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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. Increase temperature - increase in interatomic separation - thermal expansion






2. Occur when lots of dislocations move.






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






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






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






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






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. 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.






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






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






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






12. These materials are relatively unaffected by magnetic fields.






13. 1. Tc= critical temperature- if T>Tc not superconducting 2. Jc= critical current density - if J>Jc not superconducting 3. Hc= critical magnetic field - if H > Hc not superconducting






14. Defines the ability of a material to resist fracture even when a flaw exists - Directly depends on size of flaw and material properties - K(ic) is a materials constant






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






16. - 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






17. The magnetic hysteresis phenomenon: Stage 1: Initial (unmagnetized state) Stage 2: Apply H - align domains Stage 3: Remove H - alignment remains => Permanent magnet Stage 4: Coercivity - Hc negative H needed to demagnitize Stage 5: Apply -H - align d






18. 1. Stress-strain behavior is not usually determined via tensile tests 2. Material fails before it yields 3. Bend/flexure tests are often used instead.






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






20. Sigma=ln(li/lo)






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






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






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






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






25. Is analogous to toughness.






26. 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.






27. 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






28. Second phase particles with n > glass.






29. 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.






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






31. Growth of an oxide layer by the reaction of oxygen with the substrate - Provides dopant masking and device isolation - IC technology uses 1. Thermal grown oxidation (dry) 2. Wet Oxidation 3. Selective Oxidation






32. 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.






33. 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.






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






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






36. Light Amplification by Stimulated Emission of Radiation






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






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






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


40. Ohms Law: voltage drop = current * resistance






41. 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






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






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






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






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






46. Width of smallest feature obtainable on Si surface






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






48. 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."






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






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