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#1 2011-05-26 10:35:41

udc_Stdnt
Member
Registered: 2011-01-27
Posts: 29

Von misses Stress in 3D_DKT modal analisis

Hello,

I'm doing the analisys of a coque of DKT element glued with a geometry of 3D elements. I can obtain the principal stress by the SIGM_ELNO_DEPL command, in each diferent geometries 2D and 3D, but i can't obtain the equivalent stresswritting this message of error:

!---------------------------------------------------------------------------------------!
   ! <A> <CALCULEL3_8>                                                                     !
   !                                                                                       !
   ! les champs SIEF_ELGA_DEPL, SIEF_ELGA, SIGM_ELNO_COQU et SIGM_ELNO_DEPL sont absents : !
   !  on ne peut pas calculer l'option EQUI_ELNO_SIGM  avec la SD de type  MODE_MECA       !
   !                                                                                       !
   !                                                                                       !
   ! Ceci est une alarme. Si vous ne comprenez pas le sens de cette                        !
   ! alarme, vous pouvez obtenir des résultats inattendus !                                !
   !---------------------------------------------------------------------------------------!

what am I doing wrong?

another thing i don't understand is when i visualize de displacement of each mode, the scale are between 0 and 1, is it because is not defined de intesity of the wave?

thank a lot for your time and knowledgement

pd: I have attached the principal files of the study


Attachments:
C1_a.zip, Size: 16.17 KiB, Downloads: 292

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#2 2011-05-27 06:05:03

todd_alan_martin
Member
Registered: 2008-03-06
Posts: 131

Re: Von misses Stress in 3D_DKT modal analisis

Hi udc_Stdnt

I have raised this issue before here
http://www.code-aster.org/forum2/viewtopic.php?id=14646

Since then it has been quietly forgotten.

The only work-around I can suggest is to output the stresses/strains (SIGM_ELNO_DEPL,EPSI_ELNO_DEPL) for the plate and solid elements in gmesh format as a 3D tensor.

IMPR_RESU(FORMAT='GMSH',
          RESU=(_F(RESULTAT=solution,
                   TYPE_CHAM='TENS_3D',
                   NOM_CMP=('EPXX','EPYY','EPZZ','EPXY','EPXZ','EPYZ',),),),);

Then calculate the principal stresses/strains within gmesh using the EIGENVALUES/EIGENVECTORS plugin.

This should also be possible in Paraview, using Ensight output, but I haven't tried it.

Todd

Last edited by todd_alan_martin (2011-05-27 06:05:31)

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#3 2011-05-27 08:27:07

Thomas DE SOZA
Guru
From: EDF
Registered: 2007-11-23
Posts: 3,066

Re: Von misses Stress in 3D_DKT modal analisis

Hi,

The problem comes from the shells : in the current version of Code_Aster the DST element is not able to compute the Von Mises stresses (don't know why, it seems to be linked to the fact it cannot be used in NL analysis but nonetheless it should be able to compute Von Mises stresses).
If you restrict the computing of EQUI_ELNO_SIGM to the 3D part of the structure with GROUP_MA it should work.

Otherwise DKT or COQUE_3D should work. We'll try to figure out if this feature can be added in a future release.

You can also use CREA_CHAMP + FORMULE to compute it with Aster commands.

Note that the ongoing work on the post-processing in Code_Aster (see for example the new CALC_CHAMP command in the 11 branch) will soon offer simple way to compute fields such as Von Mises when the option is missing (because of a lack of completeness for example)

TdS

Last edited by Thomas DE SOZA (2011-05-27 08:36:38)

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#4 2011-05-28 14:20:43

udc_Stdnt
Member
Registered: 2011-01-27
Posts: 29

Re: Von misses Stress in 3D_DKT modal analisis

As you said, the field in the 3D body can be calculated with the use of GROUP_MA; i'll try what Thomas said about the CREA_CHAMP function.

Thanks a lot for both replays, is what I exactly nedded.

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