Preliminary Results of Prototype Insulated Joint Tests at the Facility for Accelerated Service Testing [Research Results]
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Preliminary Results of Prototype Insulated Joint Tests at the Facility for Accelerated Service Testing [Research Results]

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      As part of the Association of American Railroads (AAR) Strategic Research Initiatives Program, Transportation Technology Center, Inc. (TTCI), a wholly owned subsidiary of the AAR, in Pueblo, Colorado, is working with the Federal Railroad Administration (FRA), suppliers, and railroad companies to improve the service life of bonded insulated joints (IJs) in a heavy axle load environment at the Facility for Accelerated Service Testing (FAST). Twenty-eight prototype IJs are being tested at FAST. Prototype IJs were installed in-track by TTCI to examine the extent of improvement in IJ performance and service life using improved conventional and miter cut designs. While long-term performance of these joints remains to be determined, preliminary conclusions made are favorable. Component durability: Flexible material in and around the end post area may reduce adhesive cracking. No significant difference in the performance of bolted versus Huck® fasteners was observed. Higher metal flow was observed at the ends of lower hardness rails. Improved foundations and reduced deflections: Wider wood ties, wood frame ties, and closely spaced wood ties appear to have reduced ballast surfacing requirements under IJs. IJ deflections may be reduced by up to 30 percent by doubling the modulus of current joint bars. Higher modulus bars will also increase fatigue strength of joint bars. Reduced impacts: Due to a smoother wheel transition across the end post, miter cut joints imparted 50 percent lower dynamic loads to rail as compared to conventional IJs. These dynamic loads are comparable to open track. A 3/16-inch rail gap for conventional butt joints is optimal for reducing impacts and metal flow. Solid sawn wood ties provide greater damping as compared to composite wood ties and concrete ties with rubber pads. Reduced longitudinal stresses: Miter cut joints have 40 percent higher resistance to longitudinal loads than conventional IJs.
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