Materials and Components
Rail Steel and Defect Growth Studies
FRA will continue to support the development of rail steels that are more resistant to defect formation under repeated loading from train traffic. Studies in this area will focus on factors which control rail life and performance, including growth of fatigue cracks, influence of metallurgy, and the influence of rolling loads on residual stress formation and its relationship to fatigue defect initiation and growth. Future work will concentrate on appropriate actions to be taken to: (1) remedy detected defects; (2) improve the metallurgy through processing and post processing of rail steels; (3) assess the safety implications of various rail grinding procedures; and (4) investigate optimum rail section design to extend rail life while reducing the risk of accidents.
Rail Wear Limits
While not viewed as a major cause of accidents, worn rail is suspected of being a contributing factor in some cases. The exact nature of its contribution, though, is not well understood. It is thought that the wear pattern on the rail may be as important as the amount of wear on both the top and gage side of the rail head. The effects of worn rail continue to be investigated to provide a better understanding of what problems worn rail may create. The results will provide the Office of Railroad Safety with information needed to determine whether setting limits on rail wear is warranted, and if so, what those limits should be.
Turnouts and Track Crossings
Turnouts and track crossings are often categorized as special track work, as they include a variety of hardware, fastenings, and general construction that is different from typical track structure. Turnouts and track crossings are subjected to especially high lateral forces and large vertical impacts. The beating they receive has been increasing as heavier freight cars enter service in greater numbers. As axle loads increase, special track work components deteriorate at an accelerated rate and are more subject to rapid failure.
This project focuses on improving the geometric and material design of these components to better withstand the higher forces and impacts of heavy axle loads as well as reduce wear and deterioration rates. Promising alternatives to conventional designs will be tested on the FAST track at the Transportation Technology Center (TTC) to determine their performance and durability. Results from these tests will help to develop improved versions that will withstand expected future load levels.
Despite recent improvements in the process, welds made in the field to join sections of rail or make repairs still experience high rates of failure. Studies to date of the effects of heavier cars on track indicate that weld failure rates may increase further without better methods to achieve a higher and more consistent field weld quality. This project will support the development of improved materials and processes that will produce welds less susceptible to defect formation. Slot-welded railhead repairs of rail steels will be studied under overloading and static fracture conditions and their fatigue damage tolerances will be evaluated.
New Track Materials and Components
This project will focus on assessing the safety of track materials and components that are newly introduced to the track structure. This proactive approach assures that safety assessment is conducted before widespread use. The project will include investigations of the various new tie designs that are now emerging and those expected in the future, as the use of plastic and composite materials in structural members becomes more common. Current cooperative efforts involving laboratory, field studies, and workshops addressing priority performance and safety issues of plastic ties continue. Expected accomplishments on an on-going basis include an exchange of technical information and better guidance through appropriate periodic updates of the new Part 5 on Engineered Composite Ties now included in AREMA Railway Engineering Manual, Chapter 30, Ties.
Composite Materials for Bridges
The use of composite materials for railroad bridges will be explored for both new construction and the repair and rehabilitation of older bridges. Studies being carried out at West Virginia University and the University of Missouri at Rolla will focus on investigating load transfer characteristics between the old and new materials as well as the reliability of connections and durability of the new materials.