No Mass Matrix When Using DMIGPCH

Crashphys
Crashphys Altair Community Member
edited May 2021 in Community Q&A

Hi,

 

I ran DMIGPCH to extract the mass and stiffness matrix for the attached file. The result only extracted a stiffness matrix. There does not seem to be in input to request a mass matrix, so I assume it should be outputted automatically. Can anyone explain why I might not be getting one? Unable to attach the .pch due to huge size (350 mb).

 

Thanks

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Answers

  • Robert Lawson
    Robert Lawson Altair Community Member
    edited November 2019

    It seems like this should work as you have it, but it doesn't.  It must be being a bit lazy (or efficient?) about creating a mass matrix if it doesn't need to.

     

    Add an ANALYSIS=MODES and METHOD=? to your case control, and then an EIGRL to your bulk data.  Then it will give you a MAAX.

     

  • Crashphys
    Crashphys Altair Community Member
    edited November 2019

    Thank you for the suggestion. I'll give it a try, but my solution was eventually to just convert to a NASTRAN model (very easy) and use that. Most open source code that exists to interpret it follows NASTRAN format anyway...

  • David Vásquez
    David Vásquez New Altair Community Member
    edited May 2021
    Robert Lawson said:

    It seems like this should work as you have it, but it doesn't.  It must be being a bit lazy (or efficient?) about creating a mass matrix if it doesn't need to.

     

    Add an ANALYSIS=MODES and METHOD=? to your case control, and then an EIGRL to your bulk data.  Then it will give you a MAAX.

     

    Hi Robert, can you explain me how to add analysis and method like you said, i was looking but i didn't find where are this options.

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