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畢業(yè)設(shè)計(論文)外文資料翻譯
設(shè)計題目: 裁斷機設(shè)計（立式）
外文題目: 機械設(shè)計（方案設(shè)計過程的分析）
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附件1：外文資料翻譯譯文
機械設(shè)計
機械設(shè)計是指機械裝置和機械系統(tǒng)——機器、產(chǎn)品、結(jié)構(gòu)、設(shè)備及儀器的設(shè)計。大部分機械設(shè)計需要利用數(shù)學(xué)、材料科學(xué)和工程力學(xué)知識。
我們對整個設(shè)計過程感興趣。它是怎樣開始的？工程師是不是僅僅坐在鋪著白紙的桌旁就可以開始設(shè)計了呢？當(dāng)他記下一些設(shè)想后，下一步應(yīng)該做些什么？什么因素會影響或者控制著應(yīng)該作出的決定？最后，這一設(shè)計過程是如何結(jié)束的呢？
有時，雖然并不總是如此，工程師認識到一種需要并且決定對此做一些工作時，設(shè)計就開始了。認識到這種需要，并且語言將其清楚地敘述出來，常常是一種高度創(chuàng)造性的工作。因為這種需要可能只是一個模糊的不滿，一種不舒服的感覺，或者是感覺到了某些東西是不正確的。
這種需要往往不是很明顯的。例如，對食品包裝機械進行改進的需要，可能是由于噪音過大、包裝和重量的變化、包裝質(zhì)量的微小的但是能夠察覺得出來的變化等表現(xiàn)出來的。
敘述某種需要和隨后要解決的問題之間有著明顯的區(qū)別。要解決的問題是比較具體的。如果需要干凈的空氣，要解決的問題可能是降低發(fā)電廠煙囪的排塵量，或者是降低汽車排出的有害氣體。
確定問題階段應(yīng)該制訂設(shè)計對象所有的設(shè)計要求。這些設(shè)計要求包括輸入量、輸出量特性、設(shè)計對象所占據(jù)的空間尺寸以及對這些參量的所有制約因素。我們可以把設(shè)計對象看作是黑箱中的某種東西。在這種情況下，我們必須具體確定黑箱的輸入和輸出，以及它們的特性和制約因素。這些設(shè)計要求將規(guī)定生產(chǎn)成本、產(chǎn)量、預(yù)期壽命、工作范圍、操作溫度和可靠性。
還存在著許多由于設(shè)計人員所處的特定環(huán)境或者由于問題本身的性質(zhì)所產(chǎn)生的隱含設(shè)計要求。某個工廠中可利用的制造工藝和設(shè)備會對設(shè)計人員的工作有所限制，因而成為隱含的設(shè)計要求的一部分。例如，一個小工廠中可能沒有冷加工機械設(shè)備。因此，設(shè)計人員就必須選擇這個工廠中能夠進行的其他的金屬加工方法。工人的技術(shù)水平和市場上的競爭情況也是隱含的設(shè)計要求的組成部分。
在確定了要解決的問題，并且形成了一系列的書面的和隱含的設(shè)計要求之后，設(shè)計工作的下一階段是進行綜合以獲得最優(yōu)的結(jié)果。因為只有通過對所設(shè)計的系統(tǒng)進行分析，才能確定其性能是否滿足設(shè)計要求。因此，不進行分析和優(yōu)化就不能進行綜合。
設(shè)計工作是一個反復(fù)進行的過程。在這個過程中，我們要經(jīng)歷幾個階段，在對結(jié)果進行評價后，再返回到前面的階段。因此，我們可以先綜合系統(tǒng)中的幾個零件，對它們進行分析和優(yōu)化，然后再進行綜合，看它們對系統(tǒng)的其他部分有什么影響。分析和優(yōu)化都要求我們建立或者作出系統(tǒng)的抽象模型，以便對此進行數(shù)學(xué)分析。我們將這些模型稱為數(shù)學(xué)模型。在建立數(shù)學(xué)模型時，我們希望能夠找到一個可以很好地模擬實際物理系統(tǒng)的數(shù)學(xué)模型。
評價是整個設(shè)計過程中的一個重要階段。評價是一個成功的設(shè)計的最后檢驗，通常包括樣機的實驗室試驗。在此階段我們希望弄清楚設(shè)計能否真正滿足所有的要求。它是否可靠？在與類似的產(chǎn)品的競爭中它能否獲勝？制造和使用這種產(chǎn)品是否經(jīng)濟？它是否易于維護和調(diào)整？能否從它的銷售或作用中獲得利潤？
與其他人就設(shè)計方案進行交流和磋商是設(shè)計過程的最后和關(guān)鍵階段。毫無疑問，有許多偉大的設(shè)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(dāng)一個工程師向經(jīng)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。
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(shù)之外，還應(yīng)該精通這三種表達方式。如果一個技術(shù)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！
機械設(shè)計是一門通過設(shè)計新產(chǎn)品或者改進老產(chǎn)品來滿足人類需求的應(yīng)用技術(shù)科學(xué)。它涉及工程技術(shù)的各個領(lǐng)域，主要研究產(chǎn)品的尺寸、形狀和詳細結(jié)構(gòu)的基本構(gòu)思，還要研究產(chǎn)品在制造、銷售和使用等方面的問題。
進行各種機械設(shè)計工作的人員通常被稱為設(shè)計人員或者設(shè)計工程師。機械設(shè)計是一項創(chuàng)造性的工作。設(shè)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(xué)、動力學(xué)、工程材料、材料力學(xué)和機械制造工藝等方面具有深厚的基礎(chǔ)知識。
如前面所述，機械設(shè)計的目的是生產(chǎn)能夠滿足人類需求的產(chǎn)品。發(fā)明、發(fā)現(xiàn)和科學(xué)知識本身是并不一定能給人類帶來益處，只有當(dāng)它們被用在產(chǎn)品上才能產(chǎn)生效益。因而，應(yīng)該認識到在一個特定產(chǎn)品進行設(shè)計之前，必須先確定人們是否需要這種產(chǎn)品。
應(yīng)當(dāng)把機械設(shè)計看成是設(shè)計人員運用創(chuàng)造性的才能進行產(chǎn)品設(shè)計、系統(tǒng)分析和制訂產(chǎn)品的制造工藝的一個良機。掌握工程基礎(chǔ)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(shè)計中做出所需的全部決定。另一方面，應(yīng)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(shè)計變成錯誤的。
一個好的設(shè)計人員應(yīng)該勇于提出新的想法，而且愿意承擔(dān)一定的風(fēng)險，當(dāng)新的方法不適用時，就恢復(fù)采用原來的方法。因此，設(shè)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(shè)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(shè)計工程師應(yīng)該不斷地探索改進現(xiàn)有產(chǎn)品的辦法，在此過程中應(yīng)該認真選擇原有的、經(jīng)過驗證的設(shè)計原理，將其與未經(jīng)過驗證的新觀念結(jié)合起來。
新設(shè)計本身會有許多缺陷和未能預(yù)料的問題發(fā)生，只有當(dāng)這些缺陷和問題被解決之后，才能體現(xiàn)出新產(chǎn)品的優(yōu)越性。因此，一個性能優(yōu)越的產(chǎn)品誕生的同時，也伴隨較高的風(fēng)險。應(yīng)該強調(diào)的是，如果設(shè)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。
在設(shè)計的初始階段，應(yīng)該允許設(shè)計人員充分發(fā)揮創(chuàng)造性，不受各種約束。即使產(chǎn)生了許多不切合實際的想法，也會在設(shè)計的早期，艱險繪制生產(chǎn)圖紙之前被改正掉。只有這樣，才不至于堵塞創(chuàng)新的思路。通常要提出幾套設(shè)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。
心理學(xué)家經(jīng)常談?wù)撊绾问谷藗冞m應(yīng)他們所操作的機器。設(shè)計人員的基本職責(zé)是努力使機器來適應(yīng)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。
另一個重要問題是，設(shè)計工程師必須能夠同其他有關(guān)人員進行交流和磋商。在開始階段，設(shè)計人員必須就初步設(shè)計同管理人員進行交流和磋商，并得到批準。這一般是通過口頭討論，草圖和文字材料進行的。為了進行有效的交流，需要解決下列問題：
（1）所要設(shè)計的這個產(chǎn)品是否真正為人們所需要？
（2）此產(chǎn)品與其他公司的現(xiàn)有同類產(chǎn)品相比有無競爭能力？
（3）生產(chǎn)這種產(chǎn)品是否經(jīng)濟？
（4）產(chǎn)品的維修是否方便？
（5）產(chǎn)品有無銷路？是否可以盈利？
只有時間才能對上述問題給出正確的答案。但是，產(chǎn)品的設(shè)計、制造和銷售只能在對上述問題的初步肯定答案的基礎(chǔ)上進行。設(shè)計工程師還應(yīng)該通過零件圖和裝配圖，與制造部門一起對最終設(shè)計方案進行磋商。
通常，在制造過程中會出現(xiàn)某個問題?？赡軙髮δ硞€零件尺寸或公差作一些更改，使零件的生產(chǎn)變得容易。但是，工程上的更改必須要經(jīng)過設(shè)計人員批準，以保證不會損傷產(chǎn)品的功能。有時，在產(chǎn)品的裝配時或者裝箱外運前的試驗中才發(fā)現(xiàn)設(shè)計中的某種缺陷。這些事例恰好說明了設(shè)計是一個動態(tài)過程。總是存在著更好的方法來完成設(shè)計工作，設(shè)計人員應(yīng)該不斷努力，尋找這些更好的方法。
附件2：外文原文（復(fù)印件）
Mechanical Design
Shigley J E. Mechanical Engineering Design. New York: McGraw-Hill, 2001
Mechanical design means the design of things and systems of a mechanical nature—machines, products, structures, devices, and instruments. For the most part mechanical design utilizes mathematics, the materials sciences, and the engineering-mechanics sciences.
The total design process is of interest to us. How does it begin? Does the engineer simply sit down at his desk with a blank sheet of paper? And, as he jots down some ideas, what happens next? What factors influence or control the decisions which have to be made? Finally, then, how does this design process end?
Sometimes, but not always, design begins when an engineer recognizes a need and decides to do something about it. Recognition of the need and phrasing it in so many words often constitute a highly creative act because the need may be only a vague discontent, a feeling of uneasiness, or a sensing that something is not right.
The need is usually not evident at all. For example, the need to do something about a food-packaging machine may be indicated by the noise level, by the variation in package weight, and by slight but perceptible variations in the quality of the packaging or wrap.
There is a distinct difference between the statement of the need and the identification of the problem which follows this statement. The problem is more specific. If the end is for cleaner air, the problem might be that of reducing the dust discharge from power-plant stacks, or reducing the quantity of irritants from automotive exhausts.
Definition of the problem must include all the specifications for the thing that is to be designed. The specifications are the input and output quantities, the characteristics and dimensions of the space the thing must occupy and all the limitations on these quantities. In this case we must specify the inputs and outputs of the box together with their characteristics and limitations. The specifications define the cost, the number to be manufactured, the expected life, the range, the operating temperature, and t he reliability.
There are many implied specifications which result either from the designer’s particular environment or from the nature of the problem itself. The manufacturing processes which are available, together with the facilities of a certain plant, constitute restrictions on a designer’s freedom, and hence are a part of the implied specifications. A small plant, for instance, may not own cold-working machinery. Knowing this, the designer selects other metal-processing methods which can be performed in the plant. The labor skills available and the competitive situation also constitute implied specifications.
After the problem has been defined and a set of written and implied specifications has been obtained, the next step in design is the synthesis of an optimum solution. Now synthesis cannot take place without both analysis and optimization because the system under design must be analyzed to determine whether the performance complies with the specifications.
The design is an iterative process in which we proceed through several steps, evaluate the results, and then return to an earlier phase of the procedure. Thus we may synthesize several components of a system, analyze and optimize them, and return to synthesis to see what effect this has on the remaining parts of the system. Both analysis and optimization require that we construct or devise abstract of the system which will admit some form of mathematical analysis. We call these models mathematical models. In creating them it is our hope that we can find one which will simulate the physical system very well.
Evaluation is a significant phase of the total design process. Evaluation is the final proof of a successful design, which usually involves the testing of a prototype in the laboratory. Here we wish to discover if the design really satisfies the need or needs. Is it reliable? Will it compete successfully with similar products? Is it economical to manufacture and to use? Is it easily maintained and abjusted? Can a profit be made from its sale or use?
Communicating the design to others if the final, vital step in the design process. Undoubtedly many great designs, inventions, 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 solution to administrative, management, or supervisory persons, is attempting to sell or to prove to them that this solution is a better one. Unless this can be done successfully, the time and effort spent on obtaining the solution have been largely wasted.
Basically, there are only t here 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 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, on one will ever know how competent that person is!
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 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 presentation at all.
Machine design is the application of science and technology to devise new or improved products 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 terms of its size, shape and construction details, but also considers the various factors involved in the manufacture, marketing and use of the product.
People who perform the various functions of machine design are typically called designers, or design engineers. Machine design is basically a creative activity. However, in addition to being innovative, a design engineer must also have a soild background in the areas of mechanical drawing, kinematics, dynamics, materials engineering, strength of materials and manufacturing processes.
As stated previously, the purpose of machine design is to produce a product which will serve a need for man. Inventions, 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 need must be identified before a particular product is designed.
Good designs require trying new ideas and being willing to take a certain amount 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 completely new design generally requires 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 should constantly search for ways to improve an existing product and must decide what old, proven concepts should be used and what mew, untried ideas should be incorporated.
New designs 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 higher 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.
During the beginning stages of design, creativity 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 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 which is ultimately accepted will use ideas existing in one of the rejected designs that did not show as much overall promise.
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 task, since there is really no average person for which certain operating dimensions and procedures are optimum.
Another important point which should be recognized is that a design engineer must be able to communicate ideas to other people if they are to be incorporated. Initially, the designer must communicate a preliminary design to get management approval. This is usually done by verbal discussions in conjunction with drawing layouts and written material. To communicate effectively, the following questions must be answered:
(1)Does the design really serve a human need?
(2)Will it be competitive with existing products of rival companies?
(3)Is it economical to produce?
(4)Can it be readily maintained?
(5)Will it sell and make a profit?
Only 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 design to manufacturing through the use of detail and assembly drawings.
Quite often, a problem will occur during the manufacturing cycle. It may be that a change is required in the dimensioning or telegramming of a part so that is 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. 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 design is a living process. There is always a better way to do if and the designer should constantly strive towards finding that better way.
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