Test your basic knowledge |

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. 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)






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






3. 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.






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






5. 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






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






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






8. These materials are relatively unaffected by magnetic fields.






9. 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.






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






11. 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.






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






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






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






15. Undergo extensive plastic deformation prior to failure.






16. Diffuse image






17. 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






18. Transmitted light distorts electron clouds - The velocity of light in a material is lower than in a vacuum - Adding large ions to glass decreases the speed of light in the glass - Light can be "bent" (or refracted) as it passes through a transparent






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






20. Second phase particles with n > glass.






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






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






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






24. 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






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






26. Ohms Law: voltage drop = current * resistance






27. 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.






28. 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.






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






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






31. 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."






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






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






34. 1. Tc= critical temperature- if T>Tc not superconducting 2. Jc= critical current density - if J>Jc not superconducting 3. Hc= critical magnetic field - if H > Hc not superconducting






35. Cracks propagate along grain boundaries.






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






37. High toughness; material resists crack propagation.






38. 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.






39. Emitted light is in phase






40. - 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






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






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






43. Occur when lots of dislocations move.






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






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






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






47. 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






48. Reflectiviy is between 0.90 and 0.95 - Metal surfaces appear shiny - Most of absorbed light is reflected at the same wavelength (NO REFRACTION) - Small fraction of light may be absorbed - Color of reflected light depends on wavelength distribution of






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






50. 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)