Characterization of defects on rail surface using eddy current technique

In the present study, using eddy current technique (ECT), we explored two kinds of defects commonly found in railroad monitoring. The first one is cracks initiated on the surface of rail head which slowly progresses into vertical rail plane, the second one is squat type of defects grown on the running head surface. A reliable ECT system equipped with plus point ECT probe was developed and experiments were conducted on a 10 mm thick medium carbon steel plate with two kinds of machined defects varying on their dimensions. An optimized plus point probe was fabricated for the experimental purpose and a Lab VIEW based program was developed to interactively collect and analyze the obtained data. Predefined defects (slit, squat) with changing defect depth and length for both the cases machined on S45C medium carbon steel plate were examined. Prior to the experiments, simulation studies were conducted to fully understand the defect dimensions and optimized the experimental parameters. Response signal parameters, amplitude and phase were analyzed to characterize the defect features. The designed system shows better performance to detect the deepest defect up to 5 mm approximately, and it can be extended further with moderate signal to noise ratio. Two kinds of defects can be categorized according to the obtained signals.