I simple simulate a deformable steel ball rolling over a rigid plate in 3D using Abaqus Explicit solver, I only defined the gravity acceleration for the ball and the rotational velocity where I used a kinematic coupling constrain of all dog of ball to the reference point at the centre of the ball and have created and used a Cartesian coordinate system at that point to move with the ball. after few rotation the ball started to deform from near- upper side in a strange way. my question is why this deformation happened? and how does Abaqus define and integrate the rotation?

Regards;