1、1TECHNICAL ENGLISHMECHANICAL ENGINEERING2 Introduction to Mechanical Design39 Introduction to Mechanical DesignBug：A defect in a system or designDeficiency：The quality or condition of being deficient,incompleteness or inadequacyConstraint：One that restricts,limits,or regulates缺陷，瑕疵：系统或设计中的缺陷。约束：限定、限
2、制或制约性的事物。缺点，缺陷：不完善的性质或状况；不完整或不充足。49 Introduction to Mechanical Design Mechanical 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 origi
3、nal 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.59 Introduction to Mechanical Design Mechanical design is the application of science and technology to devise new or i
4、mproved 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,ma
5、rketing and use of the product.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求的应用技术科学和技术。它涉及工程技术的各个领域，主要研究产品的尺寸、形状和详细结构的基本构思，还要研究产品在制造、销售和使用等方面的问题。6 9 Introduction to Mechanical Design Mechanical design should be considered to be an opportunity to use innovative talents to envision a design of a product,to analyze the
6、 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
7、a good design.7 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 th
8、an 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.9 Introduction to Mechanical Design应当把机械设计看成是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
9、决定。8 During the beginning stages of design,creativity should be allowed to flourish without a great number of constraints.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,inno
10、vative ideas are not inhibited.Quite often,more than one design is developed,up to the point where they can be compared against each other.9 Introduction to Mechanical Design9 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。9 Introduction to
11、 Mechanical Design During the beginning stages of design,creativity should be allowed to flourish without a great number of constraints.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
12、 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.10 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
13、 incorporated.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.9 Introduction to M
14、echanical Design11 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.Communicating the design to others is the final,vital step in the design process.Undoubtedly many great designs,inventions,
15、and creative works have been lost to mankind simply because the originators were unable or unwilling to explain their accomplishments to others.9 Introduction to Mechanical Design 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。与其他人就设计方案进行交流和沟通是设计过程的最后和关键阶段。毫无疑问，有许多伟大的设计、发明或创造之所以没有为人类所利用，就是因为创造者不善于或者不愿意向其他人
16、介绍自己的成果。12 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 or criticism seems to accompany every really creative idea.There is a great deal to be learned from a failure,and the greatest g
17、ains are obtained by those willing to risk defeat.9 Introduction to Mechanical Design13 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 or criticism seems to accompany every really creati
18、ve idea.There is a great deal to be learned from a failure,and the greatest gains are obtained by those willing to risk defeat.9 Introduction to Mechanical Design 一个有能力的工程师不应该害怕在提出自己的方案时遭到失败的可能性。事实上，偶然的失败肯定会发生的，因为每一个真正有创造性的设想似乎总是有失败或批评伴随着它。从一次失败中可以学到很多东西，只有不怕遭受失败的人们才能够取得最大的收获。14 Translation exercise
19、:Todays technology requires that parts be specified with increasingly exact dimensions(尺寸）.Many parts made by different companies at widely separated locations must be interchangeable,which requires precise size specifications production.现代技术对零件尺寸精度的要求越来越严格。而且，目前许多零部件是由散步在各地的不同厂家生产的，因此必须对这些零件的尺寸和生产作
20、出严格的规定，以保证它们具有互换性。9 Introduction to Mechanical Design15 The technique of dimensioning parts within a required range of variation to ensure interchangeable is called tolerancing.Each dimension is allowed a certain degree of variation within a specified zone,or tolerance.For example,a part dimension m
21、ight be expressed as 200.50,which allows a tolerance(variation in size)of 1.00 mm.给零件标注尺寸使其在一个规定的区间内变动，以保证它们具有互换性的技术称为公差技术。允许每个尺寸在规定范围内具有一定的变动量，称为公差。例如，一个零件的尺寸可以被表示成200.50，其公差（尺寸变动量）为1.00 mm。9 Introduction to Mechanical Design16 A tolerance should be as large as possible without interfering with the
22、 function of the part to minimize production costs.Manufacturing costs increase as tolerance become smaller.在不影响零件性能的情况下，应当给尺寸尽可能大的公差，以把生产成本降至最低。制造成本会随着公差的降低而升高。9 Introduction to Mechanical Design17 Tolerance，公差 Basic size 基本尺寸 Actual size 实际尺寸 Deviation 偏差 Upper deviation 上偏差 Lower deviation 下偏差 Tolerance symbols 公差符号 Roughness 粗糙度 9 Introduction to Mechanical Design
