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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. 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






2. 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






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






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

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5. Different orientation of cleavage planes in grains.






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






7. Light Amplification by Stimulated Emission of Radiation






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






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






10. Occurs at a single pore or other solid by refraction n = 1 for pore (air) n > 1 for the solid - n ~ 1.5 for glass - Scattering effect is maximized by pore/particle size within 400-700 nm range - Reason for Opacity in ceramics - glasses and polymers.






11. Diffuse image






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






13. Occur when lots of dislocations move.






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






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






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






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






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

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






20. Because of ionic & covalent-type bonding.






21. - 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






22. Undergo little or no plastic deformation.






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. 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






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






26. Measures Hardness - No major sample damage - Each scales runs to 130 but only useful in range 20-100 - Minor load is 10 kg - Major load: 60 kg (diamond) - 100 kg (1/16 in. ball) - 150 kg (diamond)






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






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






29. Materials change size when temperature is changed






30. Width of smallest feature obtainable on Si surface






31. Not ALL the light is refracted - SOME is reflected. Materials with a high index of refraction also have high reflectance - High R is bad for lens applications - since this leads to undesirable light losses or interference.






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






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






34. Loss of image transmission - You get no image - There is no light transmission - and therefore reflects - scatters - or absorbs ALL of it. Both mirrors and carbon black are opaque.






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






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






37. 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.






38. Increase temperature - increase in interatomic separation - thermal expansion






39. Is analogous to toughness.






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






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






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






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






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






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






46. Stress concentration at a crack tips






47. 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.






48. 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






49. 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.






50. The Magnetization of the material - and is essentially the dipole moment per unit volume. It is proportional to the applied field. Xm is the magnetic susceptibility.