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






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






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






4. 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






5. Cracks propagate along grain boundaries.






6. 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)






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






8. Different orientation of cleavage planes in grains.






9. 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)






10. 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






11. 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.






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






13. Undergo little or no plastic deformation.






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






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






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






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






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






19. Ohms Law: voltage drop = current * resistance






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






21. 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






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






23. 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.






24. 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






25. Stress concentration at a crack tips






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






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






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






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






30. Occur when lots of dislocations move.






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






32. Emitted light is in phase






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






34. Width of smallest feature obtainable on Si surface






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






36. 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.






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






38. 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.






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






40. Undergo extensive plastic deformation prior to failure.






41. Because of ionic & covalent-type bonding.






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






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






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






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






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






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






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






49. 1. Diamagnetic (Xm ~ 10^-5) - small and negative magnetic susceptibilities 2. Paramagnetic (Xm ~ 10^-4) - small and positive magnetic susceptibilities 3. Ferromagnetic - large magnetic susceptibilities 4. Ferrimagnetic (Xm as large as 10^6) - large m






50. 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







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