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






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






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






4. Stress concentration at a crack tips






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. 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






7. Because of ionic & covalent-type bonding.






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






9. Is analogous to toughness.






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






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






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






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






14. Occur when lots of dislocations move.






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






16. 1. Electron motions 2. The spins on electrons - Net atomic magnetic moment: sum of moments from all electrons.






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






18. 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.






19. 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.






20. 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)






21. 1. Impose a compressive surface stress (to suppress surface cracks from growing) - Method 1: shot peening - Method 2: carburizing 2.Remove stress concentrators.






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






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






24. Cracks propagate along grain boundaries.






25. Ohms Law: voltage drop = current * resistance






26. 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






27. 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.






28. Without passing a current a continually varying magnetic field will cause a current to flow






29. 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






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






31. Emitted light is in phase






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






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






34. 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.






35. 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






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






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






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






39. 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






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






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






42. 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.






43. 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






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






45. Different orientation of cleavage planes in grains.






46. 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.






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






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

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49. Elastic means reversible! This is not a permanent deformation.






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