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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. 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.






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






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






4. 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.






5. 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






6. 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.






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






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






9. Undergo little or no plastic deformation.






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






11. 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






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






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






14. 1. Stress-strain behavior is not usually determined via tensile tests 2. Material fails before it yields 3. Bend/flexure tests are often used instead.






15. Second phase particles with n > glass.






16. Width of smallest feature obtainable on Si surface






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






18. 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






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






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






21. 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






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






23. - 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






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






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






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






27. 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.






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






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






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






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






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






33. 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






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






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






36. These materials are relatively unaffected by magnetic fields.






37. High toughness; material resists crack propagation.






38. Light Amplification by Stimulated Emission of Radiation






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






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






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






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

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43. Liquid polymer at room T - sandwiched between two sheets of glass - coated with transparent - electrically conductive film. - Character forming letters/ numbers etched on the face - Voltage applied disrupts the orientation of the rod- shaped molecule






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






45. Diffuse image






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






47. 1. Fluorescent Lamp - tungstate or silicate coating on inside of tube emits white light due to UV light generated inside the tube. 2. TV screen - emits light as electron beam is scanned back and forth.






48. 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.






49. 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.






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