Abaqus/CAE 2021, explicit.

I defined one initial rotation velocity for the CoG(RP-gravity) of this structure, it rotated around its axis and would be restricted by the beam, so the velocity would decrease from initial velocity to zero. But, when I checked the velocity of CoG, I found the velocity didn't decrease over time. And the deformation of structure is too big. I have no ideas why it behaves like this.

Thank you.