Search Results (22)

To address the adverse effects of Tuned Inertia Dampers (TIDs) on track slab vibrations while controlling high-frequency rail vibrations, a hybrid Finite Element-Statistical Energy Analysis (FE-SEA) method is developed for modeling the vehicle-track-bridge coupled system. Short-wavelength track irregularities are introduced as high-frequency excitation, and the accuracy and efficiency of this method are validated by comparison with the traditional finite element method (FEM). A vibration control model for track-bridge structures incorporating TIDs is designed, and the effects of the TID’s inertance, stiffness, and damping coefficients on the vertical acceleration responses of the rail and track slab are investigated in detail. The study reveals that although TIDs effectively reduce rail vibrations, they may induce adverse effects on track slab vibrations. Using the vibration acceleration amplitudes of both the rail and track slab as dual control objectives, a multi-objective optimization model is established, and the TID’s optimal parameters are determined using a multi-objective genetic algorithm. The results show that the optimized TID parameters reduce rail acceleration amplitudes by 16.43% and improve the control efficiency by 12.45%, while also addressing the negative effects on track slab vibration. The track slab’s vibration acceleration is reduced by 5.47%, and the vertical displacement and acceleration of the vehicle body are reduced by 14.22% and 47.5%, respectively, thereby enhancing passenger comfort. This study provides new insights and theoretical guidance for vibration control analysis in vehicle-track-bridge coupled systems. Full article

The structural design of rail vehicle bodies significantly influences rail vehicle performance, passenger comfort, and operational efficiency. This study presents a comparative analysis of three key concepts of a rail vehicle body, namely a differential, an integral, and a hybrid structure, with a focus on their structural principles, material utilization, and implications for manufacturability and maintenance. Three rail vehicle body variants were developed, each incorporating a low-floor configuration to enhance accessibility and interior layout flexibility. The research explores the suitable placement of technical components such as a power unit and an air-conditioning system, and it evaluates interior layouts aimed at maximizing both passenger capacity and their travelling comfort. Key features, including door and window technologies, thermal comfort solutions, and seating arrangements, are also analyzed. The study emphasizes the importance of compromises between structural stiffness, reparability, production complexity, and passenger-oriented design considerations. A part of the research includes a proposal of three variants of a rail vehicle body frame, together with their strength analysis by means of the finite element method. These analyses identified that the maximal permissible stresses for the individual versions of the frame were not exceeded. Findings contribute to the development of more efficient, accessible, and sustainable regional passenger rail vehicles. Full article

Cement–asphalt (CA) mortar voids in earth’s structure are prone to inducing abnormal vibrations in vehicle and track systems and are more difficult to recognize. In this paper, a vehicle–ballastless track coupling model considering cement–asphalt mortar voids is established and the accuracy of the model is verified. There are two main novel results: (1) The displacement of the track slab in the ballastless track structure is more sensitive to the void length. Voids can lead to blocked vibration transmission between the ballastless track slab and concrete base. (2) The wheel–rail vibration acceleration is particularly sensitive to voids in cement–asphalt mortar, making the bogie pendant acceleration a key indicator for detecting such voids through amplitude changes. Additionally, the train body pendant acceleration provides valuable feedback on the cyclic characteristics associated with single-point damage in the cement–asphalt mortar, thereby enhancing the accuracy of dynamic inspections for vehicles. In the sensitivity ordering of the identification indexes of voids, the bogie’s vertical acceleration in high-speed trains > the nodding acceleration of the bogie > the vehicle’s vertical acceleration. Adaptive suspension parameters can be designed to accommodate changes in track stiffness. Full article

The rail vehicle industry wants to produce vehicles with higher speeds, to maintain and increase its market share. However, when the speed of the vehicle increases, it may have an undesirable effect on ride comfort, in terms of ride dynamics. Recent developments towards lighter and faster vehicles make the problem of ride comfort at higher speeds increasingly important. Focusing on the behavior of flexible rather than rigid body behavior should not be neglected when designing long and light car bodies. There are several approaches to incorporate body flexibility in multibody simulations and they have some superiorities and weaknesses. In this study, an efficient and accurate vertical dynamic model for the ride comfort analysis is developed and implemented in a commercial object-oriented modeling (OOM) software Dymola (2015 FD01) which uses the open-source code Modelica. This model includes car body flexibility with the assembling of a rigid body approach. The developed model is compared to a three-dimensional vehicle model in the commercial Vampire software (Pro V5.50) at different velocities. For the vertical ride comfort analysis, the ISO 2631-1 standard was used for both the developed model and the three-dimensional model. The results are presented as acceleration history and $a^{wrms}$—weighted r.m.s (root mean square) of accelerations—as required by the standard. The developed model has shown its feasibility in terms of its efficiency and accuracy for the vertical ride comfort analysis. The accuracy of the model is evidenced by the fact that the car body vibration level at high speeds shows minor differences compared to the results of the Vampire, which is a validated commercial software in the area of rail vehicle dynamics. The approach involving the assembly of rigid bodies is applied for the first time for high-speed trains in dynamical modelling, with flexible car bodies for ride comfort analysis. Furthermore, it can be used for parametrical studies focusing on ride comfort, thereby offering a quite beneficial framework for addressing the challenges of ride comfort analysis in high-speed rail vehicles. Improvements for and analyses of other aspects are also possible, since the optimization and other useful libraries are readily available in Dymola/Modelica. Full article

The applied mechanical modeling of train and bridge structures is essential in accurately predicting structural vibrations caused by high-speed trains, particularly for the often design-relevant structural accelerations. Considering the interaction effects between the train, the superstructure, and the supporting structure yields more realistic and lower acceleration results compared to simplistic reference models disregarding interaction dynamics. The research presented in this article focuses on modeling single-span girder bridges with a ballasted superstructure as coupling beams. In this approach, the bridge is represented as two vertically coupled beams, with one representing the track (rails and sleepers) and the other representing the supporting structure. Their connection incorporates the stiffness and damping properties of the ballasted superstructure, reproducing its load distribution capacity. A numerical study encompassing a wide range of bridge parameters is conducted, focusing on the calculation of maximum structural accelerations. The results from modeling the bridge as a coupling beam model are compared to those from a simply supported Bernoulli–Euler beam. The excitation is applied as either a moving load or a multi-body model of an Austrian Railjet to evaluate the interdependencies of interaction effects between the vehicle and track and between the track and bridge structure. The comprehensive analysis considers varying bridge span, fundamental bending frequency, mass distribution, structural damping, and coupling stiffness and damping properties to identify correlations with the achievable acceleration reduction using the coupling beam model. Compared to the reference model, the coupling beam model can significantly reduce structural acceleration by up to 80%. Reduction levels primarily depend on the coupling stiffness and critical train speed relative to the bridge’s fundamental frequency, with higher fundamental frequency bridges benefiting the most. These findings provide valuable insights for future structure-specific recommendations for adopting the coupling beam and multi-body train models. Full article

A rigorous study on optimized robust control is presented for non-preview (nulling-type) high-speed tilting rail vehicles. The scheme utilizes sensors on the vehicle’s body, contrary to that of preview tilt (which uses prior rail track information). Tilt with preview is the industrial norm nowadays but is a complex scheme (both in terms of inter-vehicle signal connections and when it comes to straightforward fault detection). Non-preview tilt is simple (as it essentially involves an SISO control structure) and more effective in terms of (the localization of) failure detection. However, the non-preview tilt scheme suffers from performance limitations due to non-minimum-phase zeros in the design model (due to the compound effect of the suspension dynamic interaction and sensor combination used for feedback control) and presents a challenging control design problem. We proposed an optimized robust control design offering a highly improved non-preview tilt performance via a twofold model representation, i.e., (i) using the non-minimum phase design model and (ii) proposing a factorized design model version with the non-minimum phase characteristics treated as uncertainty. The impact of the designed controllers on tilt performance deterministic (curving acceleration response) and stochastic (ride quality) trade-off was methodically investigated. Nonlinear optimization was employed to facilitate fine weight selection given the importance of the ride quality as a bounded constraint in the design process. Full article

For high-tech manufacturing industries, developing large-scale complex nonlinear dynamic systems must be taken as one of the basic works, formulating problems to be solved, steering system design in a more preferable direction, and making correct strategic decisions. By using effective tools of big data mining, Dynamic Design Methodology was proposed to establish a technical platform for Multidiscipline Design Optimization such as High-Speed Rolling Stock, including three key technologies: analysis graph of full-vehicle stability properties and variation patterns, improved transaction strategy of flexible body to MBS interface, seamless collaboration with weldline fatigue damage assessments through correct Modal Stress Recovery. By applying the above methodology, a self-adaptive improved solution was formulated with optimal parameter configuration, which is one of the more favorable options for higher-speed bogies. While within a velocity (140–200) km/h at λ_e < 0.10, car body instability’s influence on ride comfort can be easily improved by using a semi-active vibration reduction technique between inter-vehicles through outer windshields. Comprehensive evaluations show that only under rational conditions of wheel-rail matching, i.e., 0.10 ≥ λ_eN > λ_emin and λ_emin = (0.03–0.06), can this low-cost solution achieve the three goals of low track conicity, optimal route planning, and investment benefit maximization. So, rail vehicle experts are necessary to collaborate and innovate intensively with passenger transportation and steel rail ones. Specifically, by adopting rail grinding treatment, occurrence probability is controlled at 85% and 5% for track conicity of (0.03–0.10) and (0.25–0.35). By optimizing routing planning, operating across dedicated lines of different speed grades can achieve self-cleaning of central hollow tread wear over time. According to the inherent rigid-flex coupling relationship, geometric nonlinearities of worn wheel-rail contact should be avoided as much as possible for HSR practices. Only under weak coupling interfaces in the floor frame can the structural integrity of an aluminum alloy car body be ensured. Full article

This paper analyses the dynamic behavior of a rail vehicle using experimental and simulation analysis on a multi-rigid–flex body model. The mathematical models are developed considering the car body, bogie frame, and wheel axle for rail vehicles of rigid–flexible and multi-rigid formulations, taking the car body as rigid for the rigid body analysis and the flexible car body for flex–rigid analysis. A finite element model of the car body was developed in ANSYS, and substructure and modal analyses were performed. The mathematical model is validated through an experiment conducted by the Research Design and Standards Organization. Then, the validated model is further analyzed to evaluate the running comfort, using the Sperling ride index and the running safety, by investigating the derailment coefficient and wheel load reduction rate. The impact of flexibility on the vehicle’s running stability is investigated using the rigid body dynamics model and experimental data. Compared to experimental data, the simulation results reveal that elastic vibration cannot be neglected in vehicle dynamics, since the rigid–flexible coupling model is slightly more significant than the rigid-body model for ride comfort and safety. Full article

With the rapid development of urban rail transit, metro vehicles have become preferred choices for urban transportation. It is important to accurately evaluate the fatigue strength of a car body to ensure subway safety. A new method based on multiaxial stress criteria and cumulative fatigue damage theory was proposed for the fatigue strength assessment of welded joints of an aluminium alloy head car body subjected to variable cyclic loads. A local coordinate system was established, according to the geometrical characteristics of the weld. Local stresses perpendicular and parallel to the weld seam were obtained to calculate the stress ratio, stress range, and allowable stress value corresponding to the stress component. Then, the fatigue strength utilization of the joints was estimated to determine whether the fatigue strength of the weld met the design requirements. Moreover, the estimated fatigue life of the car body was predicted with cumulative fatigue damage theory. This method considers both the material utilization degree in multiple stress states and the estimated body fatigue life of the car body. The research results provide a reference and a more comprehensive guarantee for the fatigue strength evaluation of a subway car body’s welded structure to ensure vehicle safety. Full article

An auxiliary protection device (rail holding mechanism) was proposed to control the collision attitude of subway vehicles. The dynamics model of head-on collision of subway vehicles was established and verified by the full-scale collision test of the real car; then the force element structure of the rail holding mechanism was equated; finally, the vertical lift and the pitch angle of the three characteristic sections of car body and the wheelsets were used as the evaluation indicators to study the effects of the three design parameters: the gap distance ($x_1$), the linear stage distance ($\Delta x_2$) and the stiffness of linear stage ($k_1$). The results show that the linear stage distance has little influence on the collision attitude of the car body, while the $x_1$ and $k_1$ had a greater influence on the collision attitude of the car body. The reasonable reduction of the gap distance $x_1$ and increase the $k_1$ can effectively reduce the vertical lift of the wheelsets and alleviate the nodding phenomenon of the train, and reduce the derailment and jumping phenomenon during the train collision. Full article

The configurable and multi-articulated urban bus is a new type of urban vehicle with the advantages of road vehicles and urban rail trains. However, its articulated and long body structure will bring about difficulties in steering control and trajectory following. Moreover, the following carriages easily deviate from their expected path, leading to the fishtailing and folding of the compartment. In this paper, we propose a generic framework that allows the rapid building of kinematic models for the new train. By introducing the MPC theory, we design a trajectory tracking controller for a multi-articulated vehicle with an arbitrary number of carriages. To verify our models, we establish kinematic models and a trajectory tracking controller for a multi-articulated train with different number of compositions in MATLAB. Under the double-lane-change track and serpentine road conditions, the trajectory tracking of the train is simulated. The influence of the number of carriages, velocity, and length of carriage on the trajectory tracking are further analyzed. The experimental results show the feasibility of our method. Our findings thus provide significant guidance for the design, actual configuration, and trajectory tracking control of the new multi-articulated urban bus. Full article

Based on the paucity of studies on the analysis of the coupled vibration response of the train-track-overhead System, in this article, finite element software ABAQUS was integrated with multi-body dynamics software, Universal Mechanism (UM), to construct a joint simulation model of the train-track overhead system under a railway line, with the focus on the investigation of the influence of different track irregularity levels, speeds and damping coefficients on the coupled vibration response of the vehicle-track-overhead system. The findings demonstrate that the response of the train body is sensitive to track irregularity, which primarily impacts the safety index of train operation. The results also suggest that the level of track irregularity should be rigorously regulated above AAR5 during construction. The train-track-overhead system functions well and satisfies the overhead system’s design requirements when the train travels through the reinforced line at a speed of no more than 60 km/h. When the train speed is 100 km/h, the vertical acceleration exceeds the limit for the “I” overhead system. There is a possibility of excessive lateral acceleration of the train body and excessive lateral force of the wheel and rail when the train speed is greater than 60 km/h, which endangers the safety of the driver. While it has little effect on the mid-span and vertical displacements, the damping factor of the bridge has a substantial impact on the vertical acceleration and mid-span acceleration of the vertical and horizontal beams. The study’s findings provide useful guidance. Full article

In the switch rail section of a high-speed turnout, the wheel–rail lateral impact of the forepart of the curved switch rail is the most important factor affecting the passing performance. In order to reduce the lateral impact and improve the passing safety, a complete vehicle–track multi-body dynamics model is devised in this paper. The variation of the wheel–rail relationship when the train passes through is analyzed. The lateral force and derailment coefficient are calculated under different parameters, and the wear index is also calculated under some working conditions. The results show that properly reducing the lateral damping of the curved switch rail can effectively reduce the wheel–rail lateral force and derailment coefficient of this section, while keeping the track shape undamaged. The optimization of rail cant design plays an important role in alleviating lateral wheel–rail impact. Decreasing the height reduction of the switch rail is helpful to optimize the lateral force of the forepart of the curved switch rail. The selection of a suitable cutting mode for switch blade and reasonable control of the wheel–rail impact angle as well as passing speed have positive effects on controlling the lateral wheel–rail impact of the forepart of the curved switch rail. Full article

With railway interoperability, new trains are allowed to move on the French railway network. These trains may present different designs from standard trains. This work aims to complete the current approach for vehicle admission on the railway network, which is defined in technical baselines. Historically, computation rules for traffic conditions are based on simplified analytical works, which are considerably qualitative. They have evolved through feedback and experimental campaigns to comply with the track structure evolution. An efficient methodology based on numerical simulation is needed to evaluate railway vehicle admission to answer this issue. A perspective to update these computation rules is to evaluate the structural fatigue in the rail. That is to say, fatigue is caused by bending and shear stresses. The complexity of the railway system has led to an investigation at first of the vertical response of the railway track and quantifying its contribution to the rail’s stress response. In that sense, this paper investigates the vertical track response to a moving railway vehicle at low frequencies. For this purpose, a lightweight numerical model for the track, a multi-body model for the vehicle, and a random vertical track irregularity are proposed. More explicitly, the track model consists of a two-layer discrete support model in which the rail is considered as a beam and sleepers are point masses. The rail pads and ballast layer are modelled as spring/damper couples. Numerical results show a negligible effect of track inertia forces due to high track stiffness and damping. Nevertheless, this assumption is valid for normal rail stresses but not for ballast loading, especially in the case of sleeper voids or unsupported sleepers. Hence, the prediction of the mechanical stress state in the rail for fatigue issues is achieved through a static track model where the equivalent loading is obtained from a dynamic study of a simplified vehicle model. A statistical analysis shows that the variability of the vertical track irregularity does not influence the output variabilities like the maximum in time and space of the normal and shear stress. Full article

Wear and fatigue of wheels have a great effect on the maintenance of railway vehicles and running safety. In the case of an urban railway where no rail lubrication system is installed, it is reported that the risk of wheel damage is high in curved sections. In the present study, we intended to present a method of designing a wheel profile of city trains that can minimize wear and fatigue in curved sections, using the multi-objective optimization method. In multi-objective optimization, we explored a wheel profile design that can reduce wear and fatigue of wheels at the same time, while also satisfying the design performance constraints, such as the safety against derailment and contact force between rails and wheels. A multi-body dynamic analysis was conducted for design performance evaluation, and the best wheel profile design was produced utilizing the analysis result. A wheel profile with minimized wear, a wheel profile with minimized surface fatigue, and a wheel profile with both minimized wear and surface fatigue that can improve the performance of city train wheels were presented respectively using a Pareto-optimal Solution, which is the result of multi-objective optimization. The running safety performances such as derailment and lateral force of the optimized wheel profiles showed improved characteristics when compared to those of the initial wheel profile. Full article