Optimization Study Of The Dynamic Properties Of Ladder Track To Minimize The Probability Of Rail Corrugation

ABSTRACT:With the development of the economic society of our country, the processes of urbanization become faster and increase the traffic demand. Urban rail transit with large volume, rapid, on time, convenience, safe and environmental friendly has become the first choice to solve the traffic congestion of cities. At the same time, to protect the sensitive regions along with the rail traffic (such as schools, hospitals, etc.) from vibration, more and more vibration reducing measures used in subway lines. Using ladder track to minimize the subway vibration is one of the most popular vibration reducing measures. However, serious track vibration and noise incidents were observed in some ladder track subway lines, even some abnormal rail corrugation were also observed. To solve the anomalies, this thesis analysis the generation mechanism and prevention measures based on summarizing the previous studies and researches. The research contents and conclusions main include:(1) Wheelsets model (locomotive wheelset and vehicle wheelset) are developed. Vertical and torsional vibration receptance of wheelsets are carried out using the wheelsets models, and further analysize the effect of the electric machine locations and primary suspension parameters on wheelset vertical and torsional vibration receptance. The conclusions show that:(a) the effect of the electric machine locations on wheelset vertical vibration receptance is small and on wheelset torsional vibration receptance is large. The distance of electric machine and wheelset central is larger; the second order torsional resonance frequency is larger,(b) The primary suspension parameters only affect the wheelset first order vertical vibration receptance (rigid body vibration).(2) Based on the field test, rail corrugation frequency on ladder track can be obtained. Ladder track vertical vibration receptance model and wheelset-ladder track coupling model are set up, then using these models, the ladder track vibration receptance and the relationship between ladder track vibration mode and rail corrugation are carried out. The conclusions show that the third order vertical resonance of ladder track is the main reason of rail corrugation, and the third order vertical resonance of ladder track is caused by second order bending vibration of ladder sleeper.(3) Vehicle-ladder track coupling dynamic model is developed. Using this model, the ladder track main vibration characteristics with different speeds and axle loads are carried out. The conclusions show that the rail main vibration frequency cased by vehicle speed is close to the rail corrugation frequency except less than20km/h, and the effect of train axle load on rail main vibration frequency is small. So, changing the train speed (except less than20km/h) or axle load to solve the rail corrugation is not efficient.(4) Based on the ladder track vibration receptance model and vehicle-track coupling modle, the effect of fastener parameters (fastener stiffness, fastener damping and fastener interval), ladder sleeper parameters (sleeper mass and sleeper length), and resilient material parameters (resilient material stiffness, resilient material damping and resilient material interval) on ladder track vertical vibration receptance, especially, on the third order vertical resonance of ladder track, the main reason of rail corrugation, are carried out. The conclusions show that it is difficult to minimize the chance of rail corrugation only changing one structure parameter. In order to minimize the chance of rail corrugation, optimizing the comprehensive properties of ladder track is needed.(5) In order to minimize the chance of rail corrugation in operation subway lines, optimizing the4parameters of stiffness and damping of fastener and resilient material using genetic algorithms and multipoint approximation method are carried out, respectively. The conclusions show that changing the four parameters can minimize the chance of rail corrugation, and the recommended values are obtained.(6) In order to avoid the wheel/rail resonance, control the ladder track vibration and prevent the generation of rail corrugation effectively, optimizing the7parameters of stiffness, interval and damping of fastener and resilient material and sleeper length using the multipoint approximation method are carried out. The conclusions show that changing the seven parameters can minimize the chance of rail corrugation, and the recommended values of these parameters are obtained.(7) The results of optimizing the seven parameters are better than the results of optimizing the four parameters, and the results of optimizing the four parameters are better than the results of connecting ladder sleepers. So, It should be used the optimized results first in subway lines. If there are not conditions (e.g. there are not the fastners and resilient meterials with optimized parameters.), the method of connecting ladder sleepers could be used, but it should meet two conditions:?the number of connectiong ladder sleeper should be equal or greater than15.?the resilient material damping should be equal or greater than20kN·m/s.