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Entry  Wed Nov 11 12:50:10 2009, Jenne, Update, PEM, Seismometer Noise Characteristics HuddleTest_Aug2009data.png
    Reply  Thu Apr 22 20:28:40 2010, Jenne, Update, PEM, Seismometer Noise Characteristics Gur1_Gur2_noise.png
       Reply  Thu May 27 23:59:54 2010, rana, Update, PEM, New Foam Box installed Untitled.png
          Reply  Fri May 28 00:40:53 2010, rana, Update, PEM, DAQ down 
             Reply  Fri May 28 10:44:47 2010, josephb, Update, PEM, DAQ down 
                Reply  Tue Jun 8 18:39:36 2010, rana, Update, PEM, DAQ down 
                   Reply  Tue Jun 8 20:52:25 2010, josephb, Update, PEM, DAQ up (for the moment) 
          Reply  Fri May 28 11:26:35 2010, Jenne, Update, PEM, New Foam Box installed 
          Reply  Tue Jun 1 11:47:14 2010, steve, Update, PEM, lead balls on concrete P1060269.JPG
             Reply  Wed Jun 9 19:47:08 2010, nancy, Update, PEM, lead balls on concrete 
                Reply  Thu Jun 10 07:53:14 2010, Alberto, Update, PEM, LaTeXlabs 
                   Reply  Thu Jun 10 10:58:02 2010, Koji, Update, General, LaTeXlabs 
                      Reply  Thu Jun 10 11:10:21 2010, Alberto, Update, General, LaTeXlabs 
Message ID: 3060     Entry time: Wed Jun 9 19:47:08 2010     In reply to: 3024     Reply to this: 3062
Author: nancy 
Type: Update 
Category: PEM 
Subject: lead balls on concrete 



Valera and I put the 2 Guralps and the Ranger onto the big granite slab and then put the new big yellow foam box on top of it.

There is a problem with the setup. I believe that the lead balls under the slab are not sitting right. We need to cut out the tile so the thing sits directly on some steel inserts.

You can see from the dataviewer trend that the horizontal directions got a lot noisier as soon as we put the things on the slab.

 The tiles were cut out in 1.5" ID circle to insure that the 7/16" OD lead balls would not touch the tiles on Wednesday, May 26, 2010

Granite surface plate specifications: grade B, 18" x 24" x 3" , 139 lbs

These balls and granite plate were removed by  Rana in entry log #3018 at 5-31-2010

 I tried to calculate the frequency of resonance using Rayleigh's method.  approximated the geometry of lead to be that of a perfect cylinder, and  the deformation in the lead by the deflection in a cantilever under  a shear strain.

this rough calculation gives an answer of 170Hz and depends on the dimensions of each lead, number of leads, and mass of the granite. But the flaw pointed out is that this calculation doesnot depend on the dimension of the granite slab, nor on the exact placing of the lead spheres with respect toteh COM of the slab.

I will put up the calculations details later, and also try to do a FEM analysis of the problem.


BTW, latex launched this new thing for writing pdfs. doesnot require any installations.  check  http://docs.latexlab.org

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