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Response Dynamic to evaluate FRF in a superelements assembly FEM

Genius
Genius

Dear all,

 

I am analysing an assembly FEM with one superelement created via Craig-Bampton method (SOL103 Superlement).

I want to analyse the dynamic of the structure, then I compute a modal analysis: "SOL 103 Real Eigenvalues". Notice that I cannot run a "SOL103 Response dynamic", because for superelement it is not available this solution.

 

Anyhow, after I evaluted the mode shapes and resonance frequencies, I want to extract the frequency response function (FRF) of the structure. Then press "New solution process"  ->  "Response Dynamic".

 

A warning appear that suggest to set OUGCORD = GLOBAL in the parameters list. I add this parameter and then I press again "New solution process"  ->  "Response Dynamic".
Good: now the warning do not appear.


So, I press rigth click -> "evaluate FRF" -> select DOF of input & output -> frequency range -> press ok to plot.

Usually in a model without superelements now appear the FRF,  but here is the problem. As shown in the image, appear an error message with the following text "Error: Event definition does not match with modes rapresentation".

 

How can I fix the error?

5 REPLIES 5

Re: Response Dynamic to evaluate FRF in a superelements assembly FEM

Siemens Genius Siemens Genius
Siemens Genius

The OUGCORD message is because Response Dynamics requires the Nastran results to be in the Global Cordiinate System. Evidently, initially your results were in the Basic Coordinate System.

 

Now, for the FRF response, unfortunately, Response Dynamics does not support superelement results. We have Enhancement Requests for this, but have not been able to do anything about it yet.

Re: Response Dynamic to evaluate FRF in a superelements assembly FEM

Genius
Genius

Thanks a lot @SteveP!

Are there other methods (apart from the one mentioned, that as you said it is unfeasible) to extract an FRF in a model with a superelement?

 

Regards,
Alberto

Re: Response Dynamic to evaluate FRF in a superelements assembly FEM

Siemens Genius Siemens Genius
Siemens Genius

Not using Response Dynamics. You might be able to do it  using just NX Nastran. Someone with more Nastran experience may be able to help with that.

Re: Response Dynamic to evaluate FRF in a superelements assembly FEM

Phenom
Phenom

Have you had a look at SOL111 ?

Production: NX.CAE 10.0.2.6
Development: VB.NET (amateur level !)

Re: Response Dynamic to evaluate FRF in a superelements assembly FEM

Genius
Genius

Dear @selex_ct, I do not find training material regarding SOL111. Can you suggest me some references or tutorials to learn how SOL111 works?