How do I export stiffness and mass matrices from Optistruct?

Christos Georgiadis_22397
Christos Georgiadis_22397 New Altair Community Member
edited October 21 in Community Q&A

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?

Best Answer

  • Rajashri_Saha
    Rajashri_Saha
    Altair Employee
    edited July 3 Answer ✓

    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.

    image

    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.

    image

    Next in KEYWORD search for MATRIX.

    image

    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.

    image

    Hope you will be able to create this now.

    Thanks

    Rajashri

Answers

  • Vladimir_Gantovnik
    Vladimir_Gantovnik Altair Community Member
    edited July 1

    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
    Christos Georgiadis_22397 New Altair Community Member
    edited July 2

    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
    loistf Altair Community Member
    edited July 2

    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
    Christos Georgiadis_22397 New Altair Community Member
    edited July 2
    loistf said:

    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.

    image

  • Rajashri_Saha
    Rajashri_Saha
    Altair Employee
    edited July 3 Answer ✓

    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.

    image

    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.

    image

    Next in KEYWORD search for MATRIX.

    image

    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.

    image

    Hope you will be able to create this now.

    Thanks

    Rajashri

  • Pedro_Millan
    Pedro_Millan Altair Community Member
    edited October 21

    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.

    image

    Next in KEYWORD search for MATRIX.

    image

    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.

    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