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Differential stiffness matrix extraction

Use the example files in tpl6\dynamics, prestiff103.dat and prestiff103pl.dat as our guides we can see the impact of pressure on a structure.  Let's say I want to run a study varying the PLOAD value to see the impact on the modes.  I could run STATSUB many times but by extracting the differential stiffness matrix I could simply scale it and proceed directly to solve the eigensolution.  I created an ALTER to get KDAA and proved that scaling it matches a change to PLOAD.  I also see that the OUG data block has ACODEs for Differential Stiffness.  Is there a clean way to extract KDGG or KDAA without an ALTER?  It seems to me that if OUG has those ACODE entries, there should be a "standard" request for it.  I did try a few MALTER statements to accomplish the same thing, but received the error that KDAA didn't exist.  Basically I'm looking for a simple way to get KDGG and/or KDAA into a op2, DMIGPCH or H5 file.

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  • Thank you.  My current ALTER (2024.1) looks like this:

    COMPILE SEKDR LIST NOREF
    ALTER 237
    $ Use MATMOD to DMIG punch the KDGG for later use with K2GG
    MESSAGE //'DMIG KDGG to Punch file'/ $
    MATMOD KDGG,BGPDTS,USET,,,/,/16/1/1/1/////////'KDSTIFF'/'G' $

    This generated the DMIG and I tested it with K2GG.  Is there a better way?  Better in this context means a way that works in all versions of Nastran and can easily be added back in as with K2GG.

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