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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. 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.






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






3. For a metal - there is no ______ - only reflection






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






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






6. 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.






7. 1. Ductility- % elongation - % reduction in area - may be of use in metal forming operations (e.g. - stretch forming). This is convenient for mechanical testing - but not very meaningful for most deformation processing. 2. Toughness- Area beneath str






8. Undergo little or no plastic deformation.






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






10. These materials are relatively unaffected by magnetic fields.






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






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






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






14. The ability of a material to transport heat - Atomic Perspective: Atomic vibrations and free electrons in hotter regions transport energy to cooler regions - Metals have the largest values






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






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






17. Is analogous to toughness.






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






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






20. (sigma)=K(sigma)^n . K = strength coefficient - n = work hardening rate or strain hardening exponent. Large n value increases strength and hardness.






21. 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






22. 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






23. Second phase particles with n > glass.






24. 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.






25. 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.






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






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

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






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






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






31. - 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






32. 1. Insulators: Higher energy states NOT ACCESSIBLE due to gap 2. Semiconductors: Higher energy states separated by a smaller gap.






33. Light Amplification by Stimulated Emission of Radiation






34. 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






35. Occur when lots of dislocations move.






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






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






38. 1. Stress-strain behavior is not usually determined via tensile tests 2. Material fails before it yields 3. Bend/flexure tests are often used instead.






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






40. - 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






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






42. 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.






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






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






45. Sigma=ln(li/lo)






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






47. Different orientation of cleavage planes in grains.






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






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






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