Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

CMS analysis in ANSYS Workbench 14.0

  1. Jun 18, 2012 #1

    I have a question regarding CMS analysis in ANSYS Workbench 14.0. I really hope that one of you experts out there can/is willing to help me.

    I've tried normal substructuring (Guyan) and obtained the expected results in a modal analysis. Now, since the Guyan reduction yields significant deviations for most eigenmodes, I would like to try CMS. I've chosen a simple system, namely a 3-element cantilever beam:


    I want to find the eigenmodes for this full model system by condensating the midmost element to a superelement, i.e. obtaining:

    |------o SE o------o

    The two midnodes are defined as remote points.
    I have done the procedure in analogy to the Guyan reduction, i.e. first I have generated the superelement. This is done in a separate analysis on the basis of only the midmost element (the one transformed to superelement):


    The two nodes are defined as remote points in the model. The generation command is (partially copied from a tutorial):

    NSEL, S, NODE, 1001 , N1
    NSEL, A, NODE, 1002 , N2
    M, ALL, ALL
    NUM_MODES = 100
    SEOPT, BEAM2, 2
    CMSOPT, FIX, NUM_MODES, 0, 100000
    ESLN, S

    Strangely, this doesn't result in an error as it did when using Guyan reduction (another command of course). But it generates a .sub file I've tried to use in an analysis of the reduced model (the one with the superelement in the middle). The usage command is:


    This command is taken from my Guyan reduction procedure. The analysis goes through, but I obtain completely wrong eigenfrequencies.
    Can anyone tell me where my error(s) is/are? It would be highly appreciated.

    Kind regards,
    Martin Ulriksen
    Student in structural engineering, Aalborg University, Esbjerg, Denmark.
  2. jcsd
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Can you offer guidance or do you also need help?
Draft saved Draft deleted