Youngs Modulus for Piano wire

[Dave McKibben]

Hi all:

For 7 years I did material failure analysis, and there are many things that
affect the results.
1.  For sure.......the clamping mechanism can have a huge effect.  There is
a special mechanical setup for wire to make sure a person does not put a
nick ( stress point ) into the measwured section of the wire being tested
by accident.
2.  If there is any diameter fluctuations in the wire, this can have an
impact, or any imperfections.
3.  Minor diameter differences will also.
This is why many samples would be measured, and an average # would be
recorded as the Modulus, elastic limit, yield point, plastic region etc etc.
It is my history that the recorded ' book values ' are very much an
average, and any individual measurement can vary from that book value.

Dave

> [Original Message]
> From: Stéphane Collin <collin.s at skynet.be>
> To: Pianotech List <pianotech at ptg.org>
> Date: 8/27/2006 2:47:54 PM
> Subject: Re: Youngs Modulus for Piano wire
>
> Hi John.
>
> I once had a university professor test for me the breaking strength of a 
> sample 1mm diameter Ršslau wire and a sample of 1mm diameter original 
> Bechstein wire from a 1871 piano, see how they compare.  Both samples had 
> the same breaking strength, that is sure.  Now the guy reported me the 
> breaking strength was 1500 N/mm?, which is much less than what Ršslau 
> claims.  The guy told me that the way you clamp the wire in the testing 
> machine has a tremendous effect on the measurements results.  Now, what
are 
> we measuring ?  And what do the results mean ?
> How would you do the measurement of Young's modulus ?
>
> Best regards.
>
> StŽphane Collin.
>
>
> As to the coefficient of elasticity of the wire (Young's modulus),
> rather than go by unreliable generalized values it is best to measure
> it.  It is quite simple to find out which of these two figures is
> more correct.  The more precise you want your figure the more trouble
> you'll need to take with your apparatus.
>
> JD
>
>
>
>
>