Railway Track & Structures - October 2008 - (Page 21)

TTCI R&D Development and evaluation of improved rail welding and weld treatment methods TTCI examines improvements to rail welding technologies in order to extend service life. ncreasing capacity continues to be a major focus of the railroads as they seek to meet industry demand. Often, increasing the capacity of any given rail line can mean increasing both traffic and car loads that are run on that line, resulting in increased wear and degradation of track components. Rail field welds, in particular, are affected by wheel loads and can experience shortened life. As part of the Association of American Railroads’ Strategic Research Initiatives Program, Transportation Technology Center, Inc., is investigating improved rail welding technologies in three distinct areas: • Assessment of weld treatment I methods that may improve the performance of existing thermite welds. • Evaluation of new and improved rail welding technologies as they are introduced by various rail weld vendors. • Development of alternative rail welding processes that can complement existing field weld processes. Figure 1 shows the application of UIT, a highfrequency, post-weld vibration peening treatment, to a thermite weld. Vibration-based weld treatments Weld treatment research conducted by TTCI is focused on improving thermite weld performance through two different vibration-based treatments. The first method uses a low-frequency vibration applied to the rail adjacent to a thermite weld during the welding process. The second uses a high-frequency, post-weld impact treatment that is applied directly to the weld-to-rail geometry transition. In the first treatment, a low-frequency vibration, under 100 Hz, is applied to the railhead by a mechanical shaker about three feet away from where the thermite weld is being made. The vibration reduces porosity at critical locations by increasing internal weld pool motion, which aids in dislodging gross fusion line porosity. Vibration is initiated immediately before weld preheating and is maintained throughout the weld process. During TTCI’s research, several vibration-treated thermite welds were produced for laboratory analysis. The treated welds were sectioned and examined for any change in the microstructure and for any effect of the treatment on porosity. Results indicated that the vibration had little effect on interdendritic porosity, but it may have been somewhat successful in reducing the amount of gross porosity by Daniel Gutscher, senior engineer, TTCI Railway Track & Structures October 2008 21 www.rtands.com http://www.aar.com http://www.rtands.com

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Railway Track & Structures - October 2008 Contents On Track Industry Today Supplier News AREMA News NRC News TTCI R&D Railroads Building Solid Foundation for More Capacity with Crossties Safety in High Density Areas M/W Challenges: CN Places New Bridge in Only Six Hours Products and Literature People Calendar Website Directory Advertisers Index Sales Representatives Professional Directory Classified Advertising Chicago Perspective

Railway Track & Structures - October 2008

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