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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. These materials are relatively unaffected by magnetic fields.






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






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






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






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






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






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






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






9. Light Amplification by Stimulated Emission of Radiation






10. Occur due to: restrained thermal expansion/contraction -temperature gradients that lead to differential dimensional changes sigma = Thermal Stress






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






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






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






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






15. 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






16. As the applied field (H) increases the magnetic domains change shape and size by movement of domain boundaries.






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






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






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






20. 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.






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






22. Sigma=ln(li/lo)






23. - 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






24. High toughness; material resists crack propagation.






25. 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)






26. 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






27. # of thermally generated electrons = # of holes (broken bonds)






28. Occur when lots of dislocations move.






29. Cracks propagate along grain boundaries.






30. 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






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

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32. 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






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






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






35. Ohms Law: voltage drop = current * resistance






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






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






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






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






40. 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






41. Because of ionic & covalent-type bonding.






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






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






44. 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.






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






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






47. Diffuse image






48. 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)






49. 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






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