Skip to main content

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.

    ReplyDelete
  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
  5. Hi!Thanks for the post. Could you please do a GUI version of this?

    ReplyDelete
  6. hello!, how to do this with 2 superelments?

    ReplyDelete
  7. Hello Jason,

    I need to model one of the component as a flexible body.
    For this, I need to perform finite element analysis of the component, perform Craig Bampton Model Order reduction, extract the mass and stiffness matrices of the required boundary nodes.

    I have started by performing the modal analysis of the component and extracted the mode shapes and eigen frequencies. Could you please direct me on how to proceed further so that I can obtain the required result.

    Thanks
    Goutham Sajja

    ReplyDelete

Post a Comment

Popular posts from this blog

ANSYS User Defined Results

There is an abundant of options in ANSYS classic when one wishes to post process results. ANSYS workbench default pull down menu post processing options are more limited but they can still be accessed via the User Defined Results. One way not commonly used but can come in handy is as follows: Zeroth: Under Analysis Settings, there is "Output Controls" where you can toggle to "Yes" what you would like to save before the solution starts. This is like OUTRES in APDL. Output Controls First: After solving the model, click on Solution in the tree to highlight it. Solution Second: Click on Worksheet in the toolbar. Worksheet Third: In the worksheet, you will see list of results that are saved. Right click on it to create the User Defined Results. Create User Defined Results So here we have it. You could of look up the different expressions in the help document but I find this method of accessing the results convenient.  Example: Aspec

Export Stiffness Matrix from Ansys

It is sometimes useful to extract the mass and stiffness matrix from Ansys.     *SMAT, MatK, D, IMPORT, FULL, file.full, STIFF       *PRINT, matk, matk, txt Exporting mass matrix would be similar:       *SMAT, MatM, D, import, full, file.full, MASS The above script uses APDL Math to get the job done. (Please see previous post for another example). The ordering of the matrix is unfortunately not concurrently exported. To verify the sequencing is as expected, we will work to replicate a truss example in the  Finite Element Trusses course notes by Bob Greenlee. Figure 1: Truss Problem Setup Model Creation Script to create model: /prep7 !! Creates Model to reflect course notes ! Properties et ,1,1  mp , ex, 1, 29.5e6 r , 1, 1 ! Geometry n ,1 $  n ,2, 40 $  n ,3, 40, 30 $  n ,4, 0, 30 e ,1,2 $  e ,2,3 $  e ,1,3 $  e ,3,4 ! Boundary Conditions d ,1,ux,0 $  d ,1,uy,0 d ,2,uy,0 d ,4,ux,0 $  d ,4,uy,0 f ,2,fx,20e3 f ,3,fy,-25e3 ! solves /solu eqslv , sparse

ANSYS APDL Syntax Highlighting editor

Notepad++ with APDL User Defined Language The editor of my choice is Notepad++  with the available User Defined Language Files for APDL. You can install it without administrative privileges via the zip file. The best part of it is, it's FREE! After installing Notepad++, go to "Language>Define Your Language..." then "Import" the XML file downloaded from the above link. Remember to restart Notepad++ so that the language changes will take into effect. Opening up any *.inp or *.ans files should automatically switch highlighting to APDL. I made some minor edits. Here's my XML file: LINK . I also heard Sublime Text and  Ultraedit  has more advance features but they aren't (totally) free.