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






2. Stress concentration at a crack tips






3. 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.






4. Second phase particles with n > glass.






5. High toughness; material resists crack propagation.






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






7. 1. Impose a compressive surface stress (to suppress surface cracks from growing) - Method 1: shot peening - Method 2: carburizing 2.Remove stress concentrators.






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






9. - 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






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






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






13. Cracks propagate along grain boundaries.






14. Occur when lots of dislocations move.






15. 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.






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






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

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






19. Undergo little or no plastic deformation.






20. 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.






21. 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






22. Diffuse image






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






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






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






26. 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.






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






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






29. Emitted light is in phase






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






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






32. Undergo extensive plastic deformation prior to failure.






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






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






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






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






38. Sigma=ln(li/lo)






39. 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.






40. 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






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






42. 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






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






44. Heat capacity.....- increases with temperature -for solids it reaches a limiting value of 3R






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






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






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






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






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






50. 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