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






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






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






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






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






6. Is analogous to toughness.






7. 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






8. 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.






9. 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






10. 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






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






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






13. 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."






14. Sigma=ln(li/lo)






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






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






17. 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






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






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






20. 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






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






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






23. 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.






24. 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.






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






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






27. Width of smallest feature obtainable on Si surface






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

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






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






31. 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






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






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






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






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






36. 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.






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






38. 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.






39. 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






40. Energy is stored as atomic vibrations - As temperature increases - the average energy of atomic vibrations increases.






41. Undergo extensive plastic deformation prior to failure.






42. 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.






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






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






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






46. - 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






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






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






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






50. Undergo little or no plastic deformation.