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Component Mode Synthesis (CMS) with Results Expansion in Ansys Workbench

Figure 1: Results from Full Model (Left) and CMS (Right)

Background
In a previous post on Component Mode Synthesis (CMS) in Ansys Workbench, the expansion of the results were omitted. This is remedied in this post. Figure 1 compares the results favorably between the full model to a model with the mid-section as a CMS part.

Resources
1. The archived workbench file (R18) can be downloaded here (download icon at top-right).
2. Script that is used as solution snippet can be downloaded here.
3. A key resource is available in the help documentation.
4. Some fancy graphics describing the process here.

General Setup
Figure 2: Overall Geometry (Left) & CMS Part (Right)

This example has a few prerequisites:
1. Multi-parts with shared topology (Figure 2)
2. Named Selection of the CMS part (Body1 in example)
3. Named Selection of interface on CMS part (c1a & c2a in example)
4. Command snippet under solution does everything. Between steps, no suppressing and un-suppressing part nonsense required.

Alternately, contacts could be used with additional planning.

Solution Snippet Highlights
If you go through the snippet script there is a few major differences to the purely use case. Firstly, there is an initial /filnam,full $ save. This will be used later for suppressing necessary bodies but more importantly allow for later results expansion. Secondly, the expansion pass points to earlier passes of myse generation and use pass to extract the results. Finally, the merging of the results files requires a /delete the result file before looping through results of both expanded CMS and non-CMS parts.

Discussion
It is noted in this simple example, the CMS solution time is slower to the full model. That's because the super-element preparation and expansion consumes precious time. This method would only be useful for big models where memory is an issue.

When reusing the superelement part with other iterations, special consideration is needed when bringing in the superelement. NUMOFF is needed to avoid having duplicate nodes and elements stepping on each other's toes. This requires solving in Ansys Classic as the numbering would be different to Ansys Workbench.

Good luck!

All posts on Superelements 
Reuse CMS Superelement in Ansys Workbench with Expansion Link [ Best approach! ]
Component Mode Synthesis (CMS) with Results Expansion in Ansys Workbench Link
Craig Bampton Method Overview Link
Component Mode Synthesis(CMS) Substructure in ANSYS Workbench Link

Comments

  1. This comment has been removed by the author.

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  2. Dear Jason,

    thank you for providing this model. I made it work in Ansys WB 19 adding at the beginning the following three lines to the command snippet:

    dmpopt,esav,yes
    dmpopt,emat,yes
    dmpopt,full,yes

    Best Regards
    Drago

    ReplyDelete
  3. Dear Jason
    Is it possible to couple the modal data from a experimental modal analysis with a CMS superelement?

    I have measured the frf of a clamping system and described it in a state space representation. I would like to couple this data with a workpiece that I have genererated and simulated in Ansys to improve the simulation accuracy of my modal analysis. I have already tried it with RCSA, which was difficult.

    Is there any way to couple the experimental data from the clamping system with the simulation in Ansys?

    Thanks
    Semir

    ReplyDelete
    Replies
    1. Hi Semir,

      You could take a look at FEMtools or other software that offers Modal Based Assembly and FRF Based Assembly. I've personally not done it before.


      Kind regards,
      Jason

      Delete
  4. Hi Jason,

    Nice example.
    Would you have an example of the same thing done with contacts ?

    Thanks

    ReplyDelete
    Replies
    1. A More recent post uses contacts. https://www.ansystips.com/2018/03/reuse-cms-superelement-in-ansys.html

      Delete

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