Applying Pressure with Kinematic Coupling

[Techsan123]

Here is what I have:

A slightly curved hollow cylinder (curve to allow for imperfection)

A reference point at each face with an applied kinematic coupling. All DOF are constrained.

I first stretch the cylinder by applying the appropriate BC to each ref point. No problem

I then want to be able to apply internal pressure to the cylinder but do not want the ends to be constrained by the ref point. As is now the cylinder will begin to look like a cigar because of the end effect.

I then want to apply opposite rotations to each face by applying rotation as a boundary condition to the corresponding ref points.

My question is how to I get around the cigar effect and then still apply the rotation once the pressure step is complete. I tried leaving the constrained DOFs which are in the radial directions unchecked but then my first step of stretch will not converge. My steps are initial, Stretch, Pressure, and then Rotation.

This will work fine if there is no pressure step but I need to incorporate pressure.

Any ideas...or maybe I need to elaborate more? Thanks!