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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. 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)






2. Occur due to: restrained thermal expansion/contraction -temperature gradients that lead to differential dimensional changes sigma = Thermal Stress






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






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






5. 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)






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






7. Undergo little or no plastic deformation.






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






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






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






11. 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






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






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






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






15. 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






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






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






18. High toughness; material resists crack propagation.






19. 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






20. heat flux = -(thermal conductivity)(temperature gradient) - Defines heat transfer by CONDUCTION

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






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






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






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






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






26. 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






27. Second phase particles with n > glass.






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






29. Ohms Law: voltage drop = current * resistance






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






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






32. These materials are relatively unaffected by magnetic fields.






33. Materials change size when temperature is changed






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






35. Stress concentration at a crack tips






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






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






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






39. 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.






40. Cracks propagate along grain boundaries.






41. 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






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






43. Light Amplification by Stimulated Emission of Radiation






44. Emitted light is in phase






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






46. 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






47. 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.






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






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






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