Railway Vehicle Carbody Research Articles

Testing the Effectiveness of the Anti-Bending Bar System to Reduce the Vertical Bending Vibrations of the Railway Vehicle Carbody Using an Experimental Scale Demonstrator

Testing the Effectiveness of the Anti-Bending Bar System to Reduce the Vertical Bending Vibrations of the Railway Vehicle Carbody Using an Experimental Scale Demonstrator

Basic study on vertical vibrations suppression in railway vehicle carbody by secondary suspension control using bogie vertical vibration velocity

Basic study on vertical vibrations suppression in railway vehicle carbody by secondary suspension control using bogie vertical vibration velocity

Parameters optimum of multiple underframe suspended equipment on high-speed railway vehicle carbody vibration control by using an improved genetic algorithm

Carbody vibration control and ride comfort improvement are important research parts of high-speed railway vehicle dynamic. The effectiveness of utilizing carbody underframe suspended equipment as dynamic vibration absorbers for carbody vibration suppression has been validated. While previous research has focused mainly on a single suspended equipment without considering its vibration tolerance, a balance must be struck between reducing carbody vibration and maintaining equipment performance. To address the challenging, a multi-objective and multi-parameter optimization method is employed, integrating an improved niche genetic algorithm (INGA) into the numerical simulation process. Considering carbody flexible and multi-suspended equipment, a rigid-flexible dynamics model of a high-speed railway vehicle is established and validated on a vehicle dynamics test rig. Based on the numerical analysis, the optimal parameter combination of the stiffness and the longitudinal installation position is obtained from an evaluation function that comprehensively assesses the vibration performance of both the vehicle carbody and the equipment. Comparative analysis between the results obtained from the optimal and primitive parameters demonstrates that the optimization process not only achieves significant improvements in carbody vibration reduction but also effectively controls equipment vibration within reasonable limits. The multi-objective and multi-parameter optimization method applied on carbody underframe suspended system proves to be valuable in improving the dynamic performance of high-speed railway vehicles.

The Effect of the Traction Rod on the Vertical Vibration Behavior of the Railway Vehicle Carbody

Although research has shown that through the additional rigidity introduced in the secondary suspension, traction rods can affect the vertical dynamic performance of railway vehicles, this topic has been less studied by researchers in the field. In this paper, the effect of a traction rod on the vertical vibration behavior of a carbody of a railway vehicle is analyzed, using the results obtained through numerical simulations. Numerical simulation applications are developed based on a vehicle model, where the vehicle carbody is modeled using a free-free equivalent beam Euler–Bernoulli, and the bogie chassis and wheelsets are represented by rigid bodies linked together by Kelvin-Voigt systems that model the secondary suspension and the primary suspension. The novelty element of this paper is found in the model of the traction rod. This includes traction rod damping, which has been neglected in previous research. The stiffness and damping of the traction rod are represented by a longitudinal Kelvin–Voigt system integrated into a secondary suspension model. The effect of the traction rod on the vertical vibration behavior of the vehicle carbody is analyzed based on the power spectral density of the acceleration, the root mean square of acceleration, and the ride comfort index, for three cases for analysis: a ‘without traction rod’ case, a ‘with traction rod—with damping’ case, and a ‘with traction rod—without damping’ case. The conclusions of the paper highlight the influence of the stiffness and damping of the traction rod on the vibration level of the carbody, especially in its middle. Depending on the stiffness of the traction rod, significant increases in the ride comfort index are obtained, which at high velocities can exceed 300%. Damping of the traction rod reduces the ride comfort index by up to 10%.

Influence of the Suspension Model in the Simulation of the Vertical Vibration Behavior of the Railway Vehicle Car Body

The evaluation of the vibration behavior of railway vehicle car bodies based on the results of numerical simulations requires the adoption of an appropriate theoretical model of the suspension which considers the important factors that influence the vibration level of the car body. In this paper, the influence of the secondary suspension model on the vertical vibration behavior of the railway vehicle car body is investigated, based on the results of numerical simulations on the frequency response functions of the acceleration, the power spectral density of the acceleration and the root mean square of the acceleration of the car body. Numerical simulation applications are developed based on a rigid-flexible coupled vehicle model with seven degrees of freedom, corresponding to car body vibration modes: bounce, pitch, and first vertical bending mode, and bogie vibration modes: bounce and pitch. Four different models of secondary suspension are integrated into the vehicle model, namely a reference model and four analysis models. Analysis models include systems through which the pitch vibration of the bogies is transmitted to the car body, influencing its vibration behavior and, respectively, a system that takes the relative angular displacement between the car body and the bogie and a system that models the transmission system of the longitudinal forces between the bogie and the car body are analyzed. The effects of these two systems on the vibration behavior of the railway vehicle car body are analyzed both for each system separately and together. In the conclusions of the paper, the influence of the secondary suspension model on the vibration level at the resonance frequencies of the vertical bending of the car body and the pitch of the bogie is pointed out. It also highlights the important contribution of the transmission system of the longitudinal forces between the bogie and the car body in transmitting pitch vibrations of the bogies to the car body, with effects on the vibration level of the car body at high speeds.

A strategy for lightweight designing of a railway vehicle car body including composite material and dynamic structural optimization

AbstractRolling stock manufacturers are finding structural solutions to reduce power required by the vehicles, and the lightweight design of the car body represents a possible solution. Optimization processes and innovative materials can be combined in order to achieve this goal. In this framework, we propose the redesign and optimization process of the car body roof for a light rail vehicle, introducing a sandwich structure. Bonded joint was used as a fastening system. The project was carried out on a single car of a modern tram platform. This preliminary numerical work was developed in two main steps: redesign of the car body structure and optimization of the innovated system. Objective of the process was the mass reduction of the whole metallic structure, while the constraint condition was imposed on the first frequency of vibration of the system. The effect of introducing a sandwich panel within the roof assembly was evaluated, focusing on the mechanical and dynamic performances of the whole car body. A mass saving of 63% on the optimized components was achieved, corresponding to a 7.6% if compared to the complete car body shell. In addition, a positive increasing of 17.7% on the first frequency of vibration was observed. Encouraging results have been achieved in terms of weight reduction and mechanical behaviour of the innovated car body.

Scale Models to Verify the Effectiveness of the Methods to Reducing the Vertical Bending Vibration of the Railway Vehicles Carbody: Applications and Design Elements

The purpose of this paper is to present applications and design elements of scale models of the carbody of railway vehicles integrated in experimental laboratory systems to verify the effectiveness of the methods to reduce vertical bending vibration of the carbody. In the first part of the paper, some applications of such experimental systems are presented, which include different scale models of the railway vehicle carbody. In the second part of the paper, the structure and dimensioning elements of a new demonstrative experimental system, specially designed by the authors of the present paper for testing the functionality of an original method of reducing the vertical bending vibrations of the carbody of railway vehicles, are presented. This method is based on an innovative approach that involves the use of a passive system consisting of two bars rigidly mounted on the longitudinal beams of the carbody underframe, having the role of opposing the bending of the carbody. The main element of the demonstrative experimental system is the scale model of the vehicle carbody, reduced to a beam, on which the two bars, called anti-bending bars, are mounted. For the dimensioning of the experimental model of the carbody and the anti-bending bars, original methodologies are developed in which several conditions are involved. In the case of the dimensioning of the experimental model of the carbody, the conditions refer to the convenient adoption of the scaling factor of the dimensions of the real carbody from the perspective of the practical realization of the experimental model of the carbody, ensuring the buckling stability of the demonstrative experimental system, achieving natural frequency of the vertical bending of the real carbody and avoiding the interference of the bounce vibration with the vertical bending vibration of the demonstrative experimental model of the carbody. The dimensions of the anti-bending bars are established from the condition that the vertical bending frequency of the experimental model of the carbody is outside the range of sensitivity of the human body to vertical vibration. Additionally, the natural frequency of the vertical bending vibration of the anti-bending bars must be chosen to avoid interference with the vertical bending vibration of the experimental model of the carbody. The effectiveness of the anti-bending bars in reducing the vertical bending vibration of the experimental model of the carbody is investigated with the help of numerical simulation results developed based on an original theoretical model of the experimental model of the carbody with anti-bending bars.

Basic Study of Vertical Vibrations Suppression in Railway Vehicle Carbody by Secondary Suspension Control Using Bogie Acceleration

Basic Study of Vertical Vibrations Suppression in Railway Vehicle Carbody by Secondary Suspension Control Using Bogie Acceleration

Numerical study on the effect by the structural characteristics of carbody shell faces on elastic vibrations of railway vehicle carbodies

Numerical study on the effect by the structural characteristics of carbody shell faces on elastic vibrations of railway vehicle carbodies

A novel vibration analytical model for thin-walled box-like long cylindrical structures combining elastic plates and straight and curved beams

This paper proposes a novel analytical model for elastic vibrations of thin-walled box-like long cylindrical structures, commonly observed in railway vehicle carbodies, aircraft, and buses. Here, we focus on railway vehicle carbody, where three-dimensional elastic vibrations are a significant problem for improving ride quality. The carbody is modeled as a box-like structure consisting of elastic plates and beams. The condition to connect those structural members is satisfied by introducing artificial springs at their joints. From observations of some actual carbody's elastic vibration modes, it has already been found that the relative vertical deformation between the roof and floor interacts with lateral deformation of side structures. To express this three-dimensional deformation simply, the authors introduce curved elastic beams as pillars in the side structures in this study; therefore, the newly proposed model is called the curved box model. The free vibration of the curved box model has been investigated in this paper by applying the Ritz method to derive the eigenvalue problem. The modal characteristics (natural frequencies and mode shapes) of elastic vibrations are calculated. The vibration analysis procedure is validated by comparing those results with those obtained from a finite element model. As some numerical examples, the effects of cross-sectional shape changes on the natural frequencies of elastic vibration modes are presented.

A novel vertical elastic vibration reduction for railway vehicle carbody based on minimum generalized force principle

Aiming at the vertical elastic vibration reduction of a railway vehicle carbody, the traditional technology mainly focuses on the design of modal frequency, the method of increasing damping and the design of dynamic vibration absorber (DVA), with little attention to the design of modal shape. In this paper, a novel vertical elastic vibration reduction method based on the minimum generalized force principle (MGFP) is proposed, i.e., the vertical elastic vibration of carbody is reduced by adjusting its own parameters (weight distribution and stiffness distribution) to control the first-order vertical bending (FVB) modal shape nodes to the carbody–bogie interface positions. Firstly, to better apply MGFP, a factor called generalized force factor (GFF) that can determine the level of generalized force (GF) is proposed. By improving theoretical model of a railway vehicle carbody, the traditional uniform cross-section Euler–Bernoulli beam (UCEB) is replaced by variable cross-section Euler–Bernoulli beam (VCEB) model, and the influencing factors of modal frequency and modal shape node locations can be investigated by the VCEB model. Then, the vertical vehicle system dynamics model is established based on the VCEB carbody model, and the influence of weight distribution, stiffness distribution and carbody–bogie interface positions on the elastic vibration is analyzed under a sweep frequency signal and track irregularities. Finally, the vibration reduction method is verified by a full-scale roller rig test. The theoretical analysis and experimental results show that: by changing the weight distribution or stiffness distribution of the carbody, the FVB modal shape node locations can be effectively controlled, and then combined with the design of carbody–bogie interface positions, the vertical bending elastic vibration of the carbody can be reduced. The vibration reduction method proposed in this paper can be applied to the design of new carbodies or the layout optimization of carbody subsidiary mass.

Dynamic size optimization approach to support railway carbody lightweight design process

The transition to a globalised electrical power supply pushes rolling stock manufacturers to find structural solutions for reducing the power required by the vehicles. Within a market where details can make the difference in economic terms, the concept of design optimization is becoming established. However, current industrial procedure for the evaluation of carbody structural strength, in static field and according to EN 12663-1:2015 standard, does not include any optimization process. More in general, optimization processes, and especially dynamic optimization, are not widely used for designing of railway vehicles. In this framework, the present paper proposes a new dynamic optimization approach to support the design of railway vehicle carbodies subjected to static loads. Proposed methodology aims to minimize the mass of the metallic structure, working on the thicknesses of the optimized components, maintaining the baseline geometry. The constraint function was imposed on the first natural vibration frequency of the system. The optimization strategy is based on a dynamic size optimization process in conjunction with modal analysis techniques, applied on the single carbody shell. The procedure has involved the roof assembly of a single tram vehicle body. The proposed approach is resulted numerically efficient in terms of calculation times. Encouraging results have been achieved in terms of mass saving and mechanical behaviour of the carbody shell. Optimized components were 21% lighter than the original, that corresponds to 3% if evaluated on the total mass of the single carbody metallic structure. The methodology turns out to be a useful tool for supporting designers to reduce the mass of the carbody structures, reducing overdimensioning condition that could affect the carbody structure.

Design of Experiments to determine the influence of test procedure on Experimental Modal Analysis

This study conducts a fractional factorial design to evaluate the influence of test settings on the results of Experimental Modal Analysis (EMA) which is the method often used to determine natural frequencies and damping rate of structures. The structures in this work are simple beams cut from lightweight rail-way vehicle car bodies. The original specimens have very low structural damping, whereas others have been supplemented with Constrained Layer Damping (CLD) patches to significantly increase vibration energy dissipation. It will be shown that test settings do influence Experimental Modal Analysis (EMA) results in ways that are seldom intuitive or foreseeable. The statistical significance of some factors, or combinations thereof, proves that their effects are not entirely attributable to random phenomena. The results show that a statistical analysis like the one presented in this paper should be conducted prior to extracting accurate damping data from EMA tests. The technique reduces the number of tests needed to assess the influence of settings. This technique, not only highlights the statistically significant factors, but also quantifies their influence, thus helping the researcher make an informed decision regarding test settings. • The analysis of variance determines which factors do have a significant influence on EMA analysis. • Test settings depend on beam type, modal parameters, and support configuration. • Test settings have a strong influence on modal damping. • The fractional factorial design reduces the number of tests necessary. • The proposed statistical analysis should be conducted prior to extracting accurate damping data.

Numerical study on the effect of side structure on elastic vibration characteristics of railway vehicle carbodies

Three-dimensional (3D) elastic vibrations that occur in railway vehicle carbodies can have negative impacts on ride quality, and efficient numerical analysis methods are required to study effective counter measure. The authors have proposed a method using a new vibration analysis model in which the railway vehicle carbody is modeled as a box-like structure composed of elastic plates, straight beams, and curved beams. This model can easily express complex 3D vibration shapes observed in actual carbody such as the interaction between the roof, floor, and side structures. This article reports the results of an improvement of this model and a series of studies of the effects of curveture and rigidity changes in the side structures on the natural modal characteristics of the elastic vibrations.

A study on constraint condition setting for spatial matrices identification of flat plate structures

Elastic vibrations have become a considerable problem for recent light-weighted and structurally simplified machines to increase their performance and value. In order to study vibration reduction, numerical investigations are required, and the finite element (FE) analysis is used widely for those purposes. However, a detailed FE model for elastic vibration analysis is not easy to build, particularly in cases where the target structure size is large, such as railway vehicle carbodies. Therefore, there are demands to identify spatial matrices (mass, stiffness, and damping matrices) from experimental data and use them to investigate structural modification to reduce elastic vibrations. This study aims to identify spatial matrices under the condition that the target structure consists of a lattice-like structure (each lattice point represents a vibration measurement point) and has physically reasonable constraint relations. Using the stationary excitation test data for a flat plate structure (a 1:10 scale model of the underframe of a railway vehicle), this paper applies the FRF (frequency response function) direct method to identify the spatial matrices. The four constraint conditions are introduced in the identification procedure, and the identification results are tested by measured FRFs and modal characteristics. It has been demonstrated that considering the connection with the next and two ahead lattice points leads to a good identification result.

Active Vibration Control of Railway Vehicle Car Body by Secondary Suspension Actuators and Piezoelectric Actuators

Active vibration suppression of high-speed electric multiple unit (EMU) car bodies was studied by the combined use of secondary suspension actuators and piezoelectric actuators. A vertical dynamics model was established considering secondary suspension actuators and piezoelectric actuators. The positions of the piezoelectric actuators and sensors were optimized using <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> norms. The feedback controller was designed using a robust optimal control method. The effects of the vibration devices and active control methods on the vehicle dynamic performance were simulated using MATLAB. The dynamic performance differences among the passive suspension vehicle, secondary vertical actuator installation vehicle, and active vibration control vehicle were compared and analyzed. The results show that the piezoelectric actuators and piezoelectric sensors were arranged at distances of 7.15, 12.25, and 17.35 meters from the left end of the car body, and the normalized <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> norms of the first and second order elastic modes of the car body were the largest, which can be used as piezoelectric actuators and sensor placement positions. Secondary suspension actuators can reduce rigid car body vibrations, and piezoelectric actuators can reduce elastic vibration. The higher the speed, the better is the acceleration suspension effect. When the vehicle speeds were 200 km∙h <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> and 350 km∙h <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> , the vehicle vibration acceleration decreased by 10% and 18%, respectively. Compared with the passive suspension system, the active vibration suspension system with a robust controller can reduce the rigid and elastic vibrations of the vehicle and improve ride comfort.

Development of Bogie-Mounted Dynamic Vibration Absorbers for Reducing Elastic Vibration of Railway Vehicle Carbodies

This paper describes the improvement of passenger comfort in railway trains. Elastic vibrations of railway vehicle carbodies, which occur in a frequency range that is easily perceived by humans, affect comfort of passengers. Therefore, methods to reduce elastic vibration are required. In this study, we focused on bogie vibration to develop a Bogie-Mounted Dynamic Vibration Absorbers (BMDVA) to reduce them. First, after specification study, design, and fabrication of the BMDVA, vibration test of the BMDVA alone was conducted. Second, an analytical model of a railway vehicle was created using Matlab, a numerical analysis software. Third, the vibration characteristics of this model were evaluated to demonstrate its usefulness. Finally, a railway vehicle model with the BMDVA installed was created, and vibration reduction effects were verified through excitation and running simulations. As a result, it was confirmed that the proposed BMDVA was effective in reducing elastic vibration.

Vibration Isolation of Railway Vehicle Car body using Semi-active Suspension

In the past, the magnetorheological (MR) suspension for railway vehicle has obtained great attention for the isolation of vibrations. This work presents a numerical approach to analyse skyhook and ground hook semi-active control methods for railway vehicle suspension. A 10 DoF model of the railway vehicle system is formulated for the comparative analysis between conventional passive and semi-active suspension control in the present study. The non-linear analysis is investigated in time and frequency domain for the sinusoidal excitations from the track.

Influence of Structural Stiffness and Loss Factor on Railroad Vehicle Comfort

This paper presents a new formulation for analyzing a beam on elastic supports traveling on irregular profiles. The model is a first approximation of a passenger railway vehicle car body. The main difference with previous works is the use of a complex modulus to represent structural damping rather than relying on equivalent viscous terms. The formulation groups rigid body modes with flexible modes and proposes a matrix form that is easy to interpret and solve in the frequency domain. Comfort indexes are readily obtained from weighted response spectral densities. The model is used to assess the influence of structural damping and stiffness on comfort. It will be shown that the evolution of comfort with stiffness is non-monotonic and, therefore, comfort does not always improve as stiffness increases.

In situ and experimental analysis of longitudinal load on carbody fatigue life using nonlinear damage accumulation

In this paper, a multi-disciplinary analysis method is proposed for evaluating the fatigue life of railway vehicle car body structure under random dynamic loads. Firstly, the hybrid fatigue analysis method was used with Multi-Body System simulation and finite element method for evaluating the carbody structure dynamic stress histories. The dynamics stress is calculated from the longitudinal load using longitudinal train dynamics. Secondly, the nonlinear damage accumulation model was used in fatigue analysis, and carbody structure fatigue life and fatigue damage were predicted. The mathematical model simulations are compared with results produced experimentally, showing good agreement. Finally, the mode is determined after the finite element model is established. To achieve the dynamic stress at each node, the modal response is used as excitation. The carbody damage was obtained by combining dynamics stress with the NMCCMF damage accumulation model. As a result, the effect of longitudinal load on carbody fatigue damage is investigated. The longitudinal load contributes significantly to the fatigue damage of the carbody.