Railway pads are the core components for ensuring the smoothness and stability of tracks in high-speed railways. Their performance directly affects the speed, comfort and safety redundancy of trains. Based on the operational characteristics of high-speed railways, namely "high speed, high load and high stability", the pad system must meet strict technical indicators, and the application of different types of pads has different focuses.
The rail pad is the "first buffer layer" of high-speed railway tracks and is generally made of polyurethane. Its dynamic stiffness needs to be controlled at 50-80kN/mm, and the dynamic-static stiffness ratio should be ≤1.3 to cope with the high-frequency impact generated by 350km/h trains. In the Beijing-Shanghai High-Speed Railway and other lines, the polyurethane pad with a Shore hardness of 60±3 still has an elasticity retention rate of over 85% after 3 million fatigue tests, which can reduce the wheel-rail vibration acceleration by more than 30%. At the same time, its insulation resistance is >10⁸Ω, ensuring the stable transmission of track circuit signals.
Tie plates are mostly embedded cast iron structures in ballastless tracks, with a thickness of 12-16mm, a surface processing accuracy of 0.05mm/m, and a connection error with the track plate of ≤1mm. They are rigidly fixed to the track plate by bolts, and cooperate with elastic fasteners to form a "rigid load-bearing + precise positioning" system. In CRTSⅢ slab ballastless tracks, the lateral displacement of the rails can be controlled within 0.5mm to ensure the stability of the train when passing curves.
Composite tie plates play a key role in special sections. Due to the concentrated impact of wheels and rails in the turnout area, a composite structure of "metal skeleton + polyurethane elastic layer" is adopted, with a surface friction coefficient of ≥0.8, which can resist the shear stress generated by the lateral force; lightweight aluminum alloy tie plates are used in the bridge section, which are 40% lighter than traditional cast iron, reducing the bridge load while improving corrosion resistance through anodizing treatment to adapt to the humid environment of the bridge deck.
The application of high-speed rail pads must meet the requirements of "stable performance throughout the entire life cycle", and its replacement cycle must match the track overhaul cycle (usually more than 20 years). Through material optimization (such as adding nano-enhancers) and structural innovation (such as gradual stiffness design), modern high-speed rail pad systems can maintain stable performance in an environment of -40℃ to 60℃, providing reliable track support for high-speed rails that "fly close to the ground".
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