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






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






3. 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.






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






5. Because of ionic & covalent-type bonding.






6. 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.






7. 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






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






9. 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.






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






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






12. Ohms Law: voltage drop = current * resistance






13. Different orientation of cleavage planes in grains.






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






15. 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.






16. Undergo little or no plastic deformation.






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






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






19. 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.






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






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






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






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






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






26. Stress concentration at a crack tips






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






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






29. 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






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






31. - 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






32. Resistance to plastic deformation of cracking in compression - and better wear properties.






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






34. 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






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

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36. 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






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






38. Created by current through a coil N= total number of turns L= length of turns (m) I= current (ampere) H= applied magnetic field (ampere-turns/m) Bo= magnetic flux density in a vacuum (tesla)






39. Diffuse image






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






41. Undergo extensive plastic deformation prior to failure.






42. Cp: Heat capacity at constant pressure Cv: Heat capacity at constant volume.






43. 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)






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






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






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






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






48. Materials change size when temperature is changed






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

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