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

[Christian Engwer]

Oh yes, Oli is right. You are assembling a nested matrix. On the BC setup you set the entry diagonal entry to 1, but the diagonal entry is a 3x3 matrix, which is the yet to 1 componentwise.

Best
Christian

Am 16. April 2020 11:30:10 MESZ schrieb HELFER Thomas 202608 <thomas.helfer at cea.fr>:
>Hi Olivier,
>I am sorry, I did not understand your point here. I did not want to
>replace the matrix by a diagonal one,
>just erase the row corresponding to the component upon which this
>boundary conditions acts.
>Have I missed something ?
>Thomas
>________________________________________
>De : Dune [dune-bounces at lists.dune-project.org] de la part de Oliver
>Sander [oliver.sander at tu-dresden.de]
>Envoyé : jeudi 16 avril 2020 11:11
>À : dune at lists.dune-project.org
>Objet : Re: [Dune] Help requested for my first test case in non linear
>mechanics
>
>Hi Thomas,
>
>AFAICT, your method apply_boundary_conditions contains a classic
>mistake:
>You are not setting the matrix diagonals correctly.  See Chapter
>7.3.2.1
>in my book for details.
>
>Best,
>Oliver
>
>On 16.04.20 09:39, HELFER Thomas 202608 wrote:
>> Hi Oliver,
>>
>> thanks for this feedback. I will compare my stiffness matrix to the
>one get with another code,
>> that probably the best way to go. But I felt rather confident...
>>
>> But it does seems like something nasty is happening in my code.
>>
>> Something is itching me about the linear solver: the defect becomes
>very high but the solver
>> converges to the given criterion (a reduction to 1.e-5). However, my
>Dirichlet boundary
>> conditions are not met.
>>
>> So either my handling of the Dirichlet boundaryd condtions is wrong,
>or my usage of the linear solver is
>> (or both).
>>
>> Is there an example of how to replace the linear solver by a direct
>solver ?
>>
>> Regards,
>>
>> Thomas
>> ______________________
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