Material Science and Technology.

1. Read and learn the new words, write them down into your vocabulary:

ability -здатність

absorb - поглинати

amount – кількість

application -використання

brittle - ламкий

car body -кузов автомобіля;

constituent -компонент

crack - тріщина

creep resistance –стійкість до повзучості

definition -визначення

density - щільність

ductility - еластичність

failure - пошкодження

gradual - поступовий

rigid – жорсткий

to sink -тонути

square root -квадратний корінь

stiffness - жорсткість

strain - нагрузка,

strength – міцність

stress - напруга

tensile strength - міцність на розрив

toughness - стійкість

yield strength – межа текучості

 

Make 10 sentences with the words given above.

3. Read and translate the text:

PROPERTIES OF MATERIALS

Density (specific weight) is the amount of mass in a unit volume. It is measured in kilograms per cubic metre. The density of water is 1000 kg/m3 but most materials have a higher density and sink in water. Aluminium 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 than in tension.

Ductility is the ability of a 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 that operate at high temperatures and under high tensile forces without gradually extending, for example the parts of plane engines.

 

4. 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, aluminium and steel?

4. A measure of what properties is stiffness? When stiff-ness 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.

8. What is toughness?

9. What properties of steel are necessary for the manufacturing of: a) springs, b) car body parts, c) bolts and nuts, d) cutting tools?

10. Where is aluminium mostly used because of its light weight?

 

5. Find the following words and word combi-nations in the text:

1. кількість маси в одиниці об'єму

2.тона на кубічнийметр

3.міра опору деформації

4. відношення прикладеної сили на одиницю площі до часткової пружної деформації

5.жорстка конструкція

6.міцність на стискування

7.здатність матеріалу деформуватися не руйнуючись

8.поглинати енергію шляхом деформації

9.обернено пропорційно до квадрата розміру дефекту

10.поступова зміна форми

11.підвищені температури

12.високі розтягуючі зусилля

 

6. Translate into English:

1.Щільність вимірюється в кілограмах на кубічний метр.

2.Більшість матеріалів мають вищу щільність, ніж вода і тонуть у воді.

3.Щільність матеріалу дуже важлива, особливо в авіації.

4.Модуль Юнга - відношення прикладеної сили до пружної деформації даного матеріалу.

5.Чим більш метал жорсткий, тим менш він деформується під навантаженням.

6.Коли метал розтягують, він спочатку тече, тобто пластично деформується.

7.Свинець, мідь, алюміній і золото - самі ковкі метали.

8.Опір повзучості є дуже важливою властивістю матеріалів, які використовуються в авіаційних моторах.

 

Additional text

COMPOSITE MATERIALS

The combinations 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 material 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.

 

Essential Vocabulary:

fibreglass - склопластик

fibre – волокно

reinforced - зміцнений

expansion - розширення

matrix - матриця

ceramic - керамічний

specific strength – питома жорсткість

anisotropic - анізотропний

 

7. 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 com-posites?

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?

 

8. Find equivalents in the text:

1.композитні матеріали

2.унікальні механічні якості

3.полімерні матричні композити

4.складати 60% об'єму

5.привабливі якості

6.структура, що піддається дії різно-направлених сил

 

9. Translate into Ukrainian:

1. PMC is fabricated so that all the fibres are lined up parallel to one another.

2. Forming strong connections 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.