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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. 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






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

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






4. Materials change size when temperature is changed






5. - 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






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






7. 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)






8. Cracks propagate along grain boundaries.






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






10. Undergo little or no plastic deformation.






11. 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.






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






13. 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






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






15. - 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






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






17. 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






18. Occur when lots of dislocations move.






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






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






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






22. Process by which geometric patterns are transferred from a mask (reticle) to a surface of a chip to form the device.






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






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






25. Specific heat = energy input/(mass*temperature change)






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






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






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






29. Rho=F/A - tau=G/A . Depending on what angle the force is applied - and what angle the crystal is at - it takes different amounts of force to induce plastic deformation.






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






31. 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






32. The ability of a material to transport heat - Atomic Perspective: Atomic vibrations and free electrons in hotter regions transport energy to cooler regions - Metals have the largest values






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






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






35. 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.






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






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






38. 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






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






40. The ability of a material to be rapidly cooled and not fracture






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






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






43. 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."






44. Diffuse image






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






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






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






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






49. 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.






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