Geostar (non-linear) how to release constraints

[JAGaynor]

Hello - please disregard my previous post... I'm hoping that the Lack responses was only my vagueness and not a lack of members using COSMOS anymore!

searching online and finding early press releases, I read that one of the strengths of Cosmos/m / Geostar is the ability to release and activate constraints during a non linear analysis...

Anyone know how to specifically do this?

here is my problem:

I am trying to analysis a 3d beam / truss structure with adjustable linkages...using temp curves to pretension and adjust the structure. getting this all to run to equilibrium is very tricky. I'd like to fix a few points as I bring the structure up to tension - and then release these constraints for the subsequent time steps.

I have time/temp curve defined, and associated the point constraint to this - but as far as I can figure out this just allows me to change it from 0 (fixed) to some value (prescribed displacement) - not completely disable it.

Anyone know a better way to do this?

thanks
Andrew

 

[BlasMolero]

Hello!,
It's years I don't use COSMOS/M GEOSTAR anymore, but the only feature available in any serious FEA code is RESTART feature:

Suppose that a Nonlinear problem diverged at solution step number 5. Activating restart feature you can change the solution time increment, or some other parameters like loads & BCs. If the restart feature is OFF and you run the nonlinear analysis again, the solution will start from step 1 ignoring previous results. If the restart flag is ON, the solution will continue from step 5.

Good luck!.

Best regards,
Blas.

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Blas Molero Hidalgo
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[kellnerp]

I'm racking my brain for this. I've done it before, but I don't have the docs in front of me. There is a way in the time curve to apply a constraint and then release it at a set time. I seem to remember some "magic" number like "999" or "-999" but don't quote me on that.

My 2 cents.

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[kellnerp]

1E-8 as a value in a time step.
If you do it in one jump you have to use a Dynamic Solution. If you ramp it a little you can get away with a Standard non-linear solution.

You have to activate the time curve before you define the constraint that will be effected by it.

For example executing this:

CURDEF, 1, 0,1,1,1e-8,2,1e-8

will turn off whatever boundary conditions were created after it at a time value of 1.




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