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Engineering Materials

Subject : engineering
Instructions:
  • Answer 50 questions in 15 minutes.
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  • Match each statement with the correct term.
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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. 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.






2. 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.






3. 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.






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






5. 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.






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






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






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






9. 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






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






11. Light Amplification by Stimulated Emission of Radiation






12. 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






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

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14. 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.






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






16. 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






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






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






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






20. Occur when lots of dislocations move.






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






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






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






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






25. Is analogous to toughness.






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






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






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






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






30. - 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






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






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






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






34. 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)






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






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

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37. 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






38. These materials are "attracted" to magnetic fields.






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






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






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






42. Undergo little or no plastic deformation.






43. Undergo extensive plastic deformation prior to failure.






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






45. 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






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






47. 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.






48. 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)






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






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