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






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






3. Different orientation of cleavage planes in grains.






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






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






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






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






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






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






10. 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.






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






12. These materials are relatively unaffected by magnetic fields.






13. Cracks propagate along grain boundaries.






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






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






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






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






18. Found in 26 metals and hundreds of alloys & compounds - Tc= critical temperature = termperature below which material is superconductive.






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






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






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






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






23. Sigma=ln(li/lo)






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






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






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






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






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






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






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






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






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






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






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






35. 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






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






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






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






40. Stress concentration at a crack tips






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






42. 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






43. 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






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






45. 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.






46. 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






47. 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.






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






49. The magnetic hysteresis phenomenon: Stage 1: Initial (unmagnetized state) Stage 2: Apply H - align domains Stage 3: Remove H - alignment remains => Permanent magnet Stage 4: Coercivity - Hc negative H needed to demagnitize Stage 5: Apply -H - align d






50. 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