Interface - The Journal of Wheel/Rail Interaction

TTCI TECH OVERVIEW

Meeting the Industry’s Technology Goals (continued)

The steering properties of the wheel profile have been evaluated on both tangent and curved track. A wheel profile matching the worn high rail and providing effective steering in curves has been found to produce excessive conicity and self-centering action on tangent track (see Figure 2). Rail profiles rolled and maintained by grinding to a slightly modified profile will result in lower conicities and improved dynamic behavior.

Interim solutions to the problem of loaded hunting include the use of stiffer adapter pads. Longer-term solutions include implementation of redesigned rail and wheel profiles, such as the SRI-1A, which has shown to wear less than the AAR-1B, which produces severe two-point contact with typical worn high rails on curves (see Figure 3).

Huimin Wu, Principal Engineer, reported that wheel performance was evaluated by examining track gauge spreading forces, flange and tread wear and the wear patterns. The new SRI-1A wheel profile was also tested. Results showed that the SRI-1A wheels produced lower gauge spreading force in the beginning stage of service, and less wear than the AAR-1B profile wheels in service tests (see Figure 4). The SRI-1A wheels also produced relatively even wear across wheel profile, while the AAR-1B wheels concentrated wear at wheel flange and tread.

Existing as-rolled rail profiles are also being redesigned through a joint effort with AREMA Committee 4 to be more compatible with the worn wheel shapes, Wu said. New rail grinding templates and grinding practices, which will reduce conicities, creepage, contact stresses and material flow, are also being examined.

Friction and Rail Wear
Friction Management is another aspect of vehicle/track interaction that continues to warrant attention. Toward that end, the TTCI presented the results of a two-year study of wayside-based top-of-rail (TOR) friction management in the Tehachapi Mountains. The TTCI monitored two five-mile zones: a control zone with optimized gauge-face lubrication, and a TOR zone with gauge-face and TOR lubrication. Performance was monitored for more than two years on two similar 10-degree curves with identical head-hardened rail and the same train traffic.

After 80 mgt of traffic, rail wear was reduced by up to 60% in the TOR zone, compared to the non-TOR control zone. The life of the low rail at 80 mgt per year with a 3/4-inch wear limit (not adjusted for metal removed by grinding) is projected to be nine years in the TOR zone compared to four years in the non-TOR zone.

“Top of Rail lubrication reduces rail wear and offers the potential to extend rail life,” said Joseph LoPresti, Senior Principal Engineer.

No research review would be complete without an evaluation of the performance of the latest generation of premium rail steels under heavy axle loads. The TTCI monitored the performance of five rail steels with an average hardness of 410 Bhn in a non-lubricated, 5-degree curve. After approximately 425 mgt (at the existing wear rates), 550 mgt of wear life is projected for the rails in this nonlubricated curve.

Field tests conducted in revenue service on eastern and western revenue service coal lines as part of the Heavy Axle Load monitoring show excellent wear performance. The minimum projected rail wear life (not expected life) of 5/8-inch gauge-face or head wear is 1,000 mgt for a 10-degree curve with excellent gauge-face and TOR friction modification, and 2,800 mgt for a 2-degree curve with fair gauge-face and no TOR lubrication, said Dingqing Li, Senior Principle Engineer at the TTCI. No internal defects were identified at the east coast site after 180 mgt, and after 760 mgt at the west coast site.

At the eastern site, there was no obvious rolling contact fatigue after 180 mgt, a period during which no preventive grinding was performed. At the western site, rail grinding was required after significant rolling contact fatigue (RCF) appeared on the low rails of 2-degree curves after 300-350 mgt and on the high and low rails after 680 mgt.

“Generally, we’re seeing fewer internal defects and more surface defects,” LoPresti said.

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