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Info of Eliminated stiffness matrix
Posted Aug 30, 2021, 2:34 p.m. EDT General Version 5.6 2 Replies
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Hi,
The reply from Remi Magnard perfectly answered how to extract the imformation of the assembled matrice, such as stiffness matrix "K" or mass matrix "E".
But now my question is how to extract the imformation of the eliminated matrice, such as "Kc" and "Ec". Are those informations also in the "mphxmeshinfo"? For reference, we are using those matrics to calculate the natural frequency and eigen values.
Thank you very much,
Yan
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The xmesh info is always on the full assembled system.
The relation between the full and the eliminated system can be retrieved using the constraint null-space basis matrix 
and the constraint force null-space matrix 
. These are used for the constraint elimination as:
With LiveLink for MATLAB you can extract these matrices using the command below:
str = mphmatrix(model, <soltag>, 'out', {'Null','Nullf'});
where <soltag> is the tag of the solution node.
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Thank you very much, Remi Magnard!
Very helpful!
Yan