外文翻譯--機械設計及加工工藝.doc (2)

1、<p><b>　　英文原文</b></p><p>　　Mechanical Design and Manufacturing Processes</p><p>　　Mechanical design is the application of science and technology to devise new or improved produc

2、ts for the purpose of satisfying human needs. It is a vast field of engineering technology which not only concerns itself with the original conception of the product in terms of its size, shape and construction details,

3、but also considers the various factors involved in the manufacture, marketing and use of the product.</p><p>　　People who perform the various functions of mechanical design are typically called designers, or

4、 design engineers. Mechanical design is basically a creative activity. However, in addition to being innovative, a design engineer must also have a solid background in the areas of mechanical drawing, kinematics, dynamic

5、s, materials engineering, strength of materials and manufacturing processes.</p><p>　　As stated previously, the purpose of mechanical design is to produce a product which will serve a need for man. Invention

6、s, discoveries and scientific knowledge by themselves do not necessarily benefit people; only if they are incorporated into a designed product will a benefit be derived. It should be recognized, therefore, that a human n

7、eed must be identified before a particular product is designed.</p><p>　　Mechanical design should be considered to be an opportunity to use innovative talents to envision a design of a product, to analyze th

8、e system and then make sound judgments on how the product is to be manufactured. It is important to understand the fundamentals of engineering rather than memorize mere facts and equations. There are no facts or equation

9、s which alone can be used to provide all the correct decisions required to produce a good design.</p><p>　　On the other hand, any calculations made must be done with the utmost care and precision. For exampl

10、e, if a decimal point is misplaced, an otherwise acceptable design may not function.</p><p>　　Good designs require trying new ideas and being willing to take a certain amount of risk, knowing that if the new

11、 idea does not work the existing method can be reinstated. Thus a designer must have patience, since there is no assurance of success for the time and effort expended. Creating a completely new design generally requires

12、that many old and well-established methods be thrust aside. This is not easy since many people cling to familiar ideas, techniques and attitudes. A design engineer sho</p><p>　　New designs generally have &qu

13、ot;bugs" or unforeseen problems which must be worked out before the superior characteristics of the new designs can be enjoyed. Thus there is a chance for a superior product, but only at higher risk. It should be em

14、phasized that, if a design does not warrant radical new methods, such methods should not be applied merely for the sake of change.</p><p>　　During the beginning stages of design, creativity should be allowed

15、 to flourish without a great number of constraints. Even though many impractical ideas may arise, it is usually easy to eliminate them in the early stages of design before firm details are required by manufacturing. In t

16、his way, innovative ideas are not inhibited. Quite often, more than one design is developed, up to the point where they can be compared against each other. It is entirely possible that the design which is ultimate</p&

17、gt;<p>　　Psychologists frequently talk about trying to fit people to the machines they operate. It is essentially the responsibility of the design engineer to strive to fit machines to people. This is not an easy

18、task, since there is really no average person for which certain operating dimensions and procedures are optimum.</p><p>　　Another important point which should be recognized is that a design engineer must be

19、able to communicate ideas to other people if they are to be incorporated. Communicating the design to others is the final, vital step in the design process. Undoubtedly many great designs, inventions, and creative works

20、have been lost to mankind simply because the originators were unable or unwilling to explain their accomplishments to others. Presentation is a selling job. The engineer, when presenting a new so</p><p>　　Ba

21、sically, there are only three means of communication available to us. These are the written, the oral, and the graphical forms. Therefore the successful engineer will be technically competent and versatile in all three f

22、orms of communication. A technically competent person who lacks ability in any one of these forms is severely handicapped. If ability in all three forms is lacking, no one will ever know how competent that person is!<

23、/p><p>　　The competent engineer should not be afraid of the possibility of not succeeding in a presentation. In fact, occasional failure should be expected because failure or criticism seems to accompany every

24、really creative idea. There is a great deal to be learned from a failure, and the greatest gains are obtained by those willing to risk defeat. In the final analysis, the real failure would lie in deciding not to make the

25、 presentation at all. To communicate effectively, the following questions must </p><p>　　(1) Does the design really serve a human need?</p><p>　　(2) Will it be competitive with existing products

26、 of rival companies?</p><p>　　(3) Is it economical to produce?</p><p>　　(4) Can it be readily maintained?</p><p>　　(5) Will it sell and make a profit?</p><p>　　Only tim

27、e will provide the true answers to the preceding questions, but the product should be designed, manufactured and marketed only with initial affirmative answers. The design engineer also must communicate the finalized des

28、ign to manufacturing through the use of detail and assembly drawings.</p><p>　　Quite often, a problem will occur during the manufacturing cycle [3]. It may be that a change is required in the dimensioning or

29、 tolerancing of a part so that it can be more readily produced. This fails in the category of engineering changes which must be approved by the design engineer so that the product function will not be adversely affected.

30、 In other cases, a deficiency in the design may appear during assembly or testing just prior to shipping. These realities simply bear out the fact that </p><p>　　Designing starts with a need, real or imagine

31、d. Existing apparatus may need improvements in durability, efficiently, weight, speed, or cost. New apparatus may be needed to perform a function previously done by men, such as computation, assembly, or servicing. With

32、the objective wholly or partly defined, the next step in design is the conception of mechanisms and their arrangements that will perform the needed functions.</p><p>　　For this, freehand sketching is of grea

33、t value, not only as a record of one's thoughts and as an aid in discussion with others, but particularly for communication with one's own mind, as a stimulant for creative ideas.</p><p>　　When the g

34、eneral shape and a few dimensions of the several components become apparent, analysis can begin in earnest. The analysis will have as its objective satisfactory or superior performance, plus safety and durability with mi

35、nimum weight, and a competitive east. Optimum proportions and dimensions will be sought for each critically loaded section, together with a balance between the strength of the several components. Materials and their trea

36、tment will be chosen. These important objectives c</p><p>　　Finally, a design based upon function and reliability will be completed, and a prototype may be built. If its tests are satisfactory, and if the de

37、vice is to be produced in quantity, the initial design will undergo certain modifications that enable it to be manufactured in quantity at a lower cost. During subsequent years of manufacture and service, the design is l

38、ikely to undergo changes as new ideas are conceived or as further analysis based upon tests and experience indicate alterations. Sale</p><p>　　To stimulate creative thought, the following rules are suggested

39、 for the designer.</p><p>　　1. Apply ingenuity to utilize desired physical properties and to control undesired ones.</p><p>　　The performance requirements of a machine are met by utilizing laws

40、of nature or properties of matter (e. g., flexibility, strength, gravity, inertia, buoyancy, centrifugal for, principles of the lever and inclined plane, friction, viscosity, fluid pressure, and thermal expansion), also

41、the many electrical, optical, thermal, and chemical phenomena. </p><p>　　However, what may be useful in one application may be detrimental in the next. Flexibility is desired in valve

42、springs but not in the valve camshaft; friction is desired at the clutch face but not in the clutch bearing. Ingenuity in design should be applied to utilize and control the</p><p>　　physical properties that

43、 are desired and to minimize those that are not desired.</p><p>　　2. Provide for favorable stress distribute and stiffness with minimum weight. On components subjected to fluctuating stress, particular atten

44、tion is given to a reduction in stress concentration, and to an increase of strength at fillets, threads, holes, and fits. Stress reduction are made by modification in shape, and strengthening may be done by prestressing

45、 treatments such as surface rolling and shallow hardening. Hollow shafts and tubing, and box sections give a favorable stress distribution,</p><p>　　3. Use equations to calculate and optimize dimensions. The

46、 fundamental equations of mechanics and the other sciences are the accepted bases for calculations. They are sometimes rearranged in special forms to facilitate the determination or optimization of dimensions, such as th

47、e</p><p>　　Beam and surface stress equations for determining gear-tooth size. Factors may be added to a fundamental equation for conditions not analytically determinable, e. g. , on thin steel tubes, an allo

48、wance for corrosion added to the thickness based on pressure. When it is necessary to apply a fundamental equation to shapes, materials, or conditions which only approximate the assumptions for its derivation, it is don

49、e in a manner which gives results "on the safe side". In situations where data are i</p><p>　　4. Choose materials for a combination of properties. Materials should be chosen for a combination of pe

50、rtinent properties, not only for strengths, hardness, and weight, but sometimes for resistance to impact, corrosion, and low or high temperatures. Cost and fabrication properties are factors, such as weld ability, machin

51、e ability, sensitivity to variation in heat-treating temperatures, and required coating.</p><p>　　5. Select carefully between stock and integral components. A previously developed components is frequently

52、selected by a designer and his company from the stocks of parts manufacturers, if the component meet the performance and reliability requirements and is adaptable without additional development costs to the particular ma

53、chine being designed. However, its selection should be carefully made wi'th a full knowledge of its properties, since the reputation and liability of the company suffer if</p><p>　　6. Provide for accurat

54、e location and non interference of parts in assembly. A good design provides for the correct locating of parts and for easy assembly and repair. Shoulders and pilot surfaces give accurate location without measurement dur

55、ing assembly. Shapes can be designed so that parts cannot be assembled backwards or in the wrong place. Interferences, as between screws in tapped holes, and between linkages must he foreseen and pretended. Inaccurate al

56、ignment and positioning between such a</p><p>　　The human race has distinguished itself from all other forms of life by using tools and intelligence to create items that serve to make life easier and more en

57、joyable. Through the centuries, both the tools and the energy sources to power these tools have evolved to meet the increasing sophistication and complexity of mankind's ideas.</p><p>　　In their earliest

58、 forms, tools primarily consisted of stone instruments. Considering tile relative simplicity of the items being made and the materials being shaped, stone was adequate. When iron tools were invented, durable metals and m

59、ore sophisticated articles could be produced. The twentieth century has seen the creation of products made from the</p><p>　　Most durable , consequently, the most unmachinable materials in history. In an eff

60、ort to meet the manufacturing challenges created by these materials, tools have now evolved to include materials such as alloy steel, carbide, diamond, and ceramics.</p><p>　　A similar evolution has taken pl

61、ace with the methods used to power our tools. Initially, tools were powered by muscles; either human or animal. However as the powers of water, wind, steam, and electricity were harnessed, mankind was able to further ext

62、ended manufacturing capabilities with new machines, greater accuracy, and faster machining rates.</p><p>　　Every time new tools, tool materials, and power sources are utilized, the efficiency and capabilitie

63、s of manufacturers are greatly enhanced. However as old problems are solved, new problems and challenges arise so that the manufacturers of today are faced with tough questions such as the following: How do you drill a 2

64、 mm diameter hole 670 mm deep without experiencing taper or run out? Is there a way to efficiently deburr passageways inside complex castings and guarantee 100 % that no burrs we</p><p>　　Since the 1940s,

65、a revolution in manufacturing has been taking place that once again allows manufacturers to meet the demands imposed by increasingly sophisticated designs and durable, but in many cases nearly unmachinable, materials. Th

66、is manufacturing revolution is now, as it has been in the past, centered on the use of new tools and new forms of energy.</p><p>　　The result has been the introduction of new manufacturing processes used for

67、 material removal, forming, and joining, known today as nontraditional manufacturing processes.</p><p>　　The conventional manufacturing processes in use today for material removal primarily rely on electric

68、motors and hard tool materials to perform tasks such as sawing, drilling, an broaching. Conventional forming operations are performed with the energy from electric motors, hydraulics, and gravity. Likewise, material join

69、ing is conventionally accomplished with thermal energy sources such as burning gases and electric arcs.</p><p>　　In contrast, nontraditional manufacturing processes harness energy sources considered unconv

70、entional by yesterday's standards. Material removal can now be accomplished with electrochemical reactions, high-temperature plasmas, and high-velocity jets of liquids and abrasives. Materials that in the past have b

71、een extremely difficult to form, are now</p><p>　　formed with magnetic fields, explosives, and the shock waves from powerful electric sparks. Material-joining capabilities have been expanded with the use of

72、high-frequency sound waves and beams of electrons.</p><p>　　In the past 50 years, over 20 different nontraditional manufacturing processes have been invented and successfully implemented into production. The

73、 reason there are such a large number of nontraditional processes is the same reason there are such a large number of conventional processes; each process has its own characteristic attributes and limitations, hence no o

74、ne process is best for all manufacturing situations.</p><p>　　For example, nontraditional process are sometimes applied to increase productivity either by reducing the number of overall manufacturing operati

75、ons required to produce a product or by performing operations faster than the previously used method.</p><p>　　In other cases, nontraditional processes are used to reduce the number of rejects experienced by

76、 the old manufacturing method by increasing repeatability, reducing in-process breakage of fragile work pieces, or by minimizing detrimental effects on work piece properties.</p><p>　　Because of the aforemen

77、tioned attributes, nontraditional manufacturing processes have experienced steady growth since their introduction. An increasing growth rate for these processes in the future is assured for the following reasons:</p&g

78、t;<p>　　(1) Currently, nontraditional processes possess virtually unlimited capabilities when compared with conventional processes, except for volumetric material removal rates. Great advances have been made in th

79、e past few years in increasing the removal rates of some of these processes, and there is no reason to believe that this trend will not continue into the future.</p><p>　　(2) Approximately one half of the no

80、ntraditional manufacturing processes are available with computer control of the process parameters. The use of computers lends simplicity to processes that people may be unfamiliar with, and thereby accelerates acceptanc

81、e. Additionally, computer control assures reliability and repeatability[s], which also accelerates acceptance and implementation.</p><p>　　(3) Most nontraditional processes are capable of being adaptively-co

82、ntrolled through the use of vision systems, laser gages, and other in-process inspection techniques. If, for example, the in-process inspection system determines that the size of holes being produced in a product are bec

83、oming smaller, the size can be modified without changing hard tools, such as drills.</p><p>　　(4) The implementation of nontraditional manufacturing processes will continues to increase as manufacturing engi

84、neers, product designers, and metallurgical engineers become increasingly aware of the unique capabilities and benefits that nontraditional manufacturing processes provide.</p><p><b>　　譯文</b><

85、/p><p><b>　　機械設計及加工工藝</b></p><p>　　機械設計是一門通過設計新產品或者改進老產品，滿足人類需求的應用技術科學。它涉及工程技術的各個領域，主要研究產品的尺寸、形狀和詳細結構的基本構思，還要研究產品在制造、銷售和使用等方面的問題。</p><p>　　進行各種機械設計工作的人員通常被稱為設計人員或者設計工程師。機械設

86、計是一項創(chuàng)造性的工作。設計工程師不僅在工作上要有創(chuàng)新性，還必須在機械制圖、運動學、動力學、工程材料、材料力學和機械制造工藝等方面具有深厚的基礎知識。</p><p>　　如前面所述，機械設計的目的是生產滿足人類需求的產品。發(fā)明、發(fā)現(xiàn)和科學知識本身并不一定能給人類帶來益處，只有當它們被用在產品上才能產生效益。因而，應該認識到在一個特定產品進行設計之前，必須先確定人們是否需要這種產品。</p><

87、p>　　應當把機械設計看成設計人員運用創(chuàng)造性的才能進行產品設計、系統(tǒng)分析和制訂產品的制造工藝的一個良機。掌握工程基礎知識要比熟記一些數(shù)據(jù)和公式更為重要。僅僅使用數(shù)據(jù)和公式是不足以在一個好的設計中做出所需的全部決定的。另一方面，應該認真精確地進行所有運算。例如，即使將一個小數(shù)點的位置放錯，也會使正確的設計變成錯誤的。</p><p>　　一個好的設計人員應該勇于提出新的想法，而且愿意承擔一定的風險；當新的方法

88、不適用時，就恢復采用原來的方法。因此，設計人員必須要有耐心，因為所花費的時間和努力并不能保證帶來成功。一個全新的設計，要求摒棄許多陳舊的，為人們所熟知的方法。由于許多人易于墨守成規(guī)，這樣做并不是一件容易的事情。一位設計工程師應該不斷地探索改進現(xiàn)有產品的辦法，在此過程中應該認真選擇原有的、經過驗證的設計原理，將其與未經過驗證的新觀念結合起來。</p><p>　　新設計本身會有許多缺陷和未能預料的問題發(fā)生，只有當這

89、些缺陷和問題被解決之后，才能體現(xiàn)出新產品的優(yōu)越性。因此，一個性能優(yōu)越的產品誕生的同時，也伴隨著較高的風險。應該強調的是，如果設計本身不要求采用全新的方法，就沒有必要僅僅為了變革的目的而采用新辦法。</p><p>　　在設計的初始階段，應該允許設計人員充分發(fā)揮創(chuàng)造性，不受各種約束。即使產生了許多不切合實際的想法，也會在設計的早期，即繪制生產圖紙之前被改正。只有這樣，才不致于堵塞創(chuàng)新的思路。通常要提出幾套設計方案，

90、然后加以比較。很有可能在最后選定的方案中，采用了某些未被接受的方案中的一些想法。</p><p>　　心理學家經常談論如何使人們適應他們所操作的機器。設計人員的基本職責是努力使機器來適應人們。這并不是一項容易的工作，因為實際上并不存在著一個對所有人來說都是最優(yōu)的操作范圍和操作過程。</p><p>　　另一個應該被認識到的重要問題是，設計工程師必須能夠同其他有關人員進行交流和溝通。與其他人

91、就設計方案進行交流和溝通是設計過程的最后和關鍵階段。毫無疑問，有許多偉大的設計、發(fā)明或創(chuàng)造之所以沒有為人類所利用，就是因為創(chuàng)造者不善于或者不愿意向其他人介紹自己的成果。提出方案是一種說服別人的工作。當一個工程師向經營、管理部門或者其主管人員提出自己的新方案時，就是希望向他們說明或者證明自己的方案是比較好的。只有成功地完成這項工作，為得出這個方案所花費的大量時間和精力才不會被浪費掉。</p><p>　　人們基本上

92、只有三種表達自己思想的方式，即文字材料、口頭表述和繪圖。因此，一個優(yōu)秀的工程師除了掌握技術之外，還應該精通這三種表達方式。如果一個技術能力很強的人在上述三種表達方式中的某一種的能力較差，他就會遇到很大的困難。如果上述三種能力都較差，那將永遠沒有人知道他是一個多么能干的人!</p><p>　　一個有能力的工程師不應該害怕在提出自己的方案時遭到失敗的可能性。事實上，偶然的失敗肯定會發(fā)生的，因為每個真正有創(chuàng)造性的設想

93、似乎總是有失敗或批評伴隨著它。從一次失敗中可以學到很多東西，只有不怕遭受失敗的人們才能取得最大的收獲。</p><p>　　總之，決定不把方案提交出來，才是真正的失敗。</p><p>　　為了進行有效的交流，需要解決下列問題：</p><p>　　(1)所要設計的這個產品是否真正為人們所需要?</p><p>　　(2)此產品與其他公司的現(xiàn)

94、有同類產品相比有無競爭能力?</p><p>　　(3)生產這種產品是否經濟?</p><p>　　(4)產品的維修是否方便?</p><p>　　(5)產品有無銷路?是否可以盈利?</p><p>　　只有時間才能對上述問題給出正確的答案。但是，產品的設計、制造和銷售只能在對上述問題的初步肯定答案的基礎上進行。設計工程師還應該通過零件圖和裝

95、配圖，與制造部門一起對最終設計方案進行溝通。</p><p>　　通常，在制造過程中會出現(xiàn)某個問題?？赡芤髮δ硞€零件尺寸或公差做一些更改，使零件的生產變得容易。但是，工程上的更改必須經過設計人員批準，以保證不會損傷產品的功能。有時，在產品的裝配時或者裝箱外運前的試驗中才發(fā)現(xiàn)設計中的某種缺陷。</p><p>　　這些事例恰好說明了設計是一個動態(tài)過程?？偸谴嬖谥玫姆椒▉硗瓿稍O計工作，設

96、計人員應該不斷努力，尋找這些更好的方法。</p><p>　　設計是從實際或者假想的需要開始的。對于現(xiàn)有的設備可能需要在耐用性、效率、重量、速度或成本等方面做進一些改進工作；也可能需要新的設備完成以前由人來做的工作，例如計算或者裝配。當目標完全或部分被確定以后，下一個設計步驟是對能夠完成所需要功能的機構及其布局進行總體設計。對于此項工作，徒手畫的草圖是很有價值的，它不僅可以記錄下我們的想法，而且還有助于與別人進行

97、討論，特別是和自己的大腦進行交流，從而促進創(chuàng)新想法的產生。</p><p>　　當一些零件的大致形狀和幾個尺寸被確定后，就可以開始認真的分析工作。分析工作的目的是要在重量最輕、成本最低的情況下，獲得令人滿意，即優(yōu)良的工作性能，并且還要安全耐用。對于每個關鍵承載截面，應該尋求最佳的比例和尺寸，同時要對這幾個零件的受力進行平衡。要對材料和處理方式進行選擇。只有根據(jù)力學原理進行分析才能達到這些重要目的。這些分析包括根據(jù)

98、靜力學原理分析反作用力和充分利用摩擦力，根據(jù)動力學原理分析慣性、加速度和能量；根據(jù)彈性力學和材料力學分析應力和變形；根據(jù)流體力學來分析潤滑和流體傳動。</p><p>　　最后，完成基于功能要求和可靠性所進行的設計，且要制作一臺樣機。如果試驗結果令人滿意，而且該裝置將要進行批量生產，就應該對最初提出的設計方案做一些修改，使其能以較低的成本進行批量生產。在以后的制造和使用期內，如果產生了新的想法或者根據(jù)試驗和經驗所