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






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






3. 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)






4. 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.






5. 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.






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






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






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






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






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






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






12. Sigma=ln(li/lo)






13. 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






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






15. Is analogous to toughness.






16. 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






17. 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






18. Second phase particles with n > glass.






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






20. 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






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






22. 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.






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






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






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






26. 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)






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






28. Occur when lots of dislocations move.






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






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






31. Width of smallest feature obtainable on Si surface






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






33. 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.






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






35. Emitted light is in phase






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






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






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






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






40. 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






41. Undergo extensive plastic deformation prior to failure.






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






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






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






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






46. 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






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






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






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






50. Cracks propagate along grain boundaries.