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






2. Allows flow of electrons in one direction only (useful to convert alternating current to direct current) - Result: no net current flow






3. 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)






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






5. High toughness; material resists crack propagation.






6. Degree of opacity depends on size and number of particles - Opacity of metals is the result of conduction electrons absorbing photons in the visible range.






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






8. 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






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






10. 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






11. 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."






12. Liquid polymer at room T - sandwiched between two sheets of glass - coated with transparent - electrically conductive film. - Character forming letters/ numbers etched on the face - Voltage applied disrupts the orientation of the rod- shaped molecule






13. 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)






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






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






16. Occur when lots of dislocations move.






17. Not ALL the light is refracted - SOME is reflected. Materials with a high index of refraction also have high reflectance - High R is bad for lens applications - since this leads to undesirable light losses or interference.






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






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






20. Light Amplification by Stimulated Emission of Radiation






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






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






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






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






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






26. 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






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






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






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






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






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






32. Is analogous to toughness.






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






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






35. 1. Ductility- % elongation - % reduction in area - may be of use in metal forming operations (e.g. - stretch forming). This is convenient for mechanical testing - but not very meaningful for most deformation processing. 2. Toughness- Area beneath str






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






37. Another optical property - Depends on the wavelength of the visible spectrum.






38. Undergo little or no plastic deformation.






39. - 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






40. Ohms Law: voltage drop = current * resistance






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






42. Sigma=ln(li/lo)






43. Width of smallest feature obtainable on Si surface






44. Undergo extensive plastic deformation prior to failure.






45. These materials are relatively unaffected by magnetic fields.






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






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






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






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

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50. 1. Necking 2. Cavity formation 3. Cavity coalescence to form cracks 4. Crack propagation (growth) 5. Fracture