stretching wire -- an anecdotal analysis

Richard Brekne ricb at pianostemmer.no
Sat Apr 19 12:24:37 MDT 2008


Hi Dale.

The permanent elongation in a string you seem to be asking about is as I 
am sure you already know what is known as plastic deformation and occurs 
when the string is pulled past what is known as the yield strength 
point.  The following link is provided for your convenience  
http://en.wikipedia.org/wiki/Tensile_strength

The question being thrown around here (as I understand it)  is whether 
or not there is any plastic creep over long time when the wire tension 
is kept well below this level of stress.

As to whether false beats can be created as a result of pulling a string 
beyond this plastic deformation strengths point.... I'd say there is 
plenty of evidence out there to support that claim.... quite strong support.

Cheers
RicB

Hi Kurt

Thanks for the informative article. I wrote last week about false beats 
being introduced by over stretching in the first chipping's of newer 
Steinways, (or any piano) Now that this man has stated that permanent 
elongation can happen just prior to the string actually breaking has me 
asking at what point of breaking strain does this permanent elongation 
occur. For example can a string permanently elongate in any section if 
pulled up 100 cents past it's intended tension. Or perhaps this only 
happens in the trebles where the false beats I objected to occur. Of 
course over pulling a nice short string puts an enormous amount of 
unscheduled strain on the bridge pins...........heeeeere we go!

Hmm?
Anybody
Dale







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