# Experimental Research on the Load Transfer Mechanism of Tie Plates for 400 km/h High-Speed Turnouts
## 2 Materials and Methods  
### Design Description  
The research group proposes a series of optimization for the structure of the elastic iron tie plate for 400 km/h high-speed turnout. Figure 1 shows a photograph and schematic of the elastic iron tie plate. * Side encapsulation is extended to the rail groove on the upper surface of the elastic iron tie plate to solve the cracking of the side encapsulation of the existing elastic iron tie plate. * A rubber boss is set on the vulcanized layer on the upper surface of the tie plate to replace the rubber washer on the lower surface of the cover plate, and the round hole on the cover plate used for installing the rubber washer is canceled. Thus, the problem of rubber washer failure can be solved. * The structure and size of the rubber block on the lower surface of the elastic iron tie plate are modified to adjust the stiffness. * The second-order stiffness structure design is adopted for the elastic iron tie plate to ensure the safe running of the vehicle, as shown in Figure 2.  
* A sinking design is adopted for the perimeter rubber of the steel sleeve, and it is vulcanized into a whole with a 2 mm encapsulation layer on the tie plate to improve the sealing performance and to avoid the rubber from being damaged because of outward bulging. The optimized elastic iron tie plate is expected to reduce the stiffness unevenness and track vibration effectively when a train passes through the turnout area. It can also effectively solve the existing problems in the use of elastic iron tie plates. However, note that there are certain differences in the force transmission mechanism from the original tie plate because of the change in structure of the new tie plate as the new plate uses a rubber boss instead of rubber washers, as shown in Figure 3. The main advantage of the rubber boss is that the surface of iron plate can be protected by rubber so as to reduce problems of corrosion, glue failure, etc. In addition, in the service process of the existing high speed turnout, the rubber washer can easily to fail and the structure of cover plate is too complex for the installation of a rubber washer. The above problems can be well solved by replacing the rubber washer with the structure of rubber boss. During the installation, if the original tie plate is used, the bolt preload is transferred to the cover plate; then, it is partly transferred to the bottom of the tie plate through the steel sleeve and partly to the top of the tie plate through the rubber washer inserted in the cover plate. This will cause the precompression of the tie plate. During the installation, if the new tie plate is used, the bolt preload is partly transferred through the steel sleeve and partly to the top of the tie plate through the rubber boss on the tie plate surface. Because the rubber washer of the original tie plate and the rubber boss of the new tie plate have different shapes and sizes, material properties, and stiffness characteristics, the bolt preload transferred to the upper  
Figure 1: Elastic iron tie plate. Figure 2: Second-order stiffness design. surface of the tie plate will also be different. Furthermore, this part of the bolt preload will have a specific and reasonable range of values--if the value is too small, a loose vertical space will be created for the elastic iron tie plate to undergo large vertical vibrations under the train load, and if the value is too large, excessive precompression will be applied on the elastic iron tie plate, thereby affecting the overall stiffness characteristics of the tie plate under working conditions. In summary, an in-depth study of the bolt preload transfer mechanisms of the new and original tie-plate structures is essential because changes in the tie-plate structure cause a change in the bolt preload transfer mechanism, likely affecting the vibration and the stiffness characteristics of the tie plate.