JDC01-004@MATLAB在工程控制基础课程教学中的应用研究
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JDC01-004@MATLAB在工程控制基础课程教学中的应用研究,机械毕业设计全套
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外文翻译Introduction to Machine Design and Fundamentals of Mechanical DesignDefinition 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. We can regard the thing to be designed as something in a black box. 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 the reliability. 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 its size, shape and construction details, but also considers the various factors involved in the manufacture, marketing and use of the product, or reducing the quantity of irritants from automotive exhausts. 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 solid 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 wills a benefit be derived. It should be recognized, therefore, that a human need must be identified before a particular product is designed.Machine 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 fundamentals 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 calculations made must be done with the utmost care and precision. For example, if a decimal point is misplaced, an otherwise acceptable design may not function.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 new, 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 constrains. 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 tolerance 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. In other case, 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 it and the designer should constantly strive towards finding that better way.Mechanical design means the design of things 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 toes it begin? Does the engineering simply sit down at his desk with a blank sheet of paper? And, as he jobs down and some ideas, what happen 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, of 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 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 problems are more specific. If the need is for cleaner air, the problem might be that of reducing the dust discharge from power-plant stacksThese are many implied specifications which result either from the designers 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 designers 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 models of the system which will admit some form of mathematical analysis. We call these models. In creating them it is our hope that we can find one which will simulate the real 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 needs. Is it reliable? Will it compete successfully with similar products? Is it economical to manufacture and to use? Is it easily maintained and adjusted? Can a profit be made from its sale or use?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 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 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 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, and no 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 of criticism seems to accompany every really creative idea. There is a great deal to be learned 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. 机械设计概论与基础机械设计是一门通过设计新产品或者改进老产品来满足人类需要的应用技术科学。它是一个广阔的工程技术领域，不仅要研究产品在尺寸、形状和详细结构等方面的基本构思，还要考虑产品在制造、销售和使用等方面的有关问题。进行各种机械设计工作的人员通常被称为设计人员或者设计工程师。机械设计是一项创造性的工作。设计工程师不仅在工作上要有创新性，还必须在机械制图、运动学、动力学、工程材料、材料力学和机械制造工艺等方面具有深厚的基础知识。如前面所述，机械设计的目的是生产能够满足人类需求的产品。发明、发现和科学知识本身并不一定能给人类带来益处，只有当它们被用在产品上才能产生效益。因而，应该认识到在一个特定产品进行设计之前，必须先确定人们是否需要这种产品。应当把机械设计看成是机械设计人员运用创造性的才能进行产品设计、系统分析和制订产品的制造工艺的一个良机。掌握工程基础知识要比熟记一些数据和公式更为重要。仅仅使用数据和公式是不足以在一个好的设计中做出所需的全部决定。另一方面，应该认真精确地进行所有运算。例如，即使将一个小数点的位置放错，也会使正确的设计变成错误的。一个好的设计人员应该勇于提出新的想法，而且愿意承担一定的风险，当新的方法不适用时，就恢复采用原来的方法。因此，设计人员必须要有耐心，因为所花费的时间和努力并不能保证带来成功。一个全新的设计，要求摒弃许多陈旧的，为人们所熟知的方法。由于许多人墨守成规，这样做并不是一件容易的事情。一位设计工程师应该不断地探索改进现有产品的方法，在此过程中应该认真择原有的、经过验证的设计原理，将其与未经过验证的新观念结合起来。新设计本身会有许多缺陷和未能预料的问题发生，只有当这些缺陷和问题被解决之后，才能体现出新产品的优越性。因此，一个性能优越的产品诞生的同时，也伴随着较高的风险。应该强调的是，如果设计本身不要求采用全新的方法，就没有必要仅仅为了变革的目的而采用新方法。在设计的初始阶段，应该允许设计人员充分发挥创造性，不受各种约束。即使产生了许多不切合实际的想法，也会在设计的早期，即绘制生产图纸之前被改正掉。只有这样，才不至于堵塞创新的思路。通常要提出几套设计方案，然后加以比较。很有可能在最后选定的方案中，采用了某些未被接受的方案中的一些想法。心理学家经常谈论如何使人们适应他们所操作的机器。设计人员的基本职责是努力使机器来适应人们。这并不是一项容易的工作，因为实际上并不存在着一个对所有人来说都是最优的操作范围和操作过程。另一个应该被认识到的重要问题是，设计工程师必须能够同其他有关人员进行交流和沟通。在开始阶段，设计人员必须就初步设计同管理人员进行交流和沟通，并得到批准。这一般是通过口头讨论，草图和文字材料进行的。为了有效地进行交流，需要解决下列问题：（1） 所要设计的这个产品是否真正为人们所需要？（2） 此产品与其他公司的现有同类产品相比有无竞争能力？（3） 生产这种产品是否经济？（4） 产品的维修是否方便？（5） 产品有无销路？是否可以盈利？只有时间才能对上述问题给出正确的答案。但是，产品的设计、制造和销售只能在对上述问题的初步肯定答案的基础上进行。设计工程师还应该通过零件图和装配图，在制造部门一起对最终设计方案进行沟通。通常，在制造过程中会出现某个问题。可能会要求对某个零件尺寸或公差作一些更改，使零件的生产变得容易。但是，工程上的更改必须要经过设计人员的批准，以保证不会损伤产品的功能。有时，在产品的装配时或者装箱外运前的试验中才发现设计中的某种缺陷。这些事例恰好说明了设计是一个动态过程。总是存在着更好的方法来完成设计工作，设计人员应该不断努力，寻找这些更好的方法。机械设计是指机械装置和机械系统机器、产品、结构、设备和仪器的设计。大部分机械设计需要利用数学、材料科学和工程力学。我们对整个设计过程感兴趣。它是怎样开始的？工程师是不是仅仅坐在铺着白纸的桌旁就可以开始设计了呢？当他记下一些设想后，下一步该做些什么？什么因素会影响或者控制着应该做出的决定？最后，这一设计过程是如何结束的呢？有时，虽然并不总是如此，工程师认识到一个需要并且决定对此做一些工作时，设计就开始了。认识到这各需要，并用语言将其清楚地叙述出来，常常是一种高度创造性的工作。因为这种需要可能是一个模糊的不满，一种
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