1、外文資料Introduction to Mechanical DesignMechanical 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

2、 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 mechanical design are typically called designers, or design engineers. Mechanical design is basically

3、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 engineering, strength of materials and manufacturing processes.As stated previously, the purpose of mechanical design

4、 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 i

5、dentified before a particular product is designed.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 sound judgments on how the product is to be manufactured. It is important to understand the f

6、undamentals of engineering rather than memorize mere facts and equations. There are no facts or equations which alone can be used to provide all the correct decisions required to produce a good design. On the other hand, any calculation made must be done with the utmost care and precision. For examp

7、le, if a decimal point is misplaced, a otherwise acceptable design may mot function.Good designs require trying mew ideas and being willing to take a certain amount of risk, knowing that if the mew idea does not work the existing method can be reinstated. Thus a designer must have patience, since th

8、ere 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 s

9、earch for ways to improve an existing product and must decide what old, proven concepts should be used and what new, untried ideas should be incorporated.New designs generally have “bugs” or unforeseen which must be worked out before the superior characteristics of the new designs can be enjoyed. Th

10、us 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 witho

11、ut a great number of constraints. Even though many impractical ideas may arise, it is usually easy to eliminate then 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

12、 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 the

13、y operate. It is essentially the responsibility of the 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

14、 engineer must be able to communicate ideas to other people if they ate 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 have been lost to mankind simply because the originators were

15、unable or 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

16、 done successfully, the time and effort spent on obtaining the solution have been largely wasted.Basically, there ate 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 versa

17、tile 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 competent that person is!The competent engineer should not be afraid of the possibility of

18、 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 learn from a failure, and the greatest gains ate obtained by those wiling to risk defeat. In the final analysis, the

19、real failure would lie in decoding not to make the presentation at all. 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、It is economical to profit?4、Can it be readily

20、 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 throug

21、h the use of detail and assembly drawings.Quite often, a problem will occur during the manufacturing cycle. It may be that a exchange is required in the dimensioning or tolerancing of a part so that it can be more readily produced. This falls in the category of engineering changes which must be appr

22、oved 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.Engineering design is a systematic process by which solutions to the needs of humankind are obtained. The p

23、rocess is applied to problems (needs) of varying complexity. For example, mechanical engineers will use the design process to find an effective, efficient method to convert reciprocating motion to circular motion for the drive train in an internal combustion engine; electrical engineers will use the

24、 process to design electrical generating systems using falling water as the power source; and materials engineers use the process to design ablative materials which enable astronauts to safely the earths atmosphere.The vast majority of complex problems in todays high technology society depend for so

25、lution not on a single engineering discipline, but on teams of engineers, scientists, environmentalists, economists, sociologists, and legal personnel. Solutions are not only dependent upon the appropriate applications of technology but also upon public sentiment, government regulations and politica

26、l influence. As engineers we are empowered with the technical expertise to develop new and improved products and systems, but at the same time we must be increasingly aware of the impact of our actions on society and the environment in general and work conscientiously toward the best solution in vie

27、w of all relevant factors.Design is the culmination of the engineering educational process; it is the salient feature that distinguishes engineering from other professions.A formal definition of engineering design is found in the curriculum guidelines of the Accreditation Board for Engineering and T

28、echnology (AENT). ABEN accredits curricula in engineering schools and derives its membership from the various engineering professional societies. Each accredited curriculum has a well-deigned design component which falls within the ABEN guideline. The ABEN statement on design reads as follows:Engine

29、ering design is the process of devising a system, component, or process to meet desired needs. It is a decision making process (often iterative ), in which the basic sciences, mathematic, and engineering sciences are applied to convert resources optimally to meet a stated objective. Among the fundam

30、ental elements of the design process are the establishment of objectives and criteria, synthesis, analysis, construction, testing, and evaluation. The engineering design component of a curriculum must include most of the following features: development of student creativity, use of open-ended proble

31、ms, development and use of modern design theory mad methodology, formulation of design problem statements and specifications, consideration of alternative solutions, feasibility considerations, production processes, concurrent engineering design, and detailed system descriptions. Further, it is esse

32、ntial to include a variety of realistic constraints such as economic factors, safety, reliability, aesthetics, ethics, and social impact.If anything can be said about the last half of the twentieth century, it is that we have had an explosion of information. The amount of data that can be uncovered

33、on most subjects is overwhelming. People in the upper levels of most organizations have assistants who condense most of the things that they must read, hear, or watch. When you begin a search for information, be prepared to scan many of your sources and document their location so that you can find t

34、hem easily if the date subsequently appear to be important.Some of the sources that are available include the following:1、 Exiting solutions. Much can be learned from the current status of solutions to a specific need if actual products can be located, studied and, in some cases, purchased for detai

35、led analysis. An improved solution or an innovative new solution new solution cannot be found unless the existing solutions are thoroughly understood.2、 Your library. Many universities have courses that teach you how to use your library. Such courses are easy when you compare them with those in chem

36、istry and calculus, but their importance should not be underestimated. There are many sources in the library that can lead you to the information that you are seeking. You may find what you need in an index such as the Engineering Index. There are many other indexes that provide specialized informat

37、ion. The nature of your problem will direct which ones may be helpful to you. Dont hesitate to ask for assistance from the librarian. You should use to advantage the computer databases found in libraries and often available through CD-ROM technology.3、Professional organizations. The American Society

38、 of Mechanical Engineers is a technical society that will be of interest to students majoring in mechanical engineering. Each major in your college is associated with not one but often several such societies. The National Society of Professional Engineers is an organization that most engineering stu

39、dents well eventually join, as well as at least one technical society such as the society of manufacturing engineers, the American Society of civil engineers (ASCE), or any one of dozens that serve the technical interests of the host of specialties with which professional practices seem most closely

40、 associated. May engineers are members of several associations and societies.4、Trade journals. They are published by the hundreds, usually specializing in certain classes of products and services. Money and economics are part of engineering design and decision making. We live in a society that is ba

41、sed on economics and competition. It is no doubt true that many good ideas never get tried because they are deemed to be economically infeasible. Most of us have been aware of this condition in our daily lives. We started with our parents explaining why we could not have some item that we wanted bec

42、ause it cost too much. Likewise, we will not put some very desirable component into our designs because the value gained will not return enough profit in relation to its cost. Industry is continually looking for new products of all types. Some are desired because the current product is not competing

43、 well in the marketplace. Others are tried simply because it appears that people will buy them. How do manufacturers know that a new product will be popular? They seldom know with certainty. Statistics is an important consideration in market analysis. Most of you will find that probability and stati

44、stics are an integral part of your chosen engineering curriculum. The techniques of this area of mathematics allow us to make inferences about how large groups of people react based on the reactions of a few.中文翻譯機械設(shè)計簡介機械設(shè)計是為了滿足人類需要而制定出的新產(chǎn)品或者改進舊產(chǎn)品時對科學與技術(shù)的應(yīng)用。 它是工程技術(shù)的一個巨大領(lǐng)域,這個領(lǐng)域不僅關(guān)注原先這種產(chǎn)品的尺寸，形狀以及構(gòu)造方式，

45、而且考慮涉及這種產(chǎn)品的制造，銷售和使用的其它各方面的因素。進行機械設(shè)計的各種各功能的人們被通常叫為設(shè)計者或者設(shè)計工程師。 機械設(shè)計基本上是一次創(chuàng)造活動。 然而， 除富有創(chuàng)新精神之外， 一位設(shè)計工程師也必須在機械制圖，運動學，力學，材料工程，材料強度和制造工藝有一定的背景知識。精確的說，機械設(shè)計的目的就是為了滿足人們的需求。 發(fā)明，創(chuàng)造和科學知識它們自己可能不能讓人獲益； 但是只要他們合并在一起并設(shè)計產(chǎn)品，其益處就會被得到。因此，在一種特別的產(chǎn)品被設(shè)計之前，人的需求必須被鑒定，這一點應(yīng)該被認識到。機械設(shè)計應(yīng)被視為一個機會，利用創(chuàng)新人才的設(shè)想設(shè)計一個產(chǎn)品，分析系統(tǒng)，然后就如何制造產(chǎn)品作出正確的判斷

46、。對工程基礎(chǔ)的理解而不是僅僅記住事實和方程式，這一點是很重要的。 沒有哪個事實或方程式能單獨提供要求生產(chǎn)一種好設(shè)計的全部的正確的決定。 另一方面，任何計算必須得最大限度小心和精密。 例如，一個小數(shù)點放錯，就有可能得不到所要設(shè)計得到的結(jié)果。好的設(shè)計應(yīng)該需要嘗試新的方法并且愿意承擔一定的風險，知道如果新想法不起作用，這種現(xiàn)有的方法可能被重新使用。由于為了成功所付出的時間以及努力是不能保證的，因此一個設(shè)計者必須要有耐心。創(chuàng)造一個完全新的設(shè)計一般要求很多舊的以及被建立起來的方法來推動。這并不容易因為很多人堅持舊的想法，技術(shù)和態(tài)度。設(shè)計工程師要不斷尋找方法，以改善現(xiàn)有的產(chǎn)品，并且決定哪些舊的、已被證明的

47、概念須要采納，哪些新的、未曾嘗試的想法應(yīng)該被包刮進來。在那些新設(shè)計的優(yōu)勢特性可以被享有之前,新設(shè)計一般有缺陷或者一些未預(yù)見的缺點。因此，有機會，提供優(yōu)異的產(chǎn)品，但只有在較高的風險下。應(yīng)該強調(diào)指出，如果一個設(shè)計并不需要激進的新方法，這種方法不應(yīng)適用而僅僅是為了改變。在設(shè)計的開始階段，創(chuàng)造性應(yīng)該被提倡而沒有許多限制條件。 即使很多不實用的想法可能出現(xiàn)，在穩(wěn)定的細節(jié)生產(chǎn)被要求之前，這些在設(shè)計早期通常是容易消除的。以這種方法，富創(chuàng)新精神的想法不被抑制。 經(jīng)常，不止一種設(shè)計被提出，甚至到他們可能對彼此被進行比較的方面。 這是完全可能的：最終被接受的設(shè)計將可能使用被拒絕的設(shè)計之中的一個想法。心理學家經(jīng)常談

48、論努力使他們操作的那些機器適合人。努力使機器適應(yīng)人基本上是工程師的責任。這不是一項容易的任務(wù),因為真的沒有人能夠把某一個生產(chǎn)尺寸加工到最優(yōu)化的程度。另一個要點是：一位設(shè)計工程師必須能把想法傳達給其他人，當他們的想法可以被采納時。 把設(shè)計思想傳達給其它人是最后環(huán)節(jié)，也是在設(shè)計過程里的至關(guān)重要的步驟。無疑很多重要的設(shè)計，發(fā)明和有創(chuàng)造性的作品被人們所不認同，僅僅是因為那些創(chuàng)始人不能或者不愿意對其它人解釋他們的成就。 贈送是一個出售的工作。 當提出一個新的解決方案，管理或者監(jiān)督的人的方法時，工程師， 正試圖出售或者向他們證明這個解決辦法是更好的。 除非這能被成功操作，否則關(guān)于獲得這個解決辦法所花費的時

49、間和努力基本上是浪費的?；旧希抢镏挥形覀兛捎玫?個通信手段。 它們是寫，口頭，以及圖表的形式。 因此成功的工程師將精通這3 種交際方式的能力。缺乏其中任何一個交際能力的一個技術(shù)人員就相當于嚴重殘疾。如果全部3個交際能力都缺乏的話，沒有人知道此人是多么有能力！有能力的工程師不應(yīng)該害怕推薦自己不成功的可能性。實際上，偶然的失敗應(yīng)該被期望，因為失敗或者批評好像伴隨每個真的有創(chuàng)造性的想法。 有許多都是從失敗中獲悉，巨大收獲都是從那些冒險獲得的。歸根到底，真正的失敗將在于根本不會做推薦自己。 為了有效地交流，下列問題必須被回答：(1)這設(shè)計真的能服務(wù)人需要嗎？ (2)它將與現(xiàn)有的競爭公司的產(chǎn)品競爭嗎

50、？ (3)獲益是實惠的嗎？ (4)它能被比較容易的保持嗎？ (5)它將能被出售并且贏利嗎？只有時間能提供上述問題的正確的答案，但是產(chǎn)品應(yīng)該被設(shè)計，只用最初肯定的答案生產(chǎn)并且銷售。設(shè)計工程師也必須通過使用細節(jié)和裝配圖多溝通定稿設(shè)計到生產(chǎn)。經(jīng)常，一個問題將在生產(chǎn)的循環(huán)期間產(chǎn)生。這可能是在一個部分的定尺寸或者加工過程中所要求一次交換，以便它能夠被更容易生產(chǎn)。這在被設(shè)計工程師批準的工程變化的種類方面下降，以便產(chǎn)品功能將不被相反影響。 在其他情況里，在設(shè)計過程中的一種缺陷可能在裝運之前的裝配或檢測測試期間出現(xiàn)。工程設(shè)計是一個系統(tǒng)的過程，其中的解決方案是為了滿足人類需要而得到的。進程是不同的復(fù)雜性的問題（需求）的應(yīng)用。例如，機械工程師，將利用設(shè)計過程中，以找到一個有效率的方式轉(zhuǎn)換成往復(fù)運動，在一個內(nèi)部內(nèi)燃機以圓周運動來驅(qū)動列車;電氣工程師在使用過程中，以設(shè)計電動發(fā)電機系統(tǒng)使用，水位下降為能源;材料工程師使用過程中，以設(shè)計燒蝕材料，使宇航員平安返回地球的大氣層。在今天的高科技社會,絕大多數(shù)的復(fù)雜問題賴以解決的方案不僅僅取決于單一的工程學科，而且還取決