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#2 Code_Aster usage » Material Integration error (constitutive law) » 2021-09-06 11:00:20

Bragadesh_Srivatsan
Replies: 1

Hello People,

I am working on elastoplastic 3 point bending with a cohesive zone to model crack.

I am facing the material integration:

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
   ! <S> Exception user raised but not interceptee.                          !
   ! The bases are fermees.                                                  !
   ! Type of the exception: EchecComportementError                           !
   !                                                                         !
   !  Stop following the failure of the integration of the constitutive law. !
   !  The total base is saved. It contains the pitches archived              !
   ! before the stop.                                                        !
   !                                                                         !
   !  Advices:                                                               !
   !  - Check your parameters, the coherence of the units.                   !
   !  - Try to increase ITER_INTE_MAXI, or to                                !
   ! subdivide the time step via ITER_INTE_PAS locally.                      !
   !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

I am modeling for the minus100 material curve from the .comm file and I have no problem running the minus80 curve for the same model. It would be really helpful if someone has a solution for this problem.

Thanks,
Bragadesh Srivatsan

#3 Re: Code_Aster usage » ORIE_FISSURE en 3D sur mailles 2D » 2021-06-14 18:13:10

Hello JM,

I have the same doubt, did you arrive at a solution ?

Regards,
Bragadesh Srivatsan

#6 Re: Code_Aster usage » three point beam bend nodal reac vs displacement error. » 2021-06-01 10:58:07

Hello,

Thank you Sameer for the suggestion,

1. The model converges if the bearings are of mesh size of 6mm but does not converge when the bearing size is 5mm. I have attached the model again with this post.

2. I want to define a cohesive contact for the beam, I did read about Cohesive zone model. For the cohesive zone model we need the cohesive elements to be modeled to define the crack plane. I do not want to model extra elements but just model the cohesive zone as a contact. Is it possible in code_aster ?
As of now I am trying to model this zone in a cube. I have attached the .Comm file(In the next post) .I modeled using the validation examples. I want to know where I have gone wrong

#7 Re: Code_Aster usage » three point beam bend nodal reac vs displacement error. » 2021-05-25 22:37:04

Hello,

Thank you for the suggestions Sameer and Marco, I tried that out and I get the Force Curve included in the zip file. Is there any other suggestions that will improve the result ?

I was not able to run the simulation with second order elements in support due to the computational restrictions on my personal Computer.

I was trying to simulate the model which I have included in the zip file, The model takes too much iterations to converge. Is there some way to make it converge faster ?

Thanks in advance.

Bragadesh Srivatsan

#8 Re: Code_Aster usage » three point beam bend nodal reac vs displacement error. » 2021-05-19 00:03:26

Hello,

Thank you, Mario. That really did the trick. The windows version was the problem.

But I am still having the problem with Force, CMOD plot. I have a plot from Abaqus for the same model and it is complementing with the experimental results, so I do not think it may be from the CMOD measurement. I have attached the plot with this post.

I have computed the resultant reactive forces DY from the supports, and for some reason, it shows zero reaction forces when I try to compute it at the load-bearing.

I can't figure out where I am going wrong.

Regards,
Bragadesh Srivatsan

#9 Re: Code_Aster usage » three point beam bend nodal reac vs displacement error. » 2021-05-15 17:56:50

Hello,

I did update the model using quadratic elements but I get an error termination. Floating-point error. I get the same error when I try to use finer linear mesh.

How do I overcome this error?

I have attached the log file along with the mesh file.

Thanks and Regards,
Bragadesh Srivatsan

#10 Re: Code_Aster usage » three point beam bend nodal reac vs displacement error. » 2021-05-14 09:55:58

Hello,

Ah sorry big_smile, I do not know the measurement method used for the CMOD data.



Regards,
Bragadesh Srivatsan

#11 Re: Code_Aster usage » three point beam bend nodal reac vs displacement error. » 2021-05-14 09:38:08

Hello Mario,

Thank you for your reply.

I will try out with higher-order elements.

No, it does not crack in the attached curve. I will be trying to incorporate damage to this model afterward though.

The measurement method is to find the average displacement of the edge nodes along the longitudinal direction of the beam, as shown in the figure attached.

I also want to know if am extracting the forces from the correct nodes. I have plotted these curves from the support bearing surfaces 'left_sup' and 'right_sup' which I have fixed in all directions.

Regards,
Bragadesh Srivatsan.

#12 Code_Aster usage » three point beam bend nodal reac vs displacement error. » 2021-05-14 08:24:23

Bragadesh_Srivatsan
Replies: 16

Hello,

I am trying to plot force vs CMOD(crack mouth opening displacement). The simulation runs into Green and I have defined an elastoplastic material with contact properties as defined in the attached command file. I do not know where I am going wrong but the simulation curve is not complementing the experimental curve.

I have attached the zip file of the log, mess, comm, mesh, and image of curves with this post.

It will be really helpful if someone has some insights on this.

Thank you.

Regards,
Bragadesh Srivatsan.

#13 Re: Code_Aster usage » Singularity error when trying to simulate 3D 3 point Bending. » 2021-04-26 15:10:57

Thank you, Sameer.  The file works now.

The problem with my file was the contact. Thank you very much.

#14 Re: Code_Aster usage » Singularity error when trying to simulate 3D 3 point Bending. » 2021-04-24 18:27:06

Thank you, Sameer for your help.

I have included the above command in the model to add spring elements, and I do not get the singularity error but the contact iteration does not converge even after 50 iterations. Is this because of contact condition or am I missing something else?


I have attached the mesh file, .comm file and message file for your reference.

#15 Introduce yourself / Présentez vous » Introduction » 2021-04-24 11:27:13

Bragadesh_Srivatsan
Replies: 0

I am Bragadesh Srivatsan.
I am new to code aster working on beam fracture.
Thank you for having me.

#16 Code_Aster usage » Singularity error when trying to simulate 3D 3 point Bending. » 2021-04-23 22:31:05

Bragadesh_Srivatsan
Replies: 4

Hello,

I am new to Code aster and I am trying to simulate 3 point bending of Beam in 3D.

I get a matrix singular error when I try to run the case. I learned from the forum that this error is due to the Rigid body motion of one of the components.

Here I have the displacement load in the negative y-direction and I get the error that I have not constrained the beam in the DY direction. I want the beam to be supported by the support pins in the y-direction and thus do not want to constraint in the DY direction.

The simulation ran successfully if the Beam nodes fixed in the DY direction, but this defeats the purpose of support pins in 3 point bending assembly.

I have attached the message file and mesh file and .comm file for reference.

Thanks in advance