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#1 2020-09-13 22:41:19

From: Bogotá, CO
Registered: 2015-07-31
Posts: 105

Coque_3D attached to 3D solids

Hi, I know this topic has been discussed before, and I read some threads about it, but I still can't find a solution.

I'm trying to solve a problem where a plate (COQUE_3d) is attached to a hollow semi-cylinder.

One of the key points is that the plate is smaller than the surface at which it'll be attached.

After reading several threads and documentation I found that it's quite similar to the one described in these threads: https://code-aster.org/forum2/viewtopic.php?id=18561 and https://code-aster.org/forum2/viewtopic.php?id=18946, and also similar to the procedure described in caelinux . org /wiki/index.php/Contrib:KeesWouters/shellsolid/liaisonmail

There a short description of the proposed procedure:

1) Mesh:
- Elements of mesh for 3D Solid: TETRA10
- Surface elements of the 3D solid in contact with the shell: TRIA6 [name:'srf']
- 2D Elements of the shell: TRIA7 [name: 'plate']

2) Create a mesh with CREA_MAILLAGE that copies TRIA6 (srf) elements to a new mesh 'srf_new'
3) Change the original TRIA6 (srf) into elements TRIA7, leaving the copied TRIA6 (srf_new) as they are.
4) Apply TOUT='OUI', MODELISATION='3D'. With this The TRIA6 (srf_new) elements will be included in the model (by _F(TOUT='OUI', MODELISATION='3D') but will be "void" elements.
5) Apply MODELISATION='COQUE_3D' to the group of the TRIA7 (srf) only.
5) Finally, use LIAISON_MAIL( GROUP_MA_MAIT='srf_new',
                                                       GROUP_MA_ESCL='skin', [**I really have no idea what surface skin is supposed to be]

Anyway, as I didn't know what skin was supposed to be, I tried specifying it as the group of solid 3D elements, and also as the original surface (srf), but for both it gets an error:

! <S> Exception utilisateur levee mais pas interceptee.                   !
   ! Les bases sont fermees.                                                 !
   ! Type de l'exception : error                                             !
   !                                                                         !
   !  Erreur lors de l'opération LIAISON_MAIL.                               !
   !  Le TYPE_RACCORD='MASSIF_COQUE' n'est pas utilisable avec des COQUE_3D. !

On the other hand, I think that that procedure only works if the shell has the same size as the surface in the 3D solid, because we're copying that surface to get TRIA7 and apply COQUE_3D to them. But my problem requires the shell to be smaller than the other surface.


I also tried to create a contact (DEFI_CONTACT), as I saw in another thread (I can't find it anymore) the idea is to define the contacting face of the 3D solid as DKT and then create a DEFI_CONTACT with the COQUE_3D, but it doesn't work either, as it gets to a singular matrix. I'm attaching the comm file as well (V08.comm).

The singular matrix might be a problem of a 'floating' body in space, like explained in post#2 in https://code-aster.org/forum2/viewtopic.php?id=24433. I can see that the problem is that the plate isn't fixed to anything....but that is my idea with the contact, i.e. that the plate is fully attached to the solid and deforms with it. I tried the option

Any help is really welcome,


Last edited by P929 (2020-09-14 12:48:28)


#2 2020-09-14 12:44:01

From: Bogotá, CO
Registered: 2015-07-31
Posts: 105

Re: Coque_3D attached to 3D solids

the files...

Coque_Solid_3D.zip, Size: 1.12 MiB, Downloads: 16


#3 2020-09-15 07:19:02

Registered: 2019-06-18
Posts: 118

Re: Coque_3D attached to 3D solids


I am not an expert for COQUE_3D. But, if it is of any help, I have the following suggestions:

1.) If you want your plate being 'connected' to your 'tunel' (or 'innen'), then it cannot be a DEFI_CONTACT. In your actual example your plate is free floating in space. Therefore, it can only be a LIAISON of some kind.
2.) COQUE_3D elements have 3 nodes along the thickness, you will have to tell which one will be in the LIAISON_MAIL (the upper one with larger y-coordinate in your case).

If you want to keep it simpler, I would suggest to model the plate also in 3D and do a LIAISON_MAIL with its upper surface. Any changes to your model will also be simpler (IMO), for example if your 'platte' is supported from below in any way in the future. The only drawback would be, you wouldn't be able to change its thickness quickly.

2. seems to be a common problem: h ttps://www.code-aster.org/forum2/viewtopic.php?id=19124

Hope that helps,


Last edited by mf (2020-09-15 07:21:57)