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Gather Grids from op2 or Generate .pch AND .op2

Hi Forum!Smiley Happy

I'm facing an obstacle towards a good solution for my problem.

I want to create a datafile containing the grids and stiffness/mass matrices.
My current approach was to set "PARAM EXTOUT DMIGPCH", gather all grids from the stiffness matrix and find the corresponding entries in the underlying data => Voila, Grids + Matrices in one file.

Unfortunately, some solutions are too big to be handled comfortably by .pch files.

Now I would like to create one file containing the grids and one file containing the matrices, but in binary way => .op2

Until now, I have got 2 ideas for that:

1. Create both .pch and .op2 file, but use the .pch only for the collection of information concerning the grids.

Problem 1. : I cant set EXTOUT two times ( EXTOUT DMIGPCH and EXTOUT DMIGOP2) Smiley Sad Is there a way to create the matrices in two ways simultaneously?

2. Only use the DMIGOP2.

Problem 2.: How can I gather information about the matrix entry grids from the op2 file? Is there a Nastran way to output also grid information?



Thank you very very much!






Re: Gather Grids from op2 or Generate .pch AND .op2

Hi Benny

If you output your matrix using EXTSEOUT using the MATOP4 option, the grid data you require will be in the *.pch file on the EXTRN card, and your mass/stiffness matrix will be in high precision in the op4 file. If you put FORM=FORMATTED on the ASSIGN statement for the op4 file, your op4 matrix will be in ascii format.



Re: Gather Grids from op2 or Generate .pch AND .op2

THank you Peter for your fast response. 

If I'm using EXTSEOUT, I would have to define an ASET etc., am I right?

With my current input_deck, I only want to create the stiffness/mass matrices from a present model using all grids. 

On account of this, I tried avoiding EXTSEOUT and using PARAM EXTOUT instead.


Or I am wrong?Smiley Happy



Re: Gather Grids from op2 or Generate .pch AND .op2

Hi Benny

You need to define on an ASET card each degree of freedom you want to appear in your mass/stiffness matrix.


Re: Gather Grids from op2 or Generate .pch AND .op2

Hello Peter,

but in my approach, i only want to have Stiffness and Mass Matrices and the corresponding grids.

Therefore, I only used "PARAM EXTOUT DMIGPCH".

According to documentation, there is no solution performed but the bare matrix generation from the input.

This is what I am aiming for.

Unfortunately there's no PARAM EXTOUT MATOP4, am I right?

I dont want to select an ASET. If I am using PARAM, i do not select an ASET, I am only including the .bdf file and it generates my .pch containing the stiffness and mass matrices.

I want to achieve the same but as an OP2/OP4 file.


Re: Gather Grids from op2 or Generate .pch AND .op2

PARAM, EXTOUT is the old interface to this capability. There is no MATOP4 option.


The EXTSEOUT case control is the new interface. It has been expanded to include the MATOP4 option.