What analysis would you do?

Hi All! I have a plastic part made out of PVC - it looks like a dome. It's totally symmetrical and I've got a 3d model of it, so I was thinking of analyzing a quarter of it. When it's deformed in actual use, by pressing on the top of the dome, it collapses and eventually pops back. Can I model it so that I can press it and then 'let go' to see how it would pop back?

Looking forward to your insights.




  • It sounds like snap-through buckling which you usually can't model completely with Mecway or CalculiX. You would be able to deform it up to the point where it snaps through, but probably not the post-buckling behavior after that.

    If you havn't already confirmed it, be cautious about assuming symmetry. Even if the load and geometry is symmetrical, the buckling mode might not be and would need a full 360 degree model.

    In case it's not actually snap-through buckling, and some kind of continuous folding, then it might be OK with the complete cycle, including gradually releasing the load to see it return to its original shape. This is still quite a severe nonlinearity so expect to spend a fair bit of time tweaking the model to get it to solve.
  • Thanks! How should I program in the "letting go" at the end of the deformation to see where it comes back to?
  • edited September 2017
    You can define the load as a function of time using a formula or table. Probably a linear increase then linear decrease would do, in which case, choose the Table option in the load window and enter 3 (time, force) pairs to identify the initial, maximum and final loads, something like:

    time force
    0 0
    0.5 1000
    1 0
  • Could I do a displacement instead?
  • Yes, you can do it the same way on a displacement constraint. This will need the CCX solver.

  • got it, thanks!!
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