Railway Track & Structures - October 2007 - (Page 22)

TTCI R&D Figure 2, top, shows the legend for the user interface and screenshot showing indication of a defect corresponding to a transverse defect under shelling. Figure 3 is a screenshot showing indication of defect corresponding to a vertical split head. cent for the web and eight percent for the base. The configuration is currently being integrated to achieve 100 percent inspection of the head and web along with 88 percent of the base, providing an overall rail characterization of 96 percent of the rail section. Figure 1 illustrates areas of the rail covered by current and integrated configurations. Rail inspection conducted using the U-Rail system is fully automated: acqui22 Railway Track & Structures October 2007 sition storage and processing of ultrasonic waveforms is managed by software that provides detection and location of defects. Signal pre-processing algorithms perform identification, tracking and analysis of the ultrasonic components contained in the acquired signals. Laser-based ultrasonic inspection over the RDTF on selected flaws provided positive results. Figures 2 through 6 are screenshots of the user interface (UI) from different runs on various sections of track with specific defects. The user interface shows, on the right side, amplitudes of longitudinal and surface waves on the first and second rows, respectively, for each channel. On the left, the UI provides results of postprocessed data. Each column corresponds to a single acquisition, for all transducers, related to the progressive distance in feet from the start point and the GPS coordinates. Repeated runs over the same track section gave the same UI pattern over the same defect. The prototype software provides several UI displays ranging from the rail profile measurement, ultrasonic waveforms and the data acquisition display showing defect density. Figure 2 shows a screenshot of an indication representative of a TD under shelled rail along with a legend identifying what is being displayed on the UI. Figure 3 shows another screen shot of the UI that represents a vertical split head. Ultrasonic waveforms acquired from the railhead show longitudinal and surface waves, generated simultaneously by a single laser pulse. When an internal or surface flaw is present, the longitudinal or surface waves, respectively, are attenuated. Figure 4 shows ultrasonic waveforms, from the same run during head inspection, acquired at different track locations: Figure 4a on a defect-free area and Figure 4b on a transverse defect. Both longitudinal and surface waves are attenuated, due to the presence of both a TD and shelling (surface damage). During rail base inspection, two direct surface waves propagate along the rail base in opposite directions from the generation point. A flaw in the rail modifies the signals, as one transducer detects the attenuated wave transmitted through the flaw (Figure 5a) and the other detects the reflected waves created at the flaw (Figure 5b). When monitoring the web, bulk waves propagate through the web up to the railhead, where they are detected by the air coupled transducer. If a flaw is present, it will be detected along the wave path causing an attenuation of the ultrasonic signal, as Figure 6 shows. The U-rail system has been through www.rtands.com http://www.aar.com http://www.rtands.com

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Railway Track & Structures - October 2007 Contents On Track Industry Today Supplier News AREMA News NRC News TTCI R&D Crossties by the Billions Provide Essentials for Full Support Modern Tools Manage Risk M/W Challenges: Better Management of Thermal Forces in CWR TTCI Celebrates 25 Years as Facility, 10 as Part of AAR Products and Literature People Calendar Sales Representatives Website Directory Advertisers Index Professional Directory Classified Advertising Chicago Perspective

Railway Track & Structures - October 2007

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