Railway Track & Structures - December 2008 - (Page 20)

TTCI R&D heavy-axle-loads Heavier loads, although good for business, are tough on key track components. eavy-axle-loads continue to challenge North American railroads. Increased car weights offer the promise of increased productivity and the prospect of higher track maintenance costs and earlier component failures. Research being conducted by the Transportation Technology Center, Inc., is directed toward maximizing the former, minimizing the latter and enhancing railroad safety. Testing at the Facility for Accelerated Service Testing, Pueblo, Colo., and in revenue service provides information on the effects of HALs on track components. The testing at FAST is conducted under a train of 315,000-pound cars. Most of the cars operated over the revenue service test sites weigh 286,000 pounds. Railroads use this information in selecting track components and deciding when and where to implement heavier-axle-loads. Government agencies use it for improving railway safety. The Federal Railroad Administration and the Association of American Railroads fund both programs. Major donations of track and car components by railroads and suppliers contribute to the success of the programs. Some recent test results are summarized here. Effects of on track components H Rail performance Rail is one of the highest value assets owned by railroads and rail-related failures are high on the list of track-related 20 Railway Track & Structures derailment causes. The current test at FAST of high-hardness premium rails from five suppliers has again demonstrated that rail performance is affected by a combination of parameters. Wear, though important, is only one factor in determining rail life. Poor fatigue performance can significantly shorten the life of rail that excels in wear resistance. Testing that began in 2005 has identified differences in wear and fatigue performance among the rails. In addition to differences that can be attributed to metallurgy, track geometry also has affected rail performance. Highlights from the test include: The relative wear rates among the rails have changed over time, most likely due to differences in the work hardening characteristics of the rails. There is currently about 20 percent more wear on the worst (wear) Figure 1shows the difference in rail contact fatigue. performing rail compared to the best performing rail. Rolling contact fatigue on the low rails in this test is more severe than was observed on the rails that were tested from 2001 to 2005. The current rails average 15 HB harder than the rails in the previous test. But hardness alone does not determine a rail’s propensity to develop RCF. Other metallurgical characteristics, including the size and number of hard inclusions, also affect the development of RCF. There are differences in the severity of RCF through the five-degree test curve. The differences are attributed to rail metby Joseph LoPresti and Dingqing Li, TTCI principal investigators and Leonard Allen, FRA program manager. www.rtands.com December 2008 http://www.aar.com http://www.rtands.com

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Railway Track & Structures - December 2008 Contents On Track Industry Today Supplier News AREMA News NRC News TTCI R&D Hand-Held Tools Continue Big Role in Railroad Engineering AREMA C&S Moving Ahead Optimizing Winter Speed Restrictions RTA 2008 Conference Makes Splash in Savannah, Ga. Products and Literature People Calendar Sales Representatives Advertisers Index Website Directory Professional Directory Classified Advertising Chicago Perspective

Railway Track & Structures - December 2008

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