Research On Magnetic Flux Leakage(MFL)Detection Technology For High-Speed Railway Track Defects

The structural performance and service condition of rail are very important to ensure the safety of train operation.With the increase of the train running speed and running density,the collapse of the top surface of the train track and the cracks,holes,strips and blocks at the top and bottom of the track and the waist of the train track have become important factors to endanger the train running safety.On the one hand,they increase the cost and risk of train operation,on the other hand,they may cause irreparable loss to personal safety.At present,the detection method of track defects is night manual trolley detection,which is inefficient and cannot detect enough miles within the specified time.In view of the above problems,this paper analyzes the magnetic circuit of magnetic leakage detection,COMSOL multi-physical field electromagnetic excitation and permanent magnet excitation simulation analysis models were established respectively to study the influence of characteristics of different orbital defects and ejection value on MFL signal.Analyze magnetic flux leakage signal of orbit under wheel excitation,compare and analyze the traditional excitation simulation and wheel excitation simulation,research feasibility of conventional excitation simulation and wheel excitation simulation detecting track defects.Using the existing laboratory orbital design an experimental platform for magnetic flux leakage(MFL)detection,euipped with hall sensor for track defect detection experiment.Arrange sensors at the top,waist and bottom of the rail respectively to detect the defect signal.Compare the simulation data with the experimental data to verify the accuracy of electromagnetic excitation and permanent magnet excitation.The results show that: the electromagnetic excitation magnetic circuit structure and the permanent magnet excitation magnetic circuit structure,Adjusting the parameters of electromagnetic excitation can achieve the corresponding effect with the permanent magnet excitation at the same size of magnetic circuit geometry.The trend of different stripping values,widths and depths is consistent with the theoretical results in different excitation simulations.The wheel excitation can realize the excitation of the rail top,the rail waist and the rail bottom.The sensor at the top and bottom of the rail is verified by experiments are able to detect defects near the defect location,but could not defect location at a distance of 60 mm.Sensor located at the rail waist and 80 mm from the rail top can detect defects located in the positions of rail top,rail waist and rail bottom.Magnetic flux leakage signals range from 1 to 10 mT.