Spline Coupling
In a spline coupling, displacements and axial rotation of the rotors are rigidly connected whereas rotors are free to tilt relative to each other.
If a Rotor Coupling is applied to an interior boundary, the degrees of freedom in the rotor are slit and then connected using the following constraint:
Here, uu and ud are the displacements on both sides of the interior boundary. u0 is the parallel misalignment in the coupling. θ3u and θ3d are the axial rotations of the rotors on both sides of the interior boundary.
On an exterior boundary, there is no rotor present on the other side. Therefore, displacement and tilt rotations are free for this coupling type, while the axial rotation is fixed:
Here, θ3 is the axial rotation of the rotor on the selected boundary.