Re: FDC wire length changes

[Tim Whitlatch <whitey@jlab.org>]

Good morning Dan,

I have done some calculations this morning and here is what I came up 
with.....

 From data from Fermi and Steve Christo, I use the following properties;

Field wire - BeCu - 80um diameter, E=1.24e11 Pa
Sense wire - w  - 20um diameter, E= 2.2e11 Pa

For the longest (391mm) field wire tension to change from the initial 
140g to 120g in relaxed state, the frame would deflect about 310 um 
inward. This is consistent with the tension from all the wires 
contributing to frame deflection.

For the longest (391mm) sense wire tension to change from 20g to 18g in 
the relaxed state, the frame would have to deflect about 280 um inward. 
This is consistent with the field wire deflection (close enough to 
satisfy me).

This all is in the realm of what I would have expected.

Cheers,

       Tim

Daniel S. Carman wrote:
> Tim,
>
> If you can get me some information on the expected length change
> of the sense and field wires in the center of the wire frame due
> to the wire load warping of the frame, I would appreciate this.  The
> Phase 1 contract with IUCF ends on Aug. 22 and if the tension
> phenomenon that I showed is not due to this effect, they will need
> to work on this.
>
> I have estimated for the longest sense wire (991 mm), for a
> tension change from 20 N (nominal stringing tension) to 18 N
> (measured), the length changes only by about 20 microns.  This
> seems like too small a number to me.  I have assumed a Young's
> modulus for our sense wire of 3.72e11 Pa.
>
>
> 				Regards,
>
> 					Daniel
>
>
> **********************************************************************
> *                                                                    *
> * Dr. Daniel S. Carman                   e-mail : carman@jlab.org    *
> * Staff Scientist                        office : (757)-269-5586     *
> * Jefferson Laboratory                   web: www.jlab.org/~carman   *
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