機(jī)械工程專業(yè)英語課件--L06

1、English for Mechanical Engineering機(jī)械工程專業(yè)英語1機(jī)械工程專業(yè)英語預(yù)備知識 一、Background Informationplastics Plastic is the general common term for a wide range of synthetic or semisynthetic organic amorphous solid materials suitable for the manufacture of industrial products. Plastics are typically polymers of high mo

2、lecuar mass, and may contain other substances to improve performance and/or reduce costs.The word derives from the Greek (plastikos) meaning fit for molding, and (plastos) meaning molded. It refers to their malleability, or plasticity during manufacture, that allows them to be cast, pressed, or extr

3、uded into an enormous variety of shapessuch as film, fibers, plates, tubes, bottles, boxes, and much more.Lesson 6 Plastics and Other Materialssin5Wetikadj.合成的, 人造的 非晶狀固體聚合物2機(jī)械工程專業(yè)英語預(yù)備知識 一、Background InformationplasticsDue to their relatively low cost, ease of manufacture, versatility, and imperviou

4、sness to water, plastics are used in an enormous and expanding range of products, from paper clips to spaceships. They have already displaced many traditional materials, such as wood; stone; horn and bone; leather; paper; metal; glass; and ceramic, in most of their former uses.Lesson 6 Plastics and

5、Other Materials不透明性3機(jī)械工程專業(yè)英語預(yù)備知識 一、Background InformationplasticsThe use of plastics is constrained chiefly by their organic chemistry, which seriously limits their hardness, density, and their ability to resist heat, organic solvents, oxidation, and ionizing radiation. In particular, most plastics

6、will melt or decompose when heated to a few hundred degrees celsius. While plastics can be made electrically conductive to some extent, they are still no match for metals like copper or aluminium. Plastics are still too expensive to replace wood, concrete and ceramic in bulky items like ordinary bui

7、ldings, bridges, dams, pavement, railroad ties, etc。Lesson 6 Plastics and Other Materials電離輻射攝氏度4機(jī)械工程專業(yè)英語預(yù)備知識 一、Background InformationPowder metallurgyPowder metallurgy is a forming and fabrication technique consisting of three major processing stages. First, the primary material is physically powde

8、red, divided into many small individual particles. Next, the powder is injected into a mold or passed through a die to produce a weakly cohesive structure (via cold welding) very near the dimensions of the object ultimately to be manufactured. Pressures of 10-50 tons per square inch are commonly use

9、d. Also, to attain the same compression ratio across more complex pieces, it is often necessary to use lower punches as well as an upper punch. Finally, the end part is formed by applying pressure, high temperature, long setting times (during which self-welding occurs), or any combination thereof.Le

10、sson 6 Plastics and Other Materials5機(jī)械工程專業(yè)英語預(yù)備知識 一、Background Information Two main techniques used to form and consolidate the powder are sintering and metal injection molding. Recent developments have made it possible to use rapid manufacturing techniques which use the metal powder for the products

11、. Because with this technique the powder is melted and not sintered, better mechanical strength can be accomplished. In Powder Metallurgy products are today used in a wide range of industries, from automotive and aerospace applications to power tools and household appliances. Each year the internati

12、onal PM awards highlight the developing capabilities of the technology。Lesson 6 Plastics and Other MaterialsPowder metallurgy6機(jī)械工程專業(yè)英語預(yù)備知識 一、Background Information A much wider range of products can be obtained from powder processes than from direct alloying of fused materials. In melting operations

13、 the phase rule applies to all pure and combined elements and strictly dictates the distribution of liquid and solid phases which can exist for specific compositions. In addition, whole body melting of starting materials is required for alloying, thus imposing unwelcome chemical, thermal, and contai

14、nment constraints on manufacturing. Unfortunately, the handling of aluminium/iron powders poses major problems. Other substances that are especially reactive with atmospheric oxygen, such as tin, are sinterable in special atmospheres or with temporary coatings.Lesson 6 Plastics and Other MaterialsPo

15、wer metallurgy7機(jī)械工程專業(yè)英語課文分析 Plastics have specific properties, which may made them preferable to traditional materials for certain uses. In comparison with metals, for example, plastics have both advantages and disadvantages. Metals tend to be corroded by inorganic acids, such as sulphuric acid and

16、hydrochloric acid. Plastics tend to be resistant to these acids, but can be dissolved or deformed by solvents, such as carbon tetrachloride, which have the same carbon base as the plastics. Color must be applied to the surface of metals, whereas it can be mixed in with plastics. Metals are more rigi

17、d than most plastics, while plastics are very light, with a specific gravity normally between 0.9 and 1.8. Most plastics do not readily conduct heat or electricity. Plastics soften slowly and can easily be shaped while they are soft. Lesson 6 Plastics and Other Materials 三、Text8Lesson 6 Plastics and

18、 Other Materials機(jī)械工程專業(yè)英語課文分析 塑料具有特殊的性能，對于某些用途而言，這些性能使得塑料比傳統(tǒng)材料更為可取。 Plastics have specific properties, which may made them preferable to traditional materials for certain uses.be preferable to 更好的，更可取的 In comparison with metals, for example, plastics have both advantages and disadvantages.例如，跟金屬相比較，塑

19、料既有優(yōu)點(diǎn)也有缺點(diǎn)。 Kmprisn與比較起來 9Lesson 6 Plastics and Other Materials機(jī)械工程專業(yè)英語課文分析金屬易受無機(jī)酸的腐蝕，如硫酸和鹽酸。 Metals tend to be corroded by inorganic acids, such as sulphuric acid and hydrochloric acid.slfjurikadj. 硫磺的,含硫的sulphur slfn. 硫, 硫磺 Plastics tend to be resistant to these acids, but can be dissolved or defor

20、med by solvents, such as carbon tetrachloride, which have the same carbon base as the plastics. 塑料能抵抗這些酸的腐蝕，但可被溶劑所溶解或引起變形，例如，溶劑四氯化碳與塑料具有同樣的碳基。 n:nikadj. 無機(jī)的 無組織的,haidrukl:rikadj. 氯化氫的,鹽酸的slvntn. 溶劑adj.有溶解能力的,tetrkl:raidn. 四氯化物10Lesson 6 Plastics and Other Materials機(jī)械工程專業(yè)英語課文分析 顏色必須涂到金屬的表面，否則的話就可能與塑料

21、混為一體。 Color must be applied to the surface of metals, whereas it can be mixed in with plastics. Metals are more rigid than most plastics, while plastics are very light, with a specific gravity normally between 0.9 and 1.8. 金屬的剛度比大多數(shù)塑料高，而塑料則非常輕，通常塑料密度在0.91.8之間。 11Lesson 6 Plastics and Other Materials

22、機(jī)械工程專業(yè)英語課文分析 大多數(shù)塑料不易于傳熱和導(dǎo)電 。 Most plastics do not readily conduct heat or electricity. Plastics soften slowly and can easily be shaped while they are soft. 塑料能緩慢軟化，而當(dāng)其在軟的狀態(tài)時(shí)，易于成形。 12機(jī)械工程專業(yè)英語課文分析 It is their plasticity at certain temperatures, which gives plastics their main advantage over many other

23、 materials. It permits the large-scale production of molded articles, such as containers, at an economic unit cost, where other material require laborious and often costly processes involving cutting, shaping, machining, assembly and decoration. Lesson 6 Plastics and Other Materials13Lesson 6 Plasti

24、cs and Other Materials機(jī)械工程專業(yè)英語課文分析 正是塑料在某一溫度下的塑性，使得塑料具備了超過許多其他材料的主要優(yōu)點(diǎn)。 It is their plasticity at certain temperatures, which gives plastics their main advantage over many other materials. 14Lesson 6 Plastics and Other Materials機(jī)械工程專業(yè)英語課文分析 這就容許大量生產(chǎn)單位成本低廉的模塑件，例如各種容器，而若用其他材料則需要大量勞力和往往需要昂貴的加工工藝，包括切割、成形

25、、加工、裝配和裝飾。 It permits the large-scale production of molded articles, such as containers, at an economic unit cost, where other material require laborious and often costly processes involving cutting, shaping, machining, assembly and decoration. lb:risadj. 勤勞的， 費(fèi)力的15機(jī)械工程專業(yè)英語課文分析 A plastics article ma

26、y need to differ in design and appearance form a similar article made from another material such as metal or wood. This is due not only to the properties of plastics but also to the techniques employed in fabricating plastics products. These techniques include injection molding, blow molding, compre

27、ssion molding, extrusion and vacuum forming. Lesson 6 Plastics and Other Materials16Lesson 6 Plastics and Other Materials機(jī)械工程專業(yè)英語課文分析 塑料件可能需要在設(shè)計(jì)和外形方面有別于其他材料，比如金屬或木材制作的類似的器件。 A plastics article may need to differ in design and appearance form a similar article made from another material such as metal

28、 or wood. This is due not only to the properties of plastics but also to the techniques employed in fabricating plastics products. 這不僅是由于塑料的性能不同的原因，也是由于制造塑料產(chǎn)品所用的技術(shù)不同所致。 17Lesson 6 Plastics and Other Materials機(jī)械工程專業(yè)英語課文分析 這些技術(shù)包括注塑模，吹塑模，壓縮模，擠出和真空成形等 These techniques include injection molding, blow mol

29、ding, compression molding, extrusion and vacuum forming. 18機(jī)械工程專業(yè)英語課文分析 The definition for the term powder metallurgy is “The art of producing metal powders and objects shaped from individual, mixed, or alloyed metal powders, with or without the inclusion of nonmetallic constituents, by pressing or

30、moulding objects which may be simultaneously or subsequently heated to produce a coherent mass, either without fusion, or with the fusion of a low melting constituent only”. Lesson 6 Plastics and Other Materials 對粉末冶金所下的定義是：粉末冶金是制造金屬粉末并將單一的、混合的或合金化的粉末通過成形的方法制成產(chǎn)品的技術(shù)。這一制造過程可添加或不添加非金屬成分；可通過加壓或模壓成形；可在壓制

31、時(shí)同時(shí)加熱或在制造后再進(jìn)行加熱，能使金屬粉末形成一個(gè)粘結(jié)牢固的整體；加熱過程中粉末可不熔化，或只有低熔點(diǎn)成分熔化。 粉末冶金knstitjunt成分, 部分, 要素 19機(jī)械工程專業(yè)英語課文分析 Suitable powder must first be produced. While theoretically any crystalline material may be fabricated by powder metallurgy, the production of suitable powder has presented restrictions in many cases, e

32、ither because of difficulty in obtaining adequate purity or because of economic reason. After selection and blending of the powder and manufacture of a die for the shape to be produced, the powder is pressed to size and shape. The application of heat results in crystalline growth and the production

33、of a homogeneousbody. Lesson 6 Plastics and Other Materials20Lesson 6 Plastics and Other Materials機(jī)械工程專業(yè)英語課文分析首先，必須生產(chǎn)合適的粉末。 Suitable powder must first be produced. While theoretically any crystalline material may be fabricated by powder metallurgy, the production of suitable powder has presented res

34、trictions in many cases, either because of difficulty in obtaining adequate purity or because of economic reason. 盡管理論上可以用粉末冶金的方法制造任何結(jié)晶材料，但在許多情況下，生產(chǎn)合適的粉末存在限制，或者是因難于獲得足夠純度的粉末或者是因?yàn)榻?jīng)濟(jì)上的原因。 kristlain adj. 水晶的, 結(jié)晶的，透明的, 清晰的, 21Lesson 6 Plastics and Other Materials機(jī)械工程專業(yè)英語課文分析 選擇和配制好粉末并制造好所要生產(chǎn)產(chǎn)品的模具后，就把粉末模

35、壓成符合尺寸和形狀的產(chǎn)品。 After selection and blending of the powder and manufacture of a die for the shape to be produced, the powder is pressed to size and shape. The application of heat results in crystalline growth and the production of a homogeneousbody. 加熱可以促進(jìn)晶體的生長，從而生產(chǎn)出材質(zhì)均勻的構(gòu)件來。 ,hmudi:njsadj.同種的, 同類的, 相似的, 均質(zhì)的; 均勻的22機(jī)械工程專業(yè)英語課文分析 Various combinations of heat and pressure may be used. Some sintering takes place under high pressure at room temp