For rotating objects like spin coater and motor, the torque of rotation at start, steady-state, and stop can be analyzed.
Acceleration and deceleration of the rotating body are taken into account in the stress-transient analysis. Time integration is applied to the acceleration and the deceleration to obtain the angular velocity. With further time integration, the rotation angle is obtained. It is used as a rotational displacement for a boundary condition. The time dependency is set."
An iron disc is rotated on a rotating shaft. Acceleration and deceleration are taken into account. The rotational displacement is set to the root of the shaft as a boundary condition.
As the graph of torque shows, the torques during the acceleration and deceleration are positive and negative direction.
The model has resonant mode in the rotational direction. Due to the resonance, the torque values fluctuate.
The fluctuation is seen in the graph of velocity of the rotating disc and the graph of strain energy of the rotating shaft.