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Engineering Materials

Subject : engineering
  • Answer 50 questions in 15 minutes.
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  • Match each statement with the correct term.
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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 ability of a material to be rapidly cooled and not fracture

2. 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

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

4. 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

5. 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

6. 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.

7. Process by which geometric patterns are transferred from a mask (reticle) to a surface of a chip to form the device.

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

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

10. 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.

11. Defines the ability of a material to resist fracture even when a flaw exists - Directly depends on size of flaw and material properties - K(ic) is a materials constant

12. Second phase particles with n > glass.

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

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

15. Sigma=ln(li/lo)

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

17. Materials change size when temperature is changed

18. Light Amplification by Stimulated Emission of Radiation

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

20. Created by current through a coil N= total number of turns L= length of turns (m) I= current (ampere) H= applied magnetic field (ampere-turns/m) Bo= magnetic flux density in a vacuum (tesla)

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

22. 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

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

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

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

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

27. 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

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

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

30. 1. Imperfections increase resistivity - grain boundaries - dislocations - impurity atoms - vacancies 2. Resistivity - increases with temperature - wt% impurity - and %CW

31. 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

32. 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

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

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

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

36. Occur when lots of dislocations move.

37. 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

38. 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.

39. Cracks propagate along grain boundaries.

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

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

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

43. 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.

44. Plastic means permanent! When a small load is applied - bonds stretch & planes shear. Then when the load is no longer applied - the planes are still sheared.

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

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

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

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

49. 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

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