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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. 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)






2. These materials are relatively unaffected by magnetic fields.






3. 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.






4. 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.






5. 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






6. 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






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






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






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






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






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






12. 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






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






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






15. Typical loading conditions are _____ enough to break all inter-atomic bonds






16. 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.






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






18. Undergo little or no plastic deformation.






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






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






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






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






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






24. 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.






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






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






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






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






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






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






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






32. 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






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






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






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






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






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






38. 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






39. Undergo extensive plastic deformation prior to failure.






40. Is analogous to toughness.






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






42. Ohms Law: voltage drop = current * resistance






43. 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.






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






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






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






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






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






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. 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.