MFL Sensing based NDE Technique for Defect Detection of Railroad Track
Abstract »Defects generated in a railroad track that guides the railroad vehicle have characteristics to grow fast and so the detection technology for railroad track defects is very important because defects eventually 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 was fabricated using Hall sensors and permanent magnets to adapt to the railroad. And test specimens with artificial defects that have different size on the surface were manufactured, and scanned by using the MFL sensor head to measure the magnetic flux density of the railroad specimen according to 3 levels of velocity. Resolution of Measured magnetic flux signal was improved through the signal processing, and magnetic flux leakage signals were analyzed to classify the damages of railroad. In the experimental result, MFL technique can detect the local damages successfully and they are classified according to the size of damage and the test velocity. Through the further study, it is expected that MFL based nondestructive evaluation technique can be used effectively for detecting local faults of railroad tracks by convergence of the suitable transportation equipment and IT technology.