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






2. 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






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






4. These materials are relatively unaffected by magnetic fields.






5. Allows you to calculate what happened G=F' x cos(lambda) - F=F' x cos(phi)






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






7. Undergo extensive plastic deformation prior to failure.






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






9. 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






10. 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






11. Different orientation of cleavage planes in grains.






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






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






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






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






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






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






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






19. 1. Yield = ratio of functional chips to total # of chips - Most yield loss during wafer processing - b/c of complex 2. Reliability - No device has infinite lifetime. Statistical methods to predict expected lifetime - Failure mechanisms: Diffusion reg






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






21. 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.






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






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






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






25. Stress concentration at a crack tips






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






27. 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.






28. Another optical property - Depends on the wavelength of the visible spectrum.






29. Second phase particles with n > glass.






30. 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.






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






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






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






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






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






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

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37. Growth of an oxide layer by the reaction of oxygen with the substrate - Provides dopant masking and device isolation - IC technology uses 1. Thermal grown oxidation (dry) 2. Wet Oxidation 3. Selective Oxidation






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






39. 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.






40. 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.






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






42. 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."






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






44. Light Amplification by Stimulated Emission of Radiation






45. 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






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






47. Failure under cyclic stress 1. It can cause part failure - even though (sigma)max < (sigma)c 2. Causes ~90% of mechanical engineering failures.






48. Diffuse image






49. 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)






50. 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