Ansys "Pin" constraint 1

[MikeG7]

I'm not an avid user of Ansys APDL.
How can I apply this constraint on an open ended thin walled cylinder (modeled as a volume with solid elements)?
Note: the axis of my cylinder is in the z direction

-One end fixed in all 6 DOF's
- Other end free to translate in z direction and free radial expansion only (all other DOF fixed)
I want to do this in cylindrical co-ordinate system. How can I do this?
Thanks
MikeG7

 

[flash3780]

Well, the easiest way to do that would be with beam elements... but that doesn't sound like what you're after.
Someone might have to correct me, but I think you can do what you'd like to do (a pin joint at the end of a tube) with constraint equations.
I believe the proper technique would be to create a node in the center of the tube to which you can apply your pin joint constraints. You'd then relate the displacements of that node to the tube with constraint equations.

http://lnf.umich.edu/nnin-at-michigan/wp-content/uploads/2012/11/2_03-coupling.ppt

 

[MikeG7]

Well flash3780, I read your post after I spent some time playing around. I think I managed to do it another way, selected all the nodes at the end of the tube and then changed the co-ordinate system to cylindrical. Then I applied a "NROT" command (node rotation) to rotate all the nodes into the new co-ordinate system. The "y" becomes tangtial and the "x" is radial. The "z" is along the longitudinal axis. I constrained the "z" and "y" leaving "x" (radial) free. it seemed to work.

 

[Drej]

MikeG7, the approach you describe is exactly how I would achieve what you need.


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[flash3780]

MikeG7, you got it right. I don't think I was understanding what you were after. When you said a "PIN" joint in the title, I was envisioning free rotation but fixed translation at the pinned end... like a ball-and-socket joint. After re-reading your problem more closely, that doesn't seem like what you were trying to do.

I agree that for what you're after, the way you've done it does the trick.

If you did want a ball-and-socket joint behavior, though, constraint equations would get you there.

 

[MikeG7]

Thanks Flash3780