II. READING (30 points). a) Read the text and answer the questions given below (give full answers):
a) Read the text and answer the questions given below (give full answers): MECHANICAL PROPERTIES Hardness is the property of a material to resist permanent indentation. Because there are several methods of measuring hardness, the hardness of a material is always specified in terms of the particular test that was used to measure this property. Rockwell, Vickers, or Brinell are some of the methods of testing. Of these tests, Rockwell is the one most frequently used. The basic principle used in the Rockwell test is that a hard metal can penetrate a softer one. We then measure the amount penetration and compare it to a scale. For ferrous metals, which are usually harder than nonferrous metals, a diamond tip is used and the hardness is indicated by a softer, a metal ball is used and the hardness is indicated by a Rockwell “B” number. To get an idea of the property of hardness, compare lead and steel. Lead can be scratched with a pointed wooden stick but steel cannot because it is harder than lead. Common types of stress are compression, tension, shear, torsion, impact, or combination of these stresses, such as fatigue. Compression stresses develop within a material when forces compress or crush the material. A column that supports an overhead beam is in compression, and the internal stresses that develop within the column are compression. Tension (or tensile) stresses develop when a material is subjected to a pulling load; for instance, when using a wire rope to lift a load or when using it as a guy to anchor an antenna. “Tensile strength” is defined as resistance to longitudinal stress or pull and can be measured in pounds per square inch of cross section. Shearing stresses occur within a material when external forces are applied along parallel lines in opposite directions. Shearing forces can separate material by sliding part of it in one direction and the other part in the opposite direction.
1. What is the basic principle used in the Rockwell test? 2. What is the example of tension stresses? 3. Are ferrous metals harder than non-ferrous ones? 4. When do shearing stresses occur? 5. What is hardness? 6. When do compression stresses develop? 7. What is the definition of the tensile stress? 8. What method is the most frequently used? 9. Why is the hardness of a material always specified in terms? 10. What are the common types of stress? 20 points b) Translate these sentences from Russian into English: 1. Упругая деформация – это реакция всех материалов на внешние силы, такие, как растяжение, сжатие, скручивание, изгиб и срез. 2. Усталость и ползучесть материалов являются результатом внешних сил. 3. Внешние силы вызывают постоянную деформацию и разрушение материала. 4. Когда деталь работает долгое время под циклическими напряжениями, в ней появляются небольшие растущие трещины из-за усталости металла. 5. Ползучесть – это медленное изменение размера детали под напряжением. 10 points Total Score – 50 points
|
