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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. 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.






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






3. - 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






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






5. 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






6. Emitted light is in phase






7. 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






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






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






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






11. 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.






12. 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






13. 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






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






15. 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.






16. Created by current through a coil N= total number of turns L= length of turns (m) I= current (ampere) H= applied magnetic field (ampere-turns/m) Bo= magnetic flux density in a vacuum (tesla)






17. Ohms Law: voltage drop = current * resistance






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






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






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






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






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






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






24. Width of smallest feature obtainable on Si surface






25. Sigma=ln(li/lo)






26. Because of ionic & covalent-type bonding.






27. 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.






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






29. Stress concentration at a crack tips






30. 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






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






32. Undergo extensive plastic deformation prior to failure.






33. 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






34. 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.






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






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

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






38. 1. Impose a compressive surface stress (to suppress surface cracks from growing) - Method 1: shot peening - Method 2: carburizing 2.Remove stress concentrators.






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






40. 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)






41. 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






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






43. 1. Metals: Thermal energy puts many electrons into a higher energy state. 2. Energy States: Nearby energy states are accessible by thermal fluctuations.






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






45. Second phase particles with n > glass.






46. This strength parameter is similar in magnitude to a tensile strength. Fracture occurs along the outermost sample edge - which is under a tensile load.






47. High toughness; material resists crack propagation.






48. Diffuse image






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






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