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






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






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






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






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






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






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






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






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






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






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






12. These materials are relatively unaffected by magnetic fields.






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






14. 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






15. Emitted light is in phase






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






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






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






19. Different orientation of cleavage planes in grains.






20. 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."






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






22. 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.






23. 1. Fluorescent Lamp - tungstate or silicate coating on inside of tube emits white light due to UV light generated inside the tube. 2. TV screen - emits light as electron beam is scanned back and forth.






24. 1. Necking 2. Cavity formation 3. Cavity coalescence to form cracks 4. Crack propagation (growth) 5. Fracture






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






26. 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






27. Stress concentration at a crack tips






28. 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






29. 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)






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






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






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






33. Resistance to plastic deformation of cracking in compression - and better wear properties.






34. 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.






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






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






37. Diffuse image






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






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






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






41. 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






42. 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






43. Specular: light reflecting off a mirror (average) - Diffuse: light reflecting off a white wall (local)






44. 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






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






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






47. Undergo little or no plastic deformation.






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






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






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