Music wire over time

[DanStro]

Hello,

I am trying to find information about whether music wire loses its tension over time. The diameter will be ~.030" and tension would not be terribly large, similar to what is used when they are actually in a piano (~50-75lb total force). But because of the application, some vibe and temperature fluctuation, I am worried that the tension will decrease over time and there will be no way to re-tension it.

Are there any references that someone can point me to?

Thanks,
Dan

 

[btrueblood]

" I am worried that the tension will decrease over time and there will be no way to re-tension it."

Springs made of music wire do relax over time, and certainly pianos and other string instruments with metal wires go out of tune over time...so yes, it will likely decrease. Creep theory would suggest that you would need to have the wire up near its breaking strength to have measurable relaxation/creep at room temperature. That said, most creep tests are done by people on a budget, and such tests are usually run for durations measured in hours not months or years. And, clearly local areas of a bit of wire may be under higher residual stress than others (think of the residual stress in straightening coiled wire) so it would not be unreasonable to think some "shakedown" relaxation occurs on freshly tensioned wires.

 

[geesaman.d]

Focus on the components that put the tension on the music wire that can relax or loosen, and wear points that will relax.

I would assume that a tension device is practically necessary here.

 

[TheTick]

Typically, as long as you're under yield, there will be no creep. But "yield" is a bit statistically subjective, usually incorporating a certain amount of relaxing to a free length slightly longer than original.

I typically over-tune my guitars about a half step to set the strings before relaxing to final tuning. Might be useful to do the same for whateve you're doing.

 

[EdStainless]

What is the strain on the wire?
With high strength wire the stress-strain curve is nearly straight and the yield is something like 98% of UTS.
If you are below 60% of UTS the relaxation will be in the rest of your system and not the wire. The wire can only stay as tight as its supports. In musical instruments this is usually the limit and not the wire.
I would suggest setting to a slightly higher tension and then relaxing to your desired level a few times. This should help take the 'slack' out of the system.
We had dead weight tests running at 90% of UTS for decades with the total stretch being on the order of >10ppm at RT.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed