Rail Pad Classification: Material Properties and Application Scenarios
What are the core performance differences between rubber pads and polyurethane pads?
Rubber pads are mainly made of natural rubber or synthetic rubber, with low cost, a static stiffness of 20-60kN/mm, good shock absorption effect, and can reduce vibration noise by 15-20dB. Polyurethane pads are made of high-performance polyurethane materials, combining high elasticity and high strength, with wear resistance 30% higher than rubber pads and longer service life. Rubber pads have general weather resistance and are prone to aging and hardening in high or low temperature environments, while polyurethane pads can maintain stable performance in the range of -40℃ to 70℃. The elongation of rubber pads can reach more than 500% with good elastic recovery, suitable for conventional railways and urban rail transit; polyurethane pads have stronger load-bearing capacity, adapting to heavy-haul and high-speed railways. The installation methods of the two are the same, but the replacement cycle of polyurethane pads is 2-3 times longer than that of rubber pads.
What are the main characteristics and applicable scenarios of EVA pads?
EVA pads are made of ethylene-vinyl acetate copolymer with a vinyl acetate content of about 20%, a density of 0.95-0.98g/cm³, and good elasticity and flexibility. Its insulation resistance can reach ≥1×10¹⁰Ω, which can effectively prevent current leakage and ensure the normal operation of the track signal system. The tensile strength of EVA pads is not less than 15MPa, the elongation rate exceeds 500%, the melting point is 170-190℃, and the high-temperature resistance is good. This type of pad is suitable for scenarios with high requirements for shock absorption and insulation, such as urban rail transit, bridges and tunnel lines. During installation, it can be used in combination with ordinary pads, and precise adjustment of track height can be achieved through different thickness combinations (1-30mm).
Why are HDPE pads preferred for heavy-haul lines?
HDPE pads, or high-density polyethylene pads, have an elastic modulus of 2.0-2.5MPa and a compressive strength of ≥30MPa, which can meet the requirements of heavy-haul lines with 27t axle load. Its wear resistance is 3 times that of ordinary rubber pads, which can withstand high-frequency heavy-haul impacts and reduce pad wear and deformation. HDPE pads have excellent anti-aging performance and can maintain stable performance for many years in outdoor environments without being prone to cracking or chalking. The compression of this pad is strictly controlled, with a compression of ≤2mm under 50kN load, which can effectively maintain the stability of track geometric dimensions. The wheel-rail force on heavy-haul lines is large, and the high load-bearing capacity and low deformation characteristics of HDPE pads can avoid premature failure of the pad leading to track settlement.
What are the technical requirements and application scenarios of insulating pads?
Insulating pads must be added with insulating materials such as glass fiber and epoxy resin, with an insulation resistance of ≥10⁹Ω to prevent current leakage from interfering with track signal transmission. Its appearance should be flat without bubbles or cracks, and the thickness deviation shall not exceed ±0.5mm to ensure close fit with the track. The compressive strength of the insulating pad is not less than 25MPa, and no permanent deformation occurs under long-term load, ensuring long-term stable insulation performance. It is mainly used in track circuit sections, electrified railways and urban rail transit, and is a key component to ensure the normal operation of the communication and signal system. During installation, avoid contamination of the pad surface; if the insulation resistance is lower than 500MΩ, replace it in a timely manner to prevent signal interference.
What are the design features and usage precautions of height adjustment pads?
Height adjustment pads are mostly made of polyethylene or nylon materials, with various thickness specifications (1-30mm), which can be used alone or in combination to achieve fine adjustment of track height. Its material has high hardness (Shore A ≥90) and compressive strength ≥30MPa, with minimal deformation under load, ensuring adjustment accuracy. The pad surface is flat, and the upper and lower contact surfaces have anti-slip textures to prevent displacement during use and affect track stability. When using, select the appropriate thickness according to the track settlement, and the number of superimposed layers shall not exceed 3 to avoid affecting structural stability. When replacing the adjustment pad, first measure the actual height deviation of the track, then accurately match the pad thickness to ensure that the gauge and level meet the standards.