Marc,
I can run a similar example without problem. I do not use the "snap through"-option. If I use this I too get an error message. I use a prescribed displacement, and create a measure for the reaction force. I have also used symmetry, and mapped mesh to get fewer elements.
It is not meaningful to apply an increasing load, since as you say, the direction of the force will reverse as you pass through the unstable position. Creo Simulate can't capture this; it would require an explicit solver that can capture the acceleration and the mass force as the clip snaps over to the other side. This happens very fast, so I'm not sure how one would apply a steadily increasing force. Using a prescribed displacement makes more sense, this way you analyze what happens if you slowly force the clip from one stable side to the other. The reaction force becomes negative (changes direction) as you pass the unstable position, see graph below, measure "Force" vs "Time", i.e. displacement.
Image may be NSFW.
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/Mats Lindqvist/Suède
