Do you know the application of polyamide (PA) composites in rail transit?
Rail transit refers to the use of rail trains for personnel transportation, including passenger lines, high-speed railways, urban rail transit, etc., with large capacity, fast speed, safety, punctuality, environmental protection, energy saving and land saving and other characteristics, is considered to be the fundamental way to solve the traffic problems within and between cities in the future.
Polyamide, commonly known as nylon, has good mechanical properties, electrical properties, heat resistance and toughness, excellent oil resistance, wear resistance, self-lubrication, chemical resistance and molding processability. Polyamide composite materials used in rail transit systems can effectively solve problems such as locomotive jitter and noise, ensure stable gauge, reduce maintenance times, and have excellent vibration resistance, which is essential to ensure the smooth operation of high-speed railway locomotives. Polyamide composites are widely used in rail transit.
1. Application of polyamide composite materials in railway engineering projects
High-speed railways require their track structures to have high rigidity, stability and suitable elasticity, so as to achieve high quality and low maintenance. Therefore, higher requirements are put forward for polymer material components in orbital structures. The development of the plastics industry and the progress of modification technology have further improved the variety, quantity and properties of engineering plastics and modified materials, especially the application of reinforced toughened modified polyamide composites in railway engineering is also more and more extensive.
1.1 Application fasteners in rail
Fastener systems are intermediate connecting parts connecting rails and sleepers. Its role is to fix the rail to the sleeper, maintain the gauge and prevent the longitudinal and lateral movement of the rail relative to the sleeper. On the track of concrete sleepers, the fasteners also need to provide sufficient elasticity due to the poor elasticity of concrete sleepers. Therefore, fasteners must have sufficient strength, durability and a certain elasticity, and effectively maintain a reliable connection between the rail and the sleeper. In addition, the fastener system is required to have few parts, simple installation and easy disassembly. Polyamide composite materials are wear-resistant, aging resistant, have good elasticity, high strength and good flexibility, which can meet the above requirements.
1.2 Application in railway turnouts
A turnout is a line connection device that enables rolling stock to be transferred from one strand to another; It is an important component on railway lines. Its normal operation is the basic guarantee of driving safety. With the development of China’s railway construction, railway subgrade has also continuously applied new technologies, new materials and new processes. Reducing the conversion force of turnouts and improving the operational reliability of turnouts has always been the goal of domestic and foreign railway departments. Polyamide composite material has excellent oil resistance, wear resistance, self-lubrication and good mechanical properties, so that it has achieved good results in turnouts.
2. Application of polyamide composite materials in railway vehicles
With the development of China’s high-speed railway trains in the direction of high speed, safety and lightweight, in order to meet the requirements of high-speed train operation, trains must have small weight, good performance, simple structure and good corrosion resistance. Polymer composite materials are widely used in railway vehicles, and the materials and manufacturing processes for trains have been greatly improved.
2.1 Rolling bearing cages
The wheels of passenger cars have high bearing requirements, which need to ensure the reliability and safety of the train at high speed, but also easy maintenance, so the rolling bearing cage plays a very important role. Polyamide composite materials have the characteristics of high elasticity, self-lubrication, wear resistance, impact resistance, corrosion resistance, easy processing and light weight, which can achieve the performance required by bearings, and play a key role in railway transportation safety, high speed and heavy load. This bearing cage uses glass fiber reinforced and graphite or molybdenum disulfide as lubricant, which has low density and light weight. This kind of cage has been widely used abroad, such as Sweden’s SKF company on passenger car bearings and locomotive traction motor bearings using 25% glass fiber reinforced PA66 composite material to make bearing cages. Cylindrical bearing cages for suburban transport vehicles and mainline vehicles in Germany have been tested millions of times. Russia has been installing nylon cages on truck bearings since 1986. This kind of nylon cage has excellent characteristics in temperature rise, wear and grease affinity, etc., which has significant characteristics for improving bearing load capacity and life, especially lubrication to delay bearing accidents and ensure driving safety. China’s Dalian Diesel Locomotive Research Institute and Dalian Plastics Research Institute carried out the research of glass fiber reinforced nylon plastic cage, and successfully passed the simulated high-speed test of more than 200,000 kilometers on the bearing test bench.
2.2 Bogie core disc wear disc
The bogie is one of the most important components in the train structure, playing an important role in supporting the car body and ensuring the safe operation of the vehicle. The core disc wear disc is one of the key accessories of the bogie, which is installed in the middle of the bogie pillow of the truck, and supports the entire body together with the side load. American railroads used nylon guide frame linings on bogies as early as the 60s of the last century, and expanded the application to pillow wear plates. Bogies are subjected to overload loads, requiring materials with high strength, flexibility and durability. MBT USA uses UHM-WPE material to make bogie side bearings to meet these requirements, and uses nylon as side bearing wear plates on light rail railways. Nylon side bearings and guide frame linings are used on GSI type bogies for heavy rail railways. The Chicago and Northwest Railroad used nylon for the wear pads on guide frame templates and tie rod devices, and nylon wear plates for GPSO locomotive bogies. In order to solve the wear between the upper and lower core discs, buffer the kinetic energy of the vehicle, and extend the service life of related components, self-lubricating materials are usually used as wear parts to reduce wear, which are applied to rolling stock. Polymer materials such as glass fiber reinforced toughened nylon, oil-containing cast nylon and ultra-high relative molecular weight polyethylene are used on the rolling stock to replace metal wear parts to make vehicle core plate liners. Polyamide and other modified materials have good wear resistance and self-lubrication, enabling safe operation with little or no oil. German trucks generally use PA6 to make the heart disc liner, the United States mostly uses ultra-high relative molecular weight polyethylene, and China uses toughened PA66 as the heart disc liner.
3. Application of polyamide composite materials in railway electrical systems
Railway communication signals are the nerve centers of the entire railway transportation system. Track circuits are an important part of the remote operation of automatic control of railway signaling equipment. Polyamide composite materials can be applied to track circuits that transmit higher frequency information, ensure smooth communication signals, reduce driving failures and improve driving safety.
3.1 Rail insulation equipment
Rail insulation is one of the basic components of a track circuit. In addition to ensuring the normal operation of the track circuit, the track insulation should not reduce the mechanical strength at the rail joint. This requires rail insulation materials with good insulation properties and high compressive strength. Due to the adverse effects of climate and environment and the continuous action of alternating loads of train operation, rail insulation is easily damaged. It is the weakest link in the rail. The materials of track insulation adopt PA6, PA66, PA1010, MC nylon, etc., and the main products are grooved insulation, insulated pipe gaskets, insulating gaskets, rail end insulation, etc. Track insulation technology and insulation materials have become the key to the development of track circuit equipment technology.
3.2 Insulated gauge rods
Railway rail insulated gauge rod is a device used to maintain rail distance and reinforce lines in railway track circuit sections. The use of glass fiber reinforced PA66 as insulator, and metal tie rod and other components to form an insulated gauge rod, which can not only meet the requirements of mechanical strength of tie rod, but also have good insulation, to ensure the normal operation of the track circuit.
4. Other applications of polyamide composite materials in rail transit
At present, China is in a prosperous period of rail transit development. With the rapid development of urban light rail, subway, intercity railway system in China, as well as the replacement and renewal of railway system parts, a large number of polyamide composite materials are also required.
5.Conclusion
With the development of railways in the direction of high speed, safety and lightweight, polymer materials play an increasingly important role and have become the third largest material after steel and stone. Rail transit systems will become an important field for the development of modified plastics in the future, and high-performance polyamide composites have become the most promising application products. We should seize this opportunity to accelerate the pace of in-depth research and industrialization of composite material manufacturing technology with independent intellectual property rights. Strive to improve the application level of composite materials in rail transit to promote the development of China’s rail transit.
Post time: Dec-13-2022