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






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






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






4. 1. Diamagnetic (Xm ~ 10^-5) - small and negative magnetic susceptibilities 2. Paramagnetic (Xm ~ 10^-4) - small and positive magnetic susceptibilities 3. Ferromagnetic - large magnetic susceptibilities 4. Ferrimagnetic (Xm as large as 10^6) - large m






5. These materials are relatively unaffected by magnetic fields.






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






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






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






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






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






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






12. 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.






13. A parallel-plate capacitor involves an insulator - or dielectric - between two metal electrodes. The charge density buildup at the capacitor surface is related to the dielectric constant of the material.






14. 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






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


16. 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.






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






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






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






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






21. Cracks pass through grains - often along specific crystal planes.






22. Emitted light is in phase






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






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






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






26. 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






27. 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."






28. Stress concentration at a crack tips






29. (sigma)=F/Ai (rho)=(rho)'(1+(epsilon))






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






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






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






33. - 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






34. Sigma=ln(li/lo)






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






36. Ohms Law: voltage drop = current * resistance






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






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






39. 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






40. Cracks propagate along grain boundaries.






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






42. 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.






43. 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.






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






45. Because of ionic & covalent-type bonding.






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






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






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






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






50. Diffuse image