能离旋转轴远的地方集中是最有效的。因此最好的飞轮有一个通过轮辐或圆盘连接到中心轮毂重的轮缘。

一个飞轮的运行情况完全取决于扭矩或作用在它身上的转动力。如果一个顺时针的扭矩作用在一个固定的飞轮一段时间，这个飞轮将获得一个顺时针角度方向的速度，它与平均扭矩乘以时间段的积成正比，与飞轮的惯性矩成反比。如果一个旋转飞轮受到与它旋转方向相同的一个扭矩作用，它的速度将提升；反之，速度将下降。飞轮的惯性矩越大，由一个给定的扭矩引起的速度变化将越小。如果没有扭矩作用在飞轮上，它的速度将不会改变。

在一个往复式发动机的每个旋转期间作用在曲柄轴上的扭矩都会变化。这种变化是由于在汽缸中的蒸汽或气压的不均匀性和连杆（将活塞压力转变为曲柄轴扭矩）与曲柄轴之间的变化的夹角造成的。当曲柄和连杆是共线的，这时将没有扭矩传递给曲柄，每次旋转这种情况会发生两次。在发动机上飞轮的一个附带的功能是带领曲柄轴经过这些死点位置。

所有的旋转机械都构件都具有惯性矩和像飞轮一样都会对扭矩变化作出反应。这些构件启动、暂停或速度变化所需要的扭矩被称之为惯性扭矩或惯性载荷。惯性载荷存在于所有机械中，当机械启动时它们的存在尤其明显。

飞轮在间歇地传递机械功的机械上是特别有用的。例如，在冲床上，在活塞的下行冲程期间冲压或成型金属盘所需的大的力才会发生。在下行冲程的剩余时间，整个上行冲程和冲程之间的时段，机器是空转的，来自驱动马达的所需的动力是很低的。使用一个具有传递足够大的扭矩去创造冲孔成型所需的大的力的驱动马达是不经济的。飞轮作用于储存在机器空转时由低动力马达造成的能量和在下行冲程做工部分释放部分能量。

在1880年代，一个快速旋转的飞轮被用作鱼雷推动系统的动力源；据报道，在450米的距离将获得24海里/时的速度。在飞机上，直径25厘米，转速52000转/分钟的飞轮有足够的能量去升起和降下起落架。这个飞轮储能系统重90千克，低于完成相同功能的液压系统。在公交运输方面的一个近来（1970年）的应用是在无轨电车上使用飞轮的提议。新型的高密度的钢轮，重300千克，转速为每分钟20000转，它将允许电车离开电线行驶在临近十公里的区域内。在飞轮上获得高密度储能能力的关键在于由材料可以带动的旋转引起的离心应力的大小。相同的材料，平的圆盘可以比轮缘形的轮子多储能百分之50，而锥形的等压力盘可以比轮缘形的轮子多储能百分之100。

第八单元 材料的热处理

热处理是在固态下加热和冷却材料来改变它的的物理性质的工艺。根据所使用的工序，钢可以被硬化来抵抗切割运动和磨损，或者它可以被软化来进行进一步加工。结合适当的热处理，可以消除内部应力，细化晶粒，增加韧性，或生产一个韧性的内部和硬的表面的材料。直到热处理之前，在机械车间制造的大部分产物只有很少的价值或没有价值。热处理不仅可以用于钢上面，也可以用在许多非铁金属上面，例如铝，铜和黄铜。钢热处理的工序包括硬化淬火，回火，退火和表面淬火。

在许多人处理工艺上，加热的速度是重要的。热度以一定的速率从钢的外部传导到内部。如果钢加热太快，外部将会比内部更热，不会得到均匀的结构。如果工件在形状上是不规则的，为了消除变形和裂纹，缓慢的加热速度是更加必要的。工件越重，为了达到均匀的结果，加热时间必须更久。尽管已经达到了正确的温度，工件也应该保持在这个温度相当一段时间来使它最厚的截面达到相同的温度。

1硬化

硬化是一个加热和冷却的过程来增加它的硬度和拉伸强度，降低延展性，和得到一个良好的晶粒结构。这工序包括在温度的临界点加热金属，随后快速冷却。随着金属被加热，铁和碳之间发生物理和化学的改变。这个临界点或临界温度是钢具有最理想特性的点。当钢达到在1400到1600华氏度间的某个温度，如果它被快速冷却，这个变化对制出硬，又强的材料是理想的。如果金属缓慢冷却，它将会变回原本的状态。通过把热的金属投入水，油或盐水中（淬火），可以得到所想要的特性。金属对比之前是非常强和硬的和有更少的延展性。

2回火

已经通过快速淬火硬化的钢是脆的和不适合于大部分用途。通过回火，硬度和脆性将减少到耐用条件所需要的点。随着这些性质减少，钢的抗拉强度也会减小，而在延展性和韧性会增加。这个工艺包括了淬硬钢再加热到低于临界范围的某个温度，随后以任何速度冷却。虽然这个过程软化了金属，但它完全不同于退火，在这个过程中回火有助于对物理性质的精细控制，和在大部分过程中，回火不会把金属软化到退火将达到的程度。最后从硬化金属完全回火所得到的结构被称为回火马氏体。

因为硬化金属的主要成分马氏体的不稳定性，所以回火是合理的。从300到400华氏度的低温不会造成硬度降低，它主要用于消除内部应变。随着回火温度的增高，马氏体的分解将以更快的速度发生，和在大约600华氏度，变成被称为回火马氏体的结构是非常快的。

回火工艺可以被描述成沉淀和结块，或渗碳体聚结的工艺。大量渗碳体的沉淀是在600华氏度，这会产生硬度降低。温度升高会造成碳化物的聚结，而硬度会继续降低。

3退火

退火的主要目的是软化硬的钢以致使它可以被机加工和冷加工。通常这是通过加热金属到稍稍在形成奥氏体的临界温度之上，并保持这个温度直到工件的温度处处相同，和那时以一个缓慢的可控速度冷却以致使工件的表面温度和中心温度近似相等来完成的。这个过程被称为完全退火，因为它消除了之前结构的所有的痕迹，提纯了结晶结构，和软化了金属。退火也消除了以前在金属产生的内部应力。

当硬化的金属二次加热到临界范围之上，组织将变回奥氏体，和缓慢冷却，那时将提供足够的时间完成奥氏体到更软的结构的转变。对于亚共析钢，这些结构是珠光体和铁素体。通过参考平衡态图标，可以注意到过共析钢退火温度是更低的，稍稍在A线之上。没有理由去加热到A线之上，因为在这个点硬的组织渗碳体开始析出。通过加热到更低的临界范围之上和缓慢冷却，所有的马氏体会转变成珠光体。在钢里面任何自由的渗碳体都不收这些处理的影响。

第九单元 材料的选择与机械零件的强度

1材料的选择

这些年来，工程材料的选择已经显得非常重要。此外，选择过程应该是一个对材料的连续不断的重新评价过程。新材料不断出现，而一些原有的材料的可以被利用的数量可能会减少。环境污染，材料的回收利用.工人的健康及安全等方面的关心经常会对材料选择附加新的限制条件。为了减轻重量或者节约能源，可能会要求使用不同的材料，来自国内和国际的竞争.对产品维修方便性要求的提高和顾客的反馈等方面的压力。此外，材料与材料加工之间的相互依赖关系已经被人们认识得更清楚，新的加工方法的出现通常会促使人们对被加工材料进行重新评价。因此，为了能在合理的成本和确保质量的前提下获得满意的结果，设计工程师和制造工程师都必须认真仔细地选择，确定和使用材料。

制造任何产品的第一步工作都是设计，设计通常可以分为几个明确的阶段，（a）总体设计b)功能设计c)生产设计。在总体设计阶段，设计者着重考虑产品应该具有的功能。通常要设想和考虑几个方案，然后决定这种想法是否可行；如果可行，则应该对其中一个或几个方案作进一步的改进，在此阶段，关于材料选择唯一要考虑的问题是：是否有性能符合要求的材料可供选用，如果没有的话，是否有较大的把握在成本和时间都允许的限度内研制出一种新材料。

在功能设计或工程设计阶段，要做出一个切实可行的设计，在这个阶段要绘制出和相当完整的图纸，选择并确定各种零件的材料，通常要制造出样机或者实物模型，并对其进行试验，评价产品的功能，可靠性，外观和适用性等，虽然这种试验可能会表明，在产品进入到生产阶段之间，应该更换某些材料，但是，绝对不能将这一点作为不认真选择材料的借口，应该结合产品的功能，认真仔细地考虑产品外观，成本和可靠性。一个很有成就的公司在制造所有样机时，所选用的材料应该和其在生产中使用的材料相同，并尽可能使用同样的制造技术，这样做对公司是很有的。功能完备的样机如果不能根据预期的销售量经济地制造出来，或者是样机与正式生产的装置在质量和可靠性方面有很大不同，则这种样机就没有多大的价值。设计工程师最好能在这一阶段全部完成材料的分析，选择和和确定工作，而不是将其留到生产设计阶段去做。因为，在生产设计阶段材料的更换是由其他人进行的，这些人对产品的所有功能的了解可能不如设计工程师。

在生产设计阶段中，与材料有关的主要问题是应该把材料完全确定下来，使它与现有的设备相一对一，能够利用现有设备经济地进行加工，材料的数量能够比较容易地保证供应。

在制造过程中，不可避免地会出现对使用中的材料作一些更改的情况，经验表明，可以采用某些理家材料作为替代品。然而，在大多数情况下，在进行生产以后改换材料要比在开始生产前改换材料所花费的代价要高在生产设计阶段做好材料选择工作，可以避免大多数的这种材料更换情况，在生产制造开始后出现了可供使用的新材料的。当然，这些新核燃料可能降低成本，改进产品性能。但是，必须对新材料进行认真的平价，以倚其所有性能都被人们所了解。应当时刻牢记，新材料的性能和可靠性很少能像现有材料那样为人们所了解大部分的产品失效和产品责任事故案件是由于在选用新材料作为替代材料之前，没有真正了解它们的长期使用性能而引起的。

产品的责任诉讼迫使设计人员和公司在选择材料时，采用最好的程序，在材料选择过程中，五个最觉的问题为：（A）不了解或者未能利用关于材料应用方面的最新和最好的信息资料（B）未能和考虑产品可以的合理用途，如有可能，设计人员还应进一步和考虑由于产品使用方法不当造成的后果。在近年来的许多产品责任诉讼案件中，由于错误地使用产品而受到伤害的控告生产大家，并且赢得判决（C）所使用材料的数据不全或者有些数据不确定，尤其是当具长期性能数据是如此的时候（D）质量控制方法不适当和经验证明由一些完全 不称职的人员选择材料。

通过对上违一个问题的分析，可以得出这些问题是没有充分理由存在的结论，对这些问题的分析和研究以给避免这些问题的指明方向。以往采用最好的材料选择办法也不能避免发生产品责任诉讼，设计人员工业界按照适当的程序进行最佳选择，可以大减少诉讼的数量。

因为所生产的压痕尺寸的函数，这表明由于硬度是非破坏性试验，而且不需要专门的，因而硬度是一个容易测量的性能，通常可以直接在实际的机械零件上进行硬度试验。

第十单元

车床及其他机床

车床

1.车床用于旋转工件，并朝着生成所需要加工的表面方向进给切削刀具。2.最常见的车床形式是图10-1a中以图解方式显示的六角车床，它由一个支撑着床头箱，拖板和六角刀架的水平床身组成，工件夹在卡盘和夹头中，或者安装在机床主轴端部的花盘上。3.工件的旋转由一台电机通过一个齿轮系驱动主轴提供。4.切削刀具安装在横向滑板及六角刀架上，在横向滑板上的刀具在平行于工件旋转轴线方向或在工件旋转轴线的法线方向驱动或给进。六角刀架可以通过分度头将各种刀具定位并可以沿车床的床身方向驱动或给进。

5.现代六角车床由计算机控制所有工件和刀具运动，这些车床称为计算机数字控制(CNC)车床，而且刀具或横向滑板可以在水平面上的任一方向进给以使工件上产生所需的廓形。6.图10-1b说明的是通过工件旋转以及托板沿车床床身运动所产生的柱面，这一工序称为外圆车削。

7.车床设定的进给运动也就是工件每转一圈刀具移动的距离，机床的进给量f的定义是：刀具或工件每一行程或每转一圈，刀具相对于工件在进给运动的方向的位移，这样，为了车削长度为Lw的柱面，工件的转数是Lw/f,则加工时间Tm由下式给出的Tm=Lw/(fnw)，式中nw是工件的旋转速度。

8.在此应当强调t，是刀具沿工件走一次（一次切削）的时间，但是，这一次通过并不意味着加工工序的完成，如果首次切削用于以高进给来去除大量材料（粗切），在操作过程中产生的力将有可能引起机床结构的明显挠曲，引起的精度损失可能需要以小进给量进一步加工（精切），使工件直径在规定的界限内并提供光滑的加工表面。由于这些原因，在粗切时常被加工成稍大一点的尺寸，留下少量材料在随后的精加工中去除。立式镗床

9.水平主轴的车床不适于车削沉重的大直径工件，否则机床主轴的轴线将不得不升高到机床操作工够不到固定刀具或固定工件的装置的高度，此外，在垂直的花盘上安装零件或在顶尖之间支撑零件会有困难，因此使用了一种与车窗相同的工作原理，但具有垂直轴线的机床并称为立式镗床（图10-2），这种机床像车床那样旋转工作并向刀具施加连续的,线性的进给运动。

10.（立式镗床）使用单刃刀具，而且进行的作业一般限于车削，端面车削和镗削。

11.便于定位大型工件的水平工件台由一个带有径向T型槽的，起夹持作用的旋转工作台构成

卧式镗床

12,这里介绍的另一种实用单刃刀具并具有旋转主运动的机床是卧式镗床（图10-3），这种机床主要用于沉重的圆柱形工件，在这种工件内有一个待加工的内圆柱形表面，一般讲，在描述机床时，使用卧式或立式来讲。两个词指的是提供主运动的机床轴（主轴）的姿态，可见，在卧式镗床中，主轴是水平的。

13,此类机床的主要特征是，工件在加工过程中保持静止，所有造型运动都施加在刀具上。最常见的加工工序是镗削，如图所示，镗削是通过旋转刀具来实现的，刀具安装在与主轴相连接的镗杆上，然后沿旋转线进给主轴，镗杆和刀具的进给是用于移动工件的机床运动只是用来给工件定位，在进行加工时一般不使用，端面车削工序可以通过使用专门刀具架（图10-4），在其旋转时径向进给刀具来实现。

此外先前推导的镗削和端车加工时间和金属切削率的公式仍将适用。刨床

14,刨床适用于在非常大的部件上加工平面，在这种机床（图10-5）上，线性运动作用在工件上，二刀具则垂直于该运动的方向进给，主运动通常利用变速马达通过齿条与齿轮传动来实现，而且进给运动是断续的工序用提供的T型槽固定在机床的工作台上，加工时间tm和金属切削率zw可以按下面公式估算：tm=bw/(fnr),式中bw是待加工面得宽度。Nr是切削行程的频率，f是进给量，金属切削率zw由下式给出zw=fapv，式中v是切削速度，ap是切口深度（去除材料层的深度）

第十一单元基本的加工工序——切削、镗削、和磨削

基本的加工工序

机床是从早期的埃及人的脚踏动力车床和约翰。威尔金森的镗床发展而来，它们用于为工件和刀具两者提供坚固的支撑并且可以精确控制它们的相对位置和相对速度。基本上讲，在金属切削中一个磨尖的楔形工具以紧凑变形的切削形式从有韧性的工件表面去除一条很窄的金属。切削是一种废弃的产品，与其他工件相比它相当短但是比未切削的部分厚度有相对的增加。机器表面的几何形状取决于刀具的形状和加工操作过程中刀具的路径。

大多数加工工序产出不同几何形状的部件。如果一个粗糙的圆柱形工件绕中心轴旋转而且刀具穿破工件表面并与旋转中心平行的方向前几，就会产生一个旋转面，这道工序叫做车削。如果以类似的方式加工一根空心管的内部，则这道工序叫镗削。制造一个直径均匀变化的锥形外表面叫做锥体车削。短的锥面或柱面也可以仿形车削。如果刀具尖端以一条半径可变的路径前进，就可以制造出像保龄球杆那种仿形表面。如果工件足够短（约1英寸）而且支撑具有足够的刚性，仿形表面可以通过进给一个垂直于旋转轴的仿形刀具来制造。

常常需要的是平坦的或平的表面。它们可以通过径向车削或端面车削来完成，期中刀具尖端沿垂直于旋转轴的方向运动。在其他情况下，更方便的是固定工件不动；以一系列直线式切削的方式使刀具横过工件作往复运动，在每次切削行程前具有一定横向进给量。这一工序叫做刨削，是在牛头刨床上进行的。对于大一些的工件，很容易保持刀具固定不动，而像龙门刨削那样在其厦门拉动工件。仿形面可以通过使用仿形刀具来制造。

在每次往复时进给刀具。也可以使用多刃刀具。钻削使用两刃刀具，孔深可达钻头直径的5~10倍。不管是钻头转动还是工件旋转，切削刃与工件间的相对运动是一个重要的因素。在铣削操作中，有许多切削刃的旋转铣刀与工件相接合，这种工件相对铣刀运动缓慢。根据铣刀的几何形状和进给的方式，可以加工出平面和仿形面。可以使用水平或垂直旋转轴，工件可以沿三个坐标方向中的任意一个进给。

基本的机床

机床用于以切削的形式从韧性材料上去除金属来加工特殊几何形状和精密尺寸的部件。切屑是废品，其变化形状从像钢这样的韧性材料的长的连续带状到铸铁形成的易于处理、彻底断掉的切屑，就处理的观点来讲，不想要长的连续带状屑。机床完成5种基本的金属切削工艺：车削，刨削，钻削，铣削和磨削。其他所有金属切削工艺都是这5种基本工艺的变形。因此，仅有4种使用专用可控几何形状的刀具的基本机床：

1、车床

2、刨床

3、钻床

4、磨床。例如：镗削是内部车削：铰削、攻丝和平底锪孔是修改已钻好的孔，与钻削有关；滚齿与切齿基本上是铣削作业；弓锯削和拉削是刨削和研磨的一种形式；而研磨、超精加工、抛光和磨光则是磨削和研磨切削加工作业的各种变化形式。磨削工艺形成碎屑，但是磨粒的几何形状不可控制。

不同加工工艺切削材料的量和速度可能很大，如在大型车削作业或极小，如研磨或超精加工作业，只有表面高出的点被去除。

机床完成3种主要功能：

1、刚性支撑工件或工件的夹具以及切削刀具；

2、提供工件与切削工具间的相对 运动；

3、提供了一定范围的进给和速度，通常每种情况有4~32种选择。加工中的速度和进给

切削速度、进给和深度是经济加工的3个主要变量，其他变量还有工件和刀具材料，冷却剂以及切削刀具的几何形状，金属切削的速率和加工所需的功率就取决于这些变量。

切削深度，进给和切削速率是在任何金属切削作业中都必须建立的机器设置，它们都会影响切削力，功率和对金属切削的速率。切削的深度是唱针进入唱片的量或者是槽的深度。切削速度由任意时刻唱片表面和对于拾音器臂内的唱针的速度来表示进给由唱针每圈径向向内的前进量或者把两个相邻槽的位置间来表示可以通过把它们与留声机的唱针和唱片相比较给出其定义。

第十二单元 计算机辅助设计

好的工程设计需要保证一个部件或机构正确的运转和持续相当长的一段时间。此外，在设计过程的功能性因素包含重量，强度，热性能，运动学和动力学。

第十五单元

柔性制造、一、柔性制造的定义

制造的演变用图表示为一个连续统一体，如图15-1所示。如此图显示的那样，制造的过程和系统处在把手工操作到最后实现全盟的集成制造的过度状态。计算机集成制造的前一步叫做柔性制造。

柔性在现代制造环境中是一个重要的特征。它意味着一个制造系统是用途多且适应性强，同时又能进行产量相对较大的制造。柔性制造系统是多用途的，这是因为它能制造多种多样的部件。它适应性强，因为它能很快地加以改变来制造完全不同的另一种部件。这种柔性在竞争激烈的国际市场上可能成败有别。

这是一个平衡的问题。独立的计算机数字控制（nc）机床有着高度的柔性，但是只能处理批量相对较小的制造。正相反，系列连锁生产线能进行批量较大的制造，但都不很灵活。柔性制造试图运用工业技术在灵活的与制造运行间达到最佳的平衡。这些工业技术包括自动化的材料、处理，成组技术及计算机和分布数字控制。

柔性制造系统（FMS）是一个独立的机床或一组机床服务于一个自动材料处理系统。它是由计算机控制的而且有对刀具处理的能力。由于他有刀具处理能力并受计算机控制，这样的系统可以不断的重新配置来制造更加多样的部件，这就是它被称作柔性制造系统的原因。

一个制造系统要成为柔性制造系统必须具备的要素有：

1、计算机控制

2、自动处理材料能力

3、刀具处理能力

柔性制造向全面集成化制造的目标迈进了重要的一部。它实现了自动制造过程的集成化。在柔性制造中，自动化的制造机器（如车床、铣床、钻床）和自动化材料处理系统之间，通过计算机网络进行即时的沟通。这是小规模的集成，图15-2是柔性制造系统的一个样例。

二、柔性制造的概况

通过综合几个自动化的制造概念，柔性制造系统向全面集成化的目标迈出了重要的一步，这些观念是：

1、独立机床的计算机数字控制

2、制造系统的分布式数字控制

3、自动化的材料处理系统

4、成组技术，零件族

当这些自动化工艺，机器和观念合成到一个集成的系统时，就产生柔性制造系统。在柔性制造系统中，和计算机起了重要作用，当然大的劳动量比手工操作的制造系统要小得很多。然而，人仍然在柔性制造系统的操作中起了至关重要的作用，人的任务包括几个方面：

1、设备故检、维护和修理

2、刀具的变换和设置

3、安装和拆卸系统

4、数据输入

5、部件程序的变换

6、程序的开发

柔性制造系统设备像所有制造设备一样，必须有人监管以免出现失常、机器程序错误，以及故障。当发现问题时检修人员必须确定问题的根源，然后给出正确的措施，人还要采取指定的措施来修理运行不正常的机器。甚至当所有系统正常运转时，定期的维护也是必要的。

操作人员还要根据需要设置机床，换刀具，以及重新配置系统。柔性制造系统的刀具处理能力消弱了，但并没有消除，在刀具变换和设置上仍需要人力。在装卸柔性制造系统时也是这样，一旦原材料被送到自动化材料处理系统上，它就会以规定的方式，在系统中移动。然而，初装到材料处理系统仍然是由人员完成的，成品的拆卸也是同样。

与计算机的交流仍需要人力完成，人开发零件程序，通过计算机控制柔性制造系统。当重新配置FMS制造另一种类型零件时，他们还在必要的时候变换程序。人在柔性制造系统中劳动力密集型的成分越来越少，但仍然是很重要的。

柔性制造系统中的各层控制都是由计算机来完成的。在柔性制造系统中独立的机床是由CNC来控制点。整个的系统是由DNC来控制的。自动化的材料处理系统是计算机来控制的，其他的功能如数据收集、系统监控、刀具控制、运输控制也是计算机控制的，人机交互是柔性制造系统中的关键。

二、柔性制造的历史发展

柔性制造产生于20世纪60年代中期，当时英国莫林斯有限公司开发了24号系统。24号系统是一个真正的FMS。然而，它从一开始就注定是失败的，因为自动化、集成化和计算机控制技术还没有发展到能够恰好支持这一系统的程度。第一个FMS是超前的开发。因此，最终因不能工作而被放弃。

在20世纪60年代和70年代的其余时间里，柔性制造仍然是一个学术观念。然而，随着复杂计算机控制技术在20世纪70年代末和80年代初的出现，柔性制造便成为可能。在美国最初的主要用户是汽车、卡车和拖拉机制造商。

四、柔性制造的理由 在制造中，生产率和柔性之间经常存在协调一致的问题。在该领域的一端是具有高生产率却低柔性的连续生产线，在该领域的另一端是能提供最大柔性的独立的计算机数字控制的机床，但它只能进行低生产率的制造。柔性制造处在此连续统一体的中间。在制造中总是需要一个系统，这个系统比单个机床能制造更大批量且用于更多制作过程，但仍保持其柔性。

连续生产线能以高生产率制造大量的零件。这条生产线需要大量的准备工作，但却能制造出大量的相同的零件。它的主要缺点是即使一个部件在设计上有小的改变都能造成整个生产线的停产和建构改变。这是一个致命的弱点，因为这意味着没有高成本，耗时停工和变化连锁生产线结构是不能制造出不同的零件的，即使是来自同一个零件族。

传统上计算机数字控制机床是用来制造少量在设计上稍有不同的零件。这种机床很适合这一用途。因为它们能迅速地改变程序来适应设计上小的或者更大的改变。然而，作为独立的机床它们不能大量地或高生产率地制造零件。

柔性制造系统比独立的计算机数控机床具有更大的生产能力和更高的生产率。它们在柔性方面比不上计算机数字控制机床，但它们却相差不多。柔性制造的中间性能的特殊意义在于大多数制造要求中等量的生产率来制造中等及的产品。同时有足够的柔性以快速改变结构来制造另一个零件或产品。柔性制造填补了制造中长期存在的空白。

柔性制造以其基本能力给制造者提供了许多有点：

1、在一个零件族内具有柔性

2、随意进给零件