This paper presents a model for simulating vehicle–track interaction at high frequencies for investigations of rail roughness growth. The dynamic interaction model developed employs a substructuring ...technique and the whole system consists of a number of substructures that can be modelled independently. The systems are coupled through the forces at the wheel–rail contact and the railpad. A coupled, rotating flexible wheelset, a flexible track model and a non-Hertzian/non-steady contact model have been implemented and results are presented here for a free wheelset on a symmetrical track system with initial random and sinusoidal roughness. Both rigid and flexible wheelsets are considered.
This paper outlines the historical development of the wheel and rail profiles currently used on railway vehicles. It also presents the key damage mechanisms involved in wheel-rail contact and ...summarises the methods that have recently been developed by railway engineers to predict the level of wheel and rail damage from these mechanisms. Tools for predicting the key damage modes of wear and rolling contact fatigue (RCF) are explained. Methods of optimising the wheel and rail profiles to reduce the overall damage and therefore improve the efficiency of the railway system are discussed and a case study from the UK of an ‘anti-RCF’ wheel profile is presented. Finally a novel method using a genetic algorithm is discussed which uses a penalty index to optimise the wheel profile for good running, low track forces and rail stress, low wear and RCF.
The purpose of the study was to investigate the propulsion kinetics of wheelchair racers at racing speeds and to assess how these change with an increase in speed. It was hypothesised that propulsive ...force would increase in proportion to speed, to accommodate the additional work required. Six wheelchair racers volunteered to participate in this study which required each athlete to push a racing wheelchair at 4.70 and 5.64 m s
−1 on a wheelchair ergometer (WERG). Eight pairs (16 in total) of strain gauges, mounted on four bars attached to the hand-rim of a racing wheelchair wheel, measured the medio-lateral and tangential forces applied to the hand-rim. Kinetic data were sampled at 200 Hz while a single on-line (ELITE) infrared camera operating at 100 Hz was positioned perpendicular to the WERG to record the location of the hand with respect to the hand-rim. In general, peak tangential force occurred when the hand was positioned on the hand-rim between 140 and 180°. With the increase in speed, the peak hand-rim forces applied tangentially increased from 132 to 158 N and those applied medio-laterally increased from 90 to 104 N. The ratio of tangential to total measured force was similar at both speeds (80 and 82%, respectively). In conclusion, these data indicate that wheelchair racers adopt a different propulsion strategy than that employed in everyday chairs and that the forces increase in proportion to propulsion speed.
In this paper the authors present a predictive model of train energy requirements due to the application of a top of rail friction modifier (TOR-FM) versus dry wheel/rail conditions. Using the ...VAMPIRE® Pro simulation package, train energy requirements are modeled for two sets of TOR-FM frictional conditions, one using full Kalker coefficients and the other by using a Kalker coefficient of 18%. Both scenarios use a top of rail saturated coefficient of friction of 0.35. Under both TOR-FM frictional conditions, train energy savings are shown for complete laps of the Transportation Technology Center Inc.’s (TTCI) Transit Test Track (TTT) loop, and also when isolating only the tangent section of the loop. However, the magnitude of energy savings varies greatly depending on the Kalker coefficient factor used, highlighting the need to model this relationship as accurately as possible. These simulation results are compared with data obtained from a field study, in which train energy savings of 5.3% (lap) and 7.8% (tangent) are shown due to the application of TOR-FM.
•A model for calculating train energy requirements is proposed.•Various methods for modeling friction modifiers in VAMPIRE® are investigated.•Modeling results are compared with field test results.•A field test is used to investigate the effect of friction modifiers on train energy requirements.•Field test results show energy savings of 5.3% (lap) and 7.8% (tangent).
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