I have a really simple question (most of you might know the solution from top of your head as well). I am trying to get started in ABAQUS and am in process of modeling torsion in a hollow cylinder. I constrain all DOFs on the one face and use a Reference point kinematic coupling on the other face. Then I give a BC at STEP 1 (after initial step) of rotation UR3 (in axial direction) = 1.5 (about 90 deg) to the reference point. This should theoritically proide torsion to the cylinder but what i see is that the cylinder kind of bulges. I am not sure why is this happening and how can I fix it. I am simply tyring to simulate the load (RM) required to twist it but really doing something wrong.
I am attaching some pitures showing coupling, boundary conditions and result alongwith. Can someone please tell me what is the issue with this simple problem.
ps: its been years since I touched ABAQUS, its still in the process of coming back to me...