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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 "attracted" to magnetic fields.






2. Metals are good conductors since their _______is only partially filled.






3. 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






4. Elastic means reversible! This is not a permanent deformation.






5. 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)






6. Ohms Law: voltage drop = current * resistance






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






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






9. Sigma=ln(li/lo)






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






11. - 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






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






13. 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






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






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






16. 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.






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






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






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






20. 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.






21. Not ALL the light is refracted - SOME is reflected. Materials with a high index of refraction also have high reflectance - High R is bad for lens applications - since this leads to undesirable light losses or interference.






22. 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






23. Dimples on fracture surface correspond to microcavities that initiate crack formation.






24. 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.






25. 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






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






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






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






29. Different orientation of cleavage planes in grains.






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






31. 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






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






33. 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."






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






35. Stress concentration at a crack tips






36. 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






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






38. These materials are relatively unaffected by magnetic fields.






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

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40. Is analogous to toughness.






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






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






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

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45. 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






46. 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






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






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






50. 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