Cross-sectional Compatibility Design and Interchangeability Technology for National Standard and Foreign Standard Rails
What are the core dimensional differences in the cross-section between national standard and international standard rails?
The core dimensional differences in the cross-section between national standard and international standard rails are mainly reflected in three key parts: rail head width, rail web thickness and rail base width, and the different design focuses of different standards determine the different values of the dimensions. The rail head widths of national standard 50kg/m and 60kg/m rails are designed as 70mm and 73mm, which adapt to the tread dimensions of domestic train wheel sets and ensure the smoothness of wheel-rail contact. The rail head widths of international standard UIC60 and BS113A rails are 75mm and 71mm respectively, and the rail head arc radius is also different from the national standard, matching the wheel-rail contact standards of European and British trains. In terms of rail web thickness, the national standard 60kg/m rail is 16.5mm and the UIC60 rail is 16.8mm, and the slight difference is to adapt to the clamping structures of fish plates supporting their respective standards. In terms of rail base width, the national standard 60kg/m rail is 150mm and the BS113A rail is 143mm, adapting to the sleeper support spacing and fastening system layout of different countries. These dimensional differences are the basis for ensuring the adaptability of rails with supporting components.
What cross-section inspection work is required before the interchange modification of national standard and international standard rails?
The cross-section inspection before the interchange modification of national standard and international standard rails needs to cover three categories: key dimensions, geometric tolerances and surface quality, to ensure that the modification data is accurate and the stress of the rail after modification is compliant. First, it is necessary to inspect the core dimensions of the rail head, rail web and rail base, and use a laser diameter gauge to measure the deviation between the actual size and the standard size, which should be controlled within ±0.5mm. Second, inspect the geometric tolerances such as straightness and perpendicularity of the rail, the perpendicularity deviation between the rail head and the rail web shall not exceed 0.1mm/m to avoid eccentric load after modification. It is also necessary to inspect the surface roughness of the rail cross-section, the roughness Ra of the rail head tread and rail web fitting surface shall be ≤1.6μm to prevent surface defects from affecting the fitting degree with fish plates and pressure plates. At the same time, it is necessary to inspect the material uniformity of the rail cross-section, and check the internal segregation through ultrasonic testing to avoid cracks due to material problems after modification. Finally, it is necessary to inspect the flatness of the connecting end face of the rail, the end face flatness deviation ≤0.05mm to ensure close contact with the fish plate. All inspection data shall form a record as the core basis for the modification design.
What is the core role of rail head cross-section correction in rail interchange modification?
Rail head cross-section correction is the core process of the interchange modification of national standard and international standard rails, and its role is to make the rail heads of different standard rails adapt to a unified wheel-rail contact standard, ensuring the smoothness and safety of train operation. The rail head widths and arc radii of different standard rails are different, and direct connection will lead to sudden changes in wheel-rail contact points and generate impact loads. Rail head cross-section correction can grind the special-shaped rail head to a unified size adapted to the line. The corrected rail head can ensure that the wheel-rail contact area meets the design requirements, avoid accelerated rail head wear caused by too small contact area, and extend the service life of the rail. At the same time, rail head cross-section correction can keep the wheel-rail contact stiffness at the rail connection consistent, prevent vibration amplification caused by sudden stiffness changes, and reduce the noise and bumpiness of train operation. In addition, rail head cross-section correction can adapt to the existing rail grinding cycle of the line, make the wear rate of the modified rail consistent with that of the original rail, reduce the later maintenance cost, and ensure the overall operation stability of the track.
What local modifications are required for international standard rails to adapt to national standard fastening systems?
The local modifications for international standard rails to adapt to national standard fastening systems are mainly carried out around the rail web, rail base and connecting end face, and precise adaptation to national standard elastic strips, pressure plates and bolts is achieved through minor corrections. First, it is necessary to slightly grind the clamping surface of the rail web to adjust the slight deviation of the rail web thickness, ensure that the national standard pressure plate can clamp it evenly, and the clamping force deviation is controlled within ±5kN. Second, it is necessary to level the supporting surface of the rail base to adapt to the supporting points of national standard sleepers, ensure the uniform stress on the bottom of the rail, and avoid rail base deformation caused by local stress concentration. If the bolt hole position of the international standard rail is different from the national standard, it is necessary to re-drill the hole with a CNC drilling machine, the hole position deviation ≤±1mm, and the hole wall must be chamfered after drilling to prevent stress concentration. For the connecting end face, it is necessary to re-finish grind to meet the national standard flatness requirements to ensure the close fitting degree with the national standard fish plate. At the same time, it is necessary to add adaptive gaskets at the contact between the rail and the under-rail pad to adjust the vertical height of the rail to keep it at the same level as the original rail of the line, ensuring the stress compliance of the fastening system.
What stiffness tests are required for the connecting section after the interchange modification of national standard and international standard rails?
The stiffness test of the connecting section after the interchange modification of national standard and international standard rails needs to cover vertical stiffness, lateral stiffness and torsional stiffness to ensure that the stiffness of the connecting section is consistent with the overall stiffness of the line without sudden stiffness changes. The vertical stiffness test adopts a static load test, arranges test points within 3m on both sides of the connecting section and its two sides, measures the deformation after applying vertical load, and the vertical stiffness deviation shall be ≤±5kN/mm. The lateral stiffness test measures the lateral displacement of the rail by applying lateral thrust, the lateral stiffness shall meet the line design requirements, and the displacement ≤0.5mm/10kN to prevent lateral movement of the rail. The torsional stiffness test needs to check the torsional deformation at the rail connection, the torsion angle deviation ≤0.1°/m to avoid eccentric rail head wear caused by uneven torsional stiffness. At the same time, dynamic load stiffness test is required, and vibration data is collected through train commissioning to analyze the consistency of the vibration frequency of the connecting section with the whole line, and the frequency deviation ≤2Hz. All stiffness tests shall be carried out within 24 hours after the completion of the modification, and if the test is unqualified, the accessory specifications shall be adjusted in time until the stiffness indicators meet the standards.