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






2. 1. Diamagnetic (Xm ~ 10^-5) - small and negative magnetic susceptibilities 2. Paramagnetic (Xm ~ 10^-4) - small and positive magnetic susceptibilities 3. Ferromagnetic - large magnetic susceptibilities 4. Ferrimagnetic (Xm as large as 10^6) - large m






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






4. Width of smallest feature obtainable on Si surface






5. 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






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






7. Diffuse image






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






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






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






11. 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






12. This strength parameter is similar in magnitude to a tensile strength. Fracture occurs along the outermost sample edge - which is under a tensile load.






13. High toughness; material resists crack propagation.






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






15. 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.






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






17. 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






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






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






20. 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."






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






22. Allows you to calculate what happened G=F' x cos(lambda) - F=F' x cos(phi)






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






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






25. 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.






26. Different orientation of cleavage planes in grains.






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






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






29. Digitalized data in the form of electrical signals are transferred to and recorded digitally on a magnetic medium (tape or disk) - This transference is accomplished by a recording system that consists of a read/write head - "write" or record data by






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






31. 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






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






33. These materials are relatively unaffected by magnetic fields.






34. 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.






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






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






37. Occur when lots of dislocations move.






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






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






40. 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






41. Cracks propagate along grain boundaries.






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






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






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






45. 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






46. 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






47. 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.






48. Materials change size when temperature is changed






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






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







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