Analysis Method And Application Of High-Speed Railway Ballastless Track Bed Fulcrum Reaction Force Under Multi-Factor Action

With the rapid development of railway in our country,the mileage of high-speed railway has far exceeded that of other countries in the world,the track fulcrum is an important structure for the downward transmission of train load,and its stress state directly reflects the running quality and even the safety of the train.Based on the analysis and research of the reaction force of the high-speed railway ballastless track bed Fulcrum,the field test of the reaction force of the fulcrum is carried out,this paper summarizes the problems of the existing test methods and puts forward a method based on the strain measurement of the iron backing plate and the monitoring of the fulcrum reaction force,the state representation of railway fulcrum reaction under the influence of train vertical load and temperature gradient is analyzed by establishing a finite element model.The main research contents and achievements of this paper are as follows:(1)Analyzing the mechanical characteristics of two kinds of elastic fasteners commonly used in our country’s high-speed railway,calculating the design parameters of fasteners,the mechanical properties of fasteners with iron backing plate as rigid body and elastic body were analyzed and compared by using finite element model.The embedded fiber Bragg grating sensor was used to install the sleeper,and the thin film pressure sensor was used to make the force-measuring pad for the fulcrum reaction test.The test results show that the fiber Bragg grating sensor embedded in sleeper has good response to train load,but its response value is relatively small and the pre-embedding workload is large The self-made force-measuring pad with thin film pressure sensor has obvious response characteristics to train load,but there are some problems such as low survival rate and poor durability of the sensor after installation.(2)Based on the problems existing in the field test and the deformation analysis of the iron backing plate in the design and calculation of fasteners,a kind of fiber Bragg grating sensor based on chip is proposed in this paper,based on the method of measuring fulcrum reaction force by the strain of iron backing plate,relevant indoor and in-situ tests were designed and carried out.The results show that the strain produced by the steel plate of VOSSLOH 300 fastener and WJ-8 fastener under the action of vertical force has good stability,there is a good linear relationship between the load and the strain of the iron backing plate within 45 k N,and there is an obvious nonlinear trend in the 45 ～ 80 k N stage.In order to investigate the nonlinear characteristics of mechanical properties of fasteners,the compression of fasteners,the static stiffness of elastic pads under different loads and the parameters of buckle pressure loss were measured,the results show that the static stiffness of the elastic pad is different under different loads,so the stiffness of the fastener is different under different loads.The obvious wave crests can be seen on the strain curve of the iron cushion plate when the dead weight of the Zhuan K2 bogie is loaded in the campus test,and the strain increment is calculated and compared with the data of the indoor test,the feasibility of measuring fulcrum reaction force based on iron pad is proved.(3)The finite element model is established to analyze the strain characteristics of the iron cushion plate under the action of moving load and temperature gradient,and the feature of the fulcrum reaction force under the action of different factors is analyzed through the strain of the iron cushion plate.The results show that the initial strain of the iron plate has different magnitude under the action of different temperature gradient loads,because the rail will produce flexure deformation under the action of temperature force,with the increase of the temperature,the initial deformation of the plate is also increasing.The lateral strain of the plate is better than the longitudinal strain,and the longitudinal strain is more sensitive to the vertical load of the train.(4)The suggestion of the fulcrum reaction monitoring based on the iron backing plate is put forward: the fiber Bragg grating sensor should be installed vertically and horizontally,and the iron backing plate should be calibrated before the start of the test.