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#1 2017-10-29 15:09:18

GiuliaM_91
Member
From: Italy
Registered: 2017-10-03
Posts: 16

How to use "angl_rep" or "vecteur" and what they mean

Hello everybody,

I've a question following a mistake that came out when I tried to build a structure formed by an horizontal plane, an inclined plane and a vertical plane connected all together, so I have "bottom", "bilge" and "side" plates of a ship. The bilge is a plate inclined 45 deg.

Now I build the file.comm and I've attached the med file.

The error that came out is this:

CR d'execution de JDC en MIXTE
   !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
   ! <S> Exception utilisateur levee mais pas interceptee.                    !
   ! Les bases sont fermees.                                                  !
   ! Type de l'exception : error                                              !
   !                                                                          !
   !   -> L'axe de référence pour le calcul du repère local est normal à un   !
   !      au moins un élément de plaque.                                      !
   !   -> Risque & Conseil :                                                  !
   !      Il faut modifier l'axe de référence (axe X par défaut) en utilisant !
   !      ANGL_REP ou VECTEUR.                                                !
   !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
fin CR d'execution de JDC en MIXT

I think the problem is about the inclined part of the structure, because when I did a similar example with only the side part (vertical) and the bottom (horizontal) there was no error!"

Is it true?!

Here the error suggests me to use "ANGL_REP" or "VECTEUR". I read in U4.42.01 (AFFE_CARA_MECA) about these operators... But I can't understand very well how to use them: Can you help me please?!

Because I think it is important to specify how are oriented the shell of inclined part: I must say they are inclined 45 deg around x axis!
I attach here my med file, if it is useful.

Best regards

Giulia


Attachments:
Compound_shell_beam.med, Size: 92.33 KiB, Downloads: 120

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#2 2017-11-02 13:58:41

Johannes_ACKVA
Member
From: Ingenieurbüro für Mechanik, DE
Registered: 2009-11-04
Posts: 680
Website

Re: How to use "angl_rep" or "vecteur" and what they mean

Giulia,

as you might have read  in U4.42.01 (AFFE_CARA_MECA),  ANGL_REP or (exclusivly or) VECTEUR is used to define a local coordinate system, in your case for plate or shell elements. How it works: A vector V is defined with the help of ANGL_REP or VECTEUR. This can be done group-wise. The projection of V on each element defines the local x-axis of that element. The local z-axis is given as the normal vector of the surface element. The y-axis follows (all 3 are orthogonal).

The problem in your case: V was perpendicular on (at least) 1 surface element, so the projection could not be done. Perhaps you did not use
ANGL_REP nor VECTEUR. In such a case Code-Aster used the default ANGL_REP=(0,0,). Which means that V is the global X-axis. The projection fails then for elements being in the global Y-Z-plane.

The good thing: often you do not need the stresses to be output in a special local coord system. It can be in ANY local coord system. In this case simply change VECTEUR or ANGL_REP in the manner that they do not make the default (which caused your problem). Simply try anything, for example ANGL_REP=(0.11,0.22,).

Also good: The often needed van Mises stress does not depend on the local coord system because it is a tensor invariant of the stress tensor.

here some syntax example:

# No specification of a local CoordSys for stress output. 
# The default in this situation will be: loc-X points in glob-X
Cara=AFFE_CARA_ELEM(MODELE=dkt,
                    COQUE=_F(GROUP_MA='ALL_2D',
                             EPAIS=1.0,),);

# Spec of local CoordSys for stress calc in 2 different manners: ANGL_REP or VECTEUR
CarLocal=AFFE_CARA_ELEM(MODELE=dkt,
                    COQUE=(_F(GROUP_MA='PART_1',
                             EPAIS=1.0,
                             ANGL_REP=(0,90,),),
                          _F(GROUP_MA='PART_2',
                             EPAIS=1.0,
                             VECTEUR=(1,0,0),),),);

Regards
Johannes_ACKVA

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#3 2017-11-11 18:52:36

GiuliaM_91
Member
From: Italy
Registered: 2017-10-03
Posts: 16

Re: How to use "angl_rep" or "vecteur" and what they mean

Oh, thank you soo much for your explanation!!!
Now I understand well!

Giulia

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