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# Transient Analysis - Angular Velocity BC on Rotor

Experimenter

My problem goes as follows:

I have a rotor, which is a part of a motor assembly. I want to apply an angular velocity of 10 RPM on this rotor and perform a transient analysis. The reason I am going for transient analysis is that I want to observe the transient response on my motor's housing. For this post, I am just concerned about the rotor's boundary conditions.

Try 1 ( problem file attached as *-direct_transient.dat ):

So, I created a Direct Transient Solution (SOL 109) and applied a Velocity Constraint (Axial rotational velocity = 10 RPM, Translational velocities = 0 and other rotational velocities are left free) on the center point of the rotor's end. This center point is tied to the rotor end's edge with RBE3 element.

What I got is a rotor that starts rotating and gradually expands. I understood later that SOL 109 is a linear solver, formulated on the underformed state of the object and this doesn't work for rotations (since they fall under the large displacement category - reference: https://community.plm.automation.siemens.com/t5/3D-Simulation-Simcenter-3D-Forum/Static-bearing-mode... - check Martin Kuessner's last reply marked as Solution)

Try 2( problem file attached as *-nonlin_transient.dat )::

I moved to a Non-linear Transient Solution (SOL 129), but I don't find the same velocity constraint which I found in SOL 109. I instead applied the angular velocity BC as a time-dependent Enforced Displacement Constraint at the same location. Surprisingly, the rotor doesn't move. What I get (for all solution time steps) is a zero displacement on all nodes (a definite 0.0 not a numerical zero)

Has someone experienced such a problem before or could someone with a bit more experience suggest a remedy or another way to eventually rotate this rotor ?