機械設計概論外文翻譯

1、<p><b>　　附錄2：英文資料</b></p><p>　　Introduction to Mrchanical Design</p><p>　　Mechanical design is the application of science and technology to devise new or improved products for t

2、he 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,but also c

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

4、eers.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,dynamics,materials enginee

5、ring,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. Inventions,discoveries and scie

6、ntific knowledge by themselves do not necessarily benfit people;only if they are incorporated into a designed product will a benefit be derived. It should be recognized, therefore,that a human need must be identified bef

7、ore 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 the system and then make sou

8、nd 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 equations which alone can be used t

9、o provide all the correct decisions required to produce a good design. On the other hand, any calculations made must be </p><p>　　Good designs require trying new ideas and being willing to take a certain amo

10、unt of risk,knowing that if the new 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 comple

11、tely new design generally requires that many old and wellestablished methods be thrust aside. This is not easy since many people cling to familiar ideas, techniques and attitudes. A design engineer shoul</p><p

12、>　　New design generally have “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 hig

13、her risk. It should be emphasized 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, crea

14、tivity should be allowed 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

15、 by manufacturing. In this 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 wh

16、ich is ultimately</p><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 peop

17、le. This is not an easy 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

18、design engineer must be 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, inventi

19、ons,and creative works 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 solu&

20、lt;/p><p>　　Basically, there are only three means of communication available to us. There are the written, the oral, and the graphical firms. Therefore the successful engineer will be technically competent and

21、versatile in all three forms 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 compe

22、tent that person is !</p><p>　　The competent engineer should not be afraid of the possibility of not successding in a presentation . In fact, occasional failure should be expected because failure or criticis

23、m seems to accompany every really creative idea. There is a great deal to be learened form a failure, and the greatest gains are obtained by those willing to risk defeat. In the final analysis, the real failure would lie

24、 in deciding not to make the presentation at all. To communicate effectively,the following questions mus</p><p>　　Does the design really serve a human need?</p><p>　　Will it be competitive with

25、existing products of rival companies?</p><p>　　Is it economical to produce?</p><p>　　Can it be readily maintained?</p><p>　　Will it sell and make a profit?</p><p>　　Onl

26、y time 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

27、 design to manufacturing through the use of detail and assembly drawings.</p><p>　　Quite often, a problem will occurt during the manufacturing cycle. It may be that a change is required in the dimensioning o

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

29、. 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 desi</p><p>　　Some Rules for Mechanical Design</p>

30、;<p>　　Designing starts with a need, real or imagined. Existing apparatus may need improvements in durability, efficiently, weight, speed, or cost. New apparatus may be needed to perform a function previously done

31、 by men, such as computation, assembly, or servicing. With 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. Fo

32、r this, freehand sketching is of great value, not only as a record of one’</p><p>　　When the general shape and a few dimensions of the several components become apparent, analysis can begin in earnest. The a

33、nalysis will have as its objective satisfactory or superior performance, plus safety and durability with minimum weight, and a competitive cost. Optimum proportions and dimensions will be sought for each critically loade

34、d section, together with a balance between the strength of the several components. Materials and their treatment will be chosen. These important objectives c</p><p>　　Finally, a design based upon function an

35、d reliability will be completed, and a prototype may be built. If its tests are satisfactory, and if the device is to produced in quantity, the initial design will undergo certain modifications that enable it to be manuf

36、actured in quantity at a lower cost. During subsequent years of manufacture and service, the design is likely to undergo changes as new ideas are conceived or as further analysis based upon tests and experience indicate

37、alterations .Sales a</p><p>　　To stimulate creative thought, the following rules are suggested for the designer.</p><p>　　1. Apply ingenuity to utilize desired physical properties and to control

38、 undesired ones. The performance requirements of a machine are met by utilizing laws of nature or properties of matter (e.g., flexibility, strength, gravity ,inertia ,buoyancy, centrifugal force, principles of the lever

39、and inclined plane, friction, viscosity, fluid pressure,and thermal expansion), also the many electrical, optical, thermal, and chemical phenomena. However, what may be useful in one application may be detrim</p>

40、<p>　　Provide for favorable stress distribute and stiffness with minimum werght.</p><p>　　On components subjected to fluctuating stress, particular attention is given to a reduction in stress concentrat

41、ion, 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 treatments such as surface rolling and shallow h

42、ardening. Hollow shafts and tubing, and box sections give a favorable stress distribution, together with stiffness and minimum weight. Sufficient stiffness to maintain </p><p>　　3. Use basic equations to cal

43、culate and optimize dimensions. The 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 opt

44、imization of dimensions, such as the 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 tu

45、bes, an allowance for corrosion</p><p>　　4. Choose materials for a combination of properties. Materials should be choose for a combination of pertinent properties, not only for strengths, hardness, and weigh

46、t, but sometimes for resistance to impact, corrosion, and low or high temperatures. Cost and fabrication properties are factors, such as weldability, machinability, sensitivity to variation in heat-treating temperatures,

47、 and required coating.</p><p>　　5. Select carefully between stock and integral components. A previously developed components is frequently selected by a designer and his company from the stocks of parts man

48、ufacturers, if the component meet the performance and reliability requirements and is adaptable without additional development costs to the particular machine being designed. However, its selection should be carefully m

49、ade with a full knowledge of its properties, since the reputation and liability of the company suffer if </p><p>　　6. Provide for accurate location and non-interference of parts in assembly. A good design pr

50、ovides for the correct location of parts and for easy assembly and repair. Shoulders and pilot surfaces give accurate location without measurement during assembly. Shapes can be designed so that parts cannot be assembled

51、 backwards or in the wrong place. Interferences, as between screws in tapped holes, and between linkages must be foreseen and prevended. Inaccurate alignment and positioning between such a</p><p><b>　　

52、附錄2：中文資料</b></p><p><b>　　機械設計概論</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，還要研究產品正在制造，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

53、員通常被稱為設計人員或者設計工程師。機械設計是一項創(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)現和科學知識本身并不一定能給人來帶來益處，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

54、這種產品。</p><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)分析和制定產品的制造工藝的一個良機。掌握工程基礎知識要比記一些數據和公式更為重要。僅僅使用數據和公式是不足以在一個好的設計中作出所需的全部決定的。另一方面，應該認真精確的進行所有運算。例如，即使將一個小數點的位置放錯，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

55、想法，而且愿意承擔一定的風險；當新的方法不適用時，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概念結合起來。</p><p>　　新設計本身會有許多

56、缺陷和未能預料的問題發(fā)生，只有當這些缺陷和問題被解決之后，才能體現處新產品的優(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，才不至于堵塞創(chuàng)

57、新的思路。通常要提出幾套設計方案，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

58、他人員進行交流和溝通。與其他人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>&

59、lt;p>　　人們基本上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，那就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是遭到失敗的可能性。事實上，偶然的失敗肯定會發(fā)生

60、的，因為每個真正有創(chuàng)造性的設想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才能取得最大的收獲?？傊瑳Q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>　　所要設計的這個產品是否真正為人們所需要？</p><p>　　此產品與其它公司的現有同類產品相比有無競爭力？&l

61、t;/p><p>　　生產這種產品是否經濟？</p><p>　　產品的維修是否方便？</p><p>　　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配圖，與制造部門一起對最終設計方案進行溝通。<

62、;/p><p>　　通常，在制造過程中會出現某個問題。可能要求對某個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實驗中才發(fā)現設計中的某種缺陷。這些事例恰好說明了設計是一個動態(tài)過程。總是存在著更好的方法來完成設計工作，設計人員應該不斷努力，尋找這些更好的方法。</p><p><b&g

63、t;　　機械設計準則</b></p><p>　　設計是從實際或者假想的需要開始的。對于現有的設備可能需要在耐用性，效率，重量，速度或者成本等方面做進一些改進工作；也可能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日設計。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

64、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。對于每個關鍵承載界面，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

65、靜力學原理分析反作用力和充分利用摩擦力，根據動力學原理分析慣性，加速度和能量；根據彈性力學和材料力學分析應力和變形；根據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試驗和經驗所

66、做的進一步分析結果表明，可以有更好的替代方案，則很可能對原設計方案進行修改。銷售吸引力，客戶的滿意程度和制造成本均與設計有關，而設計能力則與工程創(chuàng)新的實現是密切相關的。</p><p>　　為激發(fā)創(chuàng)造型思維，建議設計人員遵循下列準則。</p><p>　　創(chuàng)造性的利用所需要的物理性能和控制不需要的物理性能?？梢岳米匀环▌t或物質的性能（例如柔性，強度，重力，慣性，浮力，離心力；杠桿原理和斜

67、面原理，摩擦，粘性，流體壓力和熱膨脹）和許多電學，光學和化學現象來滿足一臺機器的設計要求。一種性能在某種場合下可能是有用的，而在另外一種場合下則可能是有害的。閥門的彈簧應該有柔性，而閥門的凸輪軸就不需要柔性。離合器結合面上需要有摩擦，而離合器軸承卻不需要摩擦。設計時，需要創(chuàng)造性的利用和控制所要的物理性能，將不需要的物理性能減至最小。</p><p>　　載重量最輕的情況下，提供合理的應力分布和剛度。對于承受交變應

68、力的零件，應該特別注意減輕應力集中和抬高圓角，螺紋和配合處的強度。改變零件的形狀，可以降低它所承受的應力，對零件施加預應力，如表面滾壓和淺表面硬化，均可以使其得到強化?？招妮S和空心管道，箱型界面能獲得有利的應力分布，同時具有強度高而重量最輕的特點。曲軸，凸輪軸以及含有軸承支座的外殼和構架都應有足夠的剛度以保證直線對中精度和接觸表面之間的壓力均勻分布。軸和其他零件需要有剛度。避免產生共振。</p><p>　　利用

69、基本公式進行尺寸計算和尺寸優(yōu)化。力學和其他學科的基本公式是公認的計算依據。有時需要將這些公式進行移項而化成特殊形式，以簡化尺寸的計算或者對尺寸進行優(yōu)化。例如，用梁的表面應力公式來計算齒輪的輪齒尺寸。在不能采用解析法計算的情況下，可以在基本公式內引入系數。例如，對于薄壁鋼管，考慮到腐蝕性，可以將根據壓力求得的厚度增加一些。當必須應用一個基本公式來確定形狀、材料和使用條件，而這些被確定的量僅僅與在公式推導中的假設比較相近時，要采取措施是結果

70、“偏于安全”。當數據不完全時，可以應用理論公式作為尺寸的指南，在擴展后的范圍內獲得令人滿意的設計結果</p><p>　　根據性能組合選擇材料。選擇材料時需要考慮有關的性能組合，不僅考慮強度，硬度和重量，而且有時還要考慮抗沖擊性，抗腐蝕性或者低溫的能力。成本和制造性能都是應該考慮的因素，這些因素包括可焊接性，機械加工性能，對熱處理溫度變化的敏感性和所需要的涂層等。</p><p>　　在現

71、有零件和整體零件之間進行認真的選擇。若一個以前研制的零件能夠滿足性能要求和可靠性要求，并適合與所設計的那臺機器而無須附加的研制費用，那么設計人員及其公司通常會從零件制造廠的現貨中選取該零件。但是，只有充分了解其性能，才能進行認真的選擇工作，因為任何一個機器零件的失效都會影響公司的信譽，并使公司承擔相應的責任。在其它情況下，若機器設計人員自己來設計零件，則零件的強度，可靠性和成本等方面的要求就可以更好的得到滿足?？梢詫⒛硞€零件和其它零件設

72、計成一個整體的零件，例如將幾個齒輪設計為一個鍛件或者與軸設計成一體，這種方法的優(yōu)點是緊湊。</p><p>　　保證零件在裝配中準確定位和不發(fā)生干涉。一個良好的設計能夠保證零件定位準確，裝配和修理方便容易。軸肩和導向表面在裝配過程中不需要測量就能提供準確定位。零件的形狀應該被設計得保證這個零件不會被裝反或者裝錯位置。必須能夠預見和防止諸如不同的螺紋孔的螺釘之間的干涉和不同的連桿機構之間的干涉。必須避免部件之間的找