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1、-Mechanical DesignJohn ErnstAbstract：A machine is a combination of mechanisms and other components which transforms transmits. Examples are engines, turbines, vehicles, hoists, printing presses, washing machines, and movie cameras. Many of the principles and methods of design that apply to machines
2、also apply to manufactured articles that are not true machines. The term mechanical design is used in a broader sense than machine design to include their design. The motion and structural aspects and the provisions for retention and enclosure are considerations in mechanical design. Applications oc
3、cur in the field of mechanical engineering, and in other engineering fields as well, all of which require mechanical devices, such as switches, cams, valves, vessels, and mixers.Keywords: Mechanical Design； Mechanisms Design Process；Application 1. The Design ProgressDesigning starts with a need real
4、. Existing apparatus may need improvements in durability, efficiency, weight, speed, or cost. New apparatus may be needed to perform a function previouslyDone by men, such as computation, assembly, or servicing. With the objective wholly or partlyIn the design preliminary stage, should allow to desi
5、gn the personnel fully to display the creativity, not each kind of restraint. Even if has had many impractical ideas, also can in the design early time, namely in front of the plan blueprint is corrected. Only then, only then does not send to stops up the innovation the mentality. Usually, must prop
6、ose several sets of design proposals, and then perform the comparison. Has the possibility very much in the plan which finally designated, has used certain not in plan some ideas which accepts.When the general shape and a few dimensions of the several components become apparent, analysis can begin i
7、n earnest. The analysis will have as its objective satisfactory or superior performance, plus safety and durability with minimum weight, and a competitive cost. Optimum proportions and dimensions will be sought for each critically loaded section, together with a balance between the strengths of the
8、several components. Materials and their treatment will be chosen. These important objectives can be attained only by analysis based upon the principles of mechanics, such as those of static for reaction forces and for the optimum utilization of friction; of dynamics for inertia, acceleration, and en
9、ergy; of elasticity and strength of materials for stress and deflection; of physical behavior of materials; and of fluid mechanics for lubrication and hydrodynamic drives. The analyses may be made by the same engineer who conceived the arrangement of mechanisms, or, in a large company, they may be m
10、ade by a separate analysis division or research group. Design is a reiterative and cooperative process, whether done formally or informally, and the analyst can contribute to phases other than his own. Product design requires much research and development. Many Concepts of an idea must be studied, t
11、ried, 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. Product liability suits designers and forced in material selection, using the best program. In the process of material, the most common
12、 problems for five (a) dont understand or not use about the latest application materials to the best information, (b) failed to foresee and consider the reasonable use material may (such as possible, designers should further forecast and consider due to improper use products. In recent years, many p
13、roducts liability in litigation, the use of products and hurt the plaintiff accused manufacturer, and won the decision), (c) of the materials used all or some of the data, data, especially when the uncertainty long-term performance data is so, (d) quality control method is not suitable and unproven,
14、 (e) by some completely incompetent persons choose materials.Through to the above five questions analysis, may obtain these questions is does not have the sufficient reason existence the conclusion. May for avoid these questions to these questions research analyses the appearance indicating the dire
15、ction. Although uses the best choice of material method not to be able to avoid having the product responsibility lawsuit, designs the personnel and the industry carries on the choice of material according to the suitable procedure, may greatly reduce the lawsuit the quantity. May see from the above
16、 discussion, the choice material people should to the material nature, the characteristic and the processing method have comprehensive and the basic understanding. Finally, a design based upon function, and a prototype may be built. If its tests are satisfactory, the initial design will undergo cert
17、ain modifications that enable it to be manufactured in quantity at a lower cost. During subsequent years of manufacture and service, the design is likely to undergo changes as new ideas are conceived or as further analyses based upon tests and experience indicate alterations. Sales appeal.2. Some Ru
18、les for DesignIn this section it is suggested that, applied with a creative attitude, analyses can lead to important improvements and to the conception and perfection of alternate, perhaps more functional, economical, and durable products. To stimulate creative thought, the following rules are sugge
19、sted for the designer and analyst. The first six rules are particularly applicable for the analyst.（1）A creative use of need of physical properties and control process.(2）Recognize functional loads and their significance.(3) Anticipate unintentional loads.(4) Devise more favorable loading conditions
20、.(5) Provide for favorable stress distribution and stiffness with minimum weight.(6) Use basic equations to proportion and optimize dimensions.（7）Choose materials for a combination of properties.（8）Select carefully, stock and integral components.（9）Modify a functional design to fit the manufacturing
21、 process and reduce cost.（10）Provide for accurate location and noninterference of parts in assembly.Machinery design covers the following contents.(1).Provides an introduction to the design process, problem formulation, and safety factors.(2).Reviews the material properties and static and dynamic lo
22、ading analysis, Including beam, vibration and impact loading.(3) Reviews the fundamentals of stress and defection analysis.(4)Introduces fatigue-failure theory with the emphasis on stress-life approaches to high-cycle fatigue design, which is commonly used in the design of rotation machinery.(5) Dis
23、cusses thoroughly the phenomena of wear mechanisms, surface contact stresses, and surface fatigue.(6) Investigates shaft design using the fatigue-analysis techniques.(7) Discusses fluid-film and rolling-element bearing theory and application(8) Gives a thorough introduction to the kinematics, design
24、 and stress analysis of spur gears, and a simple introduction to helical, bevel, and worm gearing.(9) Discusses spring design including compression, extension and torsion springs.(10) Deals with screws and fasteners including power screw and preload fasteners.(11) Introduces the design and specifica
25、tion of disk and drum clutches and brakes.The complete design of a machine is a complex process. The machine design is a creative work. Project engineer not only must have the creativity in the work, but also must in aspect and so on mechanical drawing, kinematics, engineering material, materials me
26、chanics and machine manufacture technology has the deep elementary knowledge.One of the first steps in the design of any product is to select the material from which each part is to be made. Numerous materials are available to todays designers. The function of the product, its appearance, the cost o
27、f the material, and the cost of fabrication are important in making a selection. A careful evaluation of the properties of a. material must be made prior to any calculations.Careful calculations are necessary to ensure the validity of a design. In case of any part failures, it is desirable to know w
28、hat was done in originally designing the defective components. The checking of calculations (and drawing dimensions) is of utmost importance. The misplacement of one decimal point can ruin an otherwise acceptable project. All aspects of design work should be checked and rechecked. The computer is a
29、tool helpful to mechanical designers to lighten tedious calculations, and provide extended analysis of available data. Interactive systems, based on computer capabilities, have made possible the concepts of computer aided design (CAD) and computer-aided manufacturing (CAM). How does the psychologist
30、 frequently discuss causes the machine which the people adapts them to operate. A design personnels basic responsibility is diligently causes the machine to adapt the people. This certainly is not an easy work, because certainly does not have to all people to say in fact all is the most superior ope
31、rating area and the operating process. Another important question, project engineer must be able to carry on the exchange and the consultation with other concerned personnel. In the initial stage, designs the personnel to have to carry on the exchange and the consultation on the preliminary design w
32、ith the administrative personnel, and is approved. This generally is through the oral discussion, the schematic diagram and the writing material carries on. If front sues, the machine design goal is the production can meet the human need the product. The invention, the discovery and technical knowle
33、dge itself certainly not necessarily can bring the advantage to the humanity, only has when they are applied can produce on the product the benefit. Thus, should realize to carries on before the design in a specific product, must first determine whether the people do need this kind of productMust re
34、gard as the machine design is the machine design personnel carries on using creative ability the product design, the system analysis and a formulation product manufacture technology good opportunity. Grasps the project elementary knowledge to have to memorize some data and the formula is more import
35、ant than. The merely service data and the formula is insufficient to the completely decision which makes in a good design needs. On the other hand, should be earnest precisely carries on all operations. For example, even if places wrong a decimal point position, also can cause the correct design to
36、turn wrongly.Good design personnel should dare to propose the new idea moreover is willing to undertake the certain risk, when the new method is not suitable, use original method. Therefore, designs the personnel to have to have to have the patience, because spends the time and the endeavor certainl
37、y cannot guarantee brings successfully. A brand-new design, the request screen abandons absolutely many, knows very well the method for the people. Because many person of conservativeness does this certainly is not an easy matter. A mechanical designer should unceasingly explore the improvement exis
38、ting product the method, should earnestly choose originally, the process confirmation principle of design in this process, with has not unified it after the confirmation new idea.Human life can not be separated from the machinery, it is everywhere, but for the mechanical manufacturing, production, a
39、nd its development and future, we know little about. After this semester, I have more knowledge and understanding of the profession of the mechanical.From the primitive society of early human use such as axes, knives and other simple tools, to a simple lever, pulley, human bicycles, animal-Kip Shum
40、car tools, developed to a more complex hydraulic drive, wind-driven Shuinian and windmills morecomplex machinery. After the 18th century British Industrial Revolution, the steam engine, internal combustion engines, electric motors, mechanical power source for the rapid development of manufacturing,
41、transport, human beings began to enter the modern civilized society. The 20th century, the computer issuing automatic control technology, information technology, infectious organic combination of technology, so that the machinery is fully modernized phase. Robotics, CNC machine tools, high-speed del
42、ivery vehicles, heavy machinery and the large number of advanced machinery and equipment to accelerate the prosperity and progress of human society, humans can travel into space, landing on the moon, you can explore the vast depths of the sea, to live and pass below the surface all of which can not
43、be separated from the machinery, the development of the machinery into the intelligent stage. Machinery has become one of the five elements of production and services of modern society. The history of the development of the mechanical history of the development of human civilization. In ancient Chin
44、ese mechanical engineering, invention and creativity is very brilliant, such as grinding technology, metal smelting technology. Chinas machinery manufacturing industry developed after 1949. After the founding of new China, the tremendous achievements of Chinas economy are inseparable from the progre
45、ss of the manufacturing sector. After decades of struggle, Chinas manufacturing components with considerable scale and level of manufacturing systems, today China have become a remarkable manufacturing country. Machinery manufacturing industry overall scale of production is constantly increasing, ma
46、chinery manufacturing is more than 100 industry, 8.57 million enterprises (large enterprises accounted for 1%) and 60,000 kinds of products a complete range of industrial system. For six consecutive years in Chinas largest export commodity status, the machinery industry production capacity is 2600 t
47、imes that of the liberation of the world 5, the machine has a world, vehicle production in the world 4. But we still need to clearly recognize that China is a big manufacturing country, far from being a manufacturing powerhouse. The overall size of the added value of product technology and per capit
48、a labor efficiency is far better than the United States, Japan and other manufacturing power. Therefore, the task of development of Chinas manufacturing industry a long way to go. With the diversification of the high-tech development and social needs of the industrial production rapidly toward large
49、-scale, integrated and complex, so that the modern industrial machinery industry is facing new opportunities and challenges, and more emphasis on the creativity and the efficiency of the workers. Therefore need to continuously enhance the level of Chinas Mechanical Design Manufacturing and Automation, thereby contributing to the development of Chinas machinery manufacturing industry.-