Knowledge on the Research and Application of New Materials for Rail Track Pads
What are the core technical advantages of microcellular polyurethane under-rail base plates?
Microcellular polyurethane base plates adopt a three-dimensional network molecular structure, achieving excellent resilience with an elastic recovery rate of ≥95% by optimizing the combination of soft and hard segments, far exceeding the 80% of traditional rubber base plates. The material has strong weather resistance, maintaining stable performance in the environment of -40℃~60℃ without obvious aging, hardening or cracking, and is suitable for extreme climates in alpine and high-temperature areas. It has outstanding stiffness stability, with a stiffness change of ≤5% after long-term stress, avoiding the decline of track smoothness caused by stiffness attenuation and ensuring stable train operation. The flat plate structure design increases the contact area with sleepers, relieving the problem of wear grooves on the sleeper rail-bearing surface and extending the service life of sleepers. Its service life can reach 12-15 years, more than twice that of traditional rubber base plates, significantly reducing replacement frequency and maintenance costs.
What improvements do composite elastomer base plates have compared with traditional rubber base plates?
Composite elastomer base plates are composed of rubber and fiber-reinforced materials, with a tensile strength increased to more than 8MPa, far exceeding the 3MPa of traditional rubber base plates, and the tear resistance is greatly enhanced. The wear resistance is significantly optimized, with a wear loss of ≤0.5mm/1 million cycles, while traditional rubber base plates can reach 1.2mm, reducing thickness loss after long-term use. It has stronger oil resistance and corrosion resistance, able to resist the erosion of oil stains and chemical media around the track, and is suitable for special environments such as tunnels and coastal areas. It has excellent fatigue resistance, with no cracks after 5 million vibration cycles, while traditional rubber base plates are prone to damage around 3 million cycles. It is 15% lighter than traditional rubber base plates, facilitating transportation and on-site installation without reducing load-bearing capacity and shock absorption effect.
What are the applicable scenarios for new-type under-rail base plates?
Microcellular polyurethane base plates are suitable for heavy-haul railways, which can effectively absorb large-traffic impact loads, reduce the risk of rail corrugation and fastener loosening, and have been widely used in heavy-haul lines such as Datong-Qinhuangdao Railway and Shuohuang Railway. Composite elastomer base plates are suitable for urban rail transit, which can maintain stable elasticity under high-frequency vibration, reduce operating noise and improve the living environment of residents along the line. Silicone rubber composite base plates are preferred for high-temperature areas, with excellent high-temperature resistance, and will not soften or deform in environments above 60℃, suitable for lines in deserts and tropical areas. Modified polyurethane base plates can be selected for alpine areas; after adding antifreeze, the low-temperature toughness is improved, and good elasticity can be maintained at -40℃ to avoid brittle fracture. Low-stiffness microcellular base plates are used for high-speed railways, with stiffness controlled at 20-30kN/mm, meeting the strict requirements of high-speed trains for smoothness.
What special requirements are there for the installation of new-type under-rail base plates?
Before installation, the surface of the base plate should be inspected to ensure there are no defects such as bubbles and cracks. For microcellular polyurethane base plates, sharp objects should be avoided to scratch the surface to prevent damage to the microcellular structure. The base plate must be completely attached to the sleeper rail-bearing surface; when installing composite elastomer base plates, a 2-3mm gap for thermal expansion and contraction should be reserved to avoid deformation caused by temperature changes. Directly hitting the base plate with a hammer is prohibited during installation; a rubber hammer should be used to tap and level it to prevent damage to the internal structure of the base plate. The surface of the base plate in contact with the rail should be kept clean, free of impurities such as sand and oil stains, to avoid affecting the shock absorption effect and service life. When installing on curved lines, thickened base plates (1-2mm thicker than the inner side) should be selected for the outer side to adapt to the superelevation design of the line and ensure rail surface smoothness.
How to detect whether the quality of new-type under-rail base plates meets the standards?
The elastic recovery rate test should use a pressure testing machine, applying 50% of the rated load for 30 minutes, and an elastic recovery rate of ≥90% is qualified, while microcellular polyurethane base plates require ≥95%. The weather resistance test simulates a cyclic environment of -40℃~60℃ through a high and low temperature test chamber, and no cracks or hardening after 100 cycles is qualified. Stiffness testing should be carried out within the load range of 10-50kN, with a stiffness fluctuation of ≤±10%, meeting the designed stiffness grade. Wear resistance is tested by a Martindale abrasion tester, and a wear loss of ≤0.8mm/1 million cycles is qualified, while composite elastomer base plates require ≤0.5mm. Mechanical performance testing should sample tensile tests, with a tensile strength of ≥6MPa and an elongation at break of ≥300%, ensuring no damage during installation and use.