ChE 361 #3

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deshayes
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53045
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ChE 361 #3
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2010-12-03 01:27:17
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Engineering materials final
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  1. What limits the pressure at which a bearing material can operate?
    yielding
  2. What limits the sliding velocity at which a bearing material can operate?
    Heating
  3. What is an asperity?
    Dendrite
  4. What is the usual cause of failure of rolling bearings?
    Fatigue
  5. What is the process by which fragments are torn from a surface where work-hardened junctions stick together?
    Adhesive wear
  6. What is the process in which hard asperities or embedded hard particles plough through a softer material?
    Abrasive wear
  7. Name four surface treatments that increase hardness or reduce friction?
    • Boriding
    • Nitriding
    • Carborizing
    • Ceramic deposition by plasma
  8. What is hydrodynamic lubrication?
    Lub by full viscous film between two surfaces
  9. What are the fixed points on the kelvin temperature scale?
    Triple point of water
  10. What is the triple point of water?
    273.16K
  11. What is the ice point of water?
    273.15K
  12. Conversion from F to C?
    F=(9/5)(C)+32
  13. What is the SI unit of heat?
    K
  14. What is the SI unit of work?
    Joule (J)
  15. What is the SI unit of power?
    Watt (W)
  16. Conversion from Calories to calories?
    1Calorie=1kilocalorie
  17. Conversion from calories to Joules?
    1cal=4.184J
  18. What is boundary lubrication?
    Chemisorbed monolayers of polar molecules
  19. Why is the negative sign required in the equation q=-(lambda)dT/dx?
    Heat flows from high to low temperature
  20. What is alpha in the equation alpha=(1/L)(dL/dT)?
    Linear thermal expansion coefficient
  21. Why is the negative sign included in the equation J=-D(dc/dx)?
    Diffusion occurs from high concentrations to low concentrations
  22. What is Q in the equation D=D0exp(-Q/RT)?
    Activation energy
  23. Why is the negative sign in the equation D=D0exp(-Q/RT)?
    Increasing activation energy decreases the diffusion coefficient
  24. What are the SI units of diffusive flux?
    mol*m-2*s-1
  25. What are the SI units of concentration?
    mol*m-3
  26. What are the SI units of the concentration gradient?
    mol*m-4
  27. Where does interstitial diffusion occur?
    In spaces between atoms in crystals
  28. What causes creep fracture?
    Creation and growth of internal cavities
  29. During which stage does creep damage accumulate?
    Tertiary creep
  30. Definition of yielding by dislocation plasticity?
    Dislocations glide in response to shear stress
  31. Definition of plastic deformation?
    Bonds stretch but do not break
  32. Definition of power-law creep?
    Dislocations glide and climb over obstacles
  33. Definition of diffusional flow?
    Diffusion extends grains in direction of stress
  34. What occurs when T=Tm?
    Phase change occurs
  35. What is climb?
    Dislocation movement out of glide plane
  36. What is the mechanism by which climb occurs?
    Diffusion of atoms away from a dislocation
  37. What results from the presence of an extra half-plane of atoms in a crystal?
    Dislocations
  38. What tends to promote creep in a metal or ceramic?
    Small grains
  39. What tends to promote creep in a polymer?
    Glassy structure
  40. What is creep relaxation in a pre-tensioned component such as bolt?
    Stress reduction by creep
  41. Which materials tend to creep the most at room temperature?
    Polymers

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