Railway Track & Structures 12/07

TTCI R&D tion under a microscope) may be a factor. The differences in rail condition through the curve appear to be related to variations in track geometry. Tensile tests were conducted at TTCI and two independent laboratories. Results were compared to AREMA specifications for high-strength steel. All rail types met the specifications for ultimate tensile strength. But most did not meet the requirements for minimum elongation (a measure of ductility). The issue has been raised with the suppliers and AREMA Committee 4 – Rail. Table 1. Wear Ratio (wear of test rail/wear of control rail) Rail Type Wear Ratio Previous test RMSM VA JFE Mittal Control Rail 1.14 1.09 1.02 1.01 .93 1.00 Ties and fasteners Railroads continue to demand, and suppliers develop, fastening systems that will provide strong, durable track. TTCI surveyed the industry in 2004 to determine what new products should be tested at FAST. Several tests that were started as a result of that survey were concluded this year after 465 mgt. The NorFast system and the Pandrol Victor system with e-clips were installed in a six-degree curve. These test zones were compared to two control zones installed at the same time. Pandrol 16-inch rolled steel tie plates with e-clips are in both control zones. Control Zone 1 uses LB&N high-strength screw spikes and Control Zone 2 uses standard No. 5760 screw spikes. Broken screw spikes and broken tie plates were a significant problem in Control Zone 1, where 44 percent of the tie plates had two or more broken LB&N high-strength screw spikes and 14 percent of the Pandrol rolled steel tie plates fractured (see Figure 2 for examples). It appears a failure cycle may have been at work in this zone, where broken screw spikes contributed to the broken tie plates, which in turn led to more broken screw spikes. When tie or plate skewing occurs, there is point loading on the plate, which increases the likelihood of plate fracture. When screw spikes break, plate movement is possible on the tie, with the result noted above. The remaining screw spikes are then left to carry higher screw spike loads. This may result in spots of weaker track, higher component loadings, a higher stress state, and additional fractures. LB&N submitted the results of a test conducted by an independent laboratory to TTCI on a single broken screw spike sample. The lab report suggested problems related to rolling laps from the threading process and decarburization. LB&N indicated these issues are continually addressed and improved in their manufacturing process. The Track Loading Vehicle was used to monitor track gauge strength in the test zones. The measurements were 22 Railway Track & Structures December 2007 www.rtands.com http://www.aar.com http://www.rtands.com

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Railway Track & Structures - December 2007 Contents On Track Industry Today Supplier News AREMA News NRC News TTCI R&D Hand-Held Tools Provide the Power to Get Big Jobs Done AREMA C&S Update Striving to Solve the Riddle of Wheel Climb RTA Stages Warm Gathering in Sunny Florida in October Products and Literature People Calendar Website Directory Advertisers Index Sales Representatives Professional Directory Classified Advertising Chicago Perspective

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