# Effect of the Anti-Yaw Damper on Carbody Vertical Vibration and Ride Comfort of Railway Vehicle
## 6 Results of Numerical Simulationsand Discussion
In terms of the anti-yaw damping effect upon the reduction in the vibrations of the carbody at the eigenfrequencies of the three vibration modes, this is examined by means of the diagrams in Figure 8, calculated for \(k=1\cdot 10^{7}\) N/m, \(\alpha=10\) degrees and \(c\) within the interval of \(1\cdot 10^{5}\)Ns/m \(\ldots\)\(5\cdot 10^{6}\)Ns/m. The power spectral density of the acceleration is noticed to continually decrease by increasing the damping up to a certain value. Should the anti-yaw damping keeps rising over this value, the power spectral density of the acceleration in the carbody starts going up.In conclusion, for a certain value of the anti-yaw damping, the minimum value of the power spectral density of the carbody acceleration is obtained. Figure 6: Influence of the damping and the anti-yaw damper stiffness upon the carbody eigenfrequencies: (a) bounce eigenfrequency; (b) pitch eigenfrequency; (c) bending eigenfrequency. Figure 7: Influence of the anti-yaw damper stiffness upon the power spectral density of the carbody acceleration: (a) at the carbody center; (b) against the front bogie; (c) against the rear bogie. Figure 9 shows the influence of the mounting angle for the anti-yaw damper upon the power spectral density of the acceleration in the carbody reference points. The results presented herein are calculated for \(k=10^{7}\) N/m and \(c=5\cdot 10^{5}\) Ns/m. They show the amplification of the vibrations regime at the carbody bending frequency and the reduction of the bounce and pitch carbody vibrations, due to the increase in the mounting angle of the anti-yaw damper. Figure 8: Influence of the anti-yaw damping upon the power spectral density of the carbody acceleration: (**a**) at the carbody center; (**b**) against the front bogie; (**c**) against the rear bogie. Figure 9: Influence of the mounting angle of the anti-yaw damper upon the power spectral density of the carbody acceleration: (**a**) at the carbody center; (**b**) against the front bogie; (**c**) against the rear bogie. Figures 10-12 highlight the influence of damping and the anti-yaw stiffness upon the ride comfort index in the carbody reference points, in correlation with the vehicle velocity. The results are obtained for \(\alpha=10\) degrees. First, the ride comfort index is noticed not to be continually increasing along with the velocity, due to the geometric filtering effect given by the vehicle wheelbases. The geometric filtering effect of the track-triggered excitations represents an important characteristic of the vertical vibrations of the railway vehicles, extensively analyzed in many papers [9; 11; 50; 51; 52; 53; 54; 55].Due to this effect, sudden decreases of the ride comfort index occur at certain velocities, called geometric filtering velocities [54]. The geometric filtering effect has a selective nature depending on the velocity, with a higher efficiency at velocities smaller than 120 km/h. The geometric filtering manifests more visibly at the carbody center, where the effect comes from both the vehicle wheelbase and the bogie wheelbase. In the carbody reference points against the two bogies, the geometric filtering effect is less efficient, asit only comes from the bogie wheelbase. As for the influence of the anti-yaw damper upon the ride comfort, except for some limited velocity intervals, a reduction in the ride comfort indices is noticed in all the carbody reference points, and that the reduction becomes more important with the increase in the stiffness of the anti-yaw damper. For instance, Figure 13 shows the percentage values of the decrease in the ride comfort indices in the carbody reference points for \(k=5\cdot 10^{7}\) N/m and the three values of the anti-yaw damping. This reduction in the ride comfort index can reach up to 35-40%, depending on velocity and the damping value. The influence of the anti-yaw damping upon the ride comfort index has to be examined in correlation with the value of the anti-yaw damper stiffness.