Employing a dynamic model of the railway wagon in three dimensions, this paper presents the results of dynamic wheel–rail forces under the presence of track irregularities. A mathematical model of the wagon system is developed using dynamic equations of the components, taking into account the vertical (bounce), pitch and roll motions of the system. The model examines the dynamics of the wagon system under arbitrary rail irregularities. The spectra of rail surface irregularities are fed into the vehicle model to extract the time histories of dynamic forces between the wheel and the rail. Using the irregularity spectra of left/right rails, vibration of the wheelsets is studied for the bounce–roll motions. The dynamic contact forces between wheels and rails are determined for three examples of the measured irregularities. Moreover, three V-shape defects are modelled as examples of the singular defects on rail surface. The results of dynamic simulations confirm the large amounts of impact forces due to the presence of rail irregularities, particularly for the cases with much unevenness between the left/right profiles.

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When a train passes over bridges, the magnitude of forces and accelerations is altered due to sudden changes in the track stiffness. These forces can change with the variation in operational parameters and are effective particularly in high-speed passenger trains, when studying ride index parameter. In addition, by increasing the speed, old bridge structures could fall into resonance, which has harmful consequences for both bridge and ride comfort index. Moreover, to harmonize the old bridges with the new operational conditions dynamic behavior of the vehicle and ride comfort need to be taken into account. In this paper, coupled vertical and roll vibration of a horizontally curved bridge are considered. During pass over the bridge, acceleration and ride comfort of a passenger vehicle are studied. The eccentric vertical and lateral forces are the major excitation sources in the analysis, an issue that is rarely noticed in the literature. A multi-body model of a normal wagon is built in three dimensions, passing over a horizontally curved bridge. The governing equations of the vehicle-bridge system are written, taking into account the wheel-rail interactions. The major variables are the cant, train speed, track quality, and radius of curvature. The paper studies the effects of the prescribed variables on ride comfort. The results show that track quality and cant have considerable influences on ride comfort index. The ride comfort is improved when the speed is approached to a so-called equivalent speed.

Systematic examinations on wear behavior of stick/slip contact around metal on metal have shown that the dissipated energy and contact forces are two important parameters of wear of wheels and rails. Nevertheless, an accurate estimation of these parameters is still a great challenge. Recent developments of non-linear dynamical models and simulation of operational conditions have tried to find a solution of this challenge. These results are used as the input to calculations of wear propagation. Though, the dynamic model should be able to predict wheel-rail interaction with high accuracy. In addition, wheel-rail wear is a function of several other parameters whose their integrated influence becomes more than the main discussed ones. In this study, with the help of multi-body dynamics (MBD), an open wagon equipped with three pieces bogies, considering non-linear effects of friction wedges and structural clearances is modeled in Universal Mechanism. Tangent and curved sections of the track considering random vertical and lateral irregularities are simulated. The simulation results are used to calculate wear of both left and right wheels separately. Specht's wear model based on Archard's wear model is used. The studied parameters are the rail side coefficient of friction, track quality, track curvature, velocity and rail side wear. Finally, the effects of mentioned parameters are studied on wear depth and wear pattern of new wheel profiles under incompatible contact (which occurs in Iran railway network). The results show different wear volume and wear pattern compared to compatible contact.

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As track components deteriorate, their interaction dynamic response will alter accelerations on the train. Measuring acceleration on train components is a method to conduct condition monitoring of track defects. The measured signal can be used for the detection of rail surface defects which implement impacts on measured accelerations. In this paper, the axle-box acceleration (ABA) is measured in a subway as a case study. Fourier transform (FFT), empirical mode decomposition (EMD) and ensemble EMD (EEMD) methods are used to study accelerations relative to the track. Wheel frequencies are calculated using finite element method (FEM) to determine frequency couplings. Velocity-dependent/independent components and source of excitation of the measured signal are distinguished. Results indicated that the FFT approach can be applied for both velocity-dependent and velocity-independent vibration components for frequencies up to 680 Hz. Also, the EEMD method can be used to distinguish the impact component of the measured signal.

One of the major concerns in the development of railway systems is to choose an optimized wheel and rail profile from a wide range of material and geometries. Although various investigations are conducted to improve the vehicle and rail behavior, there is less research on the wheel–rail interaction when a heavy vehicle passes through a light rail track. A numerical model of the train, track, and turnout is developed. The model is validated using the data obtained from field measurements conducted in the Iranian Metro network. The wheel–rail interaction is investigated by sensitivity analyses of the heavy vehicle and light track parameters including train speed, wheel profile, axle load, track gage, and curve radius. Results indicated that the derailment risk, wear rate, and wheel–rail stresses increased by up to 35%, 600%, and 120%, respectively, when a heavy vehicle passes through a light track. It was shown that consideration of specific arrangements allow better interaction between wheel and rail.