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






2. 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)






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






4. Diffuse image






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






6. Light Amplification by Stimulated Emission of Radiation






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






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






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






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






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






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






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






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






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






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






17. 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






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






19. These materials are relatively unaffected by magnetic fields.






20. Undergo little or no plastic deformation.






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






22. - 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






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






24. 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






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






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






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






28. With Increasing temperature - the saturation magnetization diminishes gradually and then abruptly drops to zero at Curie Temperature - Tc.






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. 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.






31. 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.






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






33. 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.






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






35. 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.






36. Width of smallest feature obtainable on Si surface






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






38. 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)






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






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






42. 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.






43. Stress concentration at a crack tips






44. Undergo extensive plastic deformation prior to failure.






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






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






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






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






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






50. 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."