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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. 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






2. 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






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






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


5. 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






6. 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






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






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






9. 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.






10. 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)






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






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






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






14. 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






15. Cracks propagate along grain boundaries.






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






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






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






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






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






21. 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.






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






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






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






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






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






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






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






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






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






31. 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.






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






33. 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






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






35. 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






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






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






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






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






40. 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.






41. Light Amplification by Stimulated Emission of Radiation






42. 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.






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






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






45. Sigma=ln(li/lo)






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






47. Diffuse image






48. Second phase particles with n > glass.






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






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