Rolling contact damage characterization using electromagnetic field imaging technology

摘要

As part of the Association of American Railroads' (AAR) Strategic Research Initiatives (SRI) Program, TTCI has continued working with Athena Industrial Services, Ltd., of Calgary, Alberta, Canada, to bring forward their electromagnetic field imaging (EMFI) technology-based, field-deployable inspection system for characterizing rolling contact damage (RCD) on the running surface of rails. Several tests of this in-motion, hi-rail-mounted system were conducted by TTCI to evaluate the technology readiness level (TRL) of EMFI technology for future deployment on North America's railroads. RCD is a result of the interaction of railway wheels with the railhead. Small cracks can appear on the running surface of the rails from the repeated contact stresses. These small cracks can ultimately grow and join up to form flakes that fall loose, leaving behind cavities in the running surface of the rail, commonly referred to as "head checks." The cracks also can turn downward to a limited depth forming a fatigue crack under the rail surface, known as "gauge corner cracking." Railroads perform rail grinding on a periodic basis to maintain rail profile and also for surface conditioning. Prior to grinding, rail inspection vehicles (RIV) equipped with rail profile measurement and vision systems are used to provide a quantitative estimate of the rail contour. In comparison, surface cracks are evaluated primarily through visual inspection by trained personnel. This process is more qualitative than quantitative but has proven effective, if not labor intensive. A drawback of the visual inspection is that accurate surface damage depth estimates are not reliably available as a means of informing the grinding effort required to remove the surface cracking. The depth of grind is often planned subjectively based on expert opinion. A system that can accurately measure crack depths would provide valuable information for planning rail grinding operations.