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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:

|------o------o------o

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):

o------o

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

/FILNAME, BEAM2

/SOLU

/COM

NSEL, S, NODE, 1001 , N1

NSEL, A, NODE, 1002 , N2

M, ALL, ALL

ALLSEL, ALL

CMSEL, ALL

NUM_MODES = 100

/SOLU

ANTYPE, SUBSTR

SEOPT, BEAM2, 2

CMSOPT, FIX, NUM_MODES, 0, 100000

ESLN, S

SOLVE

FINISH

SAVE

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:

/PREP7

ET,500,MATRIX50

TYPE,500

MAT,1

SE,BEAM2

FINISH

/SOLU

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.

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# CMS analysis in ANSYS Workbench 14.0

Can you offer guidance or do you also need help?

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