[hw-Multiphysics]

Thanks in advance for reading my question.

The model is shown in the figure 1. It is a 1D rotor model with different radius of cross sections.
1.JPG
Then, I build another cylinder coordinate system beside the default global coordinate system, shown in the figure 2.
2.JPG
Therefore, in the cylinder coordinate system, x-axis represents the radial movement, and the y-axis represents the tangential movement (in my own understanding).

For the input load, I apply a rotating force alongside the Z-axis (in two coordinate systems, both Z-axis represent the axial direction.

After the simulation, I got the frequency response vibration amplitude of each axis.

The problem is that the vibration amplitude of the Y-axis and Z-axis in the default global coordinate system do not corresponding to the vibration amplitude of X-axis and Y-axis in the cylinder coordinate system. In my opinion, the vibration amplitude should meet the following equation: (left side represent the default global coordinate system, and the right side represent the cylinder coordinate system)

(Y^2+Z^2)^(1/2)=(X^2+Y^2)^(1/2)

However, the results are shown below:
3.JPG

I wonder why these four figures have the same vibration amplitude. Thanks again for your answering.