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

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2. With Increasing temperature - the saturation magnetization diminishes gradually and then abruptly drops to zero at Curie Temperature - Tc.






3. 1. Electron motions 2. The spins on electrons - Net atomic magnetic moment: sum of moments from all electrons.






4. (sigma)=K(sigma)^n . K = strength coefficient - n = work hardening rate or strain hardening exponent. Large n value increases strength and hardness.






5. Undergo extensive plastic deformation prior to failure.






6. These materials are "attracted" to magnetic fields.






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






8. No appreciable plastic deformation. The crack propagates very fast; nearly perpendicular to applied stress. Cracks often propagate along specific crystal planes or boundaries.






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






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






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






12. Is analogous to toughness.






13. Width of smallest feature obtainable on Si surface






14. (sigma)=F/Ai (rho)=(rho)'(1+(epsilon))






15. Heat capacity.....- increases with temperature -for solids it reaches a limiting value of 3R






16. A parallel-plate capacitor involves an insulator - or dielectric - between two metal electrodes. The charge density buildup at the capacitor surface is related to the dielectric constant of the material.






17. 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.






18. Measures impact energy 1. Strike a notched sample with an anvil 2. Measure how far the anvil travels following impact 3. Distance traveled is related to energy required to break the sample 4. Very high rate of loading. Makes materials more "brittle."






19. Rho=F/A - tau=G/A . Depending on what angle the force is applied - and what angle the crystal is at - it takes different amounts of force to induce plastic deformation.






20. -> fluorescent light - electron transitions occur randomly - light waves are out of phase with each other.






21. Without passing a current a continually varying magnetic field will cause a current to flow






22. 1. Ability of the material to absorb energy prior to fracture 2. Short term dynamic stressing - Car collisions - Bullets - Athletic equipment 3. This is different than toughness; energy necessary to push a crack (flaw) through a material 4. Useful in






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






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






25. - 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






26. The ability of a material to absorb heat - Quantitatively: The energy required to produce a unit rise in temperature for one mole of a material.






27. 1. Tensile (opening) 2. Sliding 3. Tearing






28. Created by current through a coil N= total number of turns L= length of turns (m) I= current (ampere) H= applied magnetic field (ampere-turns/m) Bo= magnetic flux density in a vacuum (tesla)






29. The magnetic hysteresis phenomenon: Stage 1: Initial (unmagnetized state) Stage 2: Apply H - align domains Stage 3: Remove H - alignment remains => Permanent magnet Stage 4: Coercivity - Hc negative H needed to demagnitize Stage 5: Apply -H - align d






30. As the applied field (H) increases the magnetic domains change shape and size by movement of domain boundaries.






31. 1. Impose a compressive surface stress (to suppress surface cracks from growing) - Method 1: shot peening - Method 2: carburizing 2.Remove stress concentrators.






32. Stress concentration at a crack tips






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






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






35. Growing interconnections to connect devices -Low electrical resistance - good adhesion to dielectric insulators.






36. 1. Imperfections increase resistivity - grain boundaries - dislocations - impurity atoms - vacancies 2. Resistivity - increases with temperature - wt% impurity - and %CW






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






38. Sigma=ln(li/lo)






39. Diffuse image






40. If a material has ________ - then the field generated by those moments must be added to the induced field.






41. 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






42. Failure under cyclic stress 1. It can cause part failure - even though (sigma)max < (sigma)c 2. Causes ~90% of mechanical engineering failures.






43. Cracks propagate along grain boundaries.






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






45. A three terminal device that acts like a simple "on-off" switch. (the basis of Integrated Circuits (IC) technology - used in computers - cell phones - automotive control - etc) - If voltage (potential) applied to the "gate" - current flows between th






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






47. The ability of a material to be rapidly cooled and not fracture






48. Cp: Heat capacity at constant pressure Cv: Heat capacity at constant volume.






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






50. Process by which metal atoms diffuse because of a potential.