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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.
  • 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. 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






2. Is analogous to toughness.






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






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






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

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6. 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.






7. 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)






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






9. Because of ionic & covalent-type bonding.






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






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






12. 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.






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






14. 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






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






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






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






18. Diffuse image






19. Materials change size when temperature is changed






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






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






22. Plastic means permanent! When a small load is applied - bonds stretch & planes shear. Then when the load is no longer applied - the planes are still sheared.






23. 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.






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






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






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






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






28. Liquid polymer at room T - sandwiched between two sheets of glass - coated with transparent - electrically conductive film. - Character forming letters/ numbers etched on the face - Voltage applied disrupts the orientation of the rod- shaped molecule






29. 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






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






31. 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






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






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






34. Loss of image transmission - You get no image - There is no light transmission - and therefore reflects - scatters - or absorbs ALL of it. Both mirrors and carbon black are opaque.






35. High toughness; material resists crack propagation.






36. 1. Stress-strain behavior is not usually determined via tensile tests 2. Material fails before it yields 3. Bend/flexure tests are often used instead.






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






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






39. 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






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






41. 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)






42. 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






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






44. Second phase particles with n > glass.






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






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






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






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






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






50. Ohms Law: voltage drop = current * resistance