| Transportation in China has been a rail-based, rail transport responsible for60%-70%of the total freight and50%-60%of total passenger traffic, overloaded, speed, security is thedirection of development of railway technology.With the rapid development of railway high-speed, overloaded, rail failure is becomingincreasingly serious, endangering traffic safety. Therefore, improve the performance of therail to extend the useful life has become essential. And rail full-length heat treatment, inrecent years, most of the world recognized it as the most direct and economical method ofimproving rail wear and fatigue strength.The object of this paper is the rail of U75V about60kg/m, based on the theory of heattransfer, thermal elastic-plastic theory and finite element theory, using the software ofABAQUS to construct a finite element model of the rail. First simulated the cooling processof the rail in natural air, analysised the law of temperature field and bending; Second, westudy the law of rail head spraying10s and20s; And then we use infrared thermal imagingdevices to measure rail temperature during cooling of the temperature field; Finally, wemade the experiments to verify the simulation results.Simulation results show that rail in a different cooling program, temperature-changeover time is divided into three stages: Before the solid-state phase transition, the temperaturedrop rate is faster; The second stage, temperature remained almost unchanged; The thirdstage, the temperature drop rate is more slowly. At the same time, bending deformation isdivided into three stages: The first stage, rail bend to the bottom of the rail; The second stage,rail to return to the straight state; The third stage, rail bending toward the rail head. Indifferent cooling solutions, the cooling rate is also different. Rail head spray20s is the fast,the data is0.277℃/s; then10s, the data is0.184℃/s; the slowest one is air-cool, the data is0.092℃/s. Accordingly, the deflction and stress values are respectively0.5m,0.496m and0.3m,200MPa,200MPa and150MPa. Temperature variation is consistent with the threecooling potions. The curves show a temperature bump, the stage temperature is about630℃.The thesis can provide experimental datas and theoretical basis for the online heattreatment process, it also can provide effective technical support to online heat treatmentsoftware on development and application. |
