Mode Shape interpretation
Mode Shape interpretation
(OP)
Hello,
The results of a modal frequency analysis typically include a mode shape with each modal frequency. Most FEA packages can plot out displacements values of the mode shape. In a frequency analysis, there is no input load. So my question is:
What do these displacement values mean? and How are they calculated?
Thanks,
Nate.
The results of a modal frequency analysis typically include a mode shape with each modal frequency. Most FEA packages can plot out displacements values of the mode shape. In a frequency analysis, there is no input load. So my question is:
What do these displacement values mean? and How are they calculated?
Thanks,
Nate.





RE: Mode Shape interpretation
Read up in any decent dynamics text to see how they are calculated.
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Mode Shape interpretation
Mode shapes are relative displacment of the structure when vibrating at the corresponding modal frequency...
Modal frequencies and mode shapes are characteristic of the structure depending upon geometry, material and support conditions.
Regards,
Logesh.E
RE: Mode Shape interpretation
Regards
Thomas
RE: Mode Shape interpretation
corus
RE: Mode Shape interpretation
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RE: Mode Shape interpretation
I would not say that the displacement value means nothing. It's probably some kind of normalized deformation, typically normalized with respect to modal mass etc.
However, it is no "real" deformation since there is no load applied. In some FE packages you can request "max normalizing" and then you can get max displacement = 1 for all mode shapes.
All this with some reservation since I don't know how "all" FE packages work.
Regards
Thomas
RE: Mode Shape interpretation
Thanks again for your help,
Nate.