G azərbaycan respublikasi təHSİl naziRLİYİ azərbaycan texniKİ universiteti M. M. QƏNDİLova e. Q. İsmayilova

JOKES, LAUGHS, SMILES
A student in a college wrote his father,” No more. No fun. Your son.”

The father answered, “How sad. Too bad. Your dad.”

UNIT IX
He who is ignorant of foreign

languages knows not his own.

(A proverb)

PROPERTIES OF ENGINEERING MATERIALS
An airliner crashes into mountain, a train is wrecked, a bridge fails, and the loss of life and the cost of destruction may sometimes be the responsibility of the engineer. To avoid these possibilities, engineers must not only know how to determine the stresses and deformations in structures and machines under a variety of possible loading conditions. But they should also know how well the selected material of construction is to resist the loading.

In our daily lives we are constantly faced with the importance of finding suitable engineering materials. A complete knowledge of the properties of engineering materials would not only be required by engineers to prevent failure of structures and machines, but such knowledge would be also necessary in order that these materials should be made use of most economically. In recent years, the fact that some materials are available in insufficient quantities and the more effective use of new materials required that a more thorough consideration of material properties be made. The science of engineering materials has led to the development of many alloys having much greater resistance to various loading conditions.

For many products made of non-metallic materials such as, for example, the tremendous amount of things manufactured using plastics, a consideration of engineering properties might be very important. It is often required that we should get information on the properties of materials subjected to most severe conditions of temperature, corrosion, etc.

These conditions should be taken into account in the design of such constructions as gas and steam turbines for ships, rockets, jet engines, and various equipment, for atomic power stations.

The development of materials required for the construction of the many machines, structures and products used in our modern civilization is provided by many kinds of engineers and scientists. In selecting the most suitable material and in the determination of the sizes of the required members, the designer might utilize the services of a materials engineer.

Metals are widely used as construction materials. The uses of metals are based upon their physical or chemical properties. Metals vary in density, hardness, heat and electrical conductivity and weight. The lightest metal is lithium and the heaviest one is osmium. The hardness of metals depends upon the presence of other substances in them and the nature of metal itself. Metals are the best construction materials and conductors of heat and electricity.