Load-Adaptive Design of Track Fastening Systems
What are the core design requirements of the fastening system for high-speed lines?
The primary requirement of the fastening system for high-speed lines is high fastening stability, which needs to control the lateral displacement of the rail within 0.3mm to avoid aggravated wheel-rail impact. The elastic modulus of its fasteners needs to be accurately matched to ensure the track smoothness when the train passes at high speed and reduce the hazards caused by vibration. The components of the fastening system need to have excellent fatigue resistance, be able to withstand high-frequency dynamic loads, and extend the service cycle. The installation accuracy of the system is extremely high, and the deviation of the bolt tightening torque needs to be controlled within ±5N·m to ensure uniform stress on all components. At the same time, the fastening system also needs to have good insulation to adapt to the electrification needs of high-speed lines.
Why is it necessary to strengthen the anti-loosening performance of the fastening system for heavy-haul lines?
The train axle load of heavy-haul lines is large, which will bring continuous and huge static and dynamic loads to the fastening system, and it is easy to cause loosening of bolts and other components. Once the fastening components are loose, the rail will displace, which will lead to deviations in track geometric dimensions and affect driving safety. Strengthening the anti-loosening performance can make the fastening system maintain a stable clamping force under long-term heavy loads and avoid the loosening of the connection between the rail and the sleeper. The anti-loosening design can also reduce the repeated stress changes of components, reduce the risk of fatigue fracture, and ensure the long-term reliable operation of the line. In addition, the fastening system with excellent anti-loosening performance can reduce the frequency of operation and maintenance and lower the maintenance cost of the line.
What are the key points of vibration reduction design for urban rail fastening systems?
The urban rail fastening system will integrate vibration reduction cushions, and the damping factor of the cushions needs to reach more than 0.3 to effectively absorb the vibration generated by train start and stop. The elastic elements of its fasteners will use high-elastic rubber materials, which can not only provide sufficient clamping force but also buffer the transmission of vibration. The component layout of the fastening system will be optimized to reduce the stress concentration points generated by vibration and improve the overall vibration reduction effect. The system will match the small curve radius working condition of urban rail, and ensure the lateral restraint capacity of the rail while reducing vibration. In addition, the vibration reduction components need to have aging resistance to adapt to the high-density operation environment of urban rail.
How to match the fastening systems corresponding to different rail types?
Light rail lines are mostly equipped with light-duty fastening systems, whose components are small in size and moderate in tightening torque, adapting to the low-load requirements of light rail. Heavy rail lines need to adopt heavy-duty fastening systems, and the bolt strength grade is not lower than 10.9, which can withstand greater wheel-rail forces. The fastening system of crane rails will add auxiliary reinforcement components, such as special pressure plates, to ensure the track stability when lifting equipment is running. The fastening system of special-shaped rails will customize special fasteners to ensure the fit with the rail type and avoid stress concentration. The fastening system of seamless lines will adopt anti-creeper fasteners to suppress the temperature stress displacement of the rail and ensure the line integrity.
How does the anti-corrosion design of the fastening system adapt to different environments?
The components of the fastening system in coastal salt spray areas will adopt hot-dip galvanizing plus passivation treatment, and the coating thickness is not less than 85μm to isolate the corrosion of salt spray. The fastening system in alpine regions will select components made of low-temperature resistant materials, and its anti-corrosion coating must be able to withstand the low temperature of -40℃ without brittle cracking and falling off. The fastening system in desert areas will add dust-proof and sealed structures to prevent sand and dust from entering the component gaps and causing corrosion and wear. The fastening system in electrified sections will use insulating anti-corrosion coatings to ensure electrical insulation performance while preventing corrosion. The fastening system in ordinary inland areas can adopt conventional galvanizing treatment to meet the basic anti-corrosion needs.