Track pad stiffness matching and track smoothness design
What impact does the stiffness of under-rail pads have on the overall track performance?
Excessively low stiffness of under-rail pads will lead to excessive track deformation, affecting geometric accuracy and increasing maintenance costs. Excessively high stiffness will reduce vibration reduction effects, aggravate wheel-rail impact, and shorten the service life of rails and vehicles. Reasonable stiffness can achieve uniform distribution of track stiffness and reduce dynamic wheel-rail forces. High-speed lines have extremely high requirements for stiffness uniformity to avoid train jolting caused by sudden stiffness changes. The stiffness of under-rail pads is a core parameter for adjusting the overall track performance.
What are the requirements for the stiffness value of under-rail pads in heavy-haul lines?
For heavy-haul lines with a 30t axle load, the vertical stiffness of under-rail pads is recommended to be controlled at 140-160kN/mm. This stiffness range can balance track stability and vibration reduction needs, avoiding excessive track deformation caused by heavy loads. At the same time, it is necessary to match the under-block pad stiffness of 60-90kN/mm to form a reasonable stiffness gradient. The stiffness value must be comprehensively determined in combination with the embedding depth of the bearing block and the sleeve stiffness. Accurate stiffness value is the key to ensuring the gauge retention capacity of heavy-haul lines.
How to achieve uniform stiffness design of under-rail pads in turnout areas?
The turnout area needs to adjust the stiffness according to sub-structure division, and the pad stiffness in the turnout section should be slightly higher than other areas. High-stiffness pads should be selected for the common pad area of the guide curve to balance the force transmission of multiple rails. The pad stiffness in the frog section needs to be optimized through simulation to avoid sudden stiffness changes. The effective stress area of the pad rubber can be adjusted to achieve accurate stiffness matching. Uniform stiffness design can improve the smoothness of trains passing through turnouts.
What are the differences in pad stiffness requirements between high-speed lines and ordinary lines?
For high-speed lines with a speed of over 350km/h, the stiffness of under-rail pads needs to be controlled at 100-120kN/mm, focusing on vibration reduction and stiffness uniformity. The pad stiffness of ordinary railway lines can be relaxed to 120-180kN/mm, giving priority to ensuring structural stability. The stiffness deviation of high-speed line pads must be ≤±10%, while that of ordinary lines allows a deviation of ≤±15%. High-speed lines need to use rubber materials with more stable elastic modulus to avoid stiffness attenuation after long-term operation. Differences in stiffness requirements stem from the different operating speeds and load characteristics of the lines.
What impact does temperature change have on the stiffness of under-rail pads? How to deal with it?
Low-temperature environments will increase the stiffness of rubber pads and reduce vibration reduction effects; high temperatures will reduce stiffness and increase track deformation. In extremely cold regions, low-temperature resistant rubber pads should be selected, with a stiffness temperature change rate of ≤5%/℃. Heat-resistant additives can be added to the pads in high-temperature regions to maintain stiffness stability. The temperature compensation coefficient should be considered in the design to reserve stiffness adjustment space. Targeted material selection and design optimization can reduce the impact of temperature on stiffness.