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1、Unit 2 Mechanical Design and Unit 2 Mechanical Design and ManufactureManufacture What Is Machine Design Text A What Is Machine Design Text B Diagnosis of Design Malfunction Text C Grammar NEW WORDS AND PHRASES machine design 机械设计 Instrument n 器械 仪器 器具 Innovative n 有创造力的 创新 的 Fundamental a 基本的 根本的 Ki
2、nematic a 动力学的 Component n 组成部分 元素 Assembly v 组合 组装 Text A What Is Machine DesignText A What Is Machine Design I I NEW WORDS AND PHRASES Excessively a 过分地 过度地 Reasonable a 合理的 可行的 Corrosion n 腐蚀 evaluated from 通过 进行评估 Deflection n 挠曲量 Text A What Is Machine DesignText A What Is Machine Design I I Wh
3、at Is Machine Design I Machine design is the application of science and technology to device 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 original conception of the conduct in terms of its size
4、 shape and construction details but also considers the various factors involved in the manufacture marketing and use of the product A product can be defined as any manufactured item including machines structures tools and instruments People who perform the various functions of machine design are typ
5、ically called designers or design engineers Machine design is a creative activity basically However in addition to being innovative a design engineer must also have a solid background in the fundamentals of engineering technology Text A What Is Machine DesignText A What Is Machine Design I I A desig
6、n engineer must have working knowledge in the areas of mechanical drawing kinematics material engineering strength of materials and manufacturing processes The following statements will indicate how each of these basic background subjects relates to machine design Text A What Is Machine DesignText A
7、 What Is Machine Design I I Text A What Is Machine DesignText A What Is Machine Design I I 1 Mechanical Drawing Detailed drawings must be prepared noting the exact shape size and material composition for each component assembly drawings showing how the total product is put together by fastening each
8、 part in proper sequence are also needed 2 Kinematics Knowledge of this subject for example would permit analysis of the motion of the internal mechanism of Smarty Bird This analysis would include the attainment of the desired eye rolling action Normally the very creation of the toy and its internal
9、 mechanism would occur during this initial phase of machine design called kinematics 3 Mechanics Use of this subject provides an analysis of the forces which for example act upon a lawn chair when a person is seated in it Obviously a person can damage the lawn chair by carelessly jumping on the seat
10、 This motion in effect applies dynamic loading instead of the gradually applied loading taken into consideration when the lawn chair was designed The result of this misuse is excessively large forces that can cause permanent damage Therefore using the laws of mechanics a reasonable amount of dynamic
11、 loading should be taken into account during the early design phase 4 Materials of Engineering Because the lawn chair is commonly used in an outdoor environment the tubing is made of aluminum to resist corrosion The webbing is made of a plastic material that will not readily deteriorate with sustain
12、ed exposure to sunlight and moisture Obviously the proper selection of materials is a vital area of machine design Text A What Is Machine DesignText A What Is Machine Design I I 5 Strength of Materials The subject concerns itself with whether or not a part is strong enough to sustain the forces it w
13、ill experience evaluated from mechanics For example the size and shape of the aluminum tubular sections of the lawn chair are determined in such a way that failure will not occur under normal use due to excessive stresses and deflections The magnitude of stresses and deflections depends on the size
14、and shape of a given part as well as on its material composition and actual loads Text A What Is Machine DesignText A What Is Machine Design I I 6 Manufacturing Processes Smarty Bird is no simple toy How each component is produced and how the entire toy is assembled are established by using methods
15、learned in manufacturing technology It is here that a designer comes to grips with the reality of costs The flexible shafts are used in Smarty Bird because they simplify of manufacturing by eliminating expensive parts and by cutting the labor costs of installing and aligning rigid shafting In conjun
16、ction with the use of the processing fundamentals there are many significant considerations which must be detailed with the general field of machine design Among these are safety environmental effects appearance and economy Text A What Is Machine DesignText A What Is Machine Design I I Notes to the TextNotes to the Text 1 Machine design is the application of science and technology to device new or improved products for the purpose of satisfying human needs 机械设计是应用科学和科技去发明新的 或者改进型的产品以满足人们人类要求 的目的
