Composite ties are commonly used as a replacement for wood ties because of many advantages. For example, composite ties show higher decay and corrosion resistance, greater compatibility with available fastening methods, and the ability to be inter-mixed with wood ties. However, recently, premature fatigue failures of tie plates installed on composite ties have been found at the TTCI test facility, while no failures had been found in tie plates installed on wood ties. This paper presents an investigation of tie plate failures using finite element analysis. A full-scale finite element model of the involved components—consisting of axle, wheel, rail, tie plate, and tie—is developed with an application of vertical and lateral loads on the axle. Three contact interfaces—between wheel-rail, rail-tie plate, and tie plate-tie, are defined to simulate actual operational configuration. To investigate the bending stresses in tie plates as a result of wheel-rail rolling contact, a parametric study of the elastic modulus of the ties, and the applied vertical and lateral wheel loads is examined. Results show that 1) given typical vertical and lateral loads, the decrease of tie’s elastic modulus increases transverse (bending) stresses at the base of the tie plate; thus, promoting high-cycle fatigue failures, and 2) in addition to the vertical load, the lateral loads also have a significant effect on the bending stress in the tie plate, 3) spike-hole cracking is the dominant mode of failure in composite ties operated under all simulated load cases, while edge failure is dominant in wood ties operated under a large lateral load.
Under the direction of the Association of American Railroads Vehicle/Track System Committee, a laboratory test qualification formula/specification for locomotive-based top-of-rail (TOR) friction modifier application system hardware has been developed. This document describes the development and demonstration process, including measurement of the vibration field environment and an initial test of one TOR component in a laboratory vibration and thermal test. Revenue service onboard locomotive vibration environment was measured continuously during two tests in late-2001 and early-2002. The first test measured responses in a train hauling auto parts while the second measured responses in a train hauling coal. Results of the first simulation suggest that many of the issues experienced from over the road field tests, such as clogging and variable output due to temperatures, were simulated and reproduced in the laboratory simulation.
Wheel shelling is the cause of a large portion of high impact wheels. The impact loads produced by shelled wheels can have a damaging effect on track components and rolling stock components such as roller bearings. Shelling is the result of accumulated rolling contact fatigue (RCF) on the wheel tread surface. To investigate the specific conditions in which RCF occurs, wheel load environment data was collected from a car with three-piece trucks running in revenue service. This data was analyzed in order to assess the predicted wheel RCF through the use of shakedown theory. An inspection team was dispatched to several track sites to record relevant information including a visual assessment of rail RCF, rail transverse profile, rail age, and friction conditions. Track inspections were conducted at locations where RCF was predicted and at nearby locations with similar curvature where RCF was not predicted. Conclusions from this work are the following: • The curve unbalance condition, which is a combination of curvature, track superelevation, and train speed, is an important factor in RCF. • Wheel/rail coefficient of friction in curves can be a factor in RCF. • Rail profile and track condition were not found to be major factors in this analysis. • Observed rail RCF condition correlated reasonably well with predictions when considering extenuating factors such as rail age and curve unbalance conditions. • Confidence was increased in previous simulation results involving three-piece trucks due to good correlation with the results of the current work. The simulation results suggest that the use of AAR approved M-976 trucks should reduce RCF. This work was funded by the Federal Railroad Administration (FRA) and the Wheel Defect Prevention Research Consortium (WDPRC), a group that includes railroads, private car owners, and industry suppliers.
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