Test your basic knowledge |

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. 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.






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






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






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

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






6. Emitted light is in phase






7. Width of smallest feature obtainable on Si surface






8. 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.






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






10. 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.






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






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






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






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






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






16. Undergo extensive plastic deformation prior to failure.






17. 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






18. - 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






19. 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






20. 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






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






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






23. These materials are relatively unaffected by magnetic fields.






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






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






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






27. 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






28. 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.






29. 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






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






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. 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






33. Occur when lots of dislocations move.






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






35. Increase temperature - no increase in interatomic separation - no thermal expansion






36. - 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






37. Growing interconnections to connect devices -Low electrical resistance - good adhesion to dielectric insulators.






38. Digitalized data in the form of electrical signals are transferred to and recorded digitally on a magnetic medium (tape or disk) - This transference is accomplished by a recording system that consists of a read/write head - "write" or record data by






39. They are used to assess properties of ceramics & glasses.






40. Light Amplification by Stimulated Emission of Radiation






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






42. 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






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






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






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






46. 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.






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






48. Different orientation of cleavage planes in grains.






49. Because of ionic & covalent-type bonding.






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