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

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2. 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.






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






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






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






6. Different orientation of cleavage planes in grains.






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






8. Materials change size when temperature is changed






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






10. 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






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






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






13. 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






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






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. Growing interconnections to connect devices -Low electrical resistance - good adhesion to dielectric insulators.






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






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






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






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






21. The Magnetization of the material - and is essentially the dipole moment per unit volume. It is proportional to the applied field. Xm is the magnetic susceptibility.






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






23. 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.






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

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






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






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






28. 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.






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






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






31. 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.






32. 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






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






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






35. Stress concentration at a crack tips






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






37. These materials are relatively unaffected by magnetic fields.






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






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






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






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






42. High toughness; material resists crack propagation.






43. 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






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






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






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






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






48. Diffuse image






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






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