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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. Stress concentration at a crack tips






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






3. 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






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






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






6. 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






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






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






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






10. 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.






11. Undergo extensive plastic deformation prior to failure.






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






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






14. Diffuse image






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






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






17. 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.






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






19. Emitted light is in phase






20. 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.






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






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






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






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






25. 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






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






27. 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)






28. - Metals that exhibit high ductility - exhibit high toughness. Ceramics are very strong - but have low ductility and low toughness - Polymers are very ductile but are not generally very strong in shear (compared to metals and ceramics). They have low






29. High toughness; material resists crack propagation.






30. 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






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






32. Materials change size when temperature is changed






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






34. 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.






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






36. - 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






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






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






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






40. 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.






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






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






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






44. Different orientation of cleavage planes in grains.






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






46. Sigma=ln(li/lo)






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






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






49. 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.






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







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