中英文翻译--机械工程设计-精品

Mechanical engineering design1. The meaning of designTo design is to formulate a plan for the satisfaction of human need .in the beginning the particular need to the satisfied may be quite well-defined. Here are two examples of well-defined needs.1. How can we obtain large quantities of power cleanly, safely, andeconomically without using fossil fuels and without damaging the surface of the earth2. This gear shaft is giving trouble; there have been eight failures in the lastsix weeks. Do something about it.On the other hand the particular need to be satisfied may be so nebulous and ill-defined that a considerable amount of thought and effort is necessary in order to state it clearly as a problem requiring a solution. Here are two examples.1. Lots of people are killed in airplane accidents.2. In big cities there are too many automobiles on the streets and highways.This second type of design situation is characterized by the fact that neither the need nor the problem to be solved has been identified. Note, too, that the situation may contain many problems.We can classify design too. For instance:1. Clothing design 7. Bridge design2. Interior design 8. Computer-aided design3. Highway design 9. Heating system design4. Landscape design 10. Machine design5. Building design 11. Engineering design6. Ship design 12. Process designIn fact there are an endless number, since we can classify design according to the particular article or product or according to the professional field.In contrast to scientific or mathematical problems, design problems have no unique answers; it is absurd, for example, to request the “correct answer” to a design problem, because there is none. In fact a “good” answer today may well turn out to be a “poor” answer tomorrow, if there is a growth of knowledge during the period or if there are other structure or societal changes.Almost everyone is involved with design in one way or another, even in daily living, because problems are posed and situations arise which must be solved. Consider the design of a family vacation. There may be seven different places to go, all the different distances from home. The costs of transportation are different for each, and some of the options require overnight stops on the way. The children would like to go to a lake or seashore resort. The wife would prefer to go to a large city with department store shopping, theatres, and nightclubs. The husband prefers a resort with a golf course. When these needs and desires are related to time and money, various solutions may be found. Of these there may or may not be one or more optimal solutions. But the solution chosen will include the travel route, thestops, the mode of transportation, and the names and locations of resorts, motels, camping sites, or other away-from-home facilities. It is hard to see that there is really a rather large group of interrelated complex factors involved in arriving at one of the solutions to the vacation design problem.A design is always subject to certain problem-solving constraints. For example, two of the constraints on the vacation design problem are the time and money available for the vacation. Note, too, that there are also constraints on the solution, in the case above some of those constraints are the desire and needs of each of the family members. Finally, the design solution found might well be optimal. In this case an optimal solution is obtained when each and every family member can say that he or she had a good time.A design problem is not a hypothetical problem at all. Design has an authentic purpose—the creation of an end result by taking definite acting or the creation of something having physical reality. In engineering the word “design ” conveys different meaning to different persons. Some think of a designer as one who employs the drawing board to draft the details of a gear, clutch, or other machine member. Others think of design as the creation of a complex system, such as a communications network. In some areas of engineering the word design has been replaced by other terms such as systems engineering or applied decision theory. But no matter what words are used to describe the design function, in engineering it is still the process in which scientific the principles and the tools of engineering—mathematics, computers, graphics, and English—are used to produce a plan which, when carried out, will satisfy a human need.2. The phases of designThe total design process is of interest to us, how does it begin Does the engineer simply sit down at his or her desk with a blank sheet of paper and jot down some ideas What happens next What factors influence or control the decisions, which have to be made Finally, how does this design process endThe complete process, from start to finish, is often outlined as in Figure. The process begins with a recognition of a need and a decision to do something about it, after many iterations, the process ends with the presentation of the plans for satisfying the need, we should examine these steps in the design process in detail.3. Mechanical engineering designMechanical design means the design of things and system of a mechanical nature—machines, products, structures, devices, and instruments. For the most part, mechanical design utilizes mathematics, the materials sciences, and the engineering mechanical science.Mechanical engineering design includes all mechanical design, but it is a broader study because it includes all the disciplines of mechanical engineering, such as the thermal-fluids sciences, too. Aside from the fundamental sciences that are required, the first studies in mechanical engineering design are in mechanical design, and hence this is the approach taken in this book.4. Design Process and StagesMechanical design is either to formulate all engineering plan for the satisfaction for the specified need or to solve an engineering problem. It is 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 all considers the various factors involved in the manufacture, marketing and use of product. Mechanical design involves a range of disciplines in materials, mechanics, heat, flow, control, electronics and production.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 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 must be done with the utmost care and precision. For example, if a decimal point is misplaced, an otherwise acceptable design may not function.Mechanical design may be simple or enormously complex, easy or difficult, mathematical or nonmathematical, it may involve a trivial problem or one of great importance. Good design is the orderly and interesting arrangement of all idea to provide certain results and effects. A well-designed product is functional, efficient, and dependable. Such a product is less expensive than a similar poorly designed product that does not function properly and must constantly be repaired.People who perform the various functions of mechanical design are typically called designers, or 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, dynamics, materials engineering, manufacturing processes. The designer must first carefully define the problem, using an engineering approach, to ensure that any proposed solution will solve the right problem. It is important that the designer begin by identifying exactly how he or she will recognize a satisfactory alternative, and how to distinguish between two satisfactory alternatives in order to identify the better. So industrial designers must have creative imagination, knowledge of engineering, production techniques, tools, machines, and materials to design a new product for manufacture, or to improve an existing product.In the modern industrialized world, the wealth and living standards of a nation are closely linked with their capabilities design and manufacturing engineering products. It can be claimed that the advancement of mechanical design and manufacturing can remarkably promote the overall level of a country’s industrialization. Many countries are playing more and more vital role in the global manufacturing industry. To accelerate such an industrializing process, highly skilled design engineers having extensive knowledge and expertise are needed.5. Mechanical design processProduct design requires much research and development. Many concept of an idea must be studied, tried, refined, and then either used or discarded. Although the content of each engineering problem is unique, the designers follow the similar process to solve the problems. The complete process is often outlined as in figures. The design process usually begins with a specification of a solution. We sometimes allude to a design cycle, but the process may contain a design cycle plus design implementation, which involves actual production based upon the design. The design cycle can involve the original thoughts, sketches, and knowledge that in the specification stage produce engineering drawings. Computer-aid design is now employed to implement a cycle in which various designs or design ideas may be tested or simulated.6. Contents of Mechanical DesignMechanical design is an important technological basic course in mechanical engineering education. Its objective is to provide the concepts, procedures, data, and decision analysis techniques necessary to design machine elements commonly found in mechanical devices and systems; to develop engineering students’ competence of mechanical design that is the primary concern of machinery manufacturing and the key to manufacturing good products.Mechanical design covers the following contents:1．Provides an introduction to the design process, problem formulation, safetyfactors.2．Reviews the material properties and static and dynamic loading analysis,including beam, vibration and impact loading.3．Reviews the fundamentals of stress and defection analysis.4．Introduces static failure theories and fracture-mechanics analysis for staticloads.5．Introduces fatigue-failure theory with the emphasis on stress-lifeapproaches to high-cycle fatigue design, which is commonly used in thedesign of rotation machinery.6．Discusses thoroughly the phenomena of wear mechanisms, surface contactstress, and surface fatigue.7．Investigates shaft design using the fatigue-analysis techniques.8．Discusses fluid-film and rolling-element bearing theory and application.9．Gives a thorough introduction to the kinematics, design and stressanalysis of spur gears, and a simple introduction to helical, bevel, and wormgearing.10．Discusses spring design including helical compression, extension, andtorsion springs.11．Deals with screws and fasteners including power screw and preloadfasteners.12．Introduces the design and specification of disk and drum clutches andbrakes.机械工程设计1. 设计的意义设计是制定一项计划，以便满足人类的需要。