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(文档含英文原文和中文翻译)
中英文资料外文翻译
Fundamentals Of Machinery Design
This introductory chapter is a general survey of machinery design．First it presents the definition and major role of machinery design，the relationship between machinery
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and its components．Then it gives an overview of machinery design as a fundamental course and outlines a general procedure of machinery design followed by all the engineers．Finally, it lists the contents of the course and the primary goals to be achieved．
1．1 The role of machinery design
Machinery design is to formulate all engineering plan．Engineering in essence is to utilize the existing resources and natural law to benefit humanity．As a major segment of engineerin，machinery design involves a range of disciplines in materials，mechanics，heat，flow，control，electronics and production．Although many high
technologies are computerized and automated，and are rapidly merged into Our daily life，machines are indispensable for various special work that is difficult or
impracticable to be carried out by human．Moreover，machinery can significantly improve efficiency and quality of production，which is crucial in current competitive global market．
In the modern industrialized world，the wealth and living standards of a nation are closely linked with their capabilities to design and manufacture engineering products．It can be claimed that the advancement of machinery design and manufacturing can remarkable promote the overall level of a country’s
industrialization．Those nations，who do not perform well in design and manufacture fields，are not competitive in world markets．It is evident that several countries that used to be leaders in the design and manufacturing sectors until the l 960s and the 1 970s had，by the l990s，slipped back and lost their leadership．On the contrary, our Country is rapidly picking up her position in manufacturing industry since the l 9 80s and is playing a more and more vital role in the global market．To accelerate such an industrializing process of our country, highly skilled design engineers having extensive
knowledge and expertise are needed．That is why the course of machinery design is of great significance for students of engineering．
The course of machinery design is considerable different from those background subjects in science and mathematics．For many students，it is perhaps one of their basic professional engineering courses concerned with obtaining solutions to practical problem s．Definitely these solutions must clearly represent an understanding of the underlying science，usually such an understanding may not be sufficient，empirical knowledge or engineering judgement has to be also involved．Furthermore，due to be professional nature of this subject，most design problems may not have one right solution．Nevertheless it is achievable to determine a better design from all feasible solutions．
1．2 Machinery and components
A state-of-the-art machine may encompass all or part of mechanical，electrical，control，sensor，monitoring and lubricating sub—systems．In
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terms
of the functions of those parts，the machine can also be viewed to be comprised of power，transmission，execution and control／manipulation parts．Regardless of the complexity, however，the major functional part may be still the mechanical system．For
convenience of analysis，the mechanical system can be decomposed int0．mechanisms that are designed to execute some specific tasks．And the mechanism can be further decomposed into mechanical components．In this sense，the mechanical components are the fundamental elements of machinery．
On the whole，mechanical components can be classified as universal and special components．Bolts，gear and chains are the typical examples of the universal components which can be used extensively in different machines across various
industrial sectors．Turbine blades，crankshaft and aircraft propeller are the examples of
the special components，which Can be used extensively in different machines across various industrial sectors．turbine blades，crankshaft and aircraft propeller are the examples of the special components，which are designed for some specific purposes．In addition to this，if a number of components are manufactured，assembled and even equipped as an individual system，e．g．leaf spring set
in a vehicle，it is also termed as a mechanical part．
A good machine definitely requires quality individual components．Thus，the design of components is very important．When designing a machine，on the other
hand，engineers invariably find that requirements and constraints of its components are
interrelated．As a local portion，the component is expected to play a certain role on the machine and therefore must be appropriately restrained by the whole system．The design of a gear drive in a speed—reducer，for instance，depends upon not only the strength and stiffness，but also the space available for the gears in the shaft and relation with other transmission drive．This means that the design of the mechanical components inevitably requires a whole view in the whole system．
Due to relationship between a machine and its components，the process of
machinery design usually covers interconnected designs of machine，parts，and components．Any modification and adjustment in one component may considerably affect the designs of other components or parts．To present the best possible design solution，the iteration of evaluation，analysis and optimization across all the process seem indispensable．
1．3 Overview of machinery design
This course is primarily concerned with the design of specific components of machines or mechanical systems．Competence in this area is basic to the consideration and synthesis of complete machines and systems in subsequent courses and
professional practice．It Can be seen that even the design of a single bolt or spring needs the designer’s thorough understanding of the principles and methods of
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