Electromagnetic Thermoacoustic Technique for Online Dynamic Detection of High-Speed Rail Internal Defect at Early Stage: Theory, Implementation, and Field Trial

As time goes by, the rails of high-speed trains are subject to long-term extrusion and natural factors, and defects will gradually appear. Therefore, early detection of these defects is extremely important for the maintenance or replacement of rails. In this article, a set of rail internal crack detection system is proposed and developed, which can be easily and conveniently deployed for daily maintenance of the rails. To improve the detection speed, thermoacoustic technology is utilized and researched. For rail head internal defects, thermoacoustic induced by a coil antenna is used for detection. For rail foot internal defects and bottom corrosion, laser-induced thermoacoustic is used for detection. First, the thermoacoustic technique is analyzed and applied to rail defect detection. Next, it is used to analyze and confirm the effectiveness of the coil antenna and laser-based thermoacoustic detection technology through laboratory experiments and signals analysis. To validate the proposed system's design concept, a prototype of the detection trolley is constructed that generates thermoacoustic signals and conducts experiments accordingly. In the field trial, an intelligent processing approach is employed using a conventional method of outlier analysis, trained with specific features. The test results demonstrate the effective detection of rail internal defects by the proposed system.