Hello everyone,
I’m relatively new to Calculix and currently working on solving a static linear elastic problem. I’ve been trying to find a way to output the element stiffness matrix to a result file. Could someone please guide me on whether this is possible and, if so, provide instructions on how to achieve this?
Your assistance would be greatly appreciated.
Thank you in advance!
Anoop
you have it explained in the manual (v2.21), along with reference to examples provided with the software:
This (new) keyword is for substructure usage. To just write a stiffness (and mass) matrix, one can use:
*FREQUENCY, SOLVER=MATRIXSTORAGE
as the problem is linear static
I’d recommend *SUBSTRUCTURE GENERATE and *SUBSTRUCTURE MATRIX OUTPUT for earlier versions of CCX rather than *FREQUENCY, all are valid approaches but maybe these are more fitted to the request.
Does this approach produces element stiffness matrix or the Global stiffness matrix?
Conversely, I would recommend *FREQUENCY, SOLVER=MATRIXSTORAGE. The stiffness matrix generated by it should be the same as the one used in linear static analysis. Matrices used in substructures can be defined in a different manner, specific to superelements. This applies to both matrix file syntax and concepts (retained nodes in substructures, limitations of substructures and so on).
You will get a global stiffness matrix this way. Abaqus has a *MATRIX GENERATE keyword with an optional ELEMENT BY ELEMENT parameter to generate local matrices.
@JuanP74 : using *SUBSTRUCTURE GENERATE and *SUBSTRUCTURE MATRIX OUTPUT cards produces element stiffness matrix or global stiffness matrix?
It produces a global stiffness matrix unless you make a substructure consisting of just a single element. Still, I would be careful with this approach.
