Results for "railway dynamics" : Scipedia

Collection of open thesis in transport research

Identification des paramètres d’un modèle TGV

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This work investigates the applicability of identification methods to the suspension parameters of a TGV multi-body model. The aim is to adjust the model to the real system by estimating the suspension parameters from measured vehicle response data. Due to the nonlinear behavior of the system the time-domain based model updating has been chosen. It requires the definition and minimization of a misfit function in the time domain describing the distance between model and measurement. The fastest convergence is obtained by the use of gradient methods requiring the calculation of the derivatives of the misfit function relative to every parameter. Since the calculation from finite differences is time consuming and less accurate the gradients are calculated from the adjoint method. The application to a simplified bogie model with known mathematical description allows the identification of its suspension parameters. The presence of local minima in the misfit function of the TGV model requires the use of global optimization methods. The simulated annealing and the genetic algorithm method give important reductions of the misfit function and improved parameter estimations. In following work this information could be used for further applications like the condition monitoring.; Ce travail étudie l’applicabilité des méthodes d’identification aux paramètres de la suspension d’un modèle multi-corps du TGV. L’objectif est de caler le modèle par rapport au système réel par une estimation des paramètres de la suspension en utilisant la réponse du véhicule mesuré. A cause du comportement nonlinéaire du système la méthode temporelle de recalage a été choisie. Elle nécessite la définition et minimisation d’une fonction coût qui décrit la distance entre le modèle et la mesure. La convergence la plus rapide est obtenue avec des méthodes gradient qui demandent le calcul des dérivés de la fonction coût par rapport á chaque paramètre de la suspension. Comme le calcul par des différences finis est coûteux et moins précis la méthode adjoint a été implémentée. L’application à un modèle simplifié d’un bogie avec une description mathématique connue permet d’identifier les paramètres de la suspension. La présence des minima locaux dans la fonction coût du modèle TGV nécessite l’utilisation des méthodes globales. Le recuit simulé et l’algorithme génétique donnent des réductions importantes de la fonction coût et des estimations pour les paramètres du modèle TGV. Dans des travaux ultérieurs, ces informations pourraient être utilisées pour d’autre application comme le « condition monitoring ».

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Collection of open thesis in transport research

MULTIBODY APPROACH FOR RAILWAY DYNAMIC ANALYSIS

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En este trabajo se ha llevado a cabo el desarrollo de una herramienta computacional para la simulación dinámica de vehículos ferroviarios. El modelo está basado en técnicas multicuerpo debidas a Shabana. Con respecto a otras metodologías existentes, la propuesta hace uso de un conjunto de sistemas de referencia que permite el empleo de coordenadas independientes sin la posibilidad de configuraciones singulares debidas a grandes giros. El conjunto de sistemas de referencia sirve de base para formular de manera precisa el problema de contacto rueda-carril. El programa está diseñado para considerar de forma flexible distintas configuraciones de vehículo así como diversas geometrías de trazado. La estructura del programa está abierta a cambios orientados a la mejora del modelo de contacto rueda-carril o a la implementación de la dinámica estructural de la vía. Se ha implementado un modelo eficiente que permite detectar con precisión las coordenadas de los puntos en contacto localizados en la interfase entre la rueda y el carril. La herramienta de simulación desarrollada en esta tesis se ha aplicado para diferentes casos-estudio con el objetivo de validar la idoneidad de la metodología propuesta en el análisis del sistema ferroviario. Se ha realizado una comparación entre los resultados obtenidos por la herramienta de simulación presentada y los resultados ofrecidos por varios programas comerciales de simulación dinámica en el análisis del vehículo de Manchester Benchmark. Además, la herramienta se ha empleado para desarrollar un análisis dinámico del vehículo de la locomotora TGV y los resultados obtenidos se han comparado con los ofrecidos por el programa comercial SIMPACK para el mismos modelo de vehículo, bajo las mismas condiciones de operación. Finalmente, sobre la base de la calidad de los resultados, se puede concluir que la herramienta de simulación es fiable y eficiente para emplearse en el análisis dinámico de los diferentes sistemas ferroviarios.

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Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería

Structural analysis of a railway bridge using the FEM-DEM technique

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The objectives of this work are focused on giving an answer to the problems presented in the operation of a railway bridge, using the FEM-DEM numerical technique considering static and dynamic loads. The purpose is to find out the existing breakage mechanisms in the bridge.

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Collection of open conferences in research transport

ANALYTIC METHOD TO IDENTIFY TRAIN LOAD FROM INTEGRATED SLEEPER IN-SITU

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International audience; The degradation of railway tracks can be observed through several measurement techniques. Recently, a method to diagnose the railway track using Fiber Bragg gratings (FBG) has been proposed. FBG are integrated inside the railway sleeper and is named a "Smart [...]

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Collection of open conferences in research transport

WAVE FINITE ELEMENT METHOD AND MOVING LOADS FOR THE DYNAMIC ANALYSIS OF RAILWAY TRACKS

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International audience; Based on the finite element method, the wave finite element method (WFE) permits to analyze the dynamics of a periodic structure by using a wave decomposition of one period. This method reduces the number of DOF and it has advantages in calculation time. However, [...]

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Collection of open conferences in research transport

Bayesian calibration of mechanical parameters of high-speed train suspensions

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International audience; The objective of the work presented here is a bayesian calibration of parameters describing the mechanical characteristics of high-speed train suspensions for maintenance purposes. This calibration is achieved by comparing simulation results to on-track accelerometric [...]

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Collection of open conferences in research transport

Propagation in Soil of Vibrations due to a Tramway

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International audience; Tramway traffic may produce vibrations propagating in soil, which implies vibration annoyance for people living or working in neighbouring buildings. Thus vibration is one of the most important consequences to be considered when planning new lines. Dynamic performance evaluation of tramway tracks is required to validate or modify the existing means that reduce vibrations. This paper presents experimental and theoretical investigations of vibrations caused by passing tramways in Nantes, France. A method is proposed to predict ground-borne vibrations, so as to estimate a trouble gauge concerning, for example, the impact of a future tramway line. This method is applied and validated in comparison with in situ measurement data obtained previously.Numerous studies have been carried out on vibrations induced by surface railways, for example, Lefeuve-Mesgouez et al. [1], Picoux [2] and Sheng et al. [3]. In the case of a tramway line, a two-dimensional model can be used to predict the behaviour of the propagation analysis of the corresponding vibrations, considering a thin layer model for the soil and using exact dynamic stiffness matrices [4,5], expressed in the frequency-wave number domain for the layered ground and the half-space [6]. Note that other models can be applied to predict vibration propagation, such as boundary element formulations [7].In this paper, soil is characterized by measurements using the spectral analysis of surface waves, often called the SASW method. Here the usual two-station approach is used [8]. The objective is to accurately define shear moduli and layer thicknesses. Then the general Barkan relation [9] is applied to obtain the dispersion curve and the damping ratios. Soil characterisation needs further improvements using a complete inversion method such as Occam's algorithm [10]. Nonetheless this first approach, often called "equivalent depth approach" already gives sufficient soil profile information to model waves propagation.Numerical methods, such as the wavenumber matrix approach, can be used for the prediction of the soil response to a hammer impact, i.e. to obtain the transfer functions. An alternative solution is proposed: the method is based on the assumption that for each frequency, the vertical measured shear wave velocity corresponds to a homogeneous half-space [9]. The vibratory response is obtained by multiplying the load spectrum by the transfer function in order to obtain the whole contribution of tramway passage for each measurement point. Results are given in the time domain and compared with in situ measurements.

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Collection of closed articles in transport research

Secondary suspension of railway vehicles - air spring modelling : Performance and critical issues

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This paper shows the importance of modelling the components of the suspension when performing dynamics simulations of a railway vehicle. Focusing on the air spring secondary suspension, a process to define an accurate component model is proposed based on a combination of laboratory [...]

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WCCM-APCOM 2022

A SMART PASSIVE YAW DAMPER FOR THE REDUCTION OF LATERAL CONTACT FORCES IN LOW-RADIUS CURVED TRACKS

Abstract

High-speed trains are equipped with yaw dampers to prevent the arising of hunting motion. These suspension components play an important role in improving the vehicle stability. However, the presence of yaw dampers increases the steering resistance of the bogies, especially in transient [...]

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