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Using contact post-processing variable

Posted Mar 25, 2015, 11:56 a.m. EDT Parameters, Variables, & Functions 3 Replies

Gianna Marschmann
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Hello everyone,

I want to use the post-processing variable solid.gap_p1 from the Contact pair definition in defining a gap-dependent force, e.g. force = C *gap_p1.

How can I choose the gap variable in the definition of my contact force? When I simply enter solid.gap_p1
in the Global definitions -> Variables it turns red.

Can you help me out?

Thanks,
Gianna
3 Replies Last Post Apr 3, 2015, 1:35 p.m. EDT
Gianna Marschmann
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Posted: 10 years ago Mar 26, 2015, 6:26 a.m. EDT
Or maybe more generally,

I would like to implement a gap-dependent adhesive force between surface and obstacle as in the JKR model of adhesive contact.

Does anyone have experience with this?

Gianna
Or maybe more generally, I would like to implement a gap-dependent adhesive force between surface and obstacle as in the JKR model of adhesive contact. Does anyone have experience with this? Gianna
Henrik Sönnerlind COMSOL Employee

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Posted: 10 years ago Mar 26, 2015, 6:36 p.m. EDT
Hi,

The variable name solid.gap_p1 looks OK, but it is not Global. You should create your variables under Component>Definitions>Variables instead.

Regards,
Henrik
Hi, The variable name solid.gap_p1 looks OK, but it is not Global. You should create your variables under Component>Definitions>Variables instead. Regards, Henrik
Gianna Marschmann
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Posted: 10 years ago Apr 3, 2015, 1:35 p.m. EDT
Hi Henrik,

thank you very much for your fast reply. This was exactly what I was looking for. Defining solid.gap_p1 in Component->Definitions->Variables works.

However, I have not managed to implement it correctly. Attached you find my model file which I wish to extend to Hertz contact + an additional adhesive force, sth. like Fn*solid.gap_p1*(solid.gap_p1 > 0.0) on boundary 7.

I have tried to define a boundary load on boundary 7 or use the gap-dependent force as a friction force in y-direction defined on the contact pair in SolidMechanics->Contact1, in each time the solver complains about an undefined value in the residual vector.

Do you have an idea how to add the additional force on the boundary?
Thanks,
Gianna

Hi Henrik, thank you very much for your fast reply. This was exactly what I was looking for. Defining solid.gap_p1 in Component->Definitions->Variables works. However, I have not managed to implement it correctly. Attached you find my model file which I wish to extend to Hertz contact + an additional adhesive force, sth. like Fn*solid.gap_p1*(solid.gap_p1 > 0.0) on boundary 7. I have tried to define a boundary load on boundary 7 or use the gap-dependent force as a friction force in y-direction defined on the contact pair in SolidMechanics->Contact1, in each time the solver complains about an undefined value in the residual vector. Do you have an idea how to add the additional force on the boundary? Thanks, Gianna

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