Contact convergence when no contact required?

[JonathanHodgson]

Question for the Analysis gurus:

If I run an analysis with contact enabled, is it possible for it to converge if none of the contacts are actually required for equilibrium?

For the sake of illustration, let's say that I'm modelling a spring device with an 'end stop' controlled by a contact; but in fact the load applied to the spring doesn't (shouldn't) cause it to deflect far enough to make contact with the end stop.

Will this converge happily, or does the convergence depend on at least one contact being 'engaged' - will Mechanica try to somehow create a contact condition even though the load doesn't require it?

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[sdensberger]

It shouldn't. For contact convergence, the solver adjust the stiffness of the contact springs to minimize penetration between components. In your case, the solver should converge on a stiffness of nearly 0.

[mlindqvist · Accepted solution]

If you run the analysis with "large deformation" enabled, I would think it works, provided rigid body motion is prevented by constraints.

(*doing a quick test*)

Yes it works fine if you enable large deformations, and make sure rigid body deformation is enabled... here is a test I did:

[JonathanHodgson]

Hmm... Large Deformations is greyed out for me. Is that a licence thing?

[mlindqvist]

It might be, you will need the advanced version of Creo Simulate, and you need Creo 1 or later. Contact combined with large deformation was implemented in Creo 1. Or your model might contain beam or shell elements. You can't use "large deformation" analysis if your model contains beams/shells.

[JonathanHodgson]

Ah - WF5 on this project, and I don't think we have the Advanced licence. Oh well, I'll just have to use some intelligence to check whether or not I need the contacts.

Thanks all!