Composite materials

Diesel

In 1890s, Rudolf Diesel, a German engineer, invented the engine that bears his name. As distinguished from gasoline engines, diesels have no ignition system fed with electricity. The fuel is ignited simply by contact with very hot air in the cylinder.

The operation performed is like this: when taken into the cylinder the air is highly compressed, the temperature rises so the heated fuel mixture burns. The higher is the pressure, the higher is the temperature. Besides, the compressed mixture produced more power.

Diesel engines power many of the trucks, coaches, tractors, tanks, generators of electricity and other devices. They are usually used in cases when engine’s weight is not a prime factor. Their advantage is that they are simple in design and use much heavier liquid fuels than gasoline engines. The cost of a heavier fuel is much less than that of a light one. Besides, the fuel consumption of a diesel is much less then that of gasoline engines.

Although applied for many purposes diesel engines have certain disadvantages. Their weight is more than that of gasoline engines of the same power and they occupy more space. The disadvantages of diesels as passenger-car engines are slow performance, noise and smoke.

All the companies investigating diesels are trying to reduce noise and smoke, but the problems are not entirely solved. Diesel engines clatter when started on a cold weather. And the warm-up period for all diesels seems too long to drivers accustomed to gasoline models.

Who invented diesel engines?

Do diesel engines have ignition system fed with electricity?

How is the fuel ignited in the diesel engine?

What do diesel engines power?

What is the advantage of diesel engines?

What are disadvantages of diesels as passenger-car engines?

What are companies trying to reduce?

Задание 16. Восстановите предложения и переведите их.

Die selen gine sclat terw hens tarte don acol dweat her.

Thedi sadv antag esof die salsas pass enger-ca reng in esares low per form ancen oise an dsmo ke.

Di ese leng ines pow erma nyo ftheu sedve hic le san doth erde vices.

Задание 17. Напишите небольшое сочинение по предложенному плану.

1. the invention you consider to be one of the greatest in the world

2. the name of the inventor (if it is known)

3. the country and the time of the invention

4. what the thing was made for

5. how it is used now

6. how it influenced our life

Задание 18. Соотнесите английские слова с русским переводом:

1-cab 2-diesel motor 3-air-cleaner filter 4-exhaust pipe 5-blade lift cylinder 6-blade 7-cutting edge 8-frame push 9-track idler 10-track 11-track roller frame 12-ripper tooth 13-shank protector 14-ripper tip 15-ripper cylinder 16-sprocket wheel 17-crawler tractor 16-ripper 19-bulldozer

-защитная накладка стержня рыхлителя -режущая кромка - выхлопная труба - воздушный фильтр - нож (отвал) - бульдозер - гидроцилиндр подвесного механизма ножа - дизельный двигатель - гусеничный трактор - натяжное колесо гусеницы (ленивец) -острие рыхлителя -зуб рыхлителя -кабина -направляющая рама толкателя -гидроцилиндр рыхлителя -колесо-звездочка -рыхлитель -гусеница -рама опорного катка гусеницы

Задание 19. Напишите аннотацию к тексту.

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. Compo 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 disadvantages. For example, PMCs and other compositematerials tend to be highly anisotropic-that is, their strength, stiffness, and other engineering properties are different depending on the orientation of the 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.

Дата добавления: 2014-10-15