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






2. Emitted light is in phase






3. 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.






4. 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.






5. Because of ionic & covalent-type bonding.






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






7. Transmitted light distorts electron clouds - The velocity of light in a material is lower than in a vacuum - Adding large ions to glass decreases the speed of light in the glass - Light can be "bent" (or refracted) as it passes through a transparent






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






9. 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






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






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






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






13. Undergo little or no plastic deformation.






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






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






16. Sigma=ln(li/lo)






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






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






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






20. Process by which geometric patterns are transferred from a mask (reticle) to a surface of a chip to form the device.






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






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






23. Measures Hardness 1. psia = 500 x HB 2. MPa = 3.45 x HB






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






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

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






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






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






29. Cracks propagate along grain boundaries.






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






31. 1. Fluorescent Lamp - tungstate or silicate coating on inside of tube emits white light due to UV light generated inside the tube. 2. TV screen - emits light as electron beam is scanned back and forth.






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






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






34. Light Amplification by Stimulated Emission of Radiation






35. 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)






36. 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






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






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. 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






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






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






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






43. 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.






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






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






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






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






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






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






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