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Rolling Contact Damage Characterization on Railroad Rails Using Electromagnetic Field Imaging (EMFI)

This paper discusses the use of electromagnetic field imaging (EMFI) technology for rolling contact damage (RCD) characterization on railroad rails. The novelty of the research presented is on the quantification of the RCD severity and surface breaking crack depth measurement. For this, a series of tests was conducted on several 141-RE rail samples with varying types of RCD defects using an EMFI flat sensor commonly used for pipeline applications. A carriage and a sensor mount were designed to allow the sensor to scan the entire length of the railhead. The orientation of the EMFI sensor used was manually adjusted at 4 mm (0.16 in.) increments to inspect the gage face, the gage corner, and the running surface of the test rails. The scanning resolution demonstrated for this proof-of-concept study was 1 mm (0.04 in.) at 1.6 km/h (1 mph). A liftoff study was also conducted to understand the effect of an air gap on detection and characterization performance. Measurements obtained on the running surface of the rails were used for the detailed analyses. Results demonstrate the feasibility of applying the EMFI technique for RCD characterization. Also, higher liftoff values showed inconsistent responses between rail samples using flat EMFI sensors. Lower liftoff values (2 mm and below) provided consistent severity responses. Finally, destructive tests were designed to determine actual RCD depth at a specific point in the test rails. It was observed that the RCD crack depths were all around 2 mm (0.08 in.), which were consistent with the EMFI severity measurements.


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