Study On Influence Of Out-of-Round High-speed Railway Wheels On Wheel/Rail Interaction Force And Monitoring Method

The influence on dynamic response of wheel-rail system under out-of-round wheel excitation and wheel-rail force monitoring method are the topic in the thesis. Based on characteristic of wheel/rail dynamic interaction forces caused by out-of-round railway wheels, a new method based on PVDF piezoelectric sensing technology is presented for the test of vertical and horizontal wheel/rail forces. The study is very important for enhancing the stability and economy signification of rail transmission.The present situation and developing trend of the key technology related to the study of high-speed railway wheel/rail interaction force real-time monitoring method based on PVDF pieozelectric sensing technology is summarized, including the types of train-track system dynamic models, the theory of multi-body system dynamics simulation, the study methods of out-of-wheel, the testing technology of wheel/rail force, and the related piezoelectric sensing technology and its applications in railway train running safety monitoring.The main research work in the present dissertation involves:(1) On the basis of the theory of vehicle-track vertical and lateral coupling dynamics and by means of simulation software ADAMS/Rail, a three-dimensional train-track simulation model is established to study the influence on dynamic response of wheel-rail interaction forces under excitation of out-of-round wheels. The characteristics of the models are:a whole passenger car and a track are coupled in vertical and lateral; In the vehicle model, the spring damper elements are used to simulate the links between the car body and the bogie, the bogie and the wheel. Worn-tread vehicle wheels are established, and the air spring is simulated with Krettek air spring model; Track is considered as two layer continuous-point supported rail model. The rail coupling elements have a vertical and lateral translational degree of freedom related to the sleeper, which improves the efficiency under the premise of ensuring simulation accuracy; Based on Hertz contact theory and Kalker rolling contact theory, interaction and relation between wheel and rail with unroundness wheels are discussed in detail.(2) The thesis describes the characteristics of unroundness of wheel tread profile and classifies out-of-round wheels. A new method to describe out-of-round wheel profiles on high speed trains is presented. By means of vehicle-track system dynamic simulation model, the thesis systematically studies the influence on dynamic response of wheel/rail impact vibration due to flat wheels, non-circular wheels, eccentric wheels, wheel polygonaligation, etc. The variations of impact vibrations with the train running speeds are given out. The relasitonship between safety threshold of wheel unroundness and vehicle speed is set up. The view that it is of important significance to establish wheel/rail force real-time monitoring system is expanded, so that abnormal conditions caused by out-of-round wheels can be detected in time, to ensure high-speed railway traffic safety.(3) A new method based on PVDF piezoelectric sensing technology is presented for measuring wheel/rail loads. The method sticks PVDF strain sensor to rails and realizes continuous measurement of vertical and lateral wheel/rail contact forces by measuring the several places on the rail plate. First of all, the thesis analyzes the distribution rule of the rail plate strain influenced by the horizontal and vertical force, rotate speed of the wheel, and bending moment produced by the change of contact point based on the finite element analysis, combined with the characteristic of wheel/rail interaction force under excitation of out-of-roundness wheels, then the best position of stick PVDF strain patch is found through the calculation. Secondly, by means of the wheel/rail interaction characteristics, the restriction condition of track and strain sensing principle of PVDF films, theoretical model and Finite Element Model of relationship between PVDF sensor output and wheel/rail loads are set up, and principle for measuring vertical and lateral wheel/rail contact forces is proposed. Thirdly, numerical analyses by Finite Element Method and calibration test have been carried out to verify the feasibility of the method presented in this paper. Finally, a series of tests were carried out to compare the performance of PVDF strain sensors with the one of strain gauges. The results show that the PVDF strain sensor has better reliability in wheel/rail force monitoring.(4) Based on the demand of wheel/rail force monitoring, the hardware platform and the scheme of data acquisition and processing system for PVDF strain sensor is brought out. This thesis puts emphases on the software of the data acquisition and processing system. The system makes up some of the shortcomings of existing software by means of MATLAB language. The data acquisition system can take in the parameters of PVDF strain sensor, acquire the signal, display in real-time and save the data with the data acquisition toolbox of MATLAB, buffer technology and multi-threading technology of operating system. The system realizes the analysis of sensor data and signal processing based on MATLAB signal processing toolbox and MATLAB library function. The system has friendly Human-Computer Interface with MATLAB GUI. We employed Matlab Web Server technology to meet the demand of remote monitoring. The software can be transplanted in a variety of environments because of using the interface functions.