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Modal Frequency of a System having more than two components.

  1. Aug 26, 2012 #1
    I am looking for an efficient procedure to find the natural frequency of a system comprising more than two components. Like I have an assembly of system comprising compressor, condenser, piping, fan, fan bracket, and frame. I have all the designs and dimensions of the total model. How can I find out the total modal response of the overall system as well as how I relate the modal response of each components with the modal response of my total assembly.

    Any response is welcome. I have gone through some literature review, but nowhere I have not seen such a problem with some really good solution. Please, HELP ME TO FIND OUT THIS. A
     
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  3. Aug 27, 2012 #2

    Mech_Engineer

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    For complex geometry, your best bet is finite element analysis software such as ANSYS or Comsol. Each is capable of finding modal frequencies for assembled components.

    http://www.ansys.com/
    http://www.comsol.com/
    List of commercial FEA packages: http://en.wikipedia.org/wiki/List_of_finite_element_software_packages#Proprietary.2FCommercial

    For a more inexpensive option you may also look into LISA although I can't vouch for its capabilities or accuracy.

    http://www.lisa-fet.com/
    List of free/open source FEA packages: http://en.wikipedia.org/wiki/List_of_finite_element_software_packages#Free.2FOpen_source
     
  4. Aug 27, 2012 #3
    Mech_Engineer@ Thanks for your response.

    I know commercial software like ANSYS or other you specify do calculate the natural frequency of a total assembly, but What I am looking for is how can you co-relate the natural frequency of several components with the natural frequency of total assembly.

    If I got individual response of several components and mass_participation factor for all the 6 d.o.fs (means X, Y,Z, Rot X, Rot Y, Rot Z) can I co-relate form that.
     
  5. Aug 28, 2012 #4

    AlephZero

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    Google for "Component mode synthesis" or "Craig Bampton".

    That should get you started on a literature ssearch. There's a lot to read and many different variations of the general idea.
     
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