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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. Cracks propagate along grain boundaries.






2. Occur when lots of dislocations move.






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






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






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






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






7. 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.






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






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






10. Because of ionic & covalent-type bonding.






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






12. These materials are relatively unaffected by magnetic fields.






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






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. 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.






16. Stress concentration at a crack tips






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






18. 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.






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






20. Ohms Law: voltage drop = current * resistance






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






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






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






24. Is reflected - absorbed - scattered - and/or transmitted: Io=It+Ia+Ir+Is






25. 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)






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






27. 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






28. Sigma=ln(li/lo)






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






30. 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






31. Found in 26 metals and hundreds of alloys & compounds - Tc= critical temperature = termperature below which material is superconductive.






32. 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






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






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






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






36. 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






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






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






39. Diffuse image






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






41. 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.






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






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






44. 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






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






46. 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






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






48. 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.






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






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