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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.
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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. 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






2. 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






3. A measure of the ease with which a B field can be induced inside a material.






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






5. Different orientation of cleavage planes in grains.






6. Is analogous to toughness.






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






8. 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.






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






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






11. 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






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






13. Because of ionic & covalent-type bonding.






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






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






16. 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.






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






18. 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






19. 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.






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






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






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






23. Width of smallest feature obtainable on Si surface






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






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






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






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

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28. 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.






29. With Increasing temperature - the saturation magnetization diminishes gradually and then abruptly drops to zero at Curie Temperature - Tc.






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






31. 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






32. Stress concentration at a crack tips






33. 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






34. 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






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






36. Materials change size when temperature is changed






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






38. 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.






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






40. - 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






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






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






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






44. Allows flow of electrons in one direction only (useful to convert alternating current to direct current) - Result: no net current flow






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






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






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






48. Second phase particles with n > glass.






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






50. The size of the material changes with a change in temperature - polymers have the largest values