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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. Undergo extensive plastic deformation prior to failure.






2. 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."






3. 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.






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






5. 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






6. The ability of a material to be rapidly cooled and not fracture






7. Transformer cores require soft magnetic materials - which are easily magnetized and de-magnetized - and have high electrical resistivity - Energy losses in transformers could be minimized if their cores were fabricated such that the easy magnetizatio






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






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






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






11. Diffuse image






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






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






14. 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.






15. These materials are "attracted" to magnetic fields.






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






17. 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






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






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






20. 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.






21. 1. Tensile (opening) 2. Sliding 3. Tearing






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






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






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






25. To build a device - various thin metal or insulating films are grown on top of each other - Evaporation - MBE - Sputtering - CVD (ALD)






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






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






28. Materials change size when temperature is changed






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






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






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

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






33. 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.






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






35. Stress concentration at a crack tips






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






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






38. - 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






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






40. 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.






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






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






43. 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






44. 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






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






46. 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.






47. Second phase particles with n > glass.






48. 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)






49. Light Amplification by Stimulated Emission of Radiation






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