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






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






3. Stress concentration at a crack tips






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






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






6. The ability of a material to absorb heat - Quantitatively: The energy required to produce a unit rise in temperature for one mole of a material.






7. - 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






8. Occur when lots of dislocations move.






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






10. 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






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






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






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






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






15. Sigma=ln(li/lo)






16. Cracks propagate along grain boundaries.






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






18. 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






19. Different orientation of cleavage planes in grains.






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






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

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






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






25. - 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






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






27. Light Amplification by Stimulated Emission of Radiation






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






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






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






31. These materials are relatively unaffected by magnetic fields.






32. 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






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






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






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






36. 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






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






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






39. Diffuse image






40. Is analogous to toughness.






41. 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.






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

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43. Flaws and Defects - They concentrate stress locally to levels high enough to rupture bonds.






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






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






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






47. 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






48. Allows you to calculate what happened G=F' x cos(lambda) - F=F' x cos(phi)






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






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