Welcome to the forums. Please post in English or French.

You are not logged in.

#1 2019-05-16 03:01:50

nirmaljoshi
Member
From: Japan
Registered: 2018-10-12
Posts: 132

[solved] BARR can be used for nonlinear but POU_D_E cannot

If I am not wrong (based on my tests in code-aster), BARR or 2d_BARR can be used for nonlinear but POU_D_E cannot be used. Why is it so, even though both are single dimensional element (i.e. a line)? Can someone explain?

Last edited by nirmaljoshi (2019-05-20 12:02:05)

Offline

#2 2019-05-16 07:59:37

jeanpierreaubry
Guru
From: nantes (france)
Registered: 2009-03-12
Posts: 3,432

Re: [solved] BARR can be used for nonlinear but POU_D_E cannot

hello

i suppose you mean BARRE as BARR element is unknown in code_aster
regarding  POU_D_E it can be used in non linear in code_aster
there is an example in chapter 10 of my book
just replace POU_D_T by POU_D_E and run it to find out!

jean pierre aubry

Offline

#3 2019-05-16 08:26:11

mecour
Member
From: Ostrava (Czech)
Registered: 2011-04-04
Posts: 97

Re: [solved] BARR can be used for nonlinear but POU_D_E cannot

Hello,

jeanpierreaubry wrote:

regarding  POU_D_E it can be used in non linear in code_aster

I suppose you mean that it is possible tu use POU_D_E in nonlinear analysis with some other elements, but we can't use nonlinear material behavior with POU_D_E. I think that was the meaning of nirmaljoshi question.

The nonlinear material behavior with BARRE element s used with method DE_BORST. As I understand this method is used automatically with elements POU_D_EM, POU_D_TGM, GRID, GRILLE_MEMBRANE, BARRE, so with multifibre beams, layered plates and rods.

Offline

#4 2019-05-17 17:10:01

jlf
Member
Registered: 2007-11-22
Posts: 217

Re: [solved] BARR can be used for nonlinear but POU_D_E cannot

hello,

BARRE is only traction and compression. The nonlinear behavior is constant for  the element.

BEAM is traction, compression, bending. With BEAM you can have progressive nonlinear behavior in bending. You need to describe the evolution of this in the beam section. A way is to use multi-fiber beam.

Take a look [R3.08.08] Multi-fiber beam element (straight)

JLF

Offline

#5 2019-05-18 11:35:16

nirmaljoshi
Member
From: Japan
Registered: 2018-10-12
Posts: 132

Re: [solved] BARR can be used for nonlinear but POU_D_E cannot

@jeanpierreaubry
Thanks for pointing the typo.
As mecour pointed out, POU_D_E can be used in non-linear only when comportment is RELATION=ELAS, at other relation it gives error for e.g. when I use VMIS_ISOT_LINE relation, the error says "inalienable VMIS_ISOT_LINE model for the POU_D_E/d_t". You can experiment with the attached file.

@jlf
When BARRE is in traction or compression, don't its cross section also changes (poission's effect)? The nonlinear behaviour accounts for that change in cross section, dosent it? This is just my guess as I could not find it reference document.

Nirmal

Last edited by nirmaljoshi (2019-05-18 11:49:14)

Attachments:

Offline

#6 2019-05-20 08:30:53

jlf
Member
Registered: 2007-11-22
Posts: 217

Re: [solved] BARR can be used for nonlinear but POU_D_E cannot

Hello,

A BARR is 2 nodes, and area and a behavior write in 1D, you can not take into account the poisson's effect.
If you want this effect the only way is to use a 3D behavior and mesh your structure with 3D elements.

Is the same for the beam, the behavior is write in 1D, with beam's hypothesis for the stress ==> No poisson's effect.

JLF

Offline

#7 2019-05-20 12:01:13

nirmaljoshi
Member
From: Japan
Registered: 2018-10-12
Posts: 132

Re: [solved] BARR can be used for nonlinear but POU_D_E cannot

Yes I agree, BARRE will not have possions effect.

BARRE is only traction and compression. The nonlinear behavior is constant for  the element.

BEAM is traction, compression, bending. With BEAM you can have progressive nonlinear behavior in bending.

Last edited by nirmaljoshi (2019-05-20 12:02:54)

Offline