Translate into English the following sentences:

1. Упругая деформация – это реакция всех материалов на внешние силы, такие как растяжение, сжатие, скручивание, изгиб и срез.
2. Усталость и ползучесть материалов являются результатом внешних сил.
3. Внешние силы вызывают постоянную деформацию и разрушение материала.
4. Растягивающие и сжимающие силы работают одновременно, когда мы изгибаем или скручиваем материал.
5. Растяжение материала выше предела его упругости дает постоянную деформацию или разрушение.
6. Когда деталь работает долгое время под циклическими напряжениями, в ней появляются небольшие растущие трещины из-за усталости металла.
7. Ползучесть – это медленное изменение размера детали под напряжением.

 

                                                                        

Text 2.

PROPERTIES OF MATERIALS

           Density (specific weight) is the amount of mass in a unit volume. It is measured in kilograms in per cubic meter. The density of water is 1000 kg/m3 but most materials have a higher density and sink in water. Aluminum alloys, with typical densities around 2800 kg/m3 are considerably less dense than steels, which have typical densities around 7800 kg/m3. Density is important in any application where the material must not be heavy.

           Stiffness (rigidity) is a measure of the resistance to deformation such as stretching or bending. The Young modulus is a measure of the resistance to simple stretching or compression. It is the ratio of the applied force per unit area (stress) to the fractional elastic deformation (strain). Stiffness is important when a rigid structure is to be made.

           Strength is the force per unit area (stress) that a material can support without failing. The units are the same as those of stiffness, MN/m2, but in this case the deformation is irreversible. The yield strength is the stress at which a material first deforms plastically. For a metal the yield strength may be less than the fracture strength, which is the stress at which it breaks. Many materials have a higher strength in compression then in tension.

           Ductility is the ability of material to deform without breaking. One of the great advantages of metals is their ability to be formed into the shape that is needed, such as car body parts. Materials that are not ductile are brittle. Ductile materials can absorb energy by deformation but brittle materials cannot.

           Toughness is the resistance of a material to breaking when there is a crack in it. For a material of given toughness, the stress at which it will fail is inversely proportional to the square root of the size of the largest defect present. Toughness is different from strength: the toughest steels, for example, are different from the ones with highest tensile strength. Brittle materials have low toughness: glass can be broken along a chosen line by first scratching it with a diamond. Composites can be designed to have considerably greater toughness than their constituent materials. The example of a very tough composite is fiberglass that is very flexible and strong.

           Creep resistance is the resistance to a gradual permanent change of shape, and it becomes especially important at higher temperatures. A successful research has been made in materials for machine parts operate at high temperatures and under high tensile forces without gradually extending, for example the parts of plane engines.

 

           Additional vocabulary:

ability – способность

absorb – поглощать

amount – количество

application – применение

brittle – хрупкий, ломкий

car body – кузов автомобиля

constituent – компонент

crack – трещина

creep resistance – устойчивость к ползучести

definition – определение

density – плотность

ductility – ковкость, эластичность

failure – повреждение, разрушение

gradual – постепенный

rigid – жесткий

to sink – тонуть

square root – квадратный корень

stiffness – жесткость

strain – нагрузка, напряжение, деформация

strength – прочность

stress – давление, напряжение

tensile strength – прочность на разрыв

toughness – прочность, стойкость

yield strength – предел текучести

Young modulus – модель Юнга

 

Answer the questions:

1. What is the density of a material?
2. What are the units of density? Where low density is needed?
3. What are the densities of water, aluminum and steel?
4. A measure of what properties is stiffness? When stiffness is important?
5. What is Young modulus?
6. What is strength?
7. What is yield strength? Why fracture strength is always greater than yield strength?
8. What is ductility? Give the examples of ductile materials. Give the examples of brittle materials.
9. What is toughness?
10. What properties of steel are necessary for the manufacturing of: a) springs, b) car body parts, c) bolts and nuts, d) cutting tools?
11. Where is aluminium mostly used because of its light weight?

 

Find the following words and word combinations in the text:

1. количество массы в единице объема
2. тонна на кубический метр
3. мера сопротивления деформации
4. отношение приложенной силы на единицу площади к частичной упругой деформации
5. жесткая конструкция
6. прочность на сжатие
7. способность материала деформироваться не разрушаясь
8. поглощать энергию путем деформации
9. обратно пропорционально квадрату размера дефекта
10. постепенное изменение формы
11. повышение температуры
12. высокие растягивающие усилия

 

Translate into English:

1. Плотность измеряется в килограммах на кубический метр.
2. Большинство материалов имеют более высокую плотность, чем вода, и тонут в воде.
3. Плотность материала очень важна, особенно в авиации.
4. Модуль Юнга – отношение приложенной силы к упругой деформации данного материала.
5. Чем более металл жесткий, тем менее он деформируется под нагрузкой.
6. Когда металл растягивают, он сначала течет, то есть пластически деформируется.
7. Свинец, медь алюминий и золото – самые ковкие металлы.
8. Сопротивление ползучести является очень важным свойством материалов, которые используются в авиационных моторах.

 

Text 3.

COMPOSITE MATERIALS

           The combination of two or more different materials are called composite materials. They usually have unique mechanical and physical properties because they combine the best properties of different materials. For example, a fibre-glass reinforced plastic combines the high strength of thin glass fibres with the ductility and chemical resistance of plastic. Nowadays composites are being used for structures such as bridges, boat-building etc.

           Composite materials usually consist of synthetic fibres within a matrix, a material that surrounds and is tightly bound to the fibres. The most widely used type of composite materials is polymer matrix composites (PMCs). PMCs consist of fibres made of a ceramic material such as carbon or glass embedded in a plastic matrix. Usually the fibres make up about 60 per cent by volume. Composites with metal matrices or ceramic matrices are called metal matrix composites (MMCs) and ceramic matrix composites (CMCs), respectively.

           Continuous-fibre composites are generally required for structural applications. The specific strength (strength-to-density ratio) and specific stiffness (elastic modulus-to-density ratio) of continuous carbon fibre PMCs, for example, can be better than metal alloys have. Composites can also have other attractive properties, such as high thermal or electrical conductivity and a low coefficient of thermal expansion.

           Although composite materials have certain advantages over conventional materials, composites also have some disadvantages. For

example, PMCs and other composite materials tend to be highly anisotropic-that is, their strength, stiffness and other engineering properties are different depending on the orientation of the composite material. For example, if a PMC is fabricated so that all the fibres are lined up parallel to one another, then the PMC will be very stiff in the direction parallel to the fibres, but not stiff in the perpendicular direction. The designer, who uses composite materials in structures subjected to multidirectional forces, must take these anisotropic properties into account. Also, forming strong connections between separate composite material components is difficult.

The advanced composites have high manufacturing costs. Fabricating composite materials is a complex process. However, new manufacturing techniques are developed. It will become possible to produce composite materials at higher volumes and at a lower cost than is now possible, accelerating the wider exploitation of these materials.

           Additional vocabulary:

fiberglass – стеклопластик, фибергласс

fibre – волокно, нить

reinforced – упроченный

expansion – расширение

matrix – матрица

ceramic – керамический

specific strength – удельная прочность

specific stiffness – удельная жесткость

anisotropic – анизотропный

 

           Answer the questions:

1. What is called “composite materials”?
2. What are the best properties of fiberglass?
3. What do composite materials usually consist of?
4. What is used as matrix in composites?
5. What is used as filler (наполнитель) or fibers in composites?
6. How are composite materials with ceramic and metal matrices called?
7. What are the advantages of composites?
8. What are the disadvantages of composites?
9. Why anisotropic properties of composites should be taken into account?

 

Find equivalents in the text:

1. композитные материалы
2. уникальные механические качества
3. полимерные материалы
4. составлять 60% объема

 

 

1. привлекательные качества
2. структура, подвергающаяся воздействию разнонаправленных сил

 

Translate into Russian:

1. PNC is fabricated so that all the fibres are lined up parallel to one another.
2. Forming strong connection between separate composite material components is difficult.
3. Fabricating composite materials is a complex process.
4. Composite materials have certain advantages over conventional materials.
5. Nowadays, composites are being used for structures such as bridges, boat- building etc.
6. Continuous-fibre composites are generally required for structural applications.

Text 4.

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