COMSOL: Newton's Iteration reached - Stress testing sensor

AI Thread Summary
The discussion revolves around a sensor model in COMSOL experiencing convergence issues during analysis. Attempts to resolve the problem included increasing iterations, refining the mesh, and conducting parametric studies, but the error persists, particularly with a MUMPS out-of-core warning. The model uses a hyperelastic material for the block beneath the sensors, which complicates convergence when nonlinearity is enabled. Recommendations include avoiding contact definitions until the analysis stabilizes and possibly adjusting the hyperelastic model or load conditions. The source of material constants for the hyperelastic model is also questioned for further troubleshooting.
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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