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






2. Undergo little or no plastic deformation.






3. 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."






4. 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)






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






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






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

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






9. A parallel-plate capacitor involves an insulator - or dielectric - between two metal electrodes. The charge density buildup at the capacitor surface is related to the dielectric constant of the material.






10. Found in 26 metals and hundreds of alloys & compounds - Tc= critical temperature = termperature below which material is superconductive.






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






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






13. 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






14. Occur when lots of dislocations move.






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






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

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






18. Sigma=ln(li/lo)






19. Undergo extensive plastic deformation prior to failure.






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






21. Because of ionic & covalent-type bonding.






22. Is analogous to toughness.






23. 1. General yielding occurs if flaw size a < a(critical) 2. Catastrophic fast fracture occurs if flaw size a > a(critical)






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






25. - 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






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






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






28. With Increasing temperature - the saturation magnetization diminishes gradually and then abruptly drops to zero at Curie Temperature - Tc.






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






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






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






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






33. Stress concentration at a crack tips






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






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






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






37. 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






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






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






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






41. 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






42. Materials change size when temperature is changed






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






44. 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






45. 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






46. 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.






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






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






49. Width of smallest feature obtainable on Si surface






50. 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