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Engineering Materials

Subject : engineering
Instructions:
  • Answer 50 questions in 15 minutes.
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  • 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. - A magnetic field is induced in the material B= Magnetic Induction (tesla) inside the material mu= permeability of a solid






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






3. To build a device - various thin metal or insulating films are grown on top of each other - Evaporation - MBE - Sputtering - CVD (ALD)






4. 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."






5. Width of smallest feature obtainable on Si surface






6. Is analogous to toughness.






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






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






9. Light Amplification by Stimulated Emission of Radiation






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






11. Sigma=ln(li/lo)






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






13. Different orientation of cleavage planes in grains.






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






15. Stress concentration at a crack tips






16. Diffuse image






17. These materials are relatively unaffected by magnetic fields.






18. High toughness; material resists crack propagation.






19. The Magnetization of the material - and is essentially the dipole moment per unit volume. It is proportional to the applied field. Xm is the magnetic susceptibility.






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






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






22. These are liquid crystal polymers- not your normal "crystal" -Rigid - rod shaped molecules are aligned even in liquid form.

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23. 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






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






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






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






27. Ohms Law: voltage drop = current * resistance






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






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






30. 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)






31. - 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






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






33. 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.






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






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






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






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






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






39. 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






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






41. 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






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






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. 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






45. 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.






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






47. Second phase particles with n > glass.






48. Cracks propagate along grain boundaries.






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






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