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II. Translate into Ukrainian in written form. Consult various kinds of dictionaries. Metal Fatigue

Fatigue in metals occurs when the cohesion in metal (or other material structure) is gradually broken down by repeated stresses. Finally the cohesion gives way and a fracture occurs.

Cohesion is the force which tends to hold a body together and is greatly reduced by repeated stresses and then a break takes place. Most fractures in machine parts and structures are the result of fatigue, if they were subjected to repeated loading. The trouble is, of course, that it is not possible to know ahead when a part will fail because of fatigue, there are no warnings. Nothing can be seen with the naked eye.

Fatigue can be predicted only from experimental data. For this reason and also because both tensile and bending stresses involve complex prob­lems, new laboratory techniques have been developed and fatigue test­ing has become almost a separate and a most important field.

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Text 6

NON-FERROUS METALS AND THEIR ALLOYS

(Part I) copper, tin, bronze

Copper (Cu) is found in nature in the form of ores but it is sometimes found in pure state. Pure copper is of reddish colour and it has corrosion resistant qualities. Copper is the best conductor of electricity. It is used a great deal for elec­trical wiring and cables. It is a good conductor and it is sur­passed only by silver for conductivity of electricity and the making of electrical apparatus is the chief use for copper, e.g. telephone and telegraph cables; electric wiring; parts of. dynamos and electric motors. Three important copper alloys are brass, bronze and cupro-niekel (75% copper + 25% nickel), which is used for the present “silver” coins.

Tin (Sn) is a silvery metal which is not corroded by air. The chief use is for making tin plate, i.e. sheetiron coated with tin. Tin plate is suitable for cans in which acid fruit and other food-stuffs are packed because tin is not attacked by weak acids. For good containers, iron is coated with tin instead of zinc because tin is not subject to attack by acids in food.

An alloy of copper and tin (80% + 20% respectively) is called bronze. Bronze is very tough; it with­stands shock; it wears well. Bronze is used for making ship propellers, parts of machinery, subject to hard wear, and for doors and windows.

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