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Engineering Materials

Subject : engineering
Instructions:
  • Answer 50 questions in 15 minutes.
  • If you are not ready to take this test, you can study here.
  • 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. 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






2. Impurities added to the semiconductor that contribute to excess electrons or holes. Doping = intentional impurities.






3. 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






4. 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






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






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






7. A high index of refraction (n value) allows for multiple internal reactions.






8. Undergo extensive plastic deformation prior to failure.






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






10. Cracks propagate along grain boundaries.






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






12. Sigma=ln(li/lo)






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






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






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






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






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






18. 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.






19. 1. Yield = ratio of functional chips to total # of chips - Most yield loss during wafer processing - b/c of complex 2. Reliability - No device has infinite lifetime. Statistical methods to predict expected lifetime - Failure mechanisms: Diffusion reg






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






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






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






23. Is analogous to toughness.






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






25. 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






26. 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






27. Materials change size when temperature is changed






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






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






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






31. 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






32. 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.






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






34. 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






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






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






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






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






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






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






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






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






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






44. High toughness; material resists crack propagation.






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






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






47. 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






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






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






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