Applying force to a symmetry surface

[headrush]

Imagine a can. Acylinder with twoend caps. A can like a can of beans you buy at the grocery store. I want to compress this can axially. The can is made of a very soft material.


It's in a cylindrical coordinate system.


I cut it in half along the z axis. So I have half a can - a cylinder withone end cap.


I want to fix all DOF on the end cap and apply a z direction force to the symmetry surface. We don't typically apply forces to symmetry surfaces (at least I haven't used this technique before).


The correct symmetry constraints for this symmetry surface (if I were to apply the force to the end cap) are to fix translation in z and fixrot-R and rot-theta. I should simply be able to remove the constraint on trans-z and apply the force to the symmetry surface. The problem runs, but I still get rotation about theta even though the rot-theta DOF is fixed. So the edge I cut in the middle of the can bends outwards.


Ibelieve this result is caused by a bug in Mechanica, or maybe what I would term a severe limitation. Although I have now been successful at soving the problem by applying the force to the end cap, I am still surprised as to why applying the force to the symmetry surface doesn't work.


Any ideas?Does it sound like a bug to you? I am running WF3.0 M080. I couldn't find any known problemson the PTC website.
Edited by: headrush

 

[walkerone]

Hi,

Can you confirm that the can is modelled as a solid?

Then is it the surface or the edges that have the constraints applied at the end cap, or is the model constrained at the symmetry surface?

Any chance of uploading a picture of the can with the constraints / loads applied that you think should work?

Cheers, Greg

 

[headrush]

Unfortunately the can is proprietary and theactual geometry will only confuse the issue. But I should be able to make a similar, simplecan, run it and post pictures later today. The cylinder is actually more like a dome, which probably makes a difference.

 

[headrush]

Here is my simplified model. I have turned off the coordinate system display because the WCS is overlayed on the cylindrical coordinate system. Anybody know how to turn WCS display off witout turning off local coordinate system display? I am showing a section view.





Here is the result. See how the cut edge has rotation about theta.