| Rail fastener plays a very important role in the track because it is the tie that connects rail to its foundation. On high-speed railway where there is rail corrugation, fastener clips appear fracture phenomenon. Fastener clips fracture will weaken the constraint to rail which will affect driving safety. The paper focuses on the fracture of WJ-7 fastener clips under rail corrugations mainly including the following five aspects.1. The vibration analytical model for the vehicle-track coupled system at medium-high frequencies was established. Rail corrugation can excite the medium-high frequency vibration of wheel-rail system. Because the present used analytical model for the dynamics of the vehicle-track coupled system isn't suitable for the medium-high frequencies,the vibration analytical model for the vehicle-track coupled system with consideration of the vibration of wheelsets and fasteners at medium-high frequencies was established.2. The medium-high-frequency simulation model of wheelsets was established.Through the analysis on the vibration characteristics of wheelsets, two kinds of vibration model for medium-high frequencies were proposed, and the frequency range for which two models are suitable were analyzed. For analyszing the vibrations of fastenters under rail corruation, beam-plate-beam model of wheelset was suggested. Under the excitation of white noise irregularities, the effect of elastic deformation of wheelsets on the dynamic response of track system was analyzed.3. The medium-high-frequency simulation model of fasteners was established. By analyszing the simplification mode of fastener system, the fastener strip was simulated by beam element, and the iron plate was simulated by shell element. The vertical contact stiffness was provided for the connection between clip, iron plate, insulation plate and bolt.The longitudinal and transverse connection was simulated by nonlinear damping elements.The classic method and finite element method were used to analyze the contact stiffness between clip, iron plate, insulation plate and bolt. Based on the study mentioned above, the medium-high-frequency simulation model of fasteners with consideration of relative displacement between clip and connecting components as well as clip stiffness changing with frequencies was established. Finally, the dynamic characteristics of medium-high-frequency simulation model of fasteners and traditional fasteners model were compared and the influence of relative displacement between fastener clip and its contact parts on vibrations of fastener clip were analysed.4. The dynamic responses of fastener system were analyzed under the respective conditions of rail corrugation or not. The effect of rail corrugation amplitude, vehicle speed, bolt precompression and rubber plate stiffness were analyzed. The vibration analytical model for the vehicle-track coupled system at medium-high frequencies was adopted to calculate the dynamic responses of fastener system with and without rail corrugation. From the respective angle of frequency domain and time domain, the effect of rail corrugation on fastener system were analyzed. For the certain rail corrugation, the dynamic responses of fastener system for different vehicle speed were analyzed. The results show that the most unfavorable excitation frequency of WJ-7 fastener clip is about 866 Hz.5. The fatigue fracture mechanism of fastener clip under the condition of rail corrugation as well as the effect of rail corrugation amplitude, bolt precompression,vehicle speed and rubber plate stiffness on the fatigue fracture of fastener were analyzed. According to the dynamic response of fastener clip under the condition of rail corrugation, the dangerous point where the clip tends to facture crack and the loaded mode of the point were determined. The analytical method of fatigue life under the condition of multidirectional stress was adopted to calculate the fatigue life of the dangerous point of the fastener clip. The results show that the fracture of fastener clip due to rail corrugation is caused by the increase of amplitude for two major cycles. The more cycle index leads to less effect. The correction amplitude of Goodman for two major cycles under the calculated work condition with rail corrugation increases by 45.45% from that without rail corrugation. The accumulated damage of a carriage is 60 times larger than that without rail corrugation. |
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