## 5 Dynamic Simulation of High-Speed Train Passing through Turnout
### Analysis of the Carbody Vibration Acceleration Characteristics  
The changes in the carbody lateral acceleration as the train passes through the turnout are depicted in Figure 14a. According to level-one and level-two standards, 0.5-10 Hz band-pass filtering is used to evaluate the carbody lateral acceleration. The level-two alarm (0.90 m/s\({}^{2}\)) is reached by the maximum carbody lateral acceleration of 1.33 m/s\({}^{2}\) when the train passes through the turnout before grinding without polygonal wear [29]. After grinding without polygonal wear, the maximum carbody lateral acceleration as the train passes through the turnout is 0.57 m/s\({}^{2}\), which is less than the level-one alarm (0.60 m/s\({}^{2}\)) and 57.14% less than it was before grinding. The level-two alarm (0.90 m/s\({}^{2}\)) is reached by the maximum carbody lateral acceleration of 1.34 m/s\({}^{2}\) when the train goes through the turnout before grinding with polygonal wear [29]. After grinding without polygonal wear, the maximum carbody lateral acceleration while the train goes through the turnout is 0.57 m/s\({}^{2}\), which is less than the level-one alarm (0.60 m/s\({}^{2}\)) and is acceptable.  
Figure 14b depicts how the carbody vertical acceleration changes as the train goes through the turnout. For vertical acceleration, low-pass filtering at 20 Hz is used. When  
Figure 14: Changes in the carbody acceleration: (**a**) lateral; (**b**) vertical.  
the train passes through the turnout without polygonal wear, the maximum vertical acceleration is decreased from 0.31 m/s\({}^{2}\) to 0.19 m/s\({}^{2}\), which is 38.71% less than it was before grinding. As the train travels through the turnout with polygonal wear, its maximum vertical acceleration drops from 0.32 m/s\({}^{2}\) to 0.19 m/s\({}^{2}\), or 40.63%, slower than it did before grinding.  
So, whether or not polygonal wear occurs, grinding the turnout rail profile can improve the carbody lateral and vertical acceleration.  
In Figure 15, the frequency spectrum of the carbody acceleration as the train travels through the turnout is shown. Whether or not there is polygonal wear, 0-5 Hz is the main frequency of the carbody. When the train passes through the turnout following grinding with polygonal wear, the maximum lateral acceleration amplitude decreases from 0.44 m/s\({}^{2}\) to 0.20 m/s\({}^{2}\), which is 54.55% lower than that before grinding. After grinding with polygonal wear, the maximum lateral acceleration amplitude is reduced from 0.45 m/s\({}^{2}\) to 0.21 m/s\({}^{2}\), which is 53.33% less than it was before grinding. When the train passes through the turnout after grinding with polygonal wear, the maximum vertical acceleration amplitude is reduced from 0.083 m/s\({}^{2}\) to 0.059 m/s\({}^{2}\), which is 28.92% lower than that before grinding. When the train passes through the turnout after grinding with polygonal wear, the maximum vertical acceleration amplitude is dropped from 0.084 m/s\({}^{2}\) to 0.059 m/s\({}^{2}\), which is 29.76% lower than that before grinding.  
Thus, the main frequency distribution of the carbody acceleration has not changed when the train passes through the ground turnout with or without polygonal wear, but the maximum amplitude values have decreased.