[Dune] Help requested for my first test case in non linear mechanics

[Oliver Sander]

Hi Thomas,

> It almost works. I can simulate a tensile test for an elastic behaviour and a plastic behaviour.
> I probably can use any smal strain behaviour generated by MFront. The non-linearity is treated
> very crudely as we use an Newton algorithm with a fixed number of iterations.

that sounds pretty good already.

> The trouble is that it only works if the grid contains only a single element. This probably means
> that I made a mistake in the assembly of the stiffness matrix or the assembly of the inner
> forces. I reread my code several times without finding the trouble.

Did you check whether the matrix and forces are assembled correctly?
What I would do is choose a very small grid (say, 2x2), assemble everything,
and write the matrix and forces to a file (or print them to the screen).
Then compare with one of your working implementations.  This will allow you
to narrow down the cause of your problem.

Helpers for writing/printing vectors and sparse matrices can be found in dune/istl/io.hh.

Bonne chance,
Oliver



> 
> Please find enclosed my project, modified to drop the dependency to the MGIS library and
> only integrate an isotropic elastic behaviour. The relevant file is
> dune-mgis/src/dune-mgis-tensile-test.cc.
> 
> The purpose of my request is twofold:
> 
> - I would be grateful if anyone could find what I have done wrong.
> - I would be grateful if anyone could review the code to tell me what could be improved.
> 
> With kind regards,
> 
> Thomas Helfer
> 
> 
> _______________________________________________
> Dune mailing list
> Dune at lists.dune-project.org
> https://lists.dune-project.org/mailman/listinfo/dune
> 

-------------- next part --------------
A non-text attachment was scrubbed...
Name: smime.p7s
Type: application/pkcs7-signature
Size: 5198 bytes
Desc: S/MIME Cryptographic Signature
URL: <https://lists.dune-project.org/pipermail/dune/attachments/20200416/493fd3aa/attachment.bin>