Cylindrical Joint in Optistruct

Hello,

 

I am trying to add a cylindrical joint between two parts and apply a moment onto one part, something similar to a Hinge

But the elements tend to collapse (expand and scale up) and not stable

I have tried Cbeam elements with torsional moment as negligable, but having the same effect

Can you let me know how to create stable joint in Optistruct

 

Thanks and Regards

Koti