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Engineering Materials

Subject : engineering
Instructions:
  • Answer 50 questions in 15 minutes.
  • If you are not ready to take this test, you can study here.
  • 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. 1. General yielding occurs if flaw size a < a(critical) 2. Catastrophic fast fracture occurs if flaw size a > a(critical)






2. 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






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






4. 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






5. Undergo extensive plastic deformation prior to failure.






6. Because of ionic & covalent-type bonding.






7. 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.






8. No appreciable plastic deformation. The crack propagates very fast; nearly perpendicular to applied stress. Cracks often propagate along specific crystal planes or boundaries.






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






10. Emitted light is in phase






11. - 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






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






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






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

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15. 1. Data for Pure Silicon - electrical conductivity increases with T - opposite to metals






16. 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






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






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






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






20. 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."






21. Ohms Law: voltage drop = current * resistance






22. 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.






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






24. Sigma=ln(li/lo)






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






26. 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






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






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






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






30. Is analogous to toughness.






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






32. Cracks propagate along grain boundaries.






33. 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






34. 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






35. 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






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






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






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






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






40. Stress concentration at a crack tips






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






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






43. 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






44. Undergo little or no plastic deformation.






45. 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.






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






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






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






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






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