How do I export stiffness and mass matrices from Optistruct?

want to export mass and stiffness matrices from OptiStruct in order to import them into MATLAB. The only way I have found is by producing an OP2 file, which I don't know how to import. Is there any other way to get the matrices in another format or a way to open these OP2 files?

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OptiStruct

v2022.3

Accepted answers

Rajashri_Saha

My main issue is that I don't know exactly where to add the text. I have attached a screenshot of the .fem file. Thanks again.

Hi Christos,

In hypermesh, you can do CTRL+F and type OUTPUT then select the OUTPUT option which pops up in right top corner of hm window. See the image below.

Next in KEYWORD search for MATRIX.

This will create the OUTPUT,MATRIX card when you export the .fem file.

And if you want to edit it in .fem file in text editor just type OUTPUT,MATRIX above Case Control Cards like below image.

Hope you will be able to create this now.

Thanks

Rajashri

All comments

Vladimir_Gantovnik

Try to use this card in your .fem file:

OUTPUT,MATRIX

Controls the output of Stiffness, Mass, and Grid-to-DOF mapping matrices to .full.mat and .reduced.mat files (ASCII).

The description of *.full.mat file content is here:

Description of *.full.mat file

Christos Georgiadis_22397

Try to use this card in your .fem file:

OUTPUT,MATRIX

Controls the output of Stiffness, Mass, and Grid-to-DOF mapping matrices to .full.mat and .reduced.mat files (ASCII).

The description of *.full.mat file content is here:

Description of *.full.mat file

Thanks for your response. Could you please provide me with some steps on how to define this OUTPUT, MATRIX card? I don't know how to proceed.

loistf

Thanks for your response. Could you please provide me with some steps on how to define this OUTPUT, MATRIX card? I don't know how to proceed.

I would recommend you add the text in the i/o section (before the subcases) manually, with a text editor. Then, if you wish, you can import the file back to HM and you see the entity. (this is a general recommendation, for anytime that you need to add something that you don't know about other than the text, not exclusively for OUTPUT,MATRIX)

Hope it helps.

Christos Georgiadis_22397

I would recommend you add the text in the i/o section (before the subcases) manually, with a text editor. Then, if you wish, you can import the file back to HM and you see the entity. (this is a general recommendation, for anytime that you need to add something that you don't know about other than the text, not exclusively for OUTPUT,MATRIX)

Hope it helps.

My main issue is that I don't know exactly where to add the text. I have attached a screenshot of the .fem file. Thanks again.

Rajashri_Saha

My main issue is that I don't know exactly where to add the text. I have attached a screenshot of the .fem file. Thanks again.

Hi Christos,

In hypermesh, you can do CTRL+F and type OUTPUT then select the OUTPUT option which pops up in right top corner of hm window. See the image below.

Next in KEYWORD search for MATRIX.

This will create the OUTPUT,MATRIX card when you export the .fem file.

And if you want to edit it in .fem file in text editor just type OUTPUT,MATRIX above Case Control Cards like below image.

Hope you will be able to create this now.

Thanks

Rajashri

Pedro_Millan

Hi Christos,

In hypermesh, you can do CTRL+F and type OUTPUT then select the OUTPUT option which pops up in right top corner of hm window. See the image below.

Next in KEYWORD search for MATRIX.

This will create the OUTPUT,MATRIX card when you export the .fem file.

And if you want to edit it in .fem file in text editor just type OUTPUT,MATRIX above Case Control Cards like below image.

Hope you will be able to create this now.

Thanks

Rajashri

Dear Rajashri,

I am using, successfully, the OUTPUT,MATRIX,FULL,SPARSE to output the stiffness and mass matrices, however, when it comes to the mass matrix, it omits the rotational inertia of the nodes that have 6DoF (corresponding to shell elements). Do you have any idea why this is happening and/or how to solve it?

Thank you very much.

Best regards,

Pedro Millan