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






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






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






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






5. 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.






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






7. 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.






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






9. 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






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






11. 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.






12. 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






13. 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.






14. Undergo little or no plastic deformation.






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

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






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






18. 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)






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






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






21. 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






22. 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






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






24. Cracks propagate along grain boundaries.






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






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. Occur when lots of dislocations move.






28. Stress concentration at a crack tips






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






30. Second phase particles with n > glass.






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






32. 1. Imperfections increase resistivity - grain boundaries - dislocations - impurity atoms - vacancies 2. Resistivity - increases with temperature - wt% impurity - and %CW






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






34. Light Amplification by Stimulated Emission of Radiation






35. Sigma=ln(li/lo)






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






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






38. 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






39. Emitted light is in phase






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

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






42. - 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






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






44. 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






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






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






47. 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.






48. These materials are relatively unaffected by magnetic fields.






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






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