Research On High-speed Rail Defect Inspection Based On Eddy Current Testing

With the rapid development of railway industry,the security requirement for rail operation is becoming increasingly strict.The rail defect detection tends to be a research focus.Because of the long route and short interval,the traditional manual inspection method is too time-consuming and easy to miss.Therefore,the on-line rail defect detection system based on non-destructive testing(NDT)technology came into being.Although the commonly used ultrasonic testing(UT)method can cover the whole track,it doesn’t perform well on the detection of buried defects and surface defects within 5mm depth.So,the high-speed detection methods based on eddy current testing(ECT)is studied in this paper.Based on the basic theory of electromagnetics,the principles of the Electromagnetic NDT are introduced.Through the impedance and magnetic circuit analysis,the detection signal characteristics and influence factors of the Magnetic Flux leakage testing(MFL)and ECT are further learned.The frequency of the defect signal is obtained from the simulation results in Maxwell.The effects of probe parameters and excitation frequency on the performance for defect detection are studied.The high-speed rail defect inspection ECT system is built,which is then applied to the detection experiments of high-speed rail turntable and rail samples.With the further analysis of the detection results,the impact of the probe lift-off and detection speed on the defect signal is analyzed.The quantitative evaluation method of surface defects under different speeds is also studied.Considering the features of the MFL and ECT,a composite electromagnetic testing method is proposed to further realize the classification of the surface defects and buried defects.In the Maxwell software,the characteristics of the defect signals of the composite detection method are simulated and analyzed,and the influence of the probe size on the detection signals is studied.Based on the ECT system,a high-speed rail composite electromagnetic testing system is established.And the detection experiment on the high-speed rail turntable is performed with the system.The effect of speed on the MFL signal is analyzed from the experiment results,and the classification methods of surface defects and buried defects are studied.