Flexible Car-Body Modal Answers

	Frequency	Damping
Mode name	[Hz]	[%]	Description:
Lower sway	0.61	11.5	Car-body lateral and car-body roll moves in phase.
Upper sway	1.77	34.7	Car-body lateral and car-body roll moves out of phase.
Body bounce	1.09	16.7	The car-body moves vertically.
Body pitch	1.35	23.7	The car-body pitches.
Body yaw	1.31	43.8	The car-body moves mostly in yaw.
1:st bogie kinematic	4.46	21.0	The two bogies are approximately in phase.
2:d bogie kinematic	4.58	21.0	The two bogies are approximately out of phase.
Body 1:st bending	5.98	10.3	Carbody bending and bogie longitudinal vibration.
Body 1:st bending	14.45	16.8	Carbody bending and bogie longitudinal vibration, out of phase.
Body Torsion mode	10.02	2.9	The carbody structure deforms in torsion
Body 2:d bending	10.99	2.0	Carbody secondary vertical bending mode.

Comments:

Which can be seen in the eigen values above the Body bounce is now a little bit lower, due to the first bending mode is now vibrates in phase with the rigid Body bounce mode.
The traction rod and the yaw-damper couples the first car-body bending mode and the bogie longitudinal vibration mode to each other. Instead of being two separate vibration modes they are now vibrating together. When the two modes vibrates in phase the eigen value has become lower than the original eigen values. When the two modes vibrates out of phase the eigen value has become higher than the original eigen values. For a rigid car-body the bogie longitudinal vibration mode was 9.53 Hz. For the free-free car-body bending mode the eigen frequency was 9.0 Hz. When they are vibrating in phase the new eigen frequency is now 5.97, and when they are vibrating out of phase the new eigen frequency is now 14.46.
In contrast to the free-free vibration modes calculated in the FEM-program the eigen values of the car-body vibration modes are now complex. Due to the viscous dampers the vehicle model.