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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. Sigma=ln(li/lo)






2. 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






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






4. 1. Tc= critical temperature- if T>Tc not superconducting 2. Jc= critical current density - if J>Jc not superconducting 3. Hc= critical magnetic field - if H > Hc not superconducting






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






6. Is analogous to toughness.






7. 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






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






9. Cracks propagate along grain boundaries.






10. Ohms Law: voltage drop = current * resistance






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






12. 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






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






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






15. Second phase particles with n > glass.






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






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






18. These materials are relatively unaffected by magnetic fields.






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






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






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






22. 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






23. 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






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






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






26. - 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






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






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






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






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






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






32. Width of smallest feature obtainable on Si surface






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






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






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






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






37. 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.






38. 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.






39. Stress concentration at a crack tips






40. 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.






41. This strength parameter is similar in magnitude to a tensile strength. Fracture occurs along the outermost sample edge - which is under a tensile load.






42. Undergo little or no plastic deformation.






43. Light Amplification by Stimulated Emission of Radiation






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






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






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






47. Diffuse image






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






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






50. - 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







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