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The dynamic interaction between the vehicle and track is strongly influenced by out-of-round wheels and turnout rail profile geometries, which result in high-magnitude contact forces and abnormal vibrations. This study presents the dynamic response of the tram-turnout interaction due to polygonal wheel wear and analyses its transmission between the wheelsets. A three-dimensional coupled tram-turnout dynamic model was formulated, taking into account the polygonal wear on the front bogie wheelsets. Through numerical simulations, the dynamic characteristics of a tram passing through the turnout switch and crossing panels under the influence of polygonal wear were simulated. Furthermore, the impact of polygonal wear amplitudes and tram speeds on the transmission of dynamic impact forces and vibrations from the front bogie wheelset to the trailer bogie wheels are described. According to the numerical findings, when the flexible wheelset experiences polygonal wear, it can lead to substantial impact forces and vibrations as the tram moves through the turnout switch and crossing zones. Moreover, the transmission of dynamic impact forces and vibrations from the front bogie wheelset to the trailer wheels increases as the wheel wear amplitude and the vehicle speed increase. [ABSTRACT FROM AUTHOR]

The high-speed turnout is a key part of railway track infrastructure. A process of wheel-load transition and single-wheel/multi-track contact take place in the turnout area, causing significant wheel-rail interaction. Most high-speed turnouts include movable-point crossings. To investigate the wheel-rail transient rolling contact behaviour in movable-point crossings, a 3D finite element (FE) model of a wheelset rolling over a crossing was introduced. The actual geometrical profile of the wheel and the rails in turnouts, the nonlinear materials, the actual relative motion between the point/wing rail, and the moving postures of the wheelset were considered. The simulated mode shape was compared with the experimental mode shape to verify the wheel-rail coupling model. Precise frictional rolling contact solutions and dynamic response, including wheel-rail force, contact stress, equivalent stress, equivalent plastic strain, and stick-slip distribution of the contact patches, were all studied. After this, the parametric analysis of dynamic wheel-rail contact behaviour was carried out. The simulated results indicate that the proposed explicit finite element method can characterise wheel-rail coupled dynamic interaction and mesoscopic rolling contact behaviour well, and improve the understanding of wheel-rail contact behaviour in the movable-point crossing panel of the high-speed turnouts. [ABSTRACT FROM AUTHOR]

Rail joints are the weakest link in the railway track structure due to the presence of discontinuities in the track stiffness and wheel-rail contact geometry. This paper presents the dynamic response of vehicle-track interaction at the bolted rail joint (BRJ) in the presence of polygonal wheel wear. A three-dimensional coupled vehicle-track dynamic model was established using the finite element method (FEM) and the multi-body system (MBS) approach, in which the flexibilities of the wheelset and track are taken into account. The proposed dynamic model is validated by the comparisons of field measurement and calculated vertical axle-box acceleration in time and frequency domains. The effects of the flexible wheelset in the presence of polygonal wear on the vehicle-track dynamic interaction at the BRJs are illustrated through comparisons with those obtained using without polygonal wheel model. The results show that the polygonal wheel wear and the rail joint irregularities can induce high-magnitude vertical wheel-rail contact force, and exacerbate the vibration responses of the axle box, the wheelset, and the rails. The simulation results also indicate that the wheelset bending modes, the P2 resonance due to rail joint excitation, and the track vibration modes have significant effects on the vertical vehicle-track dynamic interaction at the supported and suspended BRJs. [ABSTRACT FROM AUTHOR]

During train operation, the geometric tolerance in a turnout can be very random, posing a challenge for traditional deterministic vehicle-turnout coupling studies and for daily maintenance. In light of the above situation, a coupled vehicle-switch panel model with random geometric tolerances is proposed. These tolerances result from the discrepancy in relative height difference of rail tops between the straight switch rail and the curved stock rail, and from the gap between the straight switch rail and the curved stock rail in the closure part. The model takes rail flexibility into consideration. The probability density evolution method (PDEM) is applied to capture the resultant probability density function (PDF) of dynamic wheel–rail interactions. The Monte Carlo method is employed for verification of results obtained from the PDEM. The results show that stronger randomness of the vertical wheel force is induced compared with that of the lateral wheel force. The probabilistic range of the vertical wheel force is found to be around 50 kN on the straight switch rail side. Given the largest maximum mean value of rail displacement, it is found that the part of the straight switch rail with a top width of 40 mm requires significant attention. [ABSTRACT FROM AUTHOR]

This study aims to investigate the mechanism of wheel jumping derailment in the railway switch panel after a freight wagon passes over a rail joint defect (RJD) situated before the switch. For this purpose, a 3D vehicle-track (turnout) coupled dynamic model that considers the elastic deformation of the rails and wheelsets has been established. Several extreme running conditions, including sharp curves, low-speed railway turnouts, lateral misalignment defects of RJs, and empty wagons are all considered in the simulation model. The vertical wheel rise limit for the railway switch panel is presented for the evaluation of a quasi-static derailment risk. The wheel-rail impact behaviour and the evolution of the derailment processes in the switch panel are revealed, and the effects of wagon load and misalignment width of RJ sections on the vehicle's dynamic response and running safety are investigated. The results show that the root cause of the high derailment risk in the railway switch is a lower wheel rise limit at the front region of the switch rail when compared with the mainline. This dynamic derailment limit is sensitive to the car-body load and the misalignment width. Severe lateral defects of the RJ before the switch toe should therefore be avoided. [ABSTRACT FROM AUTHOR]

The inherent structural irregularities in turnouts are an impact source during train passing. The position of the wheel–rail contact point on the rails and the wheel trajectory can help reveal the characteristics of such structural irregularities. In this work, for a given nominal turnout, several parameterised single harmonic-shaped functions are selected as analytical representations to describe the inherent structural irregularities in a crossing with moveable point using multiobjective optimisation. The objective of the optimisation is achieved by ensuring that the responses of the analytical representation applied to a plain track are close to those of the turnout model under the constraint of maximum and minimum wheel–rail contact forces as well as a correlation coefficient. Thus, a plain track with irregularity functions can be considered an equivalent model to enable a fast modelling procedure and efficient assessment of vehicles. For a robust design in different traffic situations, two stochastic variables, namely the rail pad stiffness and axle load, are selected and are found to be significant. The influence of the random distributions of the input parameters on the statistical outputs of the wheel–rail contact forces is assessed using a descriptive sampling technique for several stochastic realizations. [ABSTRACT FROM AUTHOR]

The turnout causes significant vibrations of the wheel-rail system. In this study, based on the modal superposition method and finite element method, the flexibility of wheelsets and turnouts is considered respectively, and the vehicle-turnout coupled dynamic model is established. The swept-frequency analysis is adopted to capture the natural frequencies of wheelsets and turnouts. The dynamic interaction and modal resonance performance of the wheel-rail system are investigated when the vehicle passes through the turnout. Results indicate that during the wheel load transition in the crossing, the major frequency bands of the vertical wheel-rail impact force are related to natural frequencies of the crossing. Due to the wheelset resonant modes, the vertical impact force decreases by 12% in the through route and increases by 10% in the diverging route. The wheelset flexibility affects the wheel-rail creepage and decreases the longitudinal wheel-rail force. The wheel-rail impact force has nearly converged as the cut-off frequency of wheelsets reaches 500 Hz. The dominant frequencies of axle-box and rails' vibrations correspond to the modal resonance between the bending modes of wheelsets and the crossing in the vertical direction, as well as, the wheelset's umbrella mode and the crossing's pinned-pinned mode in the lateral direction. [ABSTRACT FROM AUTHOR]

This paper compares different track model formulations for the simulation of dynamic vehicle–track interaction in switches and crossings (S&C, turnouts) in a multi-body simulation (MBS) environment. The investigations are an extension of the S&C simulation Benchmark with the addition of a finite element model of a 60E1-760-1:15 turnout. This model constitutes a common reference from which four different track formulations are derived: co-running, modal superposition, finite element incorporated into the MBS model and finite element coupled to MBS using a co-simulation approach. For the different track models, the difference in modelling technique, results, simulation time, and suitability for different simulation tasks is compared. A good agreement is found between the different track model formulations for wheel–rail contact forces and rail displacements. This study found a better agreement between co-running and structural track models compared to previous studies in the prediction of wheel–rail contact forces. This appears to be due to the increased complexity of co-running track model used in this study together with a tuning of the co-running track model to the reference model in a wider frequency range. For the reader interested to reproduce the results in this paper, the reference track model is available for download. [ABSTRACT FROM AUTHOR]

This paper presents a multi-objective optimisation method considering the switch and stock rail profiles in the switch panel. Based on the non-uniform rational B-spline (NURBS) theory, a parameterised model of the measured turnout profile is constructed to determine the variables. This study selects the vehicle dynamic performance and wheel-rail contact damage as the objective function to establish a multi-objective optimisation mathematical model that is solved using NSGA- II. Overall performances of the measured profile and the optimised profile are compared and evaluated for two aspects, dynamic performance and wheel-rail contact damage. The following are the conclusions: The maximum lateral vibration acceleration of the axle box is reduced from 2.64–2.09 m/s2, which has a 20.83% decrease. Concerning wheel-rail contact damage, the maximum wear index is reduced from 13.46–11.47 N, the reduction is 14.78%. At the same time, the cumulative surface rolling contact fatigue (RCF) is reduced from 8.29×10−5–7.38×10−5. This article can provide a profile repair method for worn turnouts, which can maximise the comprehensive performance of the turnout within a limited amount of grinding, and can reduce the wheel-rail contact damage of the turnout while taking into account driving stability. [ABSTRACT FROM AUTHOR]

Solving the wheel-turnout contact geometry is complex because the rail section is varying along its longitudinal position. Besides, a large yaw angle will occur, especially when the vehicle passes the switch panel in a diverging route. However, previous researches seldom considered the aforementioned factors simultaneously in performing wheel–rail local contact analysis. This paper therefore proposes a novel three-dimensional (3D) contact geometry method considering the combined effects of varying rail profiles and the yaw angle. This study uses S1002CN wheels and the switch panel of a 1:12 turnout as research objects to study the contact geometry, normal and tangential contact solution. The results indicate that the combined influences of rail profiles varying within the contact patch and the yaw angle on the contact solution are significant. The variable rail profiles obviously affect the position of the contact point. With a yaw angle, the normal gap, contact patch shape and stress distribution calculated by the novel 3D contact geometry method are asymmetric along the lateral and longitudinal directions, especially when the wheel flange contacts with a rail gauge corner. The proposed method can improve the accuracy of the wheel–rail contact solution and help predict rail damage in switch panels. [ABSTRACT FROM AUTHOR]

Assembly deviations of wheelsets cause differential wheelset misalignments and change the wheel-rail contact relationship in railway turnouts. In this paper, the motion conditions of wheelsets under the same bogie are analysed with differential wheelset misalignment based on the mechanical equilibrium condition. A rigid-flexible coupling model of vehicle-turnout dynamic interaction that fully considering different misalignment conditions is established to evaluate the wheel and turnout rails dynamic interaction and vehicle dynamic characteristics. The results show that wheelset misalignment can change wheel load transition position and affect wheel-rail contact conditions, especially when the misalignment direction is toward the switch rail. The larger misalignment angle will increase flange contact range and keep the normal contact stress at a higher level. Both misalignment angle and form determine the wheel-rail vertical force. The lateral force is mainly affected by the superposition effect of the eccentric load and the lateral impact of the wheel load transition. [ABSTRACT FROM AUTHOR]

Wheel flat is a form of wheel tread defect that reduces the service life and running safety of trains and tracks. Based on the multi-body system dynamics theory, a rigid-flexible vehicle-turnout dynamic coupling modelwas established, and the wheel diameter-varying flat simulation method used to create wheel flat models of different sizes. The most unfavourable phase of flats on the wheels of a vehicle crossing a turnout was studied by scanning and calculating the phase of the flats. The influence of flat size and vehicle speed on a vehicle with flats crossing a turnout was also analyzed. The results show that, compared with a normal wheel crossing a turnout and a wheel flat acting on the interval rail, a wheel flat acting on the wheel load transition of the frog area will excite greater vertical wheel-rail forces and vertical axle box vibration acceleration; in the turnout area, the main frequency band of the vertical vibration acceleration of the axle box is 550–800 Hz, which is rarely affected by the size of flats or the speed of the vehicle. The third-order bending mode of the wheel is excited when the wheel transits from the wing rail to the point rail. [ABSTRACT FROM AUTHOR]

The vibration performance of a tram vehicle running on the curved track is influenced by the speed of the running vehicle, the geometry of the track, the roughness of the wheel and rail, and environmental characteristics. This paper investigates the random vibration analysis of tram-track interaction on a curved track due to the polygonal wheel and track irregularity by the pseudo excitation method (PEM). The dynamic behaviour of tram-track interaction on a curve is modelled using the finite element method (FEM) and multi-body system (MBS). The field tests were carried out to acquire the rail vibration and deformation response, and also measuring the polygonal wheel wear profile to analyse and validate the dynamic behaviour tram-curved track model. The influence of the polygonal wheel on the vibration of tram-curved track coupled system and the wheel-rail contact responses are investigated by considering the wheelset flexibility. The results are illustrated through comparison between with and without the polygonal wheel in terms of time and frequency domain. The numerical results suggest that the wheelset flexibility under the polygonal wheel wear excitation would aggravate the vibration mode of the rail, car-body and axle-box, and also increase the dynamic wheel-rail contact force and creepage. [ABSTRACT FROM AUTHOR]

Train derailment can cause not only damage to the train itself but also secondary damage to surrounding structures. For this reason, guard rails are commonly used to prevent secondary damage caused by derailed trains on high-risk lines. In this paper, a 3D vehicle-track dynamics simulation model and a collision contact model were used to investigate the post-derailment dynamic behaviours of the train as well as the effectiveness of guard rail protections. Variables studied include derailer oblique angle, the gap between running rail and guard rail, the effect of derailing speed on the posture, and impact force after derailment. The study shows that the oblique angle has a strong influence on the dynamic derailment behaviours. At a large gap, the bogie generates a noticeable distortion, which is very detrimental to the derailed vehicles. It was found that when the gap is 200 mm, the derailed wheelsets roll on the sleepers stably. And high derailing speeds can also cause significant impact forces. These simulations further the theory of train running posture and impact response, and can inform good railway design and maintenance. This is particularly true for tracks on which guard rails are installed to reduce secondary damage. [ABSTRACT FROM AUTHOR]

Dynamic wheel–rail interaction in railway turnouts is more complicated than on ordinary track. In order to evaluate the derailment behaviour of railway wheelsets in railway turnouts, this paper presents a study of dynamic wheel–rail interaction during a wheel flange climbs on the turnout rails, by applying the elasticity positioning wheelset model. A numerical model is established based on a coupled finite element method and multi-body dynamics, and applied to study the derailment behaviour of a railway wheelset in both the facing and trailing directions in a railway turnout, as well as dynamic wheel–turnout rail interaction during the wheel flange climbing on the turnout rails. The influence of the wheel–rail attack angle and the friction coefficient on the dynamic derailment behaviour is investigated through the proposed model. The results show that the derailment safety for a wheelset passing the railway turnout in facing direction is significantly lower than that for the trailing direction and the ordinary track. The possibility of derailment for the wheelset passing the railway turnout in facing and trailing directions at positive wheel–rail attack angles will increase with an increase in the attack angles, and the possibility of derailment can be reduced by decreasing the friction coefficient. [ABSTRACT FROM AUTHOR]