Тексты для самостоятельной работы по иностранному языку по специальности Технология машиностроения

САМОСТОЯТЕЛЬНАЯ РАБОТА ДЛЯ СТУДЕНТОВ СПЕЦИАЛЬНОСТИ ТЕХНОЛОГИЯ МАШИНОСТРОЕНИЯ

2 КУРС 3 СЕМЕСТР

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Text: «METALWORKING PROCESSES»

Metals are important in industry because they can be easily deformed into useful shapes. A lot of metalworking processes have been developed for certain applica­tions. They can be divided into five broad groups:

1. rolling,

2. extrusion,

3. drawing,

4. forging,

5. sheet-metal forming.

During the first four processes metal is subjected to large amounts of strain (deformation). But if deformation goes at a high temperature, the metal will recrystallize — that is, new strain-free grains will grow instead of deformed grains. For this reason metals are usually rolled, ex­truded, drawn, or forged above their recrystallization temperature. This is called hot working. Under these conditions there is no limit to the compressive plastic strain to which the metal can be subjected.

Other processes are performed below the recrystalli­zation temperature. These are called cold working. Cold working hardens metal and makes the part stronger. However, there is a limit to the strain before a cold part cracks.

Rolling

Rolling is the most common metalworking process. More than 90 percent of the aluminum, steel and copper produced is rolled at least once in the course of produc­tion. The most common rolled product is sheet. Rolling can be done either hot or cold. If the rolling is finished cold, the surface will be smoother and the product stronger.

Extrusion

Extrusion is pushing the billet to flow through the orifice of a die. Products may have either a simple or a complex cross section. Aluminum window frames are the examples of complex extrusions.

Tubes or other hollow parts can also be extruded. The initial piece is a thick-walled tube, and the extruded part is shaped between a die on the outside of the tube and a mandrel held on the inside.

In impact extrusion (also called back-extrusion) (штамповка выдавливанием), the workpiece is placed in the bottom of a hole and a loosely fitting ram is pushed against it. The ram forces the metal to flow back around it, with the gap between the ram and the die determin­ing the wall thickness. The example of this process is the manufacturing of aluminum beer cans.

Vocabulary:

useful — полезный

shape — форма, формировать

rolling — прокатка

extrusion — экструзия, выдавливание

drawing — волочение

forging — ковка

sheet — лист

to subject — подвергать

amount — количество

condition — состояние, условие

perform — выполнять, проводить

to harden — делаться твердым, упрочняться

at least — по крайней мере

common — общий

billet — заготовка, болванка

orifice — отверстие

die — штамп, пуансон, матрица, фильера, во­лочильная доска

cross section — поперечное сечение

window frame — рама окна

tube — труба

hollow — полый

initial — первоначальный, начальный

thick-walled — толстостенный

mandrel — оправка, сердечник

impact — удар

loosely — свободно, с зазором

fitting — зд. посадка

ram — пуансон, плунжер

force — сила

gap — промежуток, зазор

to determine — устанавливать, опреде­лять

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Text: «METHODS OF STEEL HEAT TREATMENT»

Quenching is a heat treatment when metal at a high temperature is rapidly cooled by immersion in water or oil. Quenching makes steel harder and more brittle, with small grains structure.

Tempering is a heat treatment applied to steel and certain alloys. Hardened steel after quenching from a high temperature is too hard and brittle for many appli­cations and is also brittle. Tempering, that is re-heating to an intermediate temperature and cooling slowly, re­duces this hardness and brittleness. Tempering tempera­tures depend on the composition of the steel but are fre­quently between 100 and 650 °C. Higher temperatures usually give a softer, tougher product. The color of the oxide film produced on the surface of the heated metal often serves as the indicator of its temperature.

Annealing is a heat treatment in which a material at high temperature is cooled slowly. After cooling the metal again becomes malleable and ductile (capable of being bent many times without cracking).

All these methods of steel heat treatment are used to obtain steels with certain mechanical properties for cer­tain needs.

Vocabulary:

to immerse — погружать

to apply — применять

intermediate — промежуточный

oxide film — оксидная пленка

annealing — отжиг, отпуск

cracking — растрескивание

2 КУРС 4 СЕМЕСТР

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Text: «METALWORKING AND METAL PROPERTIES»

An important feature of hot working is that it pro­vides the improvement of mechanical properties of met­als . Hot-working (hot-rolling or hot-forging) eliminates porosity, directionality, and segregation that are usu­ally present in metals. Hot-worked products have better ductility and toughness than the unworked casting. Dur­ing the forging of a bar, the grains of the metal become greatly elongated in the direction of flow. As a result, the toughness of the metal is greatly improved in this direction and weakened in directions transverse to the flow. Good forging makes the flow lines in the finished part oriented so as to lie in the direction of maximum stress when the part is placed in service.

The ability of a metal to resist thinning and fracture during cold-working operations plays an important role in alloy selection. In operations that involve stretching, the best alloys are those which grow stronger with strain (are strain hardening) — for example, the copper-zinc alloy, brass, used for cartridges and the aluminum-mag­nesium alloys in beverage cans, which exhibit greater strain hardening.

Fracture of the workpiece during forming can result from inner flaws in the metal. These flaws often con­sist of nonmetallic inclusions such as oxides or sulfides that are trapped in the metal during refining. Such in­clusions can be avoided by proper manufacturing pro­cedures.

The ability of different metals to undergo strain var­ies. The change of the shape after one forming operation is often limited by the tensile ductility of the metal. Met­als such as copper and aluminum are more ductile in such operations than other metals.

Vocabulary

feature — черта, особенность

to provide — обеспечивать

improvement — улучшение

property — свойство

eliminate — ликвидировать, исключать

porosity — пористость

directional — направленный

to segregate — разделять

casting — отливка

elongated — удлиненный

to weaken — ослабевать, ослаблять

transverse — поперечный

flow — течение, поток

finished — отделанный

thinning — утончение

fracture — разрушение

strain hardening — деформационное упрочнение

brass — латунь

beverage — напиток

can — консервная банка

to exhibit — проявлять

inner — внутренний

flaws — недостатки, дефекты кристалличес­кой решетки

inclusion — включение

trapped — зд. заключенный

refining — очищать, очистка

to avoid — избегать

to undergo — подвергаться

tensile ductility — пластичность при растяжении

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ALLOYS

Bronze and brass, the first alloys in the history of metallurgy, were probably obtained by man accidentally when melting mixed metal ores. Much later alloys of iron were obtained.

Steel was made in small quantities in early times un­til the mid-19th century when it was manufactured on a large scale in the iron and steel industry.

The commercial production of pure aluminium in about 1890 began a new range of alloys and among them duralumin, an alloy of about 94 per cent aluminium, with small quantities of copper, manganese, magnesium, and silicon. Most of aluminium alloys are both light and strong.

Nickel is often mixed with other metals for special purposes: permalloy is a nickel-iron alloy that is mag­netically soft. The polarity of its magnetic field can be easily changed and it is used for transformer cores. Monel metals contain about two parts nickel to one part cop­per, plus other elements. They are stronger than nickel and extremely corrosion-resistant. These properties make them useful in chemical production.

Electrum is a natural or artificial alloy of gold and sil­ver containing 15-45 per cent of silver. It was used in the ancient world for coinage.

Bismuth is frequently used as a part of alloys with low melting-points. Today alloys can be designed for particu­lar applications with certain properties.

3 КУРС 5 СЕМЕСТР

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Text: «DIES»

Dies are tools used for the shaping solid materials, especially those employed in the pressworking of cold metals.

In presswork, dies are used in pairs. The smaller die, or punch, fits inside the larger die, called the matrix or, simply, the die. The metal to be formed, usually a sheet, is placed over the matrix on the press. The punch is mounted on the press and moves down by hydraulic or mechanical force.

A number of different forms of dies are employed for different operations. The simplest are piercing dies (пробивной штамп), used for punching holes. Bending and folding dies are designed to make single or compound bends. A combination die is designed to perform more than one of the above operations in one stroke of the press. A progressive die permits successive forming op­erations with the same die.

In coining, metal is forced to flow into two matching dies, each of which bears a engraved design.

Wiredrawing Dies

In the manufacture of wire, a drawplate (волочильная доска) is usually employed. This tool is a metal plate con­taining a number of holes, successively less in diameter and known as wire dies. A piece of metal is pulled through the largest die to make a coarse wire. This wire is then drawn through the smaller hole, and then the next, un­til the wire is reduced to the desired measurement. Wiredrawing dies are made from extremely hard mate­rials, such as tungsten carbide or diamonds.

Thread-Cutting Dies

For cutting threads on bolts or on the outside of pipes, a thread-cutting die (резьбонарезная плашка) is used. It is usually made of hardened steel in the form of a round plate with a hole in the centre. The hole has a thread. To cut an outside thread, the die is lubricated with oil and simply screwed onto an unthreaded bolt or piece of pipe, the same way a nut is screwed onto a bolt. The correspond­ing tool for cutting an inside thread, such as that inside a nut, is called a tap (метчик).

Vocabulary:

chip — стружка

sharp — острый

friction — трение

content — содержание

range — диапазон

inexpensive — недорогой

to permit — позволять, разрешать

common — обычный

tungsten — вольфрам

ingredient — ингредиент

diamond — алмаз

tips — наконечники

ceramic — керамический

truing — правка, наводка, заточка

die — матрица, штамп

matrix — матрица

to employ — применять

to pierce — протыкать, прокалывать

to punch — пробивать отверстие

matching — сочетающийся, парный

coarse — грубый

wire — проволока

to draw — тащить, волочить

thread — резьба

hardened — закаленный

to lubricate — смазывать

to screw — привинчивать

nut — гайка

outside — наружный, внешний

inside — внутри, внутренний

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TEXT A. MACHINE TOOLS —

A MEASURE OF MAN'S PROGRESS

The variety and combinations of machine tools today are unlimited. Some of them are very small and can be mounted on a work-bench¹ but others are so large that we have to construct special buildings to house them.

There are some basic operations at any workshop. They are turning, drilling, threading, etc. The main machine tool of such a workshop is the multipurpose lathe. What is a lathe? It is a power-driven machine² with special tools which can cut or form metal parts. The metal that cuts an­other metal must be very hard and so tools should ^be made of very hard steel alloys. The tool itself is very small in comparison with the mecha­nism that is to direct it.

Technological progress improves accuracy of machine tools. Today's equipment can produce parts with very high accuracy. One can find a number of³ machine tools that can measure and inspect their production themselves — machine tools that are to handle the parts mechanically and automatically. Such machines can hold the parts which are to be measured and are able to indicate precise measurements themselves. A great many of such "clever" machines can be found today in our industry.

Since machine tools become faster and more complex, automatic measurements and inspection ought to be of greater importance. Automa­tion is one of the main factors of engineering progress.

Flexible production lines form the basis for automated workshops. The main principle of such a flexible line is the fact that it can be switched over from one product to another, which has a similar structure but a different outline, almost instantaneously. It is equally efficient in conditions of both mass and small-batch production⁴ and will serve to in­crease the productivity.

Notes on the Text

1. work-bench — верстак

2. power-driven machine — станок с механическим приводом

3. number of — ряд, несколько

4. small-batch production — производство маленьких партий продукции

accuracy n — точность machine tool n — станок

alloy n — сплав main a — главный

condition n — условие mount v — помещать, устанавливать

cut (cut) v — резать multipurpose a — многоцелевой

direct v — управлять outline n — очертание, конфигурация

drill v — сверлить part n — деталь

equip v — оснащать precise a — точный

fast a — быстрый produce v — производить

flexible a — гибкий similar a — подобный

handle v — управлять steel n — сталь

hard a — твердый switch v — переключать

hold (held) v — держать thread v — делать нарезку резьбы

house v — вмещать tool n — резец

improve v — улучшать turn n — точить

increase v — увеличивать workshop n — цех

lathe n — токарный станок

3 КУРС 6 СЕМЕСТР

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TEXT A. BETTER METALS ARE VITAL TO TECHNOLOGICAL

PROGRESS

Since the earliest days the preparation of metals for mechanical use was vital to the advance of civilization.

Gold, silver and copper were the first to be used by a primitive man, as they were found free in nature. Today we know more than sixty-five metals available in large enough quantities to be used in industry.

Metals are mostly solids at ordinary temperatures and possess com­paratively high melting points with the exception of mercury. They are for the most part* good conductors of heat and electricity, and silver is the best in this respect.² They can be drawn into fine wires and ham­mered into thin sheets.

As to³ their chemical properties the first point to be mentioned is that they vary widely in degree of chemical activity: some are enor­mously active and others are inert. The Earth contains a large number of metals useful to man. Of all metals to be utilized in industry iron re­mains by far⁴ the most important. Modem industry needs considerable quantities of this metal either in the form of iron or steel.

To get the desirable characteristics in metals or to improve them the art to mix metals and other substances began to develop. The first alloys that were formed in this way were sometimes stronger, tougher, harder and more elastic than the metals of which they were composed. To esti­mate nowadays how many alloys there exist in the modem world is dif­ficult because their numbers increase daily.

To serve special uses modem metals and alloys must be lighter yet stronger, more corrosion-resistant, more suitable for automated fabrication yet less expensive than those available before.

Scientists are developing new processes and improving oid ones in order to produce metals and alloys that will meet the present-day re­quirements. One of the most interesting purposes is, for instance,⁵ to make metals stronger, in other words, to strengthen them by reinforcing them with fibres.

Today transportation, communication, farming, construction and manu­facturing all depend on the availability of suitable metals and alloys.

Notes on the Text

1. for the most part — большей частью

2. in this respect — в этом отношении

3. as to — что касается

4. by far — несомненно

1. for instance — например

available a — имеющийся melt v — таять

considerable a — значительный mention v — упоминать

copper n — медь need v — нуждаться

desirable a — нужный quantity n — количество

difficult a — трудный remain v — оставаться

draw (drew; drawn) v — тащить, тянуть resistant a — устойчивый

either ... or сj — либо..., либо sheet n — лист

enormously adv — чрезвычайно silver n — серебро

enough a — достаточный strengthen v — усиливать, укреплять

estimate v — оценивать suitable a — пригодный

exception n — исключение thin a — тонкий

expensive a — дорогостоящий tough a — прочный, жесткий

fibre n — фибра, волокно vary v — изменять(ся)

fine a — тонкий wire n — проволока

gold n — золото yet cj — однако, еще, уже

iron n — железо

to meet requirements — удовлетворять требованиям

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Text A: «MECHANICAL PROPERTIES Of MATERIALS»

Materials Science and Technology is the study of ma­terials and how they can be fabricated to meet the needs of modern technology. Using the laboratory techniques and knowledge of physics, chemistry, and metallurgy, scientists are finding new ways of using metals, plastics and other materials.

Engineers must know how materials respond to exter­nal forces, such as tension, compression, torsion, bend­ing, and shear. All materials respond to these forces by elastic deformation. That is, the materials return their original size and form when the external force disap­pears. The materials may also have permanent deforma­tion or they may fracture. The results of external forces are creep and fatigue.

Compression is a pressure causing a decrease in vol­ume. When a material is subjected to a bending, shear­ing, or torsion (twisting) force, both tensile and compressive forces are simultaneously at work. When a metal bar is bent, one side of it is stretched and subjected to a tensional force, and the other side is compressed.

Vocabulary

bar— брусок, прут

completely — полностью, совершенно

compression — сжатие

creep — ползучесть

cross-sectional area — площадь поперечного сечения

cyclic stress — циклическое напряжение

decrease — уменьшение

elastic deformation — упругая деформация

elastic limit — предел упругости

exceed — превышать

external forces — внешние силы

fatigue — усталость металла

fracture — перелом, излом

loosen — ослаблять, расшатывать

permanent deformation — постоянная деформация

remaining — оставшийся

shear — срез

simultaneously — одновременно

to stretch — растягивать

technique — методы

tension — напряженность

to propagate — распространяться

to bend — гнуть, согнуть

to extend — расширять, продолжаться

to meet the needs — отвечать требованиям

to occur — происходить

to respond — отвечать реагировать

to suffer — страдать

torsion — кручение

twisting — закручивание, изгиб

volume — объем, количество

rupture — разрыв

4 КУРС 7 СЕМЕСТР

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Text В: «DRAWING»

Drawing consists of pulling metal through a die. One type is wire drawing. The diameter reduction that can be achieved in one die is limited, but several dies in se­ries can be used to get the desired reduction.

Sheet metal forming

Sheet metal forming (штамповка листового металла) is widely used when parts of certain shape and size are needed. It includes forging, bending and shearing. One characteristic of sheet metal forming is that the thick­ness of the sheet changes little in processing. The metal is stretched just beyond its yield point (2 to 4 percent strain) in order to retain the new shape. Bending can be done by pressing between two dies. Shearing is a cutting operation similar to that used for cloth.

Each of these processes may be used alone, but often all three are used on one part. For example, to make the roof of an automobile from a flat sheet, the edges are gripped and the piece pulled in tension over a lower die. Next an upper die is pressed over the top, finishing the forming operation (штамповку), and finally the edges are sheared off to give the final dimensions.

Forging

Forging is the shaping of a piece of metal by pushing with open or closed dies. It is usually done hot in order to reduce the required force and increase the metal's plas­ticity.

Open-die forging is usually done by hammering a part between two flat faces. It is used to make parts that are too big to be formed in a closed die or in cases where only a few parts are to be made. The earliest forging machines lifted a large hammer that was then dropped on the workpiece, but now air or steam hammers are used, since they allow greater control over the force and the rate of forming. The part is shaped by moving or turning it be­tween blows.

Closed-die forging is the shaping of hot metal within the walls of two dies that come together to enclose the workpiece on all sides. The process starts with a rod or bar cut to the length needed to fill the die. Since large, complex shapes and large strains are involved, several dies may be used to go from the initial bar to the final shape. With closed dies, parts can be made to close toler­ances so that little finish machining is required.

Two closed-die forging operations are given special names. They are upsetting and coining. Coining takes its name from the final stage of forming metal coins, where the desired imprint is formed on a metal disk that is pressed in a closed die. Coining involves small strains and is done cold. Upsetting involves a flow of the metal back upon itself. An example of this process is the push­ing of a short length of a rod through a hole, clamping the rod, and then hitting the exposed length with a die to form the head of a nail or bolt.

Vocabulary:

to pull — тянуть

reduction — сокращение

to achieve — достигать

in series — серия, последовательно

beyond — выше, свыше

yield point — точка текучести металла

to retain — сохранять, удерживать

to bend — гнуть

shearing — обрезка, отрезание

edge — край

to grip — схватывать

lower die — нижний штамп

upper die — верхний штамп

forming operation — операция штампования

dimension — измерение, размеры

required — необходимый

increase — увеличение

open-die forging — ковка в открытом штампе (под­кладном)

hammering — ковка, колотить

within — внутри, в пределах

to enclose — заключать

rod — прут, стержень

bar — прут, брусок

involved — включенный

tolerance — допуск

upsetting — высадка, выдавливание

blow — удар

coining — чеканка

imprint — отпечаток

clamp — зажим

to hit — ударять

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Text A: «MECHANICAL PROPERTIES Of MATERIALS»

Fatigue is the growth of cracks under stress. It oc­curs when a mechanical part is subjected to a repeated or cyclic stress, such as vibration. Even when the maximum stress never exceeds the elastic limit, failure of the ma­terial can occur even after a short time. No deformation is seen during fatigue, but small localized cracks develop and propagate through the material until the remain­ing cross-sectional area cannot support the maximum stress of the cyclic force. Knowledge of tensile stress, elastic limits, and the resistance of materials to creep and fatigue are of basic importance in engineering.

Creep is a slow, permanent deformation that results from a steady force acting on a material. Materials at high temperatures usually suffer from this deformation. The gradual loosening of bolts and the deformation of components of machines and engines are all the exam­ples of creep. In many cases the slow deformation stops because deformation eliminates the force causing the creep. Creep extended over a long time finally leads to the rupture of the material.

Vocabulary

bar— брусок, прут

completely — полностью, совершенно

compression — сжатие

creep — ползучесть

cross-sectional area — площадь поперечного сечения

cyclic stress — циклическое напряжение

decrease — уменьшение

elastic deformation — упругая деформация

elastic limit — предел упругости

exceed — превышать

external forces — внешние силы

fatigue — усталость металла

fracture — перелом, излом

loosen — ослаблять, расшатывать

permanent deformation — постоянная деформация

remaining — оставшийся

shear — срез

simultaneously — одновременно

to stretch — растягивать

technique — методы

tension — напряженность

to propagate — распространяться

to bend — гнуть, согнуть

to extend — расширять, продолжаться

to meet the needs — отвечать требованиям

to occur — происходить

to respond — отвечать реагировать

to suffer — страдать

torsion — кручение

twisting — закручивание, изгиб

volume — объем, количество

rupture — разрыв

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