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Engineering Materials

Subject : engineering
Instructions:
  • Answer 50 questions in 15 minutes.
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  • 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. 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.






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






3. 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.






4. 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






5. Stress concentration at a crack tips






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






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






8. 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






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






10. The ability of a material to absorb heat - Quantitatively: The energy required to produce a unit rise in temperature for one mole of a material.






11. 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.






12. Emitted light is in phase






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






14. Diffuse image






15. Occur when lots of dislocations move.






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






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






18. Sigma=ln(li/lo)






19. Different orientation of cleavage planes in grains.






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






21. Hardness is the resistance of a material to deformation by indentation - Useful in quality control - Hardness can provide a qualitative assessment of strength - Hardness cannot be used to quantitatively infer strength or ductility.






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. 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






24. 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)






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






26. 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.






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






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






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






30. 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.






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






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






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






34. 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






35. This strength parameter is similar in magnitude to a tensile strength. Fracture occurs along the outermost sample edge - which is under a tensile load.






36. -> fluorescent light - electron transitions occur randomly - light waves are out of phase with each other.






37. High toughness; material resists crack propagation.






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






39. Second phase particles with n > glass.






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






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






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






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






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






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






46. 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)






47. Undergo little or no plastic deformation.






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

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49. ...occurs in bcc metals but not in fcc metals.






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