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






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






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






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






5. Different orientation of cleavage planes in grains.






6. 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






7. These materials are relatively unaffected by magnetic fields.






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






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






10. Measures Hardness - No major sample damage - Each scales runs to 130 but only useful in range 20-100 - Minor load is 10 kg - Major load: 60 kg (diamond) - 100 kg (1/16 in. ball) - 150 kg (diamond)






11. 1. Data for Pure Silicon - electrical conductivity increases with T - opposite to metals






12. 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.






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






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






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. - 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






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






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






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






20. - 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






21. 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






22. Stress concentration at a crack tips






23. Occur when lots of dislocations move.






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






25. The size of the material changes with a change in temperature - polymers have the largest values






26. Materials change size when temperature is changed






27. Is analogous to toughness.






28. 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.






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






30. Light Amplification by Stimulated Emission of Radiation






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






32. 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






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






34. Undergo little or no plastic deformation.






35. Diffuse image






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






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






38. 1. Imperfections increase resistivity - grain boundaries - dislocations - impurity atoms - vacancies 2. Resistivity - increases with temperature - wt% impurity - and %CW






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






40. Increase temperature - increase in interatomic separation - thermal expansion






41. 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






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






43. 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






44. High toughness; material resists crack propagation.






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






46. Cracks propagate along grain boundaries.






47. 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.






48. Dramatic change in impact energy is associated with a change in fracture mode from brittle to ductile.






49. - A magnetic field is induced in the material B= Magnetic Induction (tesla) inside the material mu= permeability of a solid






50. Ohms Law: voltage drop = current * resistance