Toothed Engagement Design of Fishplates and Rail Joint Stiffness Matching Technology
What are the core design parameters of the tooth profile meshing structure of fishplates?
The core design parameters of the tooth profile meshing structure of fishplates include tooth angle, tooth height and tooth pitch, and these three parameters jointly determine the meshing effect and joint stiffness. The tooth angle is usually designed as 60°, which can maximize the normal pressure between the meshing teeth and the rail contact surface, improve the bite force, and avoid tooth surface slip during train operation. The tooth height should be controlled at 3-5mm; an excessively high tooth height will cause stress concentration at the tooth tip, which is easy to cause tooth tip wear or chipping, while an excessively low tooth height cannot form effective meshing, resulting in insufficient joint stiffness. The tooth pitch is set at 10-15mm, which must match the elastic modulus of the rail to ensure uniform stress distribution during load transmission. Different rail models are adapted to different tooth profile parameters; the fishplate for 60kg/m national standard rails should have a tooth height of 4mm and a tooth pitch of 12mm to match its high base material stiffness.
What are the joint stiffness differences between tooth profile meshing fishplates and flat fishplates?
The joint stiffness differences between tooth profile meshing fishplates and flat fishplates are mainly reflected in three aspects: stiffness continuity, load transmission efficiency and deformation resistance. The joint stiffness of tooth profile meshing fishplates can reach more than 95% of the rail base material stiffness, which can realize continuous load transmission without obvious stiffness mutation when the train passes; the joint stiffness of flat fishplates is only 70%-80% of the base material, which is easy to form a stiffness breakpoint and cause wheel-rail impact. The mechanical bite force of the tooth profile meshing structure increases the load transmission efficiency by 20%-30%, makes the stress distribution more uniform, and avoids stress concentration at the joint; flat fishplates mainly rely on bolt preload to transmit loads, and stress is easy to concentrate around the bolt holes. In terms of deformation resistance, the longitudinal deformation resistance of tooth profile meshing fishplates is 40% higher than that of flat fishplates, which can effectively inhibit the expansion and contraction deformation of rail joints, especially suitable for areas with drastic temperature changes.
What are the adaptation requirements of tooth profile meshing fishplates for different rail models?
The adaptation requirements of tooth profile meshing fishplates for different rail models are core to matching rail cross-sectional dimensions and stiffness characteristics. For 50kg/m national standard rails with relatively low cross-sectional stiffness, the adapted fishplate should have a tooth height of 3mm, a tooth pitch of 10mm and a tooth angle of 60° to avoid damage to the rail contact surface due to overly deep meshing teeth. For 60kg/m national standard heavy-haul rails, it is necessary to improve the bearing capacity of the meshing teeth; the tooth height is 4mm, the tooth pitch is 12mm, and high-strength alloy steel is used to ensure that the joint stiffness matches the heavy-haul rails. For EU EN54E1 foreign standard rails, whose cross-sectional profile is different from that of national standard rails, it is necessary to customize special tooth profiles with a tooth angle adjusted to 55° and a tooth pitch of 14mm to fit the contact surface profile of foreign standard rails. For North American AAR136RE rails, due to the large axle load, a double-tooth profile meshing design is required to further improve the impact resistance of the joint.
What are the key processing technology points of tooth profile meshing fishplates?
The key processing technology points of tooth profile meshing fishplates are concentrated in two links: tooth profile processing accuracy and surface treatment, which directly affect the meshing effect. The tooth profile is processed by CNC milling, and the accuracy of the milling cutter must reach ±0.02mm to ensure that the deviation of tooth angle, tooth height and tooth pitch is controlled within ±0.1mm, avoiding insufficient meshing due to tooth profile deviation. After milling, the tooth surface must be quenched at a temperature of 820-850℃ and tempered at 350-400℃, so that the tooth surface hardness reaches HRC55-60 to improve the wear resistance of the tooth surface. The surface treatment adopts phosphating, and the thickness of the phosphating film is controlled at 5-8μm to enhance the friction force of the tooth surface and prevent slip on the meshing surface. After processing, a meshing test should be carried out to test-install the fishplate with the rail, and the contact area of the meshing surface must be ≥90% to ensure the uniformity of load transmission.
What are the on-site installation precautions for tooth profile meshing fishplates?
The on-site installation of tooth profile meshing fishplates needs to focus on meshing surface cleaning and bolt tightening sequence to ensure joint stiffness matching. Before installation, it is necessary to thoroughly clean the rust, oil stains and debris on the contact surfaces of the fishplate and the rail; it can be polished with a steel wire brush and then purged with a high-pressure air gun to ensure no foreign matter on the meshing surface and avoid affecting the meshing effect. Bolt tightening must follow the symmetrical tightening sequence from the middle to both ends: first tighten the 2 middle bolts, then tighten the bolts at both ends in turn to ensure that the fishplate and the rail are evenly fitted. The tightening torque should be adjusted according to the rail model; the tightening torque for 50kg/m rails is 250-300N·m, and for 60kg/m rails is 350-400N·m. Excessive torque is easy to cause tooth surface damage, while insufficient torque results in loose meshing. After installation, the joint stiffness should be tested with a dynamic stiffness tester to ensure that the deviation between the joint dynamic stiffness and the base material is ≤5%. In addition, the wear of the meshing surface should be inspected regularly with an inspection cycle of 6 months, and the fishplate should be replaced in time if the tooth surface is severely worn.