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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. Occur when lots of dislocations move.






2. - 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






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






4. 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.






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






6. 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.






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






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






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






10. 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.






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






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






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






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






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






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






17. High toughness; material resists crack propagation.






18. 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.






19. 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






20. Undergo little or no plastic deformation.






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






22. Sigma=ln(li/lo)






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






24. 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






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






26. A three terminal device that acts like a simple "on-off" switch. (the basis of Integrated Circuits (IC) technology - used in computers - cell phones - automotive control - etc) - If voltage (potential) applied to the "gate" - current flows between th






27. Different orientation of cleavage planes in grains.






28. Width of smallest feature obtainable on Si surface






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






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






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

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32. Cracks propagate along grain boundaries.






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

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






35. Resistance to plastic deformation of cracking in compression - and better wear properties.






36. These materials are relatively unaffected by magnetic fields.






37. Stress concentration at a crack tips






38. 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






39. 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






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






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






43. A parallel-plate capacitor involves an insulator - or dielectric - between two metal electrodes. The charge density buildup at the capacitor surface is related to the dielectric constant of the material.






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






45. 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)






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






47. Is analogous to toughness.






48. 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






49. Materials change size when temperature is changed






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