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






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

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






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

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5. Defines the ability of a material to resist fracture even when a flaw exists - Directly depends on size of flaw and material properties - K(ic) is a materials constant






6. Measures Hardness 1. psia = 500 x HB 2. MPa = 3.45 x HB






7. 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.






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






9. 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.






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






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






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






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






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






15. Materials change size when temperature is changed






16. High toughness; material resists crack propagation.






17. These materials are relatively unaffected by magnetic fields.






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






19. - 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






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






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






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






23. Loss of image transmission - You get no image - There is no light transmission - and therefore reflects - scatters - or absorbs ALL of it. Both mirrors and carbon black are opaque.






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






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






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






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






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






29. 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






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






31. 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.






32. A measure of the ease with which a B field can be induced inside a material.






33. Emitted light is in phase






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






35. 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






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






37. 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.






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






39. 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)






40. 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






41. 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






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






43. - 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






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






45. Undergo extensive plastic deformation prior to failure.






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






47. Occur when lots of dislocations move.






48. Sigma=ln(li/lo)






49. 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.






50. 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.