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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. 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






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






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






4. 1. Metals: Thermal energy puts many electrons into a higher energy state. 2. Energy States: Nearby energy states are accessible by thermal fluctuations.






5. Materials change size when temperature is changed






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






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






8. - 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






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






10. Different orientation of cleavage planes in grains.






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






12. Cracks propagate along grain boundaries.






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






14. 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."






15. 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.






16. Ohms Law: voltage drop = current * resistance






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






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






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






20. 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)






21. 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.






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






23. They are used to assess properties of ceramics & glasses.






24. Diffuse image






25. Plastic means permanent! When a small load is applied - bonds stretch & planes shear. Then when the load is no longer applied - the planes are still sheared.






26. Is analogous to toughness.






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






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






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






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






31. Undergo little or no plastic deformation.






32. Because of ionic & covalent-type bonding.






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






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






35. 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






36. Light Amplification by Stimulated Emission of Radiation






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






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

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






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






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






42. Emitted light is in phase






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






44. 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






45. 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






46. 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






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






48. Sigma=ln(li/lo)






49. 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.






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