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






2. Sigma=ln(li/lo)






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






4. 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






5. Energy is stored as atomic vibrations - As temperature increases - the average energy of atomic vibrations increases.






6. - 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






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






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






9. Undergo little or no plastic deformation.






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






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






12. 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.






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






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






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






16. 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.






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






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






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






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






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






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






23. Occur when lots of dislocations move.






24. 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






25. 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






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. 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.






28. Because of ionic & covalent-type bonding.






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






30. 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."






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






32. 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






33. 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.






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






35. 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)






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






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






38. Cracks propagate along grain boundaries.






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






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






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






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






43. The Magnetization of the material - and is essentially the dipole moment per unit volume. It is proportional to the applied field. Xm is the magnetic susceptibility.






44. 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






45. Is analogous to toughness.






46. Stress concentration at a crack tips






47. Liquid polymer at room T - sandwiched between two sheets of glass - coated with transparent - electrically conductive film. - Character forming letters/ numbers etched on the face - Voltage applied disrupts the orientation of the rod- shaped molecule






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






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






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






Can you answer 50 questions in 15 minutes?



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