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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. 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.






2. Undergo extensive plastic deformation prior to failure.






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






4. 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






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






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






7. 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."






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






9. 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.






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






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






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






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






14. Because of ionic & covalent-type bonding.






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






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






17. 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






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






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






20. Second phase particles with n > glass.






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






22. Different orientation of cleavage planes in grains.






23. 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






24. 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.






25. 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






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






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






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






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






30. 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.






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






32. These materials are relatively unaffected by magnetic fields.






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






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






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






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






37. Light Amplification by Stimulated Emission of Radiation






38. 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.






39. Stress concentration at a crack tips






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






41. Occur when lots of dislocations move.






42. Sigma=ln(li/lo)






43. 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






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






45. High toughness; material resists crack propagation.






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






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






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






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






50. Undergo little or no plastic deformation.







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