Test your basic knowledge |

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






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






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






4. High toughness; material resists crack propagation.






5. This strength parameter is similar in magnitude to a tensile strength. Fracture occurs along the outermost sample edge - which is under a tensile load.






6. 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.






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






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. These materials are relatively unaffected by magnetic fields.






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






11. 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






12. 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.






13. 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






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






15. If a material has ________ - then the field generated by those moments must be added to the induced field.






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






17. Occur when lots of dislocations move.






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






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






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






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






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






23. 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.






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






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






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






27. Emitted light is in phase






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






29. Superconductors expel magnetic fields - This is why a superconductor will float above a magnet.






30. - 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






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






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






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






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






35. 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






36. Materials change size when temperature is changed






37. 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






38. Width of smallest feature obtainable on Si surface






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






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






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


42. 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






43. 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.






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






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






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






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






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






50. 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.