2013材料工程专外试卷.doc

第 1 页 共 5 页西安建筑科技大学研究生试卷考试科目： Specializing English in Materials Science and Engineering 考试时间：2013 年 月 日 时 时 考试方式： close examination 学 号： 姓 名： 成 绩 Please translate English into Chinese. （100 points）一Vocabulary （201=20 points）1. shape memory alloys 2. smart material 3. coefficient of thermal expansion(CTE) 4. amorphous material5. grain boundaries 6. lattice parameters7. close-packed planes and direction 8. strain hardening mechanisms9. stress relaxation 10. impact toughness 11. stress- corrosion 12. texture strengthening 13. extrusion and drawing 14. hot-affected zone(HAZ) 15. homogeneous nucleation 16. nonferrous alloys 17. solidification 18. dispersion strengthening 19. lost foam casting 20. carbon-fiber-reinforced polymers 注：命题纸上一般不留答题位置。字、图清楚，请勿超出边框，以便复印。 第 2 页 共 5 页二Short Documents （810=80 points）1. Materials that can significantly change their mechanical properties (such as shape, stiffness, and viscosity), or their thermal, optical, or electromagnetic properties, in a predictable or controllable manner in response to their environment. Materials that perform sensing and actuating functions, including piezoelectrics, electrostrictors, magnetostrictors, and shape-memory alloys.2. When a material is designed for a given application, a number of factors must be considered. The material must acquire the desired physical and mechanical properties, must be capable of being processed or manufactured into the desired shape, and must provide an economical solution to the design problem. Satisfying these requirements in a manner that protects the environmentperhaps by encouraging recycling of the materialsis also essential. In meeting these design requirements, the engineer may have to make a number of tradeoffs in order to produce a serviceable, yet marketable product.注：命题纸上一般不留答题位置。字、图清楚，请勿超出边框，以便复印。第 3 页 共 5 页3. Materials with metallic bonding exhibit relatively high Youngs modulus since the bonds are strong. Metals also show good ductility since metallic bonds are non-directional. There are other important reasons related to microstructure that can explain why metals actually exhibit lower strengths and higher ductility than what we may anticipate from their bonding. Ductility refers to the ability of materials to be stretched or bent without breaking. In general, the melting points of metals are relatively high. From an optical properties viewpoint, metals make good reflectors of visible radiation. Owing to their electropositive character, many metals such as iron tend to undergo corrosion or oxidation. Many pure metals are good conductors of heat and are effectively used in many heat transfer applications.4. The hardness test measures the resistance to penetration of the surface of a material by a hard object. Hardness as a term is not defined precisely. Hardness, depending upon the context, can represent resistance to scratching or indentation and a qualitative measure of the strength of the material. In general, in macro-hardness measurements the load applied is 2N. A variety of hardness tests have been devised, but the most commonly used are the Rockwell test and the Brinell test. Hardness correlates well wear resistance.注：命题纸上一般不留答题位置。字、图清楚，请勿超出边框，以便复印。第 4 页 共 5 页5. Structure materials are designed for carrying some type of stress. Steels, concrete, and composites are used to make buildings and bridges. Steels, glasses, plastics, and composites are also used widely to make automotives. Often in these applications, combinations of strength, stiffness, and toughness are needed under different conditions of temperature and loading.6. Magnesium, which is often extracted electrolytically from concentrated magnesium chloride in seawater, is lighter than aluminum with a density of 1.74g/cm3, and it melts at a slightly lower temperature than aluminum. In many environments, the corrosion resistance of magnesium approaches that of aluminum; however, exposure to salts, such as that near a marine environment, causes rapid deterioration. Although magnesium alloys are not as strong as aluminum alloys, their specific strengths are comparable. Consequently, magnesium alloys are used in aerospace applications, high-speed machinery, and transportation and materials handling equipment. Magnesium has a low modulus of elasticity and poor resistance to fatigue, creep, and wear. Magnesium also poses a hazard during casting and machining, since it combines easily with oxygen and burns. Finally, the response of magnesium to strengthening mechanisms is relatively poor.注：命题纸上一般不留答题位置。字、图清楚，请勿超出边框，以便复印。第 5 页 共 5 页7. Deformation by slip also contributes to the ductile fracture of a metal. We know that slip occurs when the resolved shear stress reaches the critical resolved shear stress and that the resolved shear stresses are highest at a 45 angle to the applied tensile stress. These two aspects of ductile fracture give the failed surface characteristic features. In thick metal section, we expect to find evidence of necking, with a significant portion of the fracture surface having a flat face where microvoids first nucleated and coalesced, and a small shear lip, where the fracture surface is at a 45 angle to the applied stress. The shear lip, indicting that slip occurred, gives the fracture a cup and cone appearance. Simple macroscopic observation of this fracture may be sufficient to identify the ductile fracture mode.8. Fatigue is the lowing of strength or failure of a material due to repetitive stress which may be above or below the yield strength. It is a common phenomenon in load-bearing components in cars and airplanes, turbine blades, s