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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
  2. jcsd
  3. Aug 27, 2012 #2


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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.

    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.

    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


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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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