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Large magnitude impact loads caused by wheel flats may excite various vibration modes of wheelsets employed in high-speed trains and thereby contribute considerably to the dynamic response of vehicles. In this study, the wheelset is modeled as a flexible body using the modal approach, which is integrated to a multibody dynamic model of the high-speed train coupled with a flexible track slab model. The multibody dynamic model is formulated for a typical high-speed train consisting of a car body, two bogie frames, and four wheelsets. The track is modeled considering the rail as a Timoshenko beam discretely supported on a flexible track slab. The effects of the wheelset flexibility on the dynamic response are illustrated through comparisons with those obtained with a rigid wheelset considering different vehicle speeds and sizes of the wheel flat. Subsequently, the effects of wheel flats on the vehicle–track system are evaluated in terms of the wheel–rail impact forces, axle-box vertical acceleration, and dynamic stress developed in the wheelset due to a haversine wheel flat. The results suggest that the wheelset flexibility can lead to significantly higher axle-box vibration and wheelset axle stress compared to a rigid wheelset in the presence of a wheel flat.

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2010)Development of a vehicle-track model assembly and numerical method for simulation of wheel-rail dynamic interaction due to unsupported sleepers, Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility, 48:12, 1535-1552 To link to this article: http://dx.In practice, it is not very uncommon to find railway track systems with unsupported sleepers due to the uneven settlement of a ballasted track system. These unsupported sleepers are among the major vibration excitations for a train and track system when a train moves forwards on a track. The vibration induced by unsupported sleepers can cause a large dynamic contact force between wheels and rails. For heavily loaded high-speed trains, the deteriorated sleeper support may lead to accelerated degradation of the railway track and vehicle components, and may thus impose safety risk to the operation. This paper presents analyses of a coupled vehicle-track assembly consisting of a roll plane vehicle model, a continuous track system model and an adaptive wheel-rail contact model. In order to improve the simulation efficiency, a numerical approach based on the central finite difference method is proposed in this investigation. The developed model assembly and proposed simulation method are utilised to simulate the vehicle-track dynamic interaction in the presence of unsupported sleepers. The dynamic response in terms of the dynamic wheel-rail interaction force due to one or multiple unsupported sleepers is studied. Important factors influencing the dynamic wheel-rail interaction force in the presence of sleeper voids are also investigated. The results show that the vehicle speed, the gap size and the number of unsupported sleepers primarily dictate the magnitude of impact load which can be significant.