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M
mlindqvist1-Visitor
1-Visitor
August 20, 2014
Solved

Rotational degrees of freedom on a rigid link point.

  • August 20, 2014
  • 1 reply
  • 3117 views

I have a simple shell model, a square section hollow beam with datum points at the center of each end surface. I have created a rigid link between those datum points and corresponding edges. I want to create moment free constraints at the ends. At one end, I can create a point constraint and set translational AND rotational degrees of feedom as I please. At the other point, I can't set rotational degrees of freedom. Why? Each set of point+rigid link seem identical. Any suggestion?

Best regards Mats Lindqvist

Best answer by mlindqvist

I got a reply from PTC regarding this toda. Rotational DOF's can be altered only on a point that coincides with the WCS. Apparently its a bug that will be resolved in Creo 2.0 M130 which is due to be released in October...

/Mats L/.

1 reply

S
sdensberger2-Explorer
2-Explorer
August 20, 2014

I assume you're trying to create an Advanced Rigid Link, Mats? If so, are you trying to change from a Simple to an Advanced Rigid Link (after it was originally defined as a Simple)? I know that, for whatever reason, you can't change a Simple RL to an Advanced RL; you need to delete the Simple RL and create a new Advanced RL.

Now, regarding the moment free joint you want to create, I believe you need to do this with the Advanced RL and not the constraint; the latter causes the analysis to fail if I recall correctly.

M
mlindqvist1-VisitorAuthor
1-Visitor
August 21, 2014

My intention was to use simple rigid links and handle the rotations using a constraint. It works at one of the beam end, not the other which I find strange.

If you have time, check out the constraints in this model:

http://communities.ptc.com/servlet/JiveServlet/downloadBody/6275-102-1-9465/vertical_beam.prt.1.zip

In some previous release, rigid links were always sensitive to rotations, not anymore it seems.

I can solve it using a workaround, as you mentioned using an advanced RL, or a short stiff dummy beam where I can add beam release at one endpoint. I had planned to use it for educational purpose, in situations like that one shouldn't have to struggle with workarounds...

/Mats L/Lund, Sweden/

PS. It was created in Creo2...

M
mlindqvist1-VisitorAuthor
1-Visitor
August 21, 2014

Funny, now as I change to an advanced rigid link, then the rotational degrees of freedom in the constraints are no longer greyed out. So I create an advanced rigid link, then I can use the constraint to set rotations free. 😕

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