Research On Identification Of Out-of-Round Wheels Based On Wayside Monitoring

In Railway Industry,impact force induced by Out-of-Round(OOR)wheels will reduce passenger comfort,decrease service life of both vehicle and track structures,increase the cost of maintenance.Recently in China,railway wheels are inspected at workshops in their short and long periodic phases which is a time-consuming processing with low efficiency and high costs.The purpose of this research was to develop wayside monitoring method to identify OOR wheels,which will increase the measurement efficiency,evaluate wheel condition in-service monitoring,then the costs of maintenance will be decreased significantly.Wheel condition can be identified by wheel-rail vertical contact force.The research idea of this paper is to firstly study the measurement method of wheel and rail vertical force based on track dynamic response,and then evaluate whether the wheel is out of round according to the characteristics of wheel-rail force of typical out-of-circle wheel.For analyzing the characteristics of vertical wheel-rail force induced by OOR wheels,a fine FEM model of vehicle-track was developed in which wheel and rail was meshed by solid element.By using this model,the characteristics of typical OOR wheels are analyzed.Wheel flat can produce periodic impact load.High frequency transient impact load with frequency range between 400-600 Hz was induced when wheel flat contact to the rail.According the statistics of wheel rail force signal,Kurtosis value can be used in recognize the impact signal.Polygon wheel will produce sinusoidal wheel-rail force when running on rail,the main frequency is depended on train speed and the order number of polygon wheel.When train speed is between 200km/h to 300km/h,the peak value of wheel-rail force did not increase significantly with the increase of speed,while the peak value of wheel-rail force increased significantly with the increase of speed of high-order polygon wheels.Two method were proposed to measure vertical wheel rail force: Model Based Estimate Method(MBEB)and Calibration Curve Method(CCM).The principle of wheel-rail Calibration Curve Method is to acquire the transfer relationship between wheel-rail force and track dynamic response by calibration.The fine FEM Vehicletrack model was used to analyze the distribution of strain on neutral axis of rail.A novel wheelrail measurement method was proposed based on the FEM analyze results.For one span of rail,the largest output shear strain was located on 100-200 mm both sides which is the best measurement points.All measurement points' strain signal output splicing triangle potter were introduced after the levy of the calibration curve by simulation analysis compared the inversion and actual wheel/rail force,wheel/rail force proves the feasibility and accuracy of this method.To verify the feasibility of the calibration curve method,a series of low speed field tests were conducted on the track test line.Test results show that the calibration curve method can identify wheel/rail vertical force,but because of the error between calibration curve and the actual strain curve,periodic calibration error was found in wheel rail force signal.The frequency of the error is associated with speed.Calibration error on the wheel/rail force has little effect on the wheel/rail force with low speed.In frequency domain,wheel-rail force reaches the peak at about 100 Hz which is the first natural frequency of track vertical vibration.The model-based wheel-rail force identification method is to use the track dynamics calculation model to derive the dynamic transfer relationship between the dynamic response on the track structure measurement point and the vertical wheel-rail force,establish the dynamic transfer equation,and obtain the estimated value of wheel-rail force by solving the equation.The dynamic transfer equation from wheel rail force to wheel vertical displacement were deduced based on single beam model,the same process was used on the rail base strain and rail shear strain.The equation can be solved by L-curve method,then the wheel-rail force time history was acquired.Testing error and parameter estimation error was analyzed,the result shows that L-curve method can well restrain test error.For single beam model of track stiffness error produces estimates of wheel/rail force,between the approximate linear relationship.Test equipment was developed for tie-ballast interface pressure measurement.The equipment was used on heavy haul railway line of the Unit States;lots of field test data was acquired.According to the comparison between WILD data and ballast pressure testing data,the relationship between ballast pressure and wheel load was established.A wheel-rail force estimated method was developed based on double layer beam model.The wheel-rail force of heavy haul line was obtained by using this method to analyze ballast pressure data.When the kurtosis value of the time history of wheel and rail force is greater than 5,the impact effect can be clearly identified in the time history curve.The position and number of flat scar can be analyzed by polar coordinate diagram.