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

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

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. No appreciable plastic deformation. The crack propagates very fast; nearly perpendicular to applied stress. Cracks often propagate along specific crystal planes or boundaries.

5. 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

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

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

8. - Metals that exhibit high ductility - exhibit high toughness. Ceramics are very strong - but have low ductility and low toughness - Polymers are very ductile but are not generally very strong in shear (compared to metals and ceramics). They have low

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

10. Sigma=ln(li/lo)

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

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

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

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

15. - 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

16. Occur when lots of dislocations move.

17. 1. Ductility- % elongation - % reduction in area - may be of use in metal forming operations (e.g. - stretch forming). This is convenient for mechanical testing - but not very meaningful for most deformation processing. 2. Toughness- Area beneath str

18. Diffuse image

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

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

21. Ohms Law: voltage drop = current * resistance

22. 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

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

24. 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.

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

26. Cracks propagate along grain boundaries.

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

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

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

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

31. 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

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

33. 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

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

35. 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.

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

37. Specular: light reflecting off a mirror (average) - Diffuse: light reflecting off a white wall (local)

38. 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.

39. 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.

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

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

42. 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)

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

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

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

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

47. Is analogous to toughness.

48. 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.

49. 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

50. Undergo extensive plastic deformation prior to failure.