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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. Materials change size when temperature is changed






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






3. 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.






4. 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






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






6. 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






7. 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."






8. 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.






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

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






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






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






13. 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.






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






15. 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






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






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






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






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






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






21. 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






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






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






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






25. Different orientation of cleavage planes in grains.






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






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






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






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






30. 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






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






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






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. 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.






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






37. 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.






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






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






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






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






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






43. 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.






44. 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.






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






46. Wet: isotropic - under cut Dry: ansiotropic - directional






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






48. 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






49. Impurities added to the semiconductor that contribute to excess electrons or holes. Doping = intentional impurities.






50. Emitted light is in phase






Can you answer 50 questions in 15 minutes?



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