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Introduction to Mechanical EngineeringMechanical engineering is the branch of engineering that deals with machines and the production of power. It is particularly concerned with forces and motion.History of Mechanical EngineeringThe invention of the steam engine in the latter part of the 18th century, providing a key source of power for the Industrial Revolution, gave an enormous impetus to the development of machinery of all types. As a result a new major classification of engineering, separate from civil engineering and dealing with tools and machines, developed, receiving formal recognition in 1847 in the founding of the Institution of Mechanical Engineers in Birmingham, England.Mechanical engineering has evolved from the practice by the mechanic of an art based largely on trial and error to the application by the professional engineer of the scientific method in research, design, and production.The demand for increased efficiency, in the widest sense, is continually raising the quality of work expected from a mechanical engineer and requiring of him a higher degree of education and training. Not only must machines run more economically but capital costs also must be minimized.Fields of Mechanical EngineeringDevelopment of machines for the production of goods The high material standard of living in the developed countries owes much to the machinery made possible by mechanical engineering. The mechanical engineer continually invents machines to produce goods and develops machine tools of increasing accuracy and complexity to build the machines.The principal lines of development of machinery have been an increase in the speed of operation to obtain high rates of production, improvement in accuracy to obtain quality and economy in the product, and minimization of operating costs. These three requirements have led to the evolution of complex control systems.The most successful production machinery is that in which the mechanical design of the machine is closely integrated with the control system, whether the latter is mechanical or electrical in nature. A modern transfer line (conveyor) for the manufacture of automobile engines is a good example of the mechanization of a complex series of manufacturing processes. Developments are in hand to automate production machinery further, using computers to store and process the vast amount of data required for manufacturing a variety of components with a small number of versatile machine tools. One aim is a completely automated machine shop for batch production, operation on a three-shift basis but attended by a staff for only one shift per day.Development of machines for the production of power Production machinery presupposes an ample supply of power. The steam engine provided the first practical means of generating power from heat to augment the old sources of power from muscle, wind, and water. One of the first challenges to the new profession of mechanical engineering was to the steam turbine and associated large steam boilers. The 20th century has witnessed a continued rapid growth in the power output of turbines for driving electric generators, together with a steady increase in thermal efficiency and reduction in capital cost per kilowatt of large power stations. Finally, mechanical engineers acquired the resource of nuclear energy, whose application has demanded an exceptional standard of reliability and safety involving the solution of entirely new problems. The control systems of large power plants and complete nuclear power stations have become highly sophisticated networks of electronic, fluidic, electric, hydraulic, and mechanical components, all of these involving the province of the mechanical engineer.The mechanical engineer is also responsible for the much smaller internal combustion engines, both reciprocating (gasoline and diesel) and rotary (gas-turbine and Wankel) engines, with their widespread transport applications. In the transportation field generally, in air and space as well as on land and sea, the mechanical engineer has created the equipment and the power plant, collaborating increasingly with the electrical engineer, especially in the development of suitable control systems.Development of military weapons The skills applied to war by the mechanical engineer are similar to those required in civilian applications, though the purpose is to enhance destructive power rather than to raise creative efficiency. The demands of war have channeled huge resources into technical fields, however, and led to developments that have profound benefits in peace. Jet aircraft and nuclear reactors are notable examples.Bioengineering Bioengineering is a reactively new and distinct field of mechanical engineering that includes the provision of machines to replace or augment the functions of the human body and of equipment for use in medical treatment. Artificial limbs have been developed incorporating such lifelike functions as powered motion and touch feedback. Development is rapid in the direction of artificial spare-part surgery. Sophisticated heart-lung machines and similar equipment permit operations of increasing complexity and permit the vital functions in seriously injured or diseased patients to be maintained.Environmental control Some of the earliest efforts of mechanical engineers were aimed at controlling mans environment by pumping water to drain or irrigate land and by ventilating mines. The ubiquitous refrigerating and air-condition plants of the modern age are based on a reversed heat engine, where the supply of power “pumps” heat from the cold region to the warmer exterior.Many of the products of mechanical engineering, together with technological developments in other fields, have side effects on the environment and give rise to noise, the pollution of water and air, and the dereliction of land and scenery. The rate of production, both of goods and power, is rising so rapidly that regeneration by natural forces can no longer keep pace. A rapidly growing field for mechanical and other is environmental control, comprising the development of machines and processed that will produce fewer pollutants and of new equipment and techniques that can reduce or remove the pollution already generated.Functions of Mechanical EngineeringFour functions of the mechanical engineering, common to all the fields mentioned, be cited. The first is the understanding of and dealing with the bases of mechanical science. These include dynamics, concerning the relation between forces and motion, such as in vibration; automatic control; thermodynamics, dealing with the relations among the various forms of heat, energy, and power; fluid flow; heat transfer; lubrication; and properties of materials. Second is the sequence of research, design, and development. This function attempts to bring about the changes necessary to meet present and future needs. Such work requires not only a clear understanding of mechanical science and an ability to analyze a complex system into its basic factors, but also the originality to synthesize and invent.Third is production of products and power, which embraces planning, operation, and maintenance. The goal is to produce the maximum value with the minimum investment and cost while maintaining or enhancing longer term viability and reputation of the enterprise or the institution. Fourth is the coordinating functions of the mechanical engineering, including management, consulting, and, in some cases, marketing.In all of these functions there is a long continuing trend toward the use of scientific instead of traditional or intuitive methods, an aspect of the ever-growing professionalism of mechanical engineering. Operations research, value engineering, and PABLA (problem analysis by logical approach) are typical titles of such new rationalized approaches. Creativity, however, cannot be rationalized. The ability to take the important and unexpected step that opens up new solutions remains in mechanical engineering, as elsewhere, largely a personal and spontaneous characteristic.The Future of Mechanical EngineeringThe number of mechanical engineers continues to grow as rapidly as ever, while the duration and quality of their training increases. There is a growing awareness, however, among engineers and in the community at large that the exponential increase in population and living standards is raising formidable problems in pollution of the environment and the exhaustion of natural resources; this clearly heightens the need for all of the technical professions to consider the long-term social effects of discoveries and developments. There will be an increasing demand for mechanical engineering skills to provide for mans needs while reducing to a minimum the consumption of scarce raw materials and maintaining a satisfactory environment.Mechanical engineering in the information age In the early 1980s, engineers thought that massive would be needed to speedup product development. As it turn out ,less research is actually needed because shortened product development cycles encourage engineers to sue available technology .developing a revolutionary for use in a new product is risky and prone to failure. Taking short steps is a safer and usually more successful to product development. Shorter product development cycles are also beneficial in engineering world in which both capital and labor are global. People who can design and manufacture various products can be found anywhere in the world, but containing a new idea is hard. Geographic distance is no longer a barrier to others finding out about your development six months into the process. If youve got a short development cycle, the situation is not catastrophic as long as you maintain your lead. But if youre in the midst of a six-year development process and a competitor gets wind of your work, the project could be in more serious trouble. The idea that engineers need to create a new design to solve every problem is quickly becoming obsolete. The first step in the modern design process is to browse the Internet or other information systems to see if someone else has already designed a transmission, or a heat exchanger than is close to what you need. Through these information systems, you may discover that someone already has manufacturing drawing, numerical control tapes, and every else required to manufacture your product. Engineer can then focus their professional competence unsolved problems. In tackling such problem, the availability of workstations and access to the information highway dramatically enhance the capability of the engineering team and its productivity. These information age tools can give the team access to massive databases of material properties, standards, technologies, and successful design. Such protested designs can be downloaded for direct use or quickly modified to meet specific needs. Remote manufacturing, in which product instructions are sent out over a network, is also possible. You could end up with a virtual company where you dont have to see any hardware. When the product is completed, you can direct the manufacturer to drop-ship it to your customer. Periodic visit to the customer can be made to ensure that the product you designed is working according to the specifications.Although all of these developments wont apply equally to every company, the potential is there. Custom design used to be left to small companies. Big companies sneered at it they hated the idea of dealing with niche markets or small-volume custom solutions. “Here is my product,” one of big companies would say “This is best we make it you ought to like it .If you dont, theres a smaller company down the street that will work on your problem.” Today, nearly every market is a niche market, because customers are selective. If you ignore the potential for tailoring your product to specific customers needs, you will lose the major part of your market share perhaps all of it. Since these niche markets are transient, you company need to be in a position to respond to them quickly .The emergence of niche markets and design on demand has altered the way engineers conduct research. Today, research is commonly directed toward solving particular problem. Although this situation is probably temporary, much uncommitted technology, developed at government expense or written off by major corporations, is available today at every low cost .Following modest modification, such technology can often be used directly in product development, which allows many organizations to avoid the expense of an extensive research effort. Once the technology is free or major obstacles, the research effort can focus on overcoming the barriers to commercialization rather than on pursuing new and interesting, but undefined, alternatives. When viewed in this perspective, engineering research must focus primarily on removing the barriers to rapid commercialization of known technologies. Much of this effort must address quality and reliability concerns. Which are foremost in the mind of todays consume. Clearly, a reputation for poor quality is synonymous with bad business. Everything possible including through inspection at the end of the manufacturing line and automatic replacement of defective products-must be done to assure that the customer receives a properly functioning product. Research has to focus on the cost benefit of factors such as reliability.As reliability increase, manufacturing costs and the system will decrease. Having 30 percent junk at the end of a production line not only costs a fortune but also create an opportunity for a competitor to take your idea and sell it to your customers. Central to the process of improving reliability and lowering costs is intensive and widespread use of design software, which allows engineers to speed up every stage of the design process. Shortening each stage, however, may not sufficiently reduce the time required for entire process. Therefore, attention must also be devoted to concurrent engineering software with shared databases that can be accessed by all members of the design team. As we move more fully into the Information Age, success will require that the engineer possess some unique known of and experience in both the development and the management of technology .Success will required broad knowledge and skills as well as expertise in some key technologies and disciplines; it will also require a keen awareness of the social and economic factor at work in the marketplace. Increasingly , in the future routine problem will not justify heavy engineering expenditures, and engineers will be expected to work cooperatively in solving more challenging, more demanding problem in substantially less time .We have begun a new phase in the practice of engineering . It offers great promise and excitement as more and more problemsolving capability is placed in the hands of the computerized and wired engineers .To assure success , the capability of our tools and the unquenched thirst for better products and system must be matched by the joy of creation that marks all great engineering endeavors . Mechanical engineering is a great profession, and it will become even greater as we make the most of the opportunities offered by the Information Age.机械工程简介机械工程是工程学的一个分支，它研究机械和动力的产生，尤其是力和运动。机械工程的历史18世纪后期，蒸汽机的发明为工业革命提供了一个主要的动力源泉，极大地推动了各种机械的发展。这样，一个新的工程学的重要分支从民用工程学中分离出来的关于工具和机械的分支发展了起来。并随着英国伯明翰机械工程师协会的建立在1847年得到了正式承认。机械工程已经由一门主要基于试错法的技工应用的技艺发展成为职业工程师在研究、设计和生产领域使用的科学方法。从最广义的角度讲，增进效率的需求不断地促使机械工程师提高工作质量，并要求他接受更高程度的教育和训练。不仅机器运转要讲求经济，而且基建费也要降到最低。机械工程的领域商品机械的发展 在发达国家中，高水平的物质生活很大程度上取决于机械工程中得以实现的各种机械。机械工程师们不断地发明机器来生产商品，不断地开发精确性和复杂性越来越高的机械工具来生产机器。机械发展的主要线索是：为提高生产率而增加机器的运转速度、为获得物美价廉的产品而提高精度以及降低生产成本。这3个要求促进了复杂的控制系统的发展。最成功的机械制造是其机器的机械设计能与控制系统紧密融合，不论这种控制系统从本质上是机械的还是电子的。现代化的汽车发动机生产传送线（传送带）就是一系列复杂的生产工艺机械化的很好例子。人们正在着手开发以使机械生效后进一步自动化，利用计算机来存储和处理大量数据，这些数据是少量多功能机床生产多种零件所必需的。其中一个目标就是使批量生产车间完全自动化，三班轮换，但每天只需一班人员来操作。动力机械的发展 生产机械必须先有充足的动力供应。蒸汽机最先提供了用热能来产生动力的实际可行的方法，在旧有的人力、风力和水力之外增加了动力源。新的机械工程业面临的最初挑战之一就是增加热效率和动力，这一点随着蒸汽涡轮机和大的联合蒸汽锅炉的发展而基本实现了。20世纪，涡轮机为发电机提供的动力得到了持续快速的增长，同时热效率也在稳定增长，而且大电站每千瓦的资本消耗也在下降。最后，机械工程师们获得了核能源。这种核能源的应用需要有特别高的可靠性和安全性，这就需要解决许多全新的问题。大型电厂和整个核电站的控制系统已变成高度复杂的电子、流体、电、水力和机械零件的网络，这一切都涉及到机械工程师的所有学术领域。小型的内燃机，不论是往复式（汽油机和柴油机）还是旋转式（燃气轮机和旺克尔机），以及它们在运输领域的广泛应用也都要归功于机械工程师们。在整个运输业，不论是在空中和太空，还是在陆地和海洋，机械工程师创造了各种设备和动力装置。他们越来越多地与电气工程师合作，尤其是在开发适合的控制系统方面。军用武器的开发 机械工程师应用于战争的技术与民用中需要的类似，尽管其目的是增强毁坏力而不是提高生产率。喷气式飞机和核反应堆就是众所周知的例子。生物工程 生物工程是机械工程中一个相对新的和与众不同的领域，它提供用来替换或增加人体功能的机器以及用来进行医疗的设备。人造肢体已被开发出来，并且具有诸如有力的运动和触摸反应等人体功能。在人工器官移植手术方面的发展是迅速的，复杂的心肺机器和类似的设备使越来越复杂的手术得以进行，并使受重伤和重病病人的生命功能得以持续。环境控制 机械工程师的一些最初的努力是要通过抽水来排涝或灌溉土地以及给矿井通风来控制人类的环境。现代的制冷和空调厂普遍采用反向的热引擎，在这些地方动力把热从冷的地方抽出送到更热的外部。很多机械工程的产品以及其他领域的技术发展对环境有副作用，产生了噪音，引起了水和空气的污染，破坏了土地和风景。商品和动力的生产率提高太快，以致于自然力的再生跟不上步伐。对于机械工程师和他人来说，环境控制是一个快速发展的领域，它包括开发尽可能产生少量污染物的机器和生产工序，以及开发新的设备和技术来减少和消除已造成的污染。机械工程的作用机械工程师有四个通用于上述所有领域的作用。第1个作用是理解和研究机械科学的基础。它包括涉及力和运动的关系的动力学，比如在振动中的力和运动的关系；自动控制；研究各种形式的热、能量、动力之间关系的热力学；流体流动；热传递；润滑；和材料特性。第2个作用是依次地进行研究、设计和开发。该作用试图进行必要的改变以满足当前和将来的需要。这一工作不仅要求对机械科学有一个合成和发明。第3个作用是生产产品和动力，包括计划、运作和维护。其目的在于维护或提高企业或机构的较长期的和生存能力声誉的同时，以最少的投资和消耗生产出最大的价值。第4个作用是机械工程师的协调作用，包括管理、咨询、以及在某些情况下进行市场营销。 在所有这些作用中，体现出一种长期不断地使用科学的方法，而不是传统的或直觉的方法的倾向，这是不断成长的机械工程专门技术的一个方面。这些新的合理化方法的典型名称有：运筹学、工程经济学、逻辑学问题分析（简称PABLA）。然而，创造性是无法合理化的。正如在其他领域一样，在机械工程中，能够采取重要的出人意料的并能开创出新方法的能力，仍然具有个人的、即兴的特点。机械工程的未来 机械工程师的数量依旧快速增长，同时他们所受训练的时间也在延长并且质量也在提高。然而，工程师们和全体公众越来越意识到，人口和生活水平的指数增长正在造成可怕的环境污染和自然资源消耗问题。这更清楚地表明，所有的技术职业都有必要考虑开发和发展的长期社会效益。人们越来越需要机械工程技术来满足人类的需求，同时也需要将稀有的原材料的消耗降到最低，保持一个令人满意的环境。信息时代的机械工程 在20世纪80年代初期，工程师门曾经认为要加快产品的研制看法，必须进行大量的研究工作。结果是实际上只进行了较少的研究工作，这是因为产品开发周期的缩短，促
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