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Local Damage Detection for Railroad Track NDE using Multi-channel MFL Sensor



In railway maintenance, the damage detection for local defects on railway at early stage is very important. Because, damages generated in a railway track have characteristics to grow fast and damages can cause mass disaster like derailment. In this study, a magnetic flux leakage (MFL) method which is suitable for the continuum ferromagnetic structure and verified by the previous studies was applied for the railroad inspection. To verify the feasibility of the proposed technique, a multi-channel MFL sensor head that minimized the lift-off was fabricated using Hall sensors and permanent magnets to adapt to the railroad. And a series of experimental studies including a field test were carried out. Test specimens with artificial defects on the surface were manufactured, and scanned by using the MFL sensor head to measure the magnetic flux density of the railroad specimen. Resolution of Measured magnetic flux signal was improved through the signal processing. Then MFL signals were analyzed for objective damage detection by comparing with threshold value. In the experimental result, MFL based method can detect successfully the local damages in high speed condition in field. Through the further research, it is expected that MFL based NDE technique can be applied effectively for detecting local damages of railway tracks by convergence of the suitable transportation equipment and IT technology.

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