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Engineering Materials

Subject : engineering
Instructions:
  • Answer 50 questions in 15 minutes.
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  • Match each statement with the correct term.
  • Don't refresh. All questions and answers are randomly picked and ordered every time you load a test.

This is a study tool. The 3 wrong answers for each question are randomly chosen from answers to other questions. So, you might find at times the answers obvious, but you will see it re-enforces your understanding as you take the test each time.
1. Process by which metal atoms diffuse because of a potential.






2. Transformer cores require soft magnetic materials - which are easily magnetized and de-magnetized - and have high electrical resistivity - Energy losses in transformers could be minimized if their cores were fabricated such that the easy magnetizatio






3. Specular: light reflecting off a mirror (average) - Diffuse: light reflecting off a white wall (local)






4. Measures Hardness 1. psia = 500 x HB 2. MPa = 3.45 x HB






5. 1. Metals: Thermal energy puts many electrons into a higher energy state. 2. Energy States: Nearby energy states are accessible by thermal fluctuations.






6. # of thermally generated electrons = # of holes (broken bonds)






7. Stress concentration at a crack tips






8. Specific heat = energy input/(mass*temperature change)






9. 1. Stress-strain behavior is not usually determined via tensile tests 2. Material fails before it yields 3. Bend/flexure tests are often used instead.






10. Cracks propagate along grain boundaries.






11. Large coercivities - Used for permanent magnets - Add particles/voids to inhibit domain wall motion - Example: tungsten steel






12. For a metal - there is no ______ - only reflection






13. ...occurs in bcc metals but not in fcc metals.






14. Undergo extensive plastic deformation prior to failure.






15. 1. Yield = ratio of functional chips to total # of chips - Most yield loss during wafer processing - b/c of complex 2. Reliability - No device has infinite lifetime. Statistical methods to predict expected lifetime - Failure mechanisms: Diffusion reg






16. Metals are good conductors since their _______is only partially filled.






17. 1. Diamagnetic (Xm ~ 10^-5) - small and negative magnetic susceptibilities 2. Paramagnetic (Xm ~ 10^-4) - small and positive magnetic susceptibilities 3. Ferromagnetic - large magnetic susceptibilities 4. Ferrimagnetic (Xm as large as 10^6) - large m






18. Second phase particles with n > glass.






19. High toughness; material resists crack propagation.






20. Allows you to calculate what happened G=F' x cos(lambda) - F=F' x cos(phi)






21. They are used to assess properties of ceramics & glasses.






22. Loss of image transmission - You get no image - There is no light transmission - and therefore reflects - scatters - or absorbs ALL of it. Both mirrors and carbon black are opaque.






23. Flaws and Defects - They concentrate stress locally to levels high enough to rupture bonds.






24. 1. Hard disk drives (granular/perpendicular media) 2. Recording tape (particulate media)






25. 1. General yielding occurs if flaw size a < a(critical) 2. Catastrophic fast fracture occurs if flaw size a > a(critical)






26. Digitalized data in the form of electrical signals are transferred to and recorded digitally on a magnetic medium (tape or disk) - This transference is accomplished by a recording system that consists of a read/write head - "write" or record data by






27. Dimples on fracture surface correspond to microcavities that initiate crack formation.






28. Small Coercivities - Used for electric motors - Example: commercial iron 99.95 Fe






29. Growth of an oxide layer by the reaction of oxygen with the substrate - Provides dopant masking and device isolation - IC technology uses 1. Thermal grown oxidation (dry) 2. Wet Oxidation 3. Selective Oxidation






30. This strength parameter is similar in magnitude to a tensile strength. Fracture occurs along the outermost sample edge - which is under a tensile load.






31. - The emission of light from a substance due to the absorption of energy. (Could be radiation - mechanical - or chemical energy. Could also be energetic particles.) - Traps and activator levels are produced by impurity additions to the material - Whe






32. These are liquid crystal polymers- not your normal "crystal" -Rigid - rod shaped molecules are aligned even in liquid form.

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33. Increase temperature - no increase in interatomic separation - no thermal expansion






34. Different orientation of cleavage planes in grains.






35. Ohms Law: voltage drop = current * resistance






36. Energy is stored as atomic vibrations - As temperature increases - the average energy of atomic vibrations increases.






37. A measure of the ease with which a B field can be induced inside a material.






38. 1. Data for Pure Silicon - electrical conductivity increases with T - opposite to metals






39. Typical loading conditions are _____ enough to break all inter-atomic bonds






40. Measures Hardness - No major sample damage - Each scales runs to 130 but only useful in range 20-100 - Minor load is 10 kg - Major load: 60 kg (diamond) - 100 kg (1/16 in. ball) - 150 kg (diamond)






41. There is always some statistical distribution of flaws or defects.






42. Occur due to: restrained thermal expansion/contraction -temperature gradients that lead to differential dimensional changes sigma = Thermal Stress






43. - A magnetic field is induced in the material B= Magnetic Induction (tesla) inside the material mu= permeability of a solid






44. A high index of refraction (n value) allows for multiple internal reactions.






45. Impurities added to the semiconductor that contribute to excess electrons or holes. Doping = intentional impurities.






46. Materials change size when temperature is changed






47. Transmitted light distorts electron clouds - The velocity of light in a material is lower than in a vacuum - Adding large ions to glass decreases the speed of light in the glass - Light can be "bent" (or refracted) as it passes through a transparent






48. Superconductors expel magnetic fields - This is why a superconductor will float above a magnet.






49. Diffuse image






50. Width of smallest feature obtainable on Si surface