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Engineering Materials

Subject : engineering
Instructions:
  • Answer 50 questions in 15 minutes.
  • If you are not ready to take this test, you can study here.
  • 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. 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.






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






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






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






5. 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






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






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






8. The Magnetization of the material - and is essentially the dipole moment per unit volume. It is proportional to the applied field. Xm is the magnetic susceptibility.






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






10. 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.






11. 1. Tc= critical temperature- if T>Tc not superconducting 2. Jc= critical current density - if J>Jc not superconducting 3. Hc= critical magnetic field - if H > Hc not superconducting






12. 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






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






14. 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






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






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






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






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






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






21. Sigma=ln(li/lo)






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






23. Width of smallest feature obtainable on Si surface






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






25. Different orientation of cleavage planes in grains.






26. Diffuse image






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






28. 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.






29. Cracks pass through grains - often along specific crystal planes.






30. Cracks propagate along grain boundaries.






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






32. 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."






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






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


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






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






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






38. Reflectiviy is between 0.90 and 0.95 - Metal surfaces appear shiny - Most of absorbed light is reflected at the same wavelength (NO REFRACTION) - Small fraction of light may be absorbed - Color of reflected light depends on wavelength distribution of






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






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






41. 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






42. - 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






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






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






45. Process by which geometric patterns are transferred from a mask (reticle) to a surface of a chip to form the device.






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






47. Second phase particles with n > glass.






48. High toughness; material resists crack propagation.






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






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