Unit 1 Overview and Lesson 1

1、Professional English for Mechanical Engineering Lecture: Xiaobin Cui Requirements & Objectives 1.1. 熟悉專業(yè)詞匯，了解專業(yè)英語的語法特點，逐步培養(yǎng)學熟悉專業(yè)詞匯，了解專業(yè)英語的語法特點，逐步培養(yǎng)學 生具有比較熟練的專業(yè)文獻閱讀理解能力和英文學術論文生具有比較熟練的專業(yè)文獻閱讀理解能力和英文學術論文 的寫作能力。的寫作能力。 2.2.掌握國外英文專利和文獻資料的查詢方法，能以英語為工掌握國外英文專利和文獻資料的查詢方法，能以英語為工 具，獲取本專業(yè)所需信息。具，獲取本專業(yè)所需信息。 3.3.了解國

2、際學術交流的常用表達方式了解國際學術交流的常用表達方式。 Characteristics of Scientific English 1科技英語不像普通英語那樣具有感性形象思維，不具感 情色彩，其目的是使讀者容易理解而不產生太多的想象。 也不經常運用比喻、排比、夸張等修辭手段，而是要準 確表達客觀規(guī)律，按邏輯思維清晰地描述問題。 2. 科技英語的詞匯意義比較專一、穩(wěn)定，特別是大量的專 業(yè)名詞其詞義很固定、專一。即使是象do, take, make 這樣的多意義普通動詞，在科技英語中它們的詞義亦比 較固定，其表達方式也比較容易理解。 3. 科技英語主要是一種書面語言，它要求嚴謹、簡潔，不 要求在

3、文中堆積華麗的辭藻，也不要求考慮朗讀和吟誦。 4科技英語詞匯具有國際性。據有關統(tǒng)計，70%以上的科 技英語詞匯來自拉丁語、希臘語。絕大多數(shù)醫(yī)學、獸醫(yī) 學詞匯源于拉丁語、希臘語。 5. 多使用正式規(guī)范的書面動詞來替代具有同樣意義的口語 化的動詞或動詞短語。 6在語法結構上，科技英語大量使用被動語態(tài)?？萍加⒄Z 使用被動語態(tài)可以使描述減少主觀色彩，增強客觀性， 而且通過隱去人稱主語而使句子盡可能簡潔。 7.大量使用名詞或名詞短語。 8.大量使用非謂語動詞短語及分詞短語。 9. 用It作形式主語，替代后面that所引導的作為主句真正主 語的從句。 10. 常用It作形式主語替代句子后面作真正主語的動詞

4、不定 式短語。 11. 多用介詞詞組來表示用什么方法、數(shù)據、資料、什么材 料、根據什么標準等。 12. 常見包含兩個及兩個以上從句的長句。 Characteristics of Scientific English Tips(how to get English documents) 1. Electronic Document Resources at the Library Website EI: ELSEVIER: IEL(IEEE/IEE): 2. S 3. Youdao Electronic Dictionary Main Chapters to

5、Be Lectured Part I Mechanical Design Lesson 1 Introduction of Mechanical Design Lesson 2 Gears Part II Interchangeability and Measurement Lesson 7 Working Drawing Lesson 10 Sensor Technology Part III Material Science Basis and Heat Treatment Lesson 17 Engineering Materials Lesson 18 Materials Mechan

6、ical Properties Part IV Manufacturing Technology and Machine Tools Lesson 22 Machine Tool Frames Lesson 23 Centre Lathe Part I Mechanical Design Lesson 1 Introduction of Mechanical Design Lesson 1 Introduction of Mechanical Design Mechanical design is the process of designing and/or selecting mechan

7、ical components and putting them together to accomplish a desired function. Of course, machine elements must be compatible, must fit well together, and must perform safely and efficiently. compatible kmptbl adj. 兼容的；能共處的 Definition Requirements 機械設計是機械設計是一個設計和/或選擇零部件，并 將它們組裝到一起完成某種既定功能的過過 程程。 mechan

8、ical miknikl adj. 機械的；力學的 efficiently ifintli adv. 有效地；效率高地 Lesson 1 Introduction of Mechanical Design The designer must consider not only the performance of the elements being designed at a given time but also the elements with which it must interface. interface intfeis n. 接合； 連接 Requirements 設計者設計

9、者不僅要考慮考慮到在給定時間內設計的零 件要滿足的性能性能，還必須考慮它與其他零件零件 間界面間界面的干涉情況。 Lesson 1 Introduction of Mechanical Design To illustrate how the design of machine elements must be integrated with a larger mechanical design, let us consider the design of a speed reducer for the small tractor. speed reducer 減速器 tractor trkt

10、 n. 拖拉機； 牽引機 How to design 為闡述為闡述為何各零件的設計必須要結合更高 一級的機械設計來進行，這里對對小型拖拉機 的減速器設計設計進行分析分析。 integrated with 使與結合 Lesson 1 Introduction of Mechanical Design Suppose that, to accomplish the speed reduction, you decide to design a double- reduction, spur gear speed reducer. You specify four gears, three shaf

11、ts, six bearings, and a housing to hold the individual elements in proper relation to each other. The primary elements of the speed reducer are: spur gear 直齒圓柱齒輪 How to design housing 箱體 確定確定四個齒輪齒輪、三根軸軸、六個軸承軸承以及容納 這些零件并使它們彼此之間保持正確相對位 置關系的箱體箱體。 Lesson 1 Introduction of Mechanical Design Lesson 1 Intr

12、oduction of Mechanical Design l The input shaft is to be connected to the power source, a gasoline engine whose output shaft rotates at 2000rpm. A flexible coupling is to be employed to minimize difficulties with alignment. l The first pair of gears, A and B, cause a reduction in the speed of the in

13、termediate shaft proportional to the ratio of the numbers of teeth in the gears. gasoline engine 汽油發(fā)動 機 coupling 耦合器 Alignment 校準、對齊 How to design Intermediate 中間的，媒介的 第一對齒輪齒輪A和B，使使中間軸降速降速，降速 比與齒輪齒數(shù)之比成正比。 Lesson 1 Introduction of Mechanical Design Gears B and C are both mounted to intermediate shaft

14、 and rotate at the same speed. How to design l A key is used at the interface between the hub of each gear and the shaft on which is mounted to transmit torque between the gear and the shaft. 鍵被安裝鍵被安裝在每個齒輪的輪轂與軸之間的鍵 槽中，以傳遞齒輪和軸之間的扭矩。 Key 鍵 Hub 輪轂 Torque 扭矩，轉矩 Lesson 1 Introduction of Mechanical Design

15、 l The second pair of gears, C and D, further reduces the speed of gear D and the output shaft to the range of 290 rpm to 295 rpm. l The output shaft is to carry a chain sprocket. The chain drive ultimately is to be connected to the drive wheel of the tractor. Chain sprocket 鏈輪 Ultimatelyltmt 最終的 Ho

16、w to design 第二對齒輪齒輪C和D，進一步降低降低齒輪D以及 輸出軸的轉速轉速，使得轉速降至290295rpm。 Lesson 1 Introduction of Mechanical Design l Each of the three shafts is supported by two ball bearings, making them statically determinate and allowing analysis of forces and stresses using standard principles of mechanics. Ball bearing

17、滾珠軸承 Determinate 確定的 Stress 應力 How to design 三根軸中的每根軸軸都由由一對球軸承支撐支撐固 定，使其靜態(tài)穩(wěn)定并可運用標準的力學原理 來進行載荷和應力分析。 Lesson 1 Introduction of Mechanical Design l The bearings are held in a housing that is to be attached to the frame of the tractor. Note the manner of holding each bearing so that the inner race rotat

18、es with the shaft while the outer race is held stationary. l Seals are on the input and output shafts to prohibit contaminants from entering the housing. Seal 密封 Prohibit 阻止 Contaminant 污染物 How to design 注意注意固定每個軸承的方式方式是內圈隨軸轉 動而外圈固定不動。 Frame 機架 Inner race 內圈 Outer race 外圈 Lesson 1 Introduction of Me

19、chanical Design Details of how the active elements are to be installed, lubricated, and aligned are only suggested at this stage of the design process to demonstrate feasibility. One possible assembly process could be as follows: (1) Start by placing the gears, keys, spacers, and bearings on their r

20、espective shafts. Spacer 墊片 How to assemble 在這一階段僅考慮考慮如何對運動零部件進行 安裝、潤滑和連接的細節(jié)細節(jié)，以論證以論證設計的 可行性。 feasibility ,fi:zbilti n. 可行性；可能性 Lesson 1 Introduction of Mechanical Design Bearing seat 軸承座 Engaging 嚙合 How to assemble (2) Then insert input shaft into its bearing seat on the left side of the housing. (

21、3) Insert the left end of intermediate shaft into its bearing seat while engaging the teeth of gears A and B. (4) Install the center bearing support to provide support for the bearing at the right side of input shaft. (5) Install output shaft by placing its left bearing into the seat on the center b

22、earing support while engaging gears C and D. (6) Install the right side cover for the housing while placing the final two bearings in their seats. Ensure careful alignment of the shafts. Bearing support 軸承支架 (7) Place gear lubricant in the lower part of the housing. The arrangement of the gears, the

23、 placement of the bearings so that they straddle the gears and the general configuration of the housing are also design decisions. Lesson 1 Introduction of Mechanical Design How to assemble Additional considerations straddle strdl v. 跨坐 齒輪的排列方式排列方式，齒輪、軸承的安裝位安裝位 置置以及箱體的整體布局整體布局，都應應在設計中明確明確 。 The desi

24、gn process cannot rationally proceed until these kinds of decisions are made. When the overall design is conceptualized, the design of the individual machine elements in the speed reducer can proceed. You should recognize that you have already made many design decisions by rendering such a sketch. F

25、irst you choose spur gears rather than helical gears, a worm and worm gear or bevel gears. In fact, other types of speed reduction devicesbelt drives, chain drives, or many others could be appreciate. Lesson 1 Introduction of Mechanical Design Additional considerations conceptualize knseptjulaiz vt.

26、 使概念化 Helical gear 斜齒輪 Worm 蝸桿 Bevel gear 錐齒輪 1. Gears For gear pairs, you must specify the number of teeth in each gear, pitch (size) of the teeth, the pitch diameters, the face width, and the material and its heat treatment. T h e s e s p e c i f i c a t i o n s d e p e n d o n considerations of s

27、trength and wear of the gear teeth and the motion requirements (kinematics). Lesson 1 Introduction of Mechanical Design Gears Pitch of the teeth 齒節(jié)距 Pitch diameter 節(jié)圓直徑 Face width 齒寬 Kinematic 運動學 對于齒輪副，必須明確明確每個齒輪的齒輪齒輪 齒數(shù)齒數(shù)、牙型齒距牙型齒距、分度圓直徑分度圓直徑、齒輪厚度齒輪厚度、 材料材料及其熱處理工藝熱處理工藝。 You must also recognize that

28、 the gears must be mounted on shafts in a manner that ensures proper location of the gears, adequate torque transmitting capability from the gears to the shafts (as through keys) and safe shaft design. Lesson 1 Introduction of Mechanical Design Gears 必須認識到認識到，設計應確保齒輪在軸上的安裝能 正確定位，齒輪到軸能傳遞足夠的扭矩（通過 鍵連接）

29、，以及傳動軸的可靠性。 2. Shafts Having designed the gear pairs, next you will consider the shaft design. The shaft is loaded in bending and torsion because of the forces acting at the gear teeth. Thus, its design must consider strength and rigidity, and it must permit the mounting of the gears and bearings. S

30、hafts of varying diameters may be used to provide shoulders against which to seat the gears and bearings. Lesson 1 Introduction of Mechanical Design Shafts Rigidity 剛性 There may be keyseats cut into the shaft. The input and output shafts will extend beyond the housing to permit coupling with the eng

31、ine and the drive axle. The type of coupling must be considered, as it can have a dramatic effect on the shaft stress analysis. Seals on the input and output shafts protect internal components. Lesson 1 Introduction of Mechanical Design Shafts Axel 輪軸 3. Bearings Design of the bearings is next. If r

32、olling contact bearings are to be used, you will probably select commercially available bearings from a manufacturers catalog, rather than design a unique one. Lesson 1 Introduction of Mechanical Design Bearings Rolling contact bearing 滾動軸承 若使用滾動軸承，應從制造廠家的樣本里選選 擇擇通用軸承軸承，而不是進行專門設計。 You must first determine the magnitude of the loads on each bearing from the shaft analysis and the gear designs. The rotational speed and reasonable design life of the bearings and their