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5 Replies
Last post: January 17, 2012 10:51am UTC
January 16, 2012 10:43pm UTC
free finite prescribed displacement
Evening everyone,
Is there a way of modelling a finite free displacement along a direction, as in the case of components attached via bolts with axial clearance?
For example, to allow a max 0.001m free displacement in the "x" direction I've tried to apply a prescribed displacement u0 of 0.001*(u>=0.001) but it appears not to work.
Many thanks for any suggestion.
George
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January 16, 2012 11:06pm UTC in response to George Rosala
Re: free finite prescribed displacement
Hi
in structural, by default in geometry "union" mode you have continuity between two adjacent domains, sharing a common boundary. So if you displace one domain, the other will follow as if it was "glued".
You need either to tweak the default continuity conditions/equations along the desired axis, or define a geometry "assembly" mode = dedoubling the boundary and define contact "pair" and sliding boundary conditions
check the doc
--
Good luck
Ivar
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January 17, 2012 8:56am UTC in response to Ivar Kjelberg
Re: free finite prescribed displacement
Hi Ivar,
The point is, I'm trying to avoid modelling with contact; so I didn't model the bolts, I would just like to model their effect on my component.
The component should deform freely until the axial clearance (gap) in the bolts closes, and than be held fixed in that direction. Any thoughts?
Thanks,
George
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January 17, 2012 9:23am UTC in response to George Rosala
Re: free finite prescribed displacement
Hi
you could try a non linear spring, but in some sense that is a "contact" model ;)
--
Good luck
Ivar
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January 17, 2012 10:24am UTC in response to Ivar Kjelberg
Re: free finite prescribed displacement
Ivar,
Is there a non-linear spring capability in Comsol? Where?
George
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January 17, 2012 10:51am UTC in response to George Rosala
Re: free finite prescribed displacement
Hi
not directly but you must play with either "thin elastic pairs" or a combination of "spring foundations" (the latter attaches a spring to a fixed frame, the former between two domains or via "pairs". Some equation tweaking is required. You can also implement this fully by your own as weak constraints. The non linearity is depending on the spring constant values (expressions) you use.
it's worth to study the doc on the two contact implementations as these are very close to the special spring case
--
Good luck
Ivar
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