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






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






3. 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.






4. Increase temperature - increase in interatomic separation - thermal expansion






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

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6. Width of smallest feature obtainable on Si surface






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






8. Undergo little or no plastic deformation.






9. Undergo extensive plastic deformation prior to failure.






10. 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)






11. 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.






12. Ohms Law: voltage drop = current * resistance






13. 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






14. 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.






15. Second phase particles with n > glass.






16. 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






17. Stress concentration at a crack tips






18. 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.






19. 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






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






21. Occur when lots of dislocations move.






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






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






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






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






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






28. 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






29. High toughness; material resists crack propagation.






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. 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






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






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






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






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






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






37. Transformer cores require soft magnetic materials - which are easily magnetized and de-magnetized - and have high electrical resistivity - Energy losses in transformers could be minimized if their cores were fabricated such that the easy magnetizatio






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






39. A measure of the ease with which a B field can be induced inside a material.






40. Resistance to plastic deformation of cracking in compression - and better wear properties.






41. 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."






42. Materials change size when temperature is changed






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

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44. Diffuse image






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






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






47. 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






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






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






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