stretching wire

[kurt baxter]

Here is a comment from a person called "Mapes" on www.physicsforums.com:

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Creep is quite well understood today: it is the time-dependent deformation
of materials under stress, as brewnog stated.

Inkling, your guess about creep deformation is exactly right. There are
several ways creep can occur, and they all involve diffusion. Generally, the
bonds between the iron atoms in your piano string occasionally break and
re-form due to random thermal energy. Any atomic rearrangement that lets the
string be longer is favored because you are pulling on it so hard.
Eventually, the lengthening of the string is noticeable.

Creep strictly occurs in all loaded materials above 0K. It is usually
negligible in steel at room temperature, but you've found an exception,
because the stress is large and the sensitivity of your detector (the human
ear) is very good for detecting out-of-tune strings.

One of my professors liked this trick question: which creep mechanism [there
are several, including bulk diffusion, grain boundary diffusion, and
dislocation climb] is active in material xx at yy°C? The answer is always
all of them (they just might be negligible).

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Full thread here:
http://www.physicsforums.com/showthread.php?s=f59a52eac47cac840dbddef984c592bd&p=1699460#post1699460
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