Getting past a buckling point

JohnM

We occasionally have a situation where a flexible film needs to buckle as part of the loading. See figure. As the film passes through the buckling, the run will often diverge. If the "pop" succeeds, the run will once again be stable and the run will finish without issue.

A trick we use is to put a very low stiffness contact pair across both side of the film to a dummy structure. The film will get caught in the very low stiffness springs, which can be enough to keep it from diverging. This will sometimes work, but it is not completely reliable and is not always convenient. I have attached a sample model. If you suppress the contact, it should crash at t=0.02. Turn on the contact and it will run to t=1.0.

I'd like to figure out a way to put in some "inertia relief" into the system, a feature available in some codes, that essentially puts a small stiffness against the motion of each cell. It is essentially faking a dynamic inertial reaction without the overhead of a full time-based transient. Since CCX does not have this feature, I'm looking for an alternative. Dumb tricks are always welcome!