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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. 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.






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






3. 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






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






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






6. 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.






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






8. - 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






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






10. Stress concentration at a crack tips






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






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






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






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






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






16. Undergo extensive plastic deformation prior to failure.






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






18. 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






19. 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.






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






21. 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)






22. Reflectiviy is between 0.90 and 0.95 - Metal surfaces appear shiny - Most of absorbed light is reflected at the same wavelength (NO REFRACTION) - Small fraction of light may be absorbed - Color of reflected light depends on wavelength distribution of






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






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






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






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






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. Because of ionic & covalent-type bonding.






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






30. 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






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






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






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






34. These materials are relatively unaffected by magnetic fields.






35. Sigma=ln(li/lo)






36. Materials change size when temperature is changed






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






38. 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






39. 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






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






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






42. Is analogous to toughness.






43. Measures impact energy 1. Strike a notched sample with an anvil 2. Measure how far the anvil travels following impact 3. Distance traveled is related to energy required to break the sample 4. Very high rate of loading. Makes materials more "brittle."






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

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






46. 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






47. Undergo little or no plastic deformation.






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






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






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