Just a short explanation from me. As also shown in the past (e.g. here: Snap-fit contact snagging problem) CalculiX seems to struggle too much with some finite sliding snap-fit-like or gasket problems. Of course, Abaqus has general contact and much more robust contact algorithms, but maybe some smaller improvements could also make it possible to solve such problems with CalculiX. Currently, they are extremely sensitive to mesh and contact stiffness. They show some excessive snagging even with surface-to-surface contact or the mesh may explode even away from the contact region (as observed in the snap-fit example). Self-contact doesn’t seem to work well either.
So my questions, especially to the dev team, would be - do you know why CalculiX struggles so much with this class of problems, if anything can be improved in the solver and if there are any workarounds. For now, it seems that the only way is to keep changing the mesh until it doesn’t break, but it keeps failing even with extremely dense meshes, so maybe the key is also in contact settings.