Contact Question - Opposite Faces

mdsimulationgroupmdsimulationgroup
Hello,

In the attached file there are two contact setups:

"__This_Works"
"__This_Does_Not_Work"

The "__This_Works" only has contact on the ends of the film, while the "__This_Does_Not_Work" has contact on the entire surface of the film with opposite sides as the master and slave.

Can somewhat tell me why the "__This_Does_Not_Work" does not work? I have been going nuts trying to figure out why?

Thanks,
Frank

Comments

  • VictorVictor
    It seems like you can't have the master and slave directly opposite each other. My guess is it might see that as penetration and try to push them apart.

    All I can think of is to make 2 or 3 separate contacts in repeating stripes so the master for one is opposite the slave for another and doesn't interfere with it. Not sure if that quite covers all the situations you'll need though, especially with the overhanging edges due to the spiralling.

    Maybe you could ask in the CCX group https://calculix.discourse.group/ ?
  • mdsimulationgroupmdsimulationgroup
    Is there a detection distance for the surface-to-surface contact to be activated? I've summitted to the discourse group but have not received a response
  • VictorVictor
    It might be too complicated. I'm trying to reduce it to the core problem (attached).

    I noticed that it does sort of solve if you add a "no extra contact step" in the CCX branch of the outline tree. The film is still flapping around but it's winding up too. My guess is this isn't really solving the problem and just allowing CCX to reduce the contact stiffness so it doesn't completely fold itself in half.


  • mdsimulationgroupmdsimulationgroup
    I believe this to be with the was CCX searches for the contact pairs. I am able to get the expected result of a flat, overlapping wrapped film using FEBio by setting the contact search radius to not see through the film thickness.
  • disladisla
    Start with a much-reduced model to find the right contact parameters , mesh density and material model to get a better understanding of the problem. Other problems may emerge when going to the full model but big ones would be cleaned.

    The problem is really, really hard . (31.25 microns). The film is buckling under small nonuniform tension (fluttering). I don’t think this is only a FEA problem because of the contact behaviour. I would say it may happen in the real physical process.

    The nonlinear analysis is better conducted displacement driven. Drive the end of the film to the wire synchronizing rotation with film translation and adjust tension. (Vid shows slightly faster advance to check self-contact performance). Another option that also works is to move the wire against a fixed film but not to realistic unless you change the process.

    If FEBio worked for you, stay with FEBio. Good luck.


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