2 High-speed EMU axle box bearings High-speed EMU bearings include axle box bearings, gearbox bearings and traction motor bearings. This article discusses axlebox bearings that are of the highest value, reliability and safety requirements. 2.1 Types of axle box bearings There are two types of axle box bearings used in high-speed EMUs in my country: 1) SKF double row cylindrical roller bearings (Figure 3); 2) FAG, NSK, NTN double row tapered roller bearings (Figure 4) . Fig.3 Structure of double row cylindrical roller bearingFig.3 Structure of double row cylindrical roller bearingFig.4 Structure of double row tapered roller bearingFig.4 Structure of double row tapered roller bearing EMU technology source and imported bearing See Table 3 for manufacturers, and Table 3 for basic information on axlebox bearings of various types of EMUs. By 2020, the national railways will have 3,918 standard EMUs, with a total of 31,344 units. Tab.3 Technology sources of EMUs and manufacturers of imported bearings 2.2.1 Simulation analysis and digital design of bearing products Collect and compile high-speed EMU bearing load spectrum, carry out dynamic simulation analysis, product digital modeling, product overall structure optimization design and microstructure optimization design (including rolling elements and raceway convexities) degree modification, the contact state between the ball base surface of the rolling element and the rib, the hardness and roughness of each working surface match, etc.). 2.2.2 R&D and preparation of bearing steels Formulate high-speed EMU bearing steel standards, develop and prepare high-speed EMU bearing steels according to the standards, and improve the level of control over the content, size, shape, and distribution of inclusions and carbides. 2.2.3 R&D and preparation of bearing rollers R&D supports advanced manufacturing processes and digital equipment of high-precision tapered rollers and cylindrical rollers and forms production capacity. Roller roundness error, reference end face circular runout, reference end face circle R value dispersion difference, gauge value batch diameter variation, gauge value batch taper angle variation (only tapered rollers), rolling surface roughness, reference end face roughness up to Design requirements and have a large precision reserve. 2.2.4 R&D and preparation of bearing cage Establish the steady state analysis model and dynamic analysis model of the cage, establish the cage motion equation and the collision and impact vibration equation, and study the design parameters of the cage on its moment of inertia, motion trajectory, and motion stability Influence law of vibration response of resistance, impact and shock. Reasonable design parameters are determined through the above analysis to ensure the motion stability and impact resistance of the cage. Carry out research on the material application technology of engineering plastic cages from the aspects of mechanical properties, impact strength, water absorption, melting point, dimensional stability, etc.; formulate specifications and standards to guide the production, inspection, acceptance and use of engineering plastic cages, and form engineering plastics. Cage production capacity. 2.2.5 Research and development and preparation of bearing seals Research the raw rubber of seals from the aspects of tensile strength, elongation at break, hot air aging performance, hardness change rate, compression set, grease compatibility, dimensional stability, etc. The formula, rubber material manufacturing process. Research and develop and design a sealing structure with low friction torque, waterproof, dustproof and leak-proof grease, low temperature rise, and conducive to the circulation of grease the service life of the parts. Formulate specifications and standards to guide the production, inspection, acceptance and use of seals, and form the production capacity of seals. 2.2.6 Research and development and preparation of bearing grease On the basis of tribological research, study the dynamic development behavior of bearing lubrication state, oil film thickness, contact area evolution, friction and wear, and develop high-efficiency grease suitable for high-speed EMU bearings. Lubricating conditions to ensure the safe operation of bearings. Formulation of technical specifications for the production, testing and application of efficient greases. Completed the research and development of bearing lubrication condition monitoring and fault diagnosis technology. The production capacity of high-efficiency grease is formed. 2.2.7 Set up a demonstration production line for trial production of bearing samples Set up a demonstration production line to produce enough samples for inspection, testing, bench test and loading test. 2.2.8 Bearing bench test Formulate specifications for durability test, waterproof seal test, dust seal test and comprehensive performance test, and conduct corresponding performance tests. 2.2.9 Formulation of bearing product standards Vigorously promote and actively participate in the formulation of railway industry standards for bearings of high-speed EMUs. 2.2.10 Loading test and application of bearing The National Railway Group will carry out the loading test according to the test specification formulated by it, and realize the industrial application. 2.3 Market Analysis The number of high-speed EMUs produced in my country over the years is shown in Table 4.