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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. High toughness; material resists crack propagation.






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






3. Stress concentration at a crack tips






4. 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.






5. Is analogous to toughness.






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






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






8. Second phase particles with n > glass.






9. 1. Fluorescent Lamp - tungstate or silicate coating on inside of tube emits white light due to UV light generated inside the tube. 2. TV screen - emits light as electron beam is scanned back and forth.






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






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






12. The size of the material changes with a change in temperature - polymers have the largest values






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






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






15. Undergo little or no plastic deformation.






16. Ability to transmit a clear image - The image is clear.






17. Occurs at a single pore or other solid by refraction n = 1 for pore (air) n > 1 for the solid - n ~ 1.5 for glass - Scattering effect is maximized by pore/particle size within 400-700 nm range - Reason for Opacity in ceramics - glasses and polymers.






18. Plastic means permanent! When a small load is applied - bonds stretch & planes shear. Then when the load is no longer applied - the planes are still sheared.






19. Hardness is the resistance of a material to deformation by indentation - Useful in quality control - Hardness can provide a qualitative assessment of strength - Hardness cannot be used to quantitatively infer strength or ductility.






20. To build a device - various thin metal or insulating films are grown on top of each other - Evaporation - MBE - Sputtering - CVD (ALD)






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






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






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






24. Diffuse image






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






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






27. Undergo extensive plastic deformation prior to failure.






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






29. Wet: isotropic - under cut Dry: ansiotropic - directional






30. Found in 26 metals and hundreds of alloys & compounds - Tc= critical temperature = termperature below which material is superconductive.






31. 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






32. These materials are relatively unaffected by magnetic fields.






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






34. 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.






35. 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






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






37. Defines the ability of a material to resist fracture even when a flaw exists - Directly depends on size of flaw and material properties - K(ic) is a materials constant






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






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






40. 1. Insulators: Higher energy states NOT ACCESSIBLE due to gap 2. Semiconductors: Higher energy states separated by a smaller gap.






41. Elastic means reversible! This is not a permanent deformation.






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






43. Cracks propagate along grain boundaries.






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






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






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






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






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

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49. Becomes harder (more strain) to stretch (elongate)






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