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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. - 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






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


3. 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






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






5. Occur when lots of dislocations move.






6. Is analogous to toughness.






7. 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






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






9. 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.






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






11. 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






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






13. Second phase particles with n > glass.






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






15. 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






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






17. High toughness; material resists crack propagation.






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






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






20. Because of ionic & covalent-type bonding.






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






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






23. 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






24. 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.






25. These materials are relatively unaffected by magnetic fields.






26. Emitted light is in phase






27. Materials change size when temperature is changed






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






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






30. The ability of a material to transport heat - Atomic Perspective: Atomic vibrations and free electrons in hotter regions transport energy to cooler regions - Metals have the largest values






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






32. A high index of refraction (n value) allows for multiple internal reactions.






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






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






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






36. 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.






37. 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.






38. Diffuse image






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






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






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






42. Undergo extensive plastic deformation prior to failure.






43. 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.






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






45. 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.






46. Sigma=ln(li/lo)






47. Superconductors expel magnetic fields - This is why a superconductor will float above a magnet.






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






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






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