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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. High toughness; material resists crack propagation.






2. 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.






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






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






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






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






7. 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






8. 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.






9. 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






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






11. Is analogous to toughness.






12. Sigma=ln(li/lo)






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






14. - 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






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






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






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






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






19. 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






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






21. Allows you to calculate what happened G=F' x cos(lambda) - F=F' x cos(phi)






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






23. Diffuse image






24. Occur when lots of dislocations move.






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






26. 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.






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






28. The ability of a material to absorb heat - Quantitatively: The energy required to produce a unit rise in temperature for one mole of a material.






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






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






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






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






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






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






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






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






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






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






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






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






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






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






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






44. 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)






45. - 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






46. 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.






47. 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.






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






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






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