A new, stable, multi-point penetration wheel/rail (w/r) contact algorithm has been developed for the NUCARS ® vehicle/track interaction multi-body simulation program. This algorithm resolves previous problems with integration instabilities during wheel flange contact. Contact geometry comparisons using both the standard rigid and new penetration contact models show that the new penetration model correctly calculates the constrained contact geometry for a range of wheel diameters and contact angles. The critical conditions for multiple solutions for w/r profile combinations with steep flanges and the methodologies to account for this problem in NUCARS are also discussed.Applications of the new w/r contact algorithm to diamond crossing and turnout design simulations are presented and compared with test data. These results show that the revised real-time w/r penetration contact model and the flexible track model with rail profile variation capability in NUCARS provide a promising tool for the advanced analysis of special track work.
The effects of independently rolling wheels (IRW) on flange climb derailment have been investigated through simulations using Transportation Technology Center, Inc. (TTCI)’s *NUCARSTM dynamic modeling software. Simulations of single wheelsets and hypothetcal light rail vehicles equipped with IRWs show that flange angle and flange length parameters play an important role in preventing derailments. That role is especially critical for independent rolling wheels due to their lack of self-steering capability. The speed contour concept was proposed for engineers to adopt the flange angle and flange length in a logical way for wheel profile design in new vehicles and wheel profile maintenance. It is also shown that the sensitivity of IRW to flange climb is also very dependent on particular vehicle designs.
Railway bridges are critical in the transportation network and vital to the profitability of the industry. Thousands of U.S. bridge spans of more than 50 years of age are still in service. Transportation Technology Center, Inc.’s current work under the Association of American Railroads Strategic Research Initiatives Program on bridge life extension focuses on the effects of increased axle loads, on extending the safe service life of existing steel bridge spans, and on onboard inspection of bridge structural integrity. The program includes various tests at the Bridge Deflection Test Facility (BDTF) at the Transportation Technology Center, Pueblo, Colorado, as well as vehicle–track–bridge interaction modeling. This paper presents simulation and test results of a freight car and locomotive running on a railway bridge located at the BDTF. Simulation and test results of an onboard system installed on an instrumented freight car indicated that it is a useful tool for identifying some bridge condition issues. The BDTF provides adjustable bridge strength and geometry conditions. Various tests were conducted on the BDTF to investigate the potential for using onboard technology to detect bridge impairment or changes in bridge behavior. Test results were used to validate the NUCARS three-layer track model of the BDTF. Experimental and analytical case studies were conducted to develop onboard systems for dynamic inspection of bridges under varying loads.
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