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#1 2017-09-14 15:29:14

anlu
Member
Registered: 2017-07-04
Posts: 6

[SOLVED] Bending moment on 2D model

Hello,

I haven't been using code aster for long, so maybe this is a stupid question, but I have looked around in the forum and the documentation and haven't been able to find an answer, so I hope someone can help me.

I have a 2D model that I want to subject to a bending moment in order to get the stress. I can use FORCE_CONTOUR to put a force on the model, but it does not have any bending moments.

FORCE_NODALE has bending moments MX, MY and MZ, but when I try using MZ, I get an error that says that MZ is forbidden for one of the nodes. I can use the forces from FORCE_NODALE normally, though. No other FORCE commands seem to work, either.

Is it impossible to put MZ on a 2D model, or am I missing some obvious way to do this?

Last edited by anlu (2017-09-26 10:01:47)

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#2 2017-09-14 15:57:59

Johannes_ACKVA
Member
From: Ingenieurbüro für Mechanik, DE
Registered: 2009-11-04
Posts: 643
Website

Re: [SOLVED] Bending moment on 2D model

from the components FX,FY,FZ,MX,MY,MZ of FORCE_NODAL you can apply only those to the nodes where the respective degrees of freedom exist.

Your MODELISATION attributes a set of degrees of freedom to the nodes (attached to the elements to which you assigned the MODELISATION). Which is the set see in doc U3.

Example: If you have

AFFE_MODELE(..MODELISATION='D_PLAN'  or 'C_PLAN'..)

you find in U3.12.02 that the set of components is DX and DY. So you cannot apply the components FZ,MX,MY or MZ of  FORCE_NODAL.

Regards
Johannes_ACKVA

______________________________________________________________________
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     09-13 October 2017

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#3 2017-09-15 15:51:01

anlu
Member
Registered: 2017-07-04
Posts: 6

Re: [SOLVED] Bending moment on 2D model

Thank you for the reply!

You’re right, I was using C_PLAN, so that was why it didn’t work. But I’m not sure what I should do to fix it. I can’t find a modelisation that has the right degrees of freedom that works in 2D.

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#4 2017-09-15 19:33:25

Johannes_ACKVA
Member
From: Ingenieurbüro für Mechanik, DE
Registered: 2009-11-04
Posts: 643
Website

Re: [SOLVED] Bending moment on 2D model

you find in U3.12.02 the load types which you can use. For your purpose (to apply a moment):

AFFE_CHAR_MECA(...FORCE_CONTOUR(..GROUP_MA='LineElements',.....))
or
AFFE_CHAR_MECA(...PRES_REP(..GROUP_MA='LineElements',.....)..)

Imagine a rectangle with a large width and a small hight. It can be considered as a beam the small hight being the thickness of the beam. To apply a bending moment apply FORCE_CONTOUR or PRES_REP on the line elements (small hight at right) which varies over the coordinate in thickness direction.

To apply a variable load use AFFE_CHAR_MECA_F(unction)

     
     ------------------------------------------------------               ------->
     |                                                               |               ----->
     |                                                               |               -->
     |                                                               |        <--
     |                                                               |    <-----
     ------------------------------------------------------  <-------
     

Regards
Johannes_ACKVA

______________________________________________________________________
CODE-ASTER-courses at Ingenieurbüro für Mechanik, Germany

*** CODE-ASTER INTRO + CONTACT + MATERIAL
     09-13 October 2017

*** CODE-ASTER  DYNAMIC ANALYSIS
     30 Nov - 01 Dec 2017


Ingenieurbüro für Mechanik
D 91717 Wassertrüdingen / Germany

www.code-aster.de                                                Training & Support for NASTRAN and CODE-ASTER

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#5 2017-09-25 12:25:31

anlu
Member
Registered: 2017-07-04
Posts: 6

Re: [SOLVED] Bending moment on 2D model

Thanks again for your reply!

I have to admit, I still don’t really understand. When I looked at U3.12.02, I first only found COQUE_AXIS, which didn’t seem at all like what I wanted since it has rotation symmetry around the y-axis. But when I looked at an earlier version of the documentation, there was also COQUE_C_PLAN and COQUE_D_PLAN in U3.12.02, which fit better. They all have the right degrees of freedom that I want, but they are all also hulls, and I want a model of a solid?

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#6 2017-09-25 12:51:42

Johannes_ACKVA
Member
From: Ingenieurbüro für Mechanik, DE
Registered: 2009-11-04
Posts: 643
Website

Re: [SOLVED] Bending moment on 2D model

excuse me, it is document U3.13.01. You can imagine the right document always from the title (which is for U3.13.01 "Modélisations AXIS, D_PLAN, C_PLAN")

I wish you good success!

Regards
Johannes_ACKVA

______________________________________________________________________
CODE-ASTER-courses at Ingenieurbüro für Mechanik, Germany

*** CODE-ASTER INTRO + CONTACT + MATERIAL
     09-13 October 2017

*** CODE-ASTER  DYNAMIC ANALYSIS
     30 Nov - 01 Dec 2017


Ingenieurbüro für Mechanik
D 91717 Wassertrüdingen / Germany

www.code-aster.de                                                Training & Support for NASTRAN and CODE-ASTER

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#7 2017-09-26 10:01:14

anlu
Member
Registered: 2017-07-04
Posts: 6

Re: [SOLVED] Bending moment on 2D model

Ok, I think I finally understand now. I tried using FORCE_CONTOUR, and it seems to work.

Thank you for all your help!

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