Manipulating constraints within simulation

Sarvesh

Hello Expert community,
I need one help in manipulating constraints within simulation time steps. Is it possible to perform this operation with Calculix?

Victor

Hello Sarvesh

If you mean changing the value of, say, a prescribed displacement, you can do that by entering a formula that's a function of time (t), or as a table.

If you mean turning constraints on or off, CalculiX can do that but not natively through the Mecway GUI. It requires a separate *STEP section for each change in constraint status. You can add *STEP section in in Mecway with CCX -> custom step contents and define the 2nd step like

*END STEP
*STEP
... put keywords to redefine constraints here.

Mecway will add the final *END STEP after that.

Look in the CCX manual for how to change constraints. In particular, the OP parameter of *BOUNDARY:

OP=MOD is default and implies that previously prescribed displacements remain active in subsequent steps.
Specifying a displacement in the same node and direction for which a displacement was defined in a previous step replaces this value. OP=NEW implies that
previously prescribed displacements are removed.

So if you want to remove a constraint, you have to redefine all the other ones that you want to keep. You can copy and paste them from first step in the generate .inp file.

Sarvesh

Hello Victor,
Thank you for your helpful suggestions. I tried implementing them, but unfortunately I wasn’t able to achieve the desired result.
My situation involves a loading and unloading case (in two time steps), and I would like to activate a constraint specifically during the unloading step only.
If it’s not too much trouble, could you please provide a simple example to illustrate how this can be done?

JohnM

My advice is to post a sample model. You'll find the forum members often swarm these things like piranha - and that's a good thing .