To be read after Lesson б

Ceramic Application

The application which has captured the imagination of engi­neers, as well as the general public, is certainly the ceramic engine, that is the adiabatic turbo-diesel engine and the ceramic turbine for automotive use. There are some successful phototypes on the road, however, applications on a large scale have been held back by prob­lems of cost and reliability. Steady progress is being made in the in­crease of the reliability of ceramics. But the cost factor is likely to remain a problem for some time.

One should mention here that the long-term reliability in ser­vice still needs to be defined for those applications where the mate­rial must withstand very high temperatures and dynamically changing mechanical and thermal loads in a chemically aggressive environment.

Ceramic engines and turbines are but the top of the pyramid with respect to applications. At lower levels of performance there are numerous other applications, in which the operating conditions are less severe, for example, ceramic heat exchangers for chemical plants. Ceramics finds application in bearings and engine parts be­cause of its high hardness and high abrasion resistance.

There are three main materials used in making pipes: metal, rubber and plastic.

Metal is stronger than rubber and plastic. It is also heavier and more rigid than rubber and plastic. Metal is the strongest material, but it is also the heaviest, and the most rigid. It is also the most ex­pensive of the three materials.

Rubber is weaker than metal or plastic. It is also more flexible than the other two materials. Rubber is the most flexible of the three materials, but it is the weakest.

Plastic is lighter than metal. It is also less expensive than steel or rubber. Plastic is the lightest material. It is also the least expen­sive of the three materials.

Glass is used for making windows because you can see through it, and it is very hard and therefore cannot be cut easily. But at the same time it is very brittle and therefore it can break easily.

Wood is soft and therefore it can be cut easily. It can be used in fires because it is combustible.

Car tyres are made of rubber because rubber is flexible.

A car panel is made by three methods. First, sheet steel is made. This is done by pushing a piece of steel between two rollers, which squeeze the metal and make it longer and thinner. This method is called rolling. Not all metals can be rolled. For example, iron can­not be rolled because it is too brittle. But steel can be rolled because it is tough and malleable (ковкий) enough.

Next, the steel is cut into a flat shape. This is done by placing the sheet onto a die, and then cutting a hole in it with a punch. The method is called punching. The steel can be cut easily because it is now very thin.

Finally, the sheet steel is bent and pressed into a rounded shape. This is done by putting the sheet onto a die and then bend­ing the sheet around the die with a press. This method is called pressing. It is not difficult to press sheet steel because it is thin and malleable.

Дата добавления: 2014-12-17