MxV Rail worked in conjunction with Canada-based Athena Industrial Services, Ltd. (Athena) to introduce in-motion electromagnetic field imaging (EMFI) technology as a means of detecting and characterizing rolling contact fatigue (RCF) in rails. A technology originally developed for mapping corrosion and determining stress corrosion cracking in pipelines for the oil and gas industry, EMFI has been repurposed for RCF detection and characterization under the Association of American Railroads’ (AAR) Strategic Research Initiatives (SRI) program.

As a non-contact NDE method, EMFI uses an exciter core and coil to generate a focused electromagnetic field (EMF) in the rail head. A total energy sensor is used to measure the exact strength of the field emitted by the exciter coil assembly. The sensor also uses a series of antennas (receivers) precisely placed around the periphery of the excitation field to create a full three-dimensional (3D) map of the EMF shape changes. The changes in the local magnetic field strength of the back EMF generated by the surface eddy currents are measured by these antennas. In turn, the antenna coils produce a sine wave-like signal that is proportional to the position of the average magnetic field passing through each sensor element. The change in signal level is proportional to the depth of the encountered cracks, i.e., the deeper the crack, the larger the shift or deviation from the undisturbed field, thereby allowing the depth of the crack to be quantified. Outside literature describes the details of the technology.

Read the full article at rtands.com.