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Problem : big element deformation

Hi,

I modelize an impact of a rigid body on a very soft object (Young modulus = 1 MPa). I am doing a test convergence on mesh size. I have 3 models of different mesh size.

With the 4mm model mesh size, the computation goes well. But for the other models, the computation stops (negative volume) or there is a problem with some elements at the contact interface (see attached file).

I use TYPE 7 Contact interface. I have tested different parameters (default, advised...) but always the same problem.

For the element formulation, I use HEPH (Isolid = 24).

Do you have an idea of what could be the reason of my problem ?

Thank you for your asnwers,

Benjamin

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Altair Forum User

Hi Benjamin,

Can you try with Isolid=17 and also recheck the material parameters.

If possible, please share the files (model file, h3d and T01 file) through the secure dropbox link so that we can review and update you.

Altair Forum User

Hi,

Thank you for your answer. Nothing has changed. I have always the same problem.

The slave component is meshed with tetra element (4mm) and the master component is meshed with mixed element (5mm / 2D / rigid body).

I have checked the material parameters and all is ok. I use elastic material card for all the parts.

Unfortunately, I can't share the files (confidential project).

Altair Forum User

Hi Benjamin,

Can you please plot the global energy plot (IE,KE,TE, hourglass energy and contact energy) of this run (from T01 file) and upload the same.

Please note that the files shared through the Secure Dropbox will not be shared outside and will be secure. Or else you can share only this part of the model.

Altair Forum User

Hi,

Here is the global energy plot.

I will share the files through the secure dropbox. You will only have the part where the problem occurs.

<?xml version="1.0" encoding="UTF-8"?>

Altair Forum User

Hi Benjamin,

For the self interface provide a Gapmin value (0.001) and run the analysis. Also assign the suggested parameters for the Type 7 contact.

The suggested parameters for TYPE7 contact are:

Istf=4

Igap=2

Fscale_Gap=0.8

INACTI=6

Gap_min

Fric = 0.1

Iform=2

Altair Forum User

Hi,

I have always the same problem with the suggested parameters.

I have removed the self contact in the area of the problem (no self contact in this area) but nothing has changed.

Altair Forum User

Hi Benjamin,

I just modified the parameters as mentioned above.

<?xml version="1.0" encoding="UTF-8"?>

Altair Forum User

Ok, and you don't have big deformation on the elements between 0.025 and 0.035 s ?

Altair Forum User

Hi Benjamin,

Yes, I don't see that kind of high deformation.

Altair Forum User

Ok and the suggested parameters are also for the self contact ?

What type of element formulation have you used ? Isolid = 17 or 24 ?

Because, with the suggested parameters I have always high deformation of elements.

Altair Forum User

Hi,

Thank you for your help.

Yes, I use elastic model for the moment but I am doing hyperelastic model with law 69 + prony (with strain-stress curve from experimental data). Il will assign my components with these new models. I hope it will resolve the problem.

Benjamin