Impact: problem with NL material

AndreaAndrea
I have started to set up a study for an impact between a machine component and the safe guard to check if the thickness is enough to absorb the impact.
The attached study is very simple: sphere against plate. With infinitely elastc material I have a solution but switching to NL material I have appcrash on W7 and nothing happens on W10. (obviously with CCX solver)

Comments

  • VictorVictor
    Not sure what you mean by W7 and W10. Also, the file doesn't have nonlinear materials ?

    But I got a solution by doing this:

    A ) Increased contact stiffness per unit area to 10000 GPa/m (~ E/thickness).

    B ) Increased time period to 0.05 s. It won't actually solve all the way to 0.05 s but this is to get around the following problem. When CCX stops with

    *ERROR: max. # of increments reached

    it doesn't mean there's anything wrong with the model, but just that CCX was told (by Mecway) to stop after a certain number of increments, which is Time period / Time step. In models where the increment size gets automatically reduced and not increased, it can hit that limit. I'm not sure how to get around this issue because raising the limit arbitrarily could lead to huge solutions and near-endless solve times, and there will still be a limit that it might reach after you've waited patiently all day.
  • AndreaAndrea
    Windows 7 - 10!
    Try to insert plastic property to the material model. I change material property on your model and I had the same problem (see attached picture)

  • disladisla
    Hello Andrea,

    Nice to hear you . You have been in silence for a while.
    I think your problem is about initial distance between ball and target for contact to solve properly. Check attached file. Solution is less than 3 min.
    Solver stops once you are about 15mm far from the target.

    By other hand , ¿would it be possible to forget about the projectile at certain time step to avoid computing time and possible solution breaks ?
    I mean, once the impact is done to erase the ball and keep computing to see the evolution of the target.

  • AndreaAndrea
    Try to insert plastic properties on material window!
    For example Bilinear isotropic hardening : Yeld strenght 355 MPa Et 1000 MPa

    Your model has indefinitely elastic material and with this material model I also have a solution. The problem is when I try to insert plastic properties and at this time the solver crash

  • disladisla
    Upps. Ok. I thought you file already had the right material.
  • AndreaAndrea
    ...I have attached the first test with linear material.
  • VictorVictor
    This is pretty weird. It looks like having all 3 of:
    • dynamic response
    • bilinear plastic material
    • contact
    fails that way.

    It works with the Ramberg-Osgood plastic material model though. So if you calculate those coefficients, there's some hope there. However, I wasn't able to get it to complete after contact was made with enough stress to cause plastic deformation. Not sure if that's an unrelated issue or I didn't set up the parameters correctly.
  • AndreaAndrea
    Yes, with R-O model runs!
    Maybe the combination above (dynamic response+bilinear plastic + contact) must be checked on Linux OS to know if the problem is inside the solver or inside the CCX version for Windows. I remeber that I had a similar problem (appcrash) with RBE and CCX 2.9 or 2.10 (if I remeber correctly). Under Linux that problem vanished
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