III. Find in the text sentences containing the following words and translate them into Russian.
1) solid crystals
2) composition
3) surface
4) cooling
5) electrical resistance
6) lightweight metals
7) to leak
8) resistivity
9) the solidified mass
10) denseness
IV.
Find 13 words on the topic in the crossword-puzzle and give their Russian equivalents.
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Unit 3. MECHANICAL PROPERTIES OF METALS AND ALLOYS
Strength. - The strength of a material is the property of resistance to external loads or stresses without incurring structural damage.
The strength of metals and alloys depends upon two factors, namely, the strength of the crystals of which the metals are constructed and the tenacity of adherence between these crystals.
Stress and Strain. - A stress is the force within a body which resists deformation due to an externally applied load. If this load acts upon a surface of unit area, it is called a unit force and the stress resisting it a unit stress.
When an external force acts upon an elastic material, the material is deformed and the deformation is in proportion to the load. This distortion or deformation is strain.
Elasticity. - Any material subjected to an external load is distorted or strained. Elastically stressed materials return to their original dimensions when the load is released if the load is not too great. The property of regaining the original dimensions upon removal of the external load is known as elasti city.
The Nature of Elasticity. - The elasticity of a metallic substance is a resistance of its atoms to separation or compression or rotation about one another, and thus is a fundamental property of the material. So elasticity is demonstrated as a function of atomic forces.
Yield Point. - This is a point on the stress - strain curve at which the stress levels off or actually decreases while strain continues. The term is strictly applicable only to mild steels.
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Ultimate Strength. - The greatest load that the specimen has supported divided by the original cross-sectional area is called the ultimate tensile strength or the ultimate strength of the piece.
Ductility. - Ductility is the capacity of a metal to be permanently deformed in tension without breaking.
Toughness. - Toughness has been defined as the property of absorbing considerable energy before fracture. The toughness of a metal is indicated by the amount of slip which may occur within the crystals without resulting in rupture of the metal.
Malleability. - Malleability is the property of a metal which permits permanent deformation by compression without rupture.
Brittleness. - Brittleness implies sudden failure. It is the property of breaking without warning, i.e., without visible permanent deformation.
Failure of metals and alloys under repeated or alternating stresses, too small to produce even a permanent deformation when applied statically, is called fatigue failure.
Corrosion Fatigue. - Failure by corrosion fatigue is a fatigue failure in which corrosion has lowered the endurance limit by the formation of pits that act as centers for the development of fatigue cracks.
Hardness. - The quality of hardness is a combination of a number of physical and mechanical properties.
NOTES AND COMMENTARY
| depends upon - зависит of which the metals are constructed – из которых состоит металл tenacity of adherence – прочность сцепления force within a body – сила, действующая в теле due to – зд. в результате a unit force – единичная сила a unit stress - напряжение is in proportion to the load – пропорционален нагрузке subjected to – подвергнутый original dimentions – первоначальные размеры too great – слишком большой upon removal – после устранения about one another – один вокруг другого yield point – предел текучести strain curve – кривая деформации levels off – понижается (спадает) mild steels – малоуглеродистые стали | ultimate tensile strength – предел прочности при растяжении, сопротивление разрыву ultimate strength – предел прочности to be permanently deformed in ten sion – постоянно деформироваться в растяжении is indicated by the amount of slip which may occur within the cry stals – определяется величиной сдвига, который может произойти в кристаллах breaking without warning – внезапный разрыв, разрыв без предупреждения under repeated or alternating stres ses – при повторяющихся или чередующихся напряжениях fatigue failure – излом усталости number of physical and mechanical properties – ряд физических и механических свойств |
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EXERCISES
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