Can't fix overlap on contact interfaces

[mpai60]

Hello!
I am developing a model of a single graphite crystal in which one material (graphite) has irradiation and thermal expansion eigenstrains, and is surrounded by a second material (binder) constraining that expansion. I am having some issues with the contact module in this setup.

As the crystal expands, the constraint from the binder should close the three cracks. Once they close, the contact between them should force the crystal and binder to expand. I have set up the crystal in 4 subdomains so there are separate meshes at the contact boundaries. The crystal is glued to the binder, and the crystal subdomains are also glued to each other.

The issue: I have tried changing the penalty value but I can’t eliminate the overlap shown in the attached image (top is undeformed, bottom is deformed). All the horizontal interfaces have some overlap, mostly visible where the top of the blue block clips into the yellow one. What changes can I make to fix this?

Input file: https://github.com/mpai60/graphite_meso

Thanks,
Mihir

[GiudGiud]

Hello

If penalty contact is failing you can try one of the other formulations. Notably mortar contact

If you want to look further into penalty contact I recommend you work on scaling the equations manually and check our instructions for troubleshooting failed solves. It s possible convergence is called too early

Guillaume

[mpai60]

Hi Guillaume,

Regarding mortar contact:
I have tried the mortar formulation, I got an error saying it does not support glued contact. I get the following error with frictionless contact:

*** ERROR ***
Nodes on primary and secondary surfaces are aligned. This is causing trouble when identifying projections from secondary nodes when performing primary node projections.

I have tried making some adjustments to the mesh, but it hasn't solved the issue. Do I need to create a gap between the contact surfaces?

Regarding looking further into penalty contact:

By "scaling the equations manually," are you referring to adjusting nl_rel_tol? I have tried setting that to 1e-15, it did not affect the results.

If I use frictionless penalty contact, I get this error:

Nonlinear solve did not converge due to DIVERGED_LINE_SEARCH iterations 4

As suggested by the troubleshooting failed solves page, I tried deactivating the line search, which did not converge (the residual would swing up and down over the 50 iterations):

Nonlinear solve did not converge due to DIVERGED_MAX_IT iterations 50

I also tried adjusting the damping, which did converge, but gave a nonphysical solution regardless of the nl_rel_tol value.

[GiudGiud]

scaling the equations manually,

you set the scaling = in each Variable block

As suggested by the troubleshooting failed solves page

is the problem well posed? on that same page you have a method to check that

I also tried adjusting the damping, which did converge, but gave a nonphysical solution regardless of the nl_rel_tol value.

This is what is making me think it could be ill posed

[mpai60]

Hi Guillaume,

Sorry for the delayed reply. Regarding scaling, my variables are two displacements that are the same order of magnitude and roughly equal. I did try tinkering with scaling, it didn't seem to make much of a difference, but I may have done it wrong.

I spent a lot of time trying to make a smaller version of my mesh to run SVD on, and yes the problem is ill posed. The SVD results are below. I made the mesh dimensions smaller and quartered the geometry with Dirichlett BCs at the planes of symmetry, so that should remove some rigid body motion. However, I am uncertain how to improve it any further.

Edited to add: I have also put the new mesh in the public github repo linked in the first post.

 0 Nonlinear |R| = 1.233794e+11
      SVD: condition number 2.293428165014e+13, 0 of 7992 singular values are (nearly) zero
      SVD: smallest singular values: 6.101994517976e-02 6.178648135090e-02 6.709758817887e-02 6.907618890082e-02 7.676748118987e-02
      SVD: largest singular values : 1.398103318580e+12 1.399448609027e+12 1.399448609027e+12 1.399448609027e+12 1.399448609029e+12
      0 Linear |R| = 1.233794e+11
      1 Linear |R| = 8.498416e-02
 1 Nonlinear |R| = 7.278849e+10
      SVD: condition number 2.285350428893e+13, 0 of 7992 singular values are (nearly) zero
      SVD: smallest singular values: 6.123562458649e-02 6.176688068555e-02 6.184129317954e-02 6.882942422548e-02 7.676534260246e-02
      SVD: largest singular values : 1.398103318601e+12 1.399448609027e+12 1.399448609027e+12 1.399448609073e+12 1.399448609123e+12
      0 Linear |R| = 7.278849e+10
      1 Linear |R| = 2.832783e-02
 2 Nonlinear |R| = 8.929717e+08
      SVD: condition number 2.279762240566e+13, 0 of 7992 singular values are (nearly) zero
      SVD: smallest singular values: 6.138572628964e-02 6.174592273861e-02 6.179957012559e-02 6.182545932495e-02 7.676544782315e-02
      SVD: largest singular values : 1.398103318585e+12 1.399448609027e+12 1.399448609027e+12 1.399448609027e+12 1.399448609048e+12
      0 Linear |R| = 8.929717e+08
      1 Linear |R| = 1.545606e-02
 3 Nonlinear |R| = 8.524611e+08
      SVD: condition number 2.267109527370e+13, 0 of 7992 singular values are (nearly) zero
      SVD: smallest singular values: 6.172831934901e-02 6.174429271045e-02 6.174592273861e-02 6.176033203645e-02 7.676919653323e-02
      SVD: largest singular values : 1.398103318584e+12 1.399448609027e+12 1.399448609027e+12 1.399448609027e+12 1.399448609047e+12
      0 Linear |R| = 8.524611e+08
      1 Linear |R| = 1.085361e-02
 4 Nonlinear |R| = 8.441696e+08
      SVD: condition number 2.267117401197e+13, 0 of 7992 singular values are (nearly) zero
      SVD: smallest singular values: 6.172810496308e-02 6.174592273861e-02 6.174623573018e-02 6.175875292478e-02 7.676990181384e-02
      SVD: largest singular values : 1.398103318584e+12 1.399448609027e+12 1.399448609027e+12 1.399448609027e+12 1.399448609047e+12
      0 Linear |R| = 8.441696e+08
      1 Linear |R| = 1.052570e-02
 5 Nonlinear |R| = 6.220790e+08
      SVD: condition number 2.266606024730e+13, 0 of 7992 singular values are (nearly) zero
      SVD: smallest singular values: 6.174203164456e-02 6.174592273861e-02 6.178161983177e-02 6.180727050794e-02 7.676544252913e-02
      SVD: largest singular values : 1.398103318584e+12 1.399448609027e+12 1.399448609027e+12 1.399448609027e+12 1.399448609046e+12
      0 Linear |R| = 6.220790e+08
      1 Linear |R| = 2.114898e-03
 6 Nonlinear |R| = 5.802088e+08
      SVD: condition number 2.267087690174e+13, 0 of 7992 singular values are (nearly) zero
      SVD: smallest singular values: 6.172891393269e-02 6.174592273861e-02 6.175692554435e-02 6.177835583455e-02 7.676744994624e-02
      SVD: largest singular values : 1.398103318584e+12 1.399448609027e+12 1.399448609027e+12 1.399448609027e+12 1.399448609046e+12
      0 Linear |R| = 5.802088e+08
      1 Linear |R| = 1.951334e-03
 7 Nonlinear |R| = 5.773410e+08
      SVD: condition number 2.266645362984e+13, 0 of 7992 singular values are (nearly) zero
      SVD: smallest singular values: 6.174096009460e-02 6.174592273861e-02 6.176321041689e-02 6.182621529351e-02 7.676172865362e-02
      SVD: largest singular values : 1.398103318584e+12 1.399448609027e+12 1.399448609027e+12 1.399448609027e+12 1.399448609046e+12
      0 Linear |R| = 5.773410e+08
      1 Linear |R| = 2.009634e-03
 8 Nonlinear |R| = 5.745505e+08
      SVD: condition number 2.266825486926e+13, 0 of 7992 singular values are (nearly) zero
      SVD: smallest singular values: 6.173605410376e-02 6.174197156034e-02 6.174592273861e-02 6.174864861812e-02 7.676904849702e-02
      SVD: largest singular values : 1.398103318584e+12 1.399448609027e+12 1.399448609027e+12 1.399448609027e+12 1.399448609046e+12
      0 Linear |R| = 5.745505e+08
      1 Linear |R| = 1.968332e-03
 9 Nonlinear |R| = 5.742788e+08
      SVD: condition number 2.266638667598e+13, 0 of 7992 singular values are (nearly) zero
      SVD: smallest singular values: 6.174114247018e-02 6.174592273861e-02 6.175593305672e-02 6.178002309753e-02 7.676820727163e-02
      SVD: largest singular values : 1.398103318584e+12 1.399448609027e+12 1.399448609027e+12 1.399448609027e+12 1.399448609046e+12
      0 Linear |R| = 5.742788e+08
      1 Linear |R| = 1.959725e-03
10 Nonlinear |R| = 5.740078e+08
      SVD: condition number 2.266517038881e+13, 0 of 7992 singular values are (nearly) zero
      SVD: smallest singular values: 6.174445570182e-02 6.174592273861e-02 6.175386358025e-02 6.179994716175e-02 7.676507919273e-02
      SVD: largest singular values : 1.398103318584e+12 1.399448609027e+12 1.399448609027e+12 1.399448609027e+12 1.399448609046e+12
      0 Linear |R| = 5.740078e+08
      1 Linear |R| = 1.953731e-03
11 Nonlinear |R| = 5.737375e+08
      SVD: condition number 2.266587267111e+13, 0 of 7992 singular values are (nearly) zero
      SVD: smallest singular values: 6.174254260369e-02 6.174592273861e-02 6.175235971137e-02 6.182342564720e-02 7.676864542979e-02
      SVD: largest singular values : 1.398103318584e+12 1.399448609027e+12 1.399448609027e+12 1.399448609027e+12 1.399448609046e+12
      0 Linear |R| = 5.737375e+08
      1 Linear |R| = 2.014779e-03
12 Nonlinear |R| = 5.734679e+08
      SVD: condition number 2.266547547971e+13, 0 of 7992 singular values are (nearly) zero
      SVD: smallest singular values: 6.174362458441e-02 6.174592273861e-02 6.175247026268e-02 6.183048764312e-02 7.676615980432e-02
      SVD: largest singular values : 1.398103318584e+12 1.399448609027e+12 1.399448609027e+12 1.399448609027e+12 1.399448609046e+12
      0 Linear |R| = 5.734679e+08
      1 Linear |R| = 1.870965e-03
13 Nonlinear |R| = 5.731990e+08
      SVD: condition number 2.267927843437e+13, 0 of 7992 singular values are (nearly) zero
      SVD: smallest singular values: 6.170604647302e-02 6.172771097922e-02 6.174482837149e-02 6.174592273861e-02 7.676859957264e-02
      SVD: largest singular values : 1.398103318584e+12 1.399448609027e+12 1.399448609027e+12 1.399448609027e+12 1.399448609046e+12
      0 Linear |R| = 5.731990e+08
      1 Linear |R| = 1.936418e-03
14 Nonlinear |R| = 5.729309e+08
      SVD: condition number 2.266728497371e+13, 0 of 7992 singular values are (nearly) zero
      SVD: smallest singular values: 6.173869568716e-02 6.174363833635e-02 6.174592273861e-02 6.178923408167e-02 7.676783260468e-02
      SVD: largest singular values : 1.398103318584e+12 1.399448609027e+12 1.399448609027e+12 1.399448609027e+12 1.399448609046e+12
      0 Linear |R| = 5.729309e+08
      1 Linear |R| = 1.898576e-03
      ```

[GiudGiud]

Nothing from me.
@mpai60 did Ben's proposed fix on Toy Geometry 1 work?

[mpai60]

Yes, but I'm more worried about the issue in 2 and 3. As of now, I still don't have a solution for that.

[mpai60]

Wanted to follow up on this again @GiudGiud . I have tried lowering the displacement of the inner block in case the magnitude of the displacement was not possible, it doesn't seem to have resolved the issue.

[GiudGiud]

No progress from me.
I would try the other contact models, notably mortar contact which is the most developed.

I think you have a decent MWE at this point if contact developers want to take a look @recuero @lindsayad

[lindsayad]

@mpai60 if you shared the input in which you are getting the error with mortar, I would be willing to run it and see what's going on there. As coarse a mesh as is convenient for you to create would be great