Material definition

Hello

Anybody know how can I do to model an elastoplastic material?
With elas and ecro_line, after I use a load+unload cycle, the part results undeformed, I would like to have residual stres and strain.

Maybe are there any material library ready to use?

Thanks
Roberto

Hello,

to solve an elasto-plastic problem, you will need to use the STAT_NON_LINE nonlinear solver instead of the linear elastic solver MECA_STATIQUE.

To have an overview of a typical Aster .comm file for elasto-plasticity you can have a look at:
1) the Advanced Examples
www.caelinux.com/CMS/index.php?option=co...;id=25&Itemid=40
(try to read the comm fil in a text editor as it has not been updated for Aster v9.0)
2) the excellent tutorial on Plasticity written by P. Carrico
www.caelinux.org/wiki/downloads/docs/PCarrico/

The key thing to understand with STAT_NON_LINE is that you need to specify, in the COMP_INCR keyword, the actual constitutive model which will be integrated by the solver. The data entered in DEFI_MATERIAU is only seen as a property database and defining an elasto-plastic behaviour in DEFI_MATERIAU does not mean that the solver will treat the material as elasto-plastic.

In your present case, you will need to use STAT_NON_LINE -> COMP_INCR with the keyword RELATION=VMIS_ISOT_LINE.

Best regards,

J.Cugnoni
www.caelinux.com

Hello joel!

Thanks, it's an honor to be helped straight by you!
Thanks for the excellent work, I'm one of your fan!

I already use
STAT_NON_LINE -> COMP_INCR
RELATION=VMIS_ISOT_LINE

But I also use DEFI_FONCTION to create a load ramp followed by an unload ramp.
I see a great plastic deformation at the top of the load ramp.
After unload cycle the part return undeformed as the beginning!

In the meanwhile I solved the problem putting
MATRICE ELASTIQUE (instead of TANGENTE)
Now I can see residual deplacement.
Maybe because I use linear mesh?

Best regards
Roberto

I have run in to this as well. I would also like to have permanent deformations. Currently the ECRO_LINE material behaves like an elastic bilinear material without plastic deformation.

I have tried reading the Code_Aster documentation, but as I don't speak French I am having some difficulties.

In desperation I even tried to use DYNA_NON_LINE type of analysis, but to no avail.

Any help will be appreciated.

Hello,

nice to see such interest! Could you post some example files so I can work on it to see what fails?

Concerning the results, in the meanwhile, you can try to output the plastic strain tensor EPSP to see if you have accumulated plastic strains...

Regards,

J.Cugnoni

PS: thank you very much for your encouragements !!

Hello Joel,

kampar, I had you exact behavour too.
Somehow I obtained a better result, basicaly trying, as I understand a bit french only because it's quite similar to Italian.

Attached there are jpeg images of the results, a beam loaded then unloaded with permanent defotmation.
I attached the comm too.

I used contact and I applied a force ramp, then an unload ramp, at the extremity of the beam.
I'm also a bit worried about convergence, I had to decrease precision to reach (RESI_GLOB_RELA=0.1).

I'm trying to include EPSP in results too.

Best Regards
Roberto