Sheet Metal Bending-Contact/BC set up
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8 years 4 months ago #8479
by Alibay
Replied by Alibay on topic Re: Sheet Metal Bending-Contact/BC set up
Thanks your explanation.
Yes indeed, I am still using DYNA_NON_LINE. I looked into your model, you also used STAT_NON_LINE.
So this means mesh elements without density can only be used in case of STAT_NON_LINE, right?
Do you have any advice how I can manage to to it if I still use DYNA_NON_LINE?
Yes indeed, I am still using DYNA_NON_LINE. I looked into your model, you also used STAT_NON_LINE.
So this means mesh elements without density can only be used in case of STAT_NON_LINE, right?
Do you have any advice how I can manage to to it if I still use DYNA_NON_LINE?
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8 years 4 months ago #8480
by Alibay
Replied by Alibay on topic Re: Sheet Metal Bending-Contact/BC set up
I tried with STAT_NON_LINE, added springs. but it does not go beyond the first step. It gives the 'singular matrix' error. I can not figure out where I went wrong, in BC, in contact, or in solution? Really appreciated if some one can have a look at my comm files and help me figure out the problem.
Here are my comm file and mesh.
sheet metal bending
Thanks.
Here are my comm file and mesh.
sheet metal bending
Thanks.
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8 years 4 months ago - 8 years 4 months ago #8481
by Claus
Code_Aster release : STA11.4 on OpenSUSE 12.3 64 bits - EDF/Intel version
Replied by Claus on topic Re: Sheet Metal Bending-Contact/BC set up
I have a simple example here, you can try to recreate. Once it works in 2D, you can go to 3D.
This example works with 12.0.something, so you might have to adjust it.
/C
Edit: caelinux.org/wiki/index.php/File:Simple_punch.zip
This example works with 12.0.something, so you might have to adjust it.
/C
Edit: caelinux.org/wiki/index.php/File:Simple_punch.zip
Code_Aster release : STA11.4 on OpenSUSE 12.3 64 bits - EDF/Intel version
Last edit: 8 years 4 months ago by Claus.
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8 years 3 months ago - 8 years 3 months ago #8490
by Alibay
Replied by Alibay on topic Re: Sheet Metal Bending-Contact/BC set up
Claws, I looked into your simulation and now able to run the simulation without error 
. But there are still problems.
Now convergence became the main issue since the simulation is involved contact+friction, non-linear material , large deformation.
For this some advices were given in Code_Aster forum. Briefly summarizing these would be: (1) refining mesh (2) using quadratic elements + reduced integration (_SI) in order to take into account incompressibility (3) using CONTINUE method with smoothing (4) in solution use 'PREDICTION='ELASTIQUE' (5) Set all to 'NEWTON' in contact resolution.
I refined my mesh and geometry and tried 3 cases:
a) HEXA20 for sheet and Linear Tet4 for the rest. It gives me error 'Singular Matrix'
b) HEXA20 + reduced integration (_SI) for sheet and Linear Tet4 for the rest. It gives me error 'Singular Matrix'
c) HEXA8 for sheet and Tet4 for the rest. it runs until some point but again fails with the error 'fails to integrate constitutive law'. In addition, it requires very small time step (0.0005 even smaller).
Here is my mesh and mess file bending_hexa8 .
So what can I do improve the convergence of simulation.
Thanks.
. But there are still problems.Now convergence became the main issue since the simulation is involved contact+friction, non-linear material , large deformation.
For this some advices were given in Code_Aster forum. Briefly summarizing these would be: (1) refining mesh (2) using quadratic elements + reduced integration (_SI) in order to take into account incompressibility (3) using CONTINUE method with smoothing (4) in solution use 'PREDICTION='ELASTIQUE' (5) Set all to 'NEWTON' in contact resolution.
I refined my mesh and geometry and tried 3 cases:
a) HEXA20 for sheet and Linear Tet4 for the rest. It gives me error 'Singular Matrix'
b) HEXA20 + reduced integration (_SI) for sheet and Linear Tet4 for the rest. It gives me error 'Singular Matrix'
c) HEXA8 for sheet and Tet4 for the rest. it runs until some point but again fails with the error 'fails to integrate constitutive law'. In addition, it requires very small time step (0.0005 even smaller).
Here is my mesh and mess file bending_hexa8 .
So what can I do improve the convergence of simulation.
Thanks.
Last edit: 8 years 3 months ago by Alibay.
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8 years 3 months ago - 8 years 3 months ago #8526
by Alibay
Replied by Alibay on topic Re: Sheet Metal Bending-Contact/BC set up
Now I have some progress in my simulation. But it ran more than 80 hours to give me some result. Thus reducing computation time becomes priority. So I wanted to model all other components except the sheet as rigid surface, but there has been some errors that I do not understand why.
The test case SSNP155 utilized the same technique with DYNA_NON_LINE for 2D cases.
And TdS explained in code-aster forum as following:
I followed the same procedure for my 3D case with DYNA_NON_LINE, but it gave me singular matrix error with this alarm;
What am I missing?
here is mess file and mesh.
Bending-rigid-surface
The test case SSNP155 utilized the same technique with DYNA_NON_LINE for 2D cases.
And TdS explained in code-aster forum as following:
n the U2.04.04 manual (offline for the moment but should hopefully be back soon), you'll find advices on how to model rigid tools. In a nutshell it is usually done this way :
- model the tool in the mesher. Two possibilities arise : either you model only the border or the whole body. The advantage of modelling the whole body is that it will be easier to orient its normal
- orient the normal either with ORIE_PEAU_* or ORIE_NORM_COQUE depending what you chose at the previous step
- add only the border of the tool to the model (and apply a 3D modelization)
- constrain all the dofs of the tool with AFFE_CHAR_CINE so as not to add any additional dofs in the mode
I followed the same procedure for my 3D case with DYNA_NON_LINE, but it gave me singular matrix error with this alarm;
!-------------------------------------------------------------------------------------!
! <A> <CALCULEL2_63> !
! !
! -> La maille M1707 porte un élément fini de bord, mais elle ne borde !
! aucun élément ayant une "rigidité". !
! !
! -> Risque & Conseil : !
! Cela peut entraîner des problèmes de "pivot nul" lors de la résolution. !
! Si la résolution des systèmes linéaires ne pose pas de problèmes, vous !
! pouvez ignorer ce message. !
! Sinon, vérifier la définition du modèle (AFFE_MODELE) en évitant l'utilisation !
! de l'opérande TOUT='OUI'. !
! !
! !
! Ceci est une alarme. Si vous ne comprenez pas le sens de cette !
! alarme, vous pouvez obtenir des résultats inattendus ! !
!-------------------------------------------------------------------------------------!
!-------------------------------------------------------------------------------------!
! <A> <CALCULEL2_63> !
! !
! -> La maille M1708 porte un élément fini de bord, mais elle ne borde !
! aucun élément ayant une "rigidité". !
! !
! -> Risque & Conseil : !
! Cela peut entraîner des problèmes de "pivot nul" lors de la résolution. !
! Si la résolution des systèmes linéaires ne pose pas de problèmes, vous !
! pouvez ignorer ce message. !
! Sinon, vérifier la définition du modèle (AFFE_MODELE) en évitant l'utilisation !
! de l'opérande TOUT='OUI'. !
! !
! !
! Ceci est une alarme. Si vous ne comprenez pas le sens de cette !
! alarme, vous pouvez obtenir des résultats inattendus ! !
!-------------------------------------------------------------------------------------!
!-------------------------------------------------------------------------------------!
! <A> <CALCULEL2_63> !
! !
! -> La maille M1709 porte un élément fini de bord, mais elle ne borde !
! aucun élément ayant une "rigidité". !
! !
! -> Risque & Conseil : !
! Cela peut entraîner des problèmes de "pivot nul" lors de la résolution. !
! Si la résolution des systèmes linéaires ne pose pas de problèmes, vous !
! pouvez ignorer ce message. !
! Sinon, vérifier la définition du modèle (AFFE_MODELE) en évitant l'utilisation !
! de l'opérande TOUT='OUI'. !
! !
! !
! Ceci est une alarme. Si vous ne comprenez pas le sens de cette !
! alarme, vous pouvez obtenir des résultats inattendus ! !
!-------------------------------------------------------------------------------------!
!-------------------------------------------------------------------------------------!
! <A> <CALCULEL2_63> !
! !
! -> La maille M1710 porte un élément fini de bord, mais elle ne borde !
! aucun élément ayant une "rigidité". !
! !
! -> Risque & Conseil : !
! Cela peut entraîner des problèmes de "pivot nul" lors de la résolution. !
! Si la résolution des systèmes linéaires ne pose pas de problèmes, vous !
! pouvez ignorer ce message. !
! Sinon, vérifier la définition du modèle (AFFE_MODELE) en évitant l'utilisation !
! de l'opérande TOUT='OUI'. !
! !
! !
! Ceci est une alarme. Si vous ne comprenez pas le sens de cette !
! alarme, vous pouvez obtenir des résultats inattendus ! !
!-------------------------------------------------------------------------------------!
!-------------------------------------------------------------------------------------!
! <A> <CALCULEL2_63> !
! !
! -> La maille M1711 porte un élément fini de bord, mais elle ne borde !
! aucun élément ayant une "rigidité". !
! !
! -> Risque & Conseil : !
! Cela peut entraîner des problèmes de "pivot nul" lors de la résolution. !
! Si la résolution des systèmes linéaires ne pose pas de problèmes, vous !
! pouvez ignorer ce message. !
! Sinon, vérifier la définition du modèle (AFFE_MODELE) en évitant l'utilisation !
! de l'opérande TOUT='OUI'. !
! !
! !
! Ceci est une alarme. Si vous ne comprenez pas le sens de cette !
! alarme, vous pouvez obtenir des résultats inattendus ! !
!-------------------------------------------------------------------------------------!
!--------------------------------------------------------------------------------!
! <A> <CATAMESS_41> !
! !
! Le message d'alarme 'CALCULEL2_63' a été émis 5 fois, il ne sera plus affiché. !
! !
! !
! Ceci est une alarme. Si vous ne comprenez pas le sens de cette !
! alarme, vous pouvez obtenir des résultats inattendus ! !
!--------------------------------------------------------------------------------!What am I missing?
here is mess file and mesh.
Bending-rigid-surface
Last edit: 8 years 3 months ago by Alibay.
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8 years 3 months ago #8527
by Alibay
Replied by Alibay on topic Re: Sheet Metal Bending-Contact/BC set up
I found the reason. It gave singular matrix because all the rigid surfaces are be contained using AFFE_CHAR_CINE and I did not constrain the rigid surface which represented the blank-holder. Instead what I did was that I applied pressure load on that surface.
Now I applied very small displacement on the surface in order not to have singular matrix. Plus I applied the ramped pressure load again on the same rigid surface that represents blank-holder. It runs without problem.
But here comes another question:
the displacement applied on the blank-holder surface is constant throughout whole simulation. The pressure applied on the same surface is ramped. So does the displacement prevent the ramped pressure load to effect the blank-holder gradually? in another words, does the surface stay at the same position under the displacement or it can move further because of the pressure load?
Now I applied very small displacement on the surface in order not to have singular matrix. Plus I applied the ramped pressure load again on the same rigid surface that represents blank-holder. It runs without problem.
But here comes another question:
the displacement applied on the blank-holder surface is constant throughout whole simulation. The pressure applied on the same surface is ramped. So does the displacement prevent the ramped pressure load to effect the blank-holder gradually? in another words, does the surface stay at the same position under the displacement or it can move further because of the pressure load?
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