COMSOL: Newton's Iteration reached - Stress testing sensor

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SUMMARY

The discussion centers on resolving convergence issues in COMSOL when analyzing a sensor with a fixed surface and prescribed displacement. Users reported encountering a "MUMPS out of core" warning and difficulties with convergence when using hyperelastic materials. Recommendations include avoiding contact definitions until the analysis converges with Form Union and adjusting the material model to ensure stability. It is crucial to consider geometric nonlinearity and the specific hyperelastic model used to achieve successful convergence.

PREREQUISITES
  • Familiarity with COMSOL Multiphysics, particularly version 5.6 or later.
  • Understanding of hyperelastic material modeling and its implications on convergence.
  • Knowledge of geometric nonlinearity in finite element analysis.
  • Experience with mesh refinement techniques in computational simulations.
NEXT STEPS
  • Explore COMSOL's documentation on Form Union and its impact on convergence.
  • Research hyperelastic material models and their stability under various strain conditions.
  • Learn about geometric nonlinearity settings in COMSOL and their effects on simulation outcomes.
  • Investigate strategies for optimizing mesh refinement to improve simulation performance.
USEFUL FOR

This discussion is beneficial for engineers, researchers, and analysts working with COMSOL Multiphysics, particularly those involved in nonlinear material modeling and convergence troubleshooting in finite element analysis.

uppityd
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It is a sensor with a fixed surface and a prescribed displacement on the opposite

To remove this message error,

I have tried to
  1. Increase iterations
  2. Refined mesh
  3. Applied parametric studies
  4. And some other ideas from forums
However it still cannot be solved

It also has a warning of MUMPS out of core
 

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How are these parts connected ? Do you use contact in this analysis ?
 
FEAnalyst said:
How are these parts connected ? Do you use contact in this analysis ?
They are joined using form union, i would like to put contact between the sensors together in later.
 
uppityd said:
They are joined using form union, i would like to put contact between the sensors together in later.
Right, it’s better to avoid contact until the analysis converges with Form Union. Especially that contact in Comsol is very susceptible to convergence difficulties.

Contact is not used here but there are other forma of nonlinearity in this model, right ? Do you have the geometric nonlinearity enabled ? What about the material model - which one do you use ?
 
FEAnalyst said:
Right, it’s better to avoid contact until the analysis converges with Form Union. Especially that contact in Comsol is very susceptible to convergence difficulties.

Contact is not used here but there are other forma of nonlinearity in this model, right ? Do you have the geometric nonlinearity enabled ? What about the material model - which one do you use ?
Sorry, I should have specified a lot better.

The main reason is that the block underneath the spherical disks is a hyperelastic material. If the whole model were to be set as a linear material then it converges, however when set as a hyperelastic material, the block underneath, then it does not.Non linearity is enabled.
 
The hyperelastic material might be unstable in a given strain range. Try with a lower load and maybe a different hyperelastic model. What is the source of data for material constants in this case ?
 

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