Study On The Characteristics And Influence Of Temperature-Dependent Stiffness Of Fastener Used In Unballasted Track Of High-Speed Railway

The rubber pad of fastener system is made of polymer material, and its mechanical properties are significantly affected by temperature. In the unballasted track used in high-speed line, fastener is almost the only provider of track elasticity, and its parameters will directly affect the strength of the interaction of wheel/rail system. Therefore, it has important significance in researching the influence law of temperature on fastener elastic in unballasted track, and analyzing the influence on the interaction of wheel/rail system.Firstly, combined with the range of statistical domestic rail temperature, this paper has took the WJ-7, WJ-8 and Vossloh 300 type fastener which is commonly used in unballasted track of 250km/h and 350km/h speed line as test object, and designed an experiment which is researches the change of static stiffness of the rubber pad with temperature to analysis the variation law of fastener stiffness with temperature in the range of -60℃-70℃, the results show:(l)fastener stiffness shows stability in high temperature and sensitivity in low temperature;(2)in all the fasteners used in 250km/h unballasted track, WJ-8A type fastener shows better stability at low temperature, it is recommended to use it in extremely cold area;(3)in all the fasteners used in 350km/h unballasted track, Vossloh 300 type fastener shows better stability at low temperature, it is recommended to use it in extremely cold area.Secondly, based on the wheel/rail dynamics and power flow theory, this paper has derived the calculation formula of the power flow input of the wheel/rail system, vehicle system and track system in the process of random vibration, analyzed the size and distribution of the power flow in each system, studied the influence low of train axle load, stiffness and damping of fastener, driving speed on the power flow transfer to each system, and the results showed:(1)in the process of vertical interaction of wheel/rail system, low frequency energy is mainly transferred to the vehicle system, while the high frequency energy is transferred to the track system; (2)with the increase of train axle load and driving speed, the energy input of wheel/rail system increased in the whole frequency domain;(3)with the increase of fastener stiffness, it causes the energy input of wheel/rail system transfer to a high frequency range and the distribution of the energy in each subsystem; (4)with the increase of fastener damping, it causes the energy input of wheel/rail system transfer decreased, and the high frequency energy will transfer to the vehicle system from the track system.Thirdly, this paper has analyzed the influence of temperature-dependent stiffness of rail pads on running safety and stability, the results showed:in the range of-60℃-70℃, the safety and stability index of the train is not exceeded.Finally, based on the evaluation index of acceleration and power flow, the paper has evaluated and analyzed the influence of temperature-dependent stiffness of rail pads on broadband vibration of wheel/rail system, and compared the similarities and differences between the two kinds of indexes, the results showed:(1)in the vehicle system, with the decrease of temperature, the vertical vibration response which center frequency under 63Hz changes small, the vertical vibration response which center frequency in the range of 63Hz-250Hz increased significantly, the vertical vibration response which center frequency more than 250Hz decreased a little;(2) in the track system, with the decrease of temperature, the vertical vibration response which center frequency under 63 Hz decreased significantly, the vertical vibration response which center frequency in the range of 63Hz-160Hz increased significantly, the vertical vibration response which center frequency more than 160Hz changes small;(3) the lower the temperature, the more obvious the change of the vertical vibration response of wheel/rail system;(4) although the two indicators acceleration and power flow index shows a certain difference, which is the acceleration index reflects the magnitude of the vibration strength of the structure and the power flow index reflects the size of energy transfer to the structure, but they can get approximate evaluation results.