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non convergence in hyperelastic model for heavy loads

Posted Jul 30, 2024, 5:48 a.m. EDT 2 Replies

Akshay Saxena
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Thanks for the fruitful information.

I am facing an issue with nonconvergence of nearly bat 30kPa while applying compressive load up to 300kPa on ecoflex 0030 material. Nonlinear solid mechanics has been used with different hyperelastic models such as mooney rivlin 20 parameters, odgen, and neo Hookean. Can somebody help me with the issue of finding out the probable reason behind nonconvergence?

Note its a 2D block of 5mm by 2mm made of ecoflex 0030.

Also, do this problem need to be solved with moving mesh? I am facing a problem with moving the mesh as I am unable to describe/utilize it properly.

2 Replies Last Post Aug 8, 2024, 3:56 a.m. EDT
Henrik Sönnerlind COMSOL Employee

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Posted: 8 months ago Aug 1, 2024, 10:47 a.m. EDT
Updated: 8 months ago Aug 1, 2024, 10:49 a.m. EDT

I think the problem is that the singularity at the two ends of the fixed constraint causes extreme strains, and a very high biaxiality ratio. This throws the hyperelastic models out of the stability region. If you make a finer mesh there, the failure will come earlier, since the singular strains are then resolved into even higher values.

You may need a more realistic boundary condition.

You cannot use a moving mesh in a domain controlled by Solid Mechanics. Moving mesh would typically be used in a fluid domain which is deformed by an adjacent solid.

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Henrik Sönnerlind
COMSOL
I think the problem is that the singularity at the two ends of the fixed constraint causes extreme strains, and a very high biaxiality ratio. This throws the hyperelastic models out of the stability region. If you make a finer mesh there, the failure will come earlier, since the singular strains are then resolved into even higher values. You may need a more realistic boundary condition. You cannot use a moving mesh in a domain controlled by Solid Mechanics. Moving mesh would typically be used in a fluid domain which is deformed by an adjacent solid.
Akshay Saxena
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Posted: 8 months ago Aug 8, 2024, 3:56 a.m. EDT
Updated: 8 months ago Aug 8, 2024, 4:01 a.m. EDT

Dear Mr. Henrik,

Thank you so much for answering my query. I have tried to keep the ecoflex between the two SS plate the bottom one fixed and top to apply load to avoid the singularity earlier.

I have followed the hyperelastic seal tutorial (properties of the material as well) to provide better boundry conditions. however i am still unable to run the simulation. i am attaching the file for reference as well.

Dear Mr. Henrik, Thank you so much for answering my query. I have tried to keep the ecoflex between the two SS plate the bottom one fixed and top to apply load to avoid the singularity earlier. I have followed the hyperelastic seal tutorial (properties of the material as well) to provide better boundry conditions. however i am still unable to run the simulation. i am attaching the file for reference as well.

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