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Entry  Thu Jan 31 14:00:00 2013, Kristen Holtz, Notes, PMC, PMC Longitudinal Testing and Modal Analysis PMCphoto_circclamps.JPGPMC_ringdown_Jan28.JPGPMC_unconstrainedringdown_Jan28.JPGPMC_Excitation_Diagram_1-28-13.JPG
    Reply  Wed Mar 27 01:52:34 2013, tara, Notes, PMC, PMC Longitudinal Testing and Modal Analysis pmc_eigen.png
       Reply  Sun Mar 31 03:03:28 2013, tara, Notes, PMC, PMC Longitudinal Testing and Modal Analysis psl_log.pngpsl_log2.png
          Reply  Sun Mar 31 14:42:05 2013, Evan, Notes, PMC, PMC Longitudinal Testing and Modal Analysis 
             Reply  Sun Mar 31 20:06:16 2013, tara, Notes, PMC, PMC Longitudinal Testing and Modal Analysis 
       Reply  Mon Apr 1 20:59:19 2013, tara, Notes, PMC, PMC Longitudinal Testing and Modal Analysis 
          Reply  Thu Apr 4 23:55:12 2013, Evan, Notes, PMC, PMC Longitudinal Testing and Modal Analysis mirrorsag_coarse.pdfmirrorsag_fine.pdf
    Reply  Thu Apr 4 11:44:14 2013, Evan, Notes, PMC, 270 Hz clamped PMC twisting mode pmc_clamp_twist_mode.jpg
Message ID: 1136     Entry time: Sun Mar 31 20:06:16 2013     In reply to: 1135
Author: tara 
Type: Notes 
Category: PMC 
Subject: PMC Longitudinal Testing and Modal Analysis 

Quote:

I think the analytical formula in terms of rho is going to be (1.57/2*pi) * sqrt(E / rho * L^2), since the Roark formula is (1.57/2*pi) * sqrt(A* E * g / w * L^2) and the weight per unit length is w = m * g / L = rho * A * g. With your values for L, A, E, and rho, this gives f1 = 16 kHz. Since A does not appear in the analytical formula, this also explains why changing the area in the Comsol model doesn't change the frequency.

 

 

 good catch! Thanks. Then both analytical and FEA results are the same. So our COMSOL results for PMC should be valid, the first body for a stainless steel PMC, see psl:1131,at 16 kHz is reasonable.

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