Questions
Quick questions
You should be able to answer these questions without too much difficulty after studying this TLP. If not, then you should go through it again!
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Which of the following statements is false?
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Which of the following statements best describes the nature of dislocations in an amorphous material?
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What are the conventional units of dislocation density?
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How would you make a stack of ham sandwiches look like a screw dislocation?
Deeper questions
The following questions require some thought and reaching the answer may require you to think beyond the contents of this TLP.
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Do the explanations of these experimental observations involve the concept of dislocations? (Answer yes or no for each)
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The energy per unit length, U, associated with an edge dislocation is given by
U ~ 0.5(Gb2)
where b is the magnitude of the Burgers vector b and G is the shear modulus. Estimate the energy per unit length of a dislocation in silver.
Data for silver: Crystal system is cubic F, a = 0.409 nm. b lies parallel to <110> directions. Shear modulus G = 28.8 GPa.
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Determine whether the following dislocations in sodium chloride are edge, screw or mixed. Identify the slip plane in which the dislocation lies. (Sodium chloride is cubic F and slips on {110}
slip systems.) Burgers vector b parallel to: Line vector l parallel to: a [110] [ 0]b [001] [ 10]c [100] [111] -
Which of the following statements is true? (answer yes or no for each)
Open-ended questions
The following questions are not provided with answers, but intended to provide food for thought and points for further discussion with other students and teachers.
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Is dislocation glide always the mechanism of plastic flow? How might other mechanisms operate?
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Why might the presence of dislocations in materials used for electronic components (such as integrated circuits) be a problem? How might the problem be reduced or solved?
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Plastically deforming a material requires energy input. In what ways is this energy dissipated? Is any of it stored in the material?