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






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






3. 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






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






5. Is reflected - absorbed - scattered - and/or transmitted: Io=It+Ia+Ir+Is






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






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






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






9. 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.






10. heat flux = -(thermal conductivity)(temperature gradient) - Defines heat transfer by CONDUCTION

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11. Width of smallest feature obtainable on Si surface






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






13. 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.






14. 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






15. 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)






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






17. These materials are relatively unaffected by magnetic fields.






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






19. 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






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






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






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






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






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






25. Is analogous to toughness.






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






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






28. 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






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






30. Dramatic change in impact energy is associated with a change in fracture mode from brittle to ductile.






31. 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






32. Sigma=ln(li/lo)






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






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






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






36. 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.






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






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






39. 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)






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






41. - Metals that exhibit high ductility - exhibit high toughness. Ceramics are very strong - but have low ductility and low toughness - Polymers are very ductile but are not generally very strong in shear (compared to metals and ceramics). They have low






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






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






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






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. 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






47. 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






48. 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.






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






50. 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.