Detection And Analysis Of Rail Temperature Force And Rail Vibration State Of High Speed Railway

As one of the most important component in the track structure,the rail has the capability of guiding the train moving forward as well as supporting the whole train to transmit the dynamic load to the ground.Therefore,the condition of the rail has a heavy impact on the safety and stability of the train operation.Over the last decades,seamless rails have been widely used in the high-speed railways.This type of railway can hardly expand because of the constraint form the fasten system.However,this constraint system could also result in a large temperature force inside the rail when the railway experiences a large environment temperature fluctuation.Besides,when the railway is under operation,the interaction between the train and the rail will also induce an intense vibration on the railway,and interestingly,this vibration in turn can reflect the stiffness and load condition of the railway structure.In this thesis,it is aimed to investigate the combined effect of the rail longitudinal strain distribution and the vibration characteristics from the train-rail coupling in a ballastless railway system.All these train-track-temperature coupling dynamic analysis provide a solid foundation for the real-time on-line detection of the track internal temperature force and vibration variations.The main contents in this dissertation can be classified into the following aspects:(1)The longitudinal strain and vibration characteristics of the rail under the influence of the environmental temperature has been studied and a scaled railway experimental platform has been built to validate the theoretical results.Initially,the relationship between the railway temperature and longitudinal strain has been investigated and the experimental research method of rail temperature and longitudinal strain has been established.After that,the longitudinal strain distribution of Ballastless rail under the influence of the environment temperature has been studied based on the numerical model and the relationship between the environment temperature and longitudinal strain distribution can be obtained In particular,the influence of vertical inertia force and moment of inertia in bending direction has been considered and the calculation model of rail vibration under temperature can be established using the Timshenko beam.In the end,the scaled railway experimental platform,which includes rails,fasteners,sensors,load-exerting devices,etc,has been established.It can simulate rail temperature change,fastener loosening,rail fracture,and the measurement of longitudinal strain and dynamic characteristics of rails under the influence of temperature force can also be realized.(2)The distributions of rail acceleration and dynamic strain under the impact of the train has been analyzed.A train-track coupling dynamic simulation model has been used to this coupling phenomenal and the rail vibration variation during the operation has been studied.The distributions of rail acceleration and dynamic strain on the outer side of the rail has been chosen.The effectiveness of choosing this location has been tested and simulated via the established experimental platform and this analysis provides a basis for the installation and layout of rail detection sensors.(3)A variational modal decomposition parameter optimization method has been established to analyze the non-stationary vibration signal of rail under the train-rail interaction.The rail vibration signal has been obtained by testing at the National Railway Experimental Center.After wavelet denoising,these signals have been decomposed into variational modes and the marginal spectrum can be calculated correspondingly.The influence of train speed on the vibration characteristics of rail has also been studied.The results show that the locomotive speed can affect the vibration energy in the high frequency band.More details,it has been found that the higher the train speed,the higher the rail vibration amplitude and the frequency around 2000 Hz has been found to be impacted most while frequencies in the lower band have found to be minimum.(4)The information entropy method has been used as a diagnostic tool for judging the failure of loose fastener.The acceleration of rail under different fastener locking forces has been studied on the experimental platform and the fastener different conditions has then been investigated based on the information entropy method.The results show that the entropy value will increase with the deterioration of the fastener locking force and in addition,the acceleration entropy value will decrease when the temperature force increases.