This thesis investigates the influence of wheelset structural flexibility and track flexibility on the vehicle-track dynamic interaction, mainly in terms of wheel-rail forces up to 200 Hz, using simulations and measurements. The previous knowledge in this field is first reviewed and summarized, then two case studies are selected for investigation. The first case study involves a locomotive running on a tangent track section at a speed of 140 km/h, while the second one deals with a newly designed motor coach running at two adjacent and tangent track sections with different track components and at speeds up to 280 km/h. For the locomotive case study, the wheelset dynamic properties are first investigated through experimental modal analysis (EMA) for a frequency range of 0-500 Hz, assuming free boundary conditions. The EMA results showed relatively low wheelset eigenfrequencies. A three-dimensional finite element (FE) model, which also includes the wheelset gear-box, is then developed and validated against the measurements for frequencies up to 200 Hz with good agreement. The FE results displayed a significant influence of the wheels’ flexibility on the wheelset’s total structural flexibility. In order to assure proper representation of the track flexibility the vertical and lateral dynamic track properties at a sleeper are measured through a special vehicle at standstill, and measured track irregularities are used. In the numerical simulations, the wheelset structural flexibility is introduced using the calculated eigenmodes above while so-called moving track models are used to model the track flexibility. The simulated wheel-rail forces are then validated against measured ones obtained from corresponding on-track measurements. Results from the simulations highlight the importance of proper track flexibility modelling and track data and also show a significant influence of the wheelset structural flexibility on the lateral track forces. For the motor coach case study, the wheelset dynamic properties are determined through numerical modal analysis using a rather simple FE model and a number of eigenmodes are then introduced in the simulations. The vertical and lateral track dynamic properties at selected track sections are measured using the standstill technique but rolling stiffness measurements, where the vertical track flexibility in the frequency range 5-50 Hz is measured continuously along the track, are also included. The track flexibility is introduced through moving track models. Measured track irregularity and vertical track roughness are also considered. Basic numerical simulations, where the calculated track forces are compared to measured ones, are first performed and followed by a set of parametric studies. The results display a significant influence of the track flexibility on vertical wheel-rail forces for frequencies above 80 Hz, with higher forces for the stiffer track (but weaker rails). The effect of wheelset structural flexibility on the lateral force is also confirmed. The parametric studies highlight the importance of track flexibility modelling and show that modifications of the vertical track receptance, motivated by uncertainties in the pertinent measurements, can improve the simulated forces. / QC 20100701

Orientador: Euclides de Mesquita Neto / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-15T00:21:00Z (GMT). No. of bitstreams: 1 Sousa_AmilcarDanielOgazde_M.pdf: 3046046 bytes, checksum: 289cbf406a5a9496df2d904d50f26fe8 (MD5) Previous issue date: 2007 / Resumo: A presente dissertação descreve a resposta de um sistema dinâmico constituído por um rotor, uma fundação rígida e um solo homogêneo. O rotor considerado é um modelo de Jeffcott (Laval) com amortecimento externo. O rotor está fixado em uma fundação rígida que, por sua vez, está assentada em um solo homogêneo modelado como um semi-espaço viscoelástico. O sistema é analisado no plano do rotor. Uma cuidadosa dedução das equações de movimento é apresentada. A resposta dinâmica do solo é sintetizada com auxílio do Método dos Elementos de Contorno. A análise é conduzida no domínio da freqüência, reproduzindo o comportamento estacionário do rotor e da fundação. A influência de diversos parâmetros do sistema, sobre a resposta dinâmica do rotor e fundação é estudada. Entre os parâmetros geométricos considerados estão a altura do centro geométrico da fundação em relação ao solo e a altura do rotor em relação à fundação. O papel das razões de inércia entre rotor e fundação é investigado. A influência do amortecimento interno e do amortecimento geométrico do solo é analisada. O tipo de contato entre a fundação rígida e o solo também á estudada. / Abstract: The present work describes the dynamic response of a system consisting of a rotor, a rigid foundation and a homogeneous soil profile. The rotor is considered a Jeffcott (Laval) model with external damping which is attached to a rigid foundation. The foundation is supported by a viscoelastic half-space. The analysis is conducted in the plane of the rotor. A detailed deduction of the system's equation of motion is presented. The soil response is synthesized by the Boundary Element Method. The analysis is conducted in the frequency domain, leading thus to the stationary response of rotor and foundation. The influence of distinct system parameters of the dynamic response of rotor and foundation is addressed. The geometric parameters include the distance of the foundation mass center to the soil-foundation interface and the height of the rotor with respect to the foundation. The effect of rotor to foundation inertia ratio is investigated. The role of soil internal and geometric damping on the system response is also addressed. The influence of the contact type at the soil foundation interface, bonded or smooth, is also considered. / Mestrado / Mecanica dos Sólidos e Projeto Mecanico / Mestre em Engenharia Mecânica

Please read the abstract in the section 00front of this document / Thesis (PhD)--University of Pretoria, 2009. / Civil Engineering / unrestricted

M.S. / Electronics, wearable devices are important in nowadays informationalized lifestyle. One prominent problem with those electronic devices is that almost all of them depend on batteries as power sources, which has become a bottleneck due to the limited life span. Constantly replacing or recharging batteries is inconvenient, burdensome, and sometimes even impossible. This problem is more intractable when the power cannot be accessed conveniently (such as during fieldwork, hiking, and military missions). What’s more, no matter how much energy the battery stores, it will drain eventually. In addition, large battery will add extra weight and occupy space. Substitute power supply that conquer these aforementioned dilemmas are thus highly desirable. Energy harvesting by its nature could be an inexhaustible replacement for batteries. This insight inspires so many energy harvesting researchers tirelessly working and trying to make it happen. Suspended backpack is an effective way to harvest energy from human motions.This study evaluates different energy harvesting backpack configurations and comprehensively assessed the power generation, dynamic interaction and human comfort. Dynamic modelling considering the dynamic interaction between human body and backpack is established to optimize the design. Bench tests and treadmill tests are carried out to evaluate the real performance. Experimental results show that the harvesting energy from human motion via a suspended energy-harvesting backpack could incessantly generate considerable electricity applicable for charging carry-on electronic devices. The potential application scenarios of this technology include solders, field-workers as well as outdoor adventure.

O problema da interação dinâmica entre ponte rodoviária e veículo pesado tem sido, há pouco mais de uma década, tema de muitos estudos. O objetivo é considerar as ações dinâmicas de forma mais realista e definir novos critérios de projeto. Este trabalho contribui com um estudo teórico, por elementos finitos, sobre as respostas dinâmicas de pontes considerando a interação com as respostas do veículo. A interação entre ambos é tratada por meio do acoplamento das suas matrizes, e as respostas no tempo do sistema ponte/veículo acoplado são calculadas pelo método de Newmark. A estrutura é representada por elementos de placa de 9 nós e o veículo por modelo tridimensional com 7 e 11 graus de liberdade para veículos com 2 e 3 eixos, respectivamente. Os modelos são elaborados com dimensões e características de estruturas reais. A travessia do veículo é representada pela mudança de posição dos pneus de nó em nó do modelo da estrutura. Para cada posição do veículo são obtidas as matrizes de massa, amortecimento e rigidez do sistema acoplado, desde a entrada do 1° eixo até a saída do último. As respostas são calculadas para diversas condições de operação simuladas pela combinação de diferentes peso e velocidade do veículo com diferentes rugosidades da pista. Os resultados numéricos se mostraram coerentes com os resultados de análises dinâmicas realizadas experimentalmente, obtidos na literatura, e possibilitaram visualizar alguns dos problemas observados em pontes reais. / Since the past decade, the problem of interaction between vehicle and structure responses has been object of many studies. The objectives are to consider the dynamic loads in a more realistic way and to define new design criteria aiming safety and economy. In this thesis, a theoretical investigation on the dynamic response of highway bridge submitted to heavy vehicle, using the finite elements method, is presented. This analysis considers the interaction between vehicle response and structure response through the coupling matrices of both. The detailed models are idealized with magnitude and characteristics of real structures. The bridge is idealized with plate elements of 9 nodes, and the vehicle, with a three-dimensional model. The traffic is considered by changing tires\' position node by node on bridge model, hence the mass, stiffness and damping matrices are updated in agreement with the position of the vehicle. It allows the evaluation of the behavior of the structure from the first axle entrance to last axle exit. The applied forces to the structure are related, besides to the dynamic characteristics of the vehicle, to its speed and the surface irregularities. The time-dependent responses are calculated by Newmark\'s method. The numeric results have allowed the visualization some of the observed problems in real bridges.

O problema da interação dinâmica entre ponte rodoviária e veículo pesado tem sido, há pouco mais de uma década, tema de muitos estudos. O objetivo é considerar as ações dinâmicas de forma mais realista e definir novos critérios de projeto. Este trabalho contribui com um estudo teórico, por elementos finitos, sobre as respostas dinâmicas de pontes considerando a interação com as respostas do veículo. A interação entre ambos é tratada por meio do acoplamento das suas matrizes, e as respostas no tempo do sistema ponte/veículo acoplado são calculadas pelo método de Newmark. A estrutura é representada por elementos de placa de 9 nós e o veículo por modelo tridimensional com 7 e 11 graus de liberdade para veículos com 2 e 3 eixos, respectivamente. Os modelos são elaborados com dimensões e características de estruturas reais. A travessia do veículo é representada pela mudança de posição dos pneus de nó em nó do modelo da estrutura. Para cada posição do veículo são obtidas as matrizes de massa, amortecimento e rigidez do sistema acoplado, desde a entrada do 1° eixo até a saída do último. As respostas são calculadas para diversas condições de operação simuladas pela combinação de diferentes peso e velocidade do veículo com diferentes rugosidades da pista. Os resultados numéricos se mostraram coerentes com os resultados de análises dinâmicas realizadas experimentalmente, obtidos na literatura, e possibilitaram visualizar alguns dos problemas observados em pontes reais. / Since the past decade, the problem of interaction between vehicle and structure responses has been object of many studies. The objectives are to consider the dynamic loads in a more realistic way and to define new design criteria aiming safety and economy. In this thesis, a theoretical investigation on the dynamic response of highway bridge submitted to heavy vehicle, using the finite elements method, is presented. This analysis considers the interaction between vehicle response and structure response through the coupling matrices of both. The detailed models are idealized with magnitude and characteristics of real structures. The bridge is idealized with plate elements of 9 nodes, and the vehicle, with a three-dimensional model. The traffic is considered by changing tires\' position node by node on bridge model, hence the mass, stiffness and damping matrices are updated in agreement with the position of the vehicle. It allows the evaluation of the behavior of the structure from the first axle entrance to last axle exit. The applied forces to the structure are related, besides to the dynamic characteristics of the vehicle, to its speed and the surface irregularities. The time-dependent responses are calculated by Newmark\'s method. The numeric results have allowed the visualization some of the observed problems in real bridges.

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[EN] The aim of the present Thesis is to develop models for the study of very high-frequency phenomena associated with the coupling dynamics of a railway vehicle with the track. Through these models, this Thesis intends to address squeal noise as a particular case of rolling noise when the train negotiates a small radius curve. Wheel/rail interaction is the predominant source of noise emission in railway operations. Rolling contact couples the wheel and the rail through a very small area, characterised by strongly non-linear and non-steady state dynamics that differentiates rolling noise from any other noise problem. Wheel/rail contact problem is studied based on Kalker's variational theory and the local falling behaviour of the coefficient of friction is introduced by means of a regularisation of Coulomb's law. Its implementation shows that the influence of the falling friction on the creep curves can be assumed negligible, thus rolling contact is finally modelled using a constant coefficient of friction. Flexibility is introduced in railway substructures through the Finite Element (FE) method in order to cover the high-frequency range. This work adopts a rotatory wheelset model that takes computational advantage of its rotational symmetry. It also develops a cyclic flexible rail model that fixes the translational contact force in a spatial point of the mesh through a technique called Moving Element (ME) method. A modal approach is used to reduce significantly the number of degrees of freedom of the global problem and a diagonalisation technique permits to decouple the resulting modal equations of motion in order to increase the computational velocity of the time integrator. Simulations in curving conditions in the time domain are carried out for constant friction conditions in order to study if the proposed interaction model can reproduce squeal characteristics for different curve radii and coefficients of friction. / [ES] El objetivo de la presente Tesis es desarrollar modelos para el estudio de fenómenos de muy alta frecuencia asociados a la dinámica acoplada de un vehículo ferroviario con la vía. A través de estos modelos, esta Tesis pretende abordar el fenómeno de los chirridos como un caso particular de ruido de rodadura en condiciones de curva cerrada. La interacción rueda/carril es la fuente predominante de ruido en las operaciones ferroviarias. El contacto es el responsable del acoplamiento entre la rueda y el carril a través de un área muy pequeña caracterizada por una dinámica fuertemente no lineal y no estacionaria. El problema de contacto rueda/carril se estudia mediante la teoría variacional de Kalker y la caída local del coeficiente de fricción se introduce por medio de una regularización de la ley de Coulomb, que muestra que su influencia sobre las curvas de fluencia se puede despreciar. Como consecuencia, el coeficiente de fricción se considera constante. La flexibilidad se introduce en las subestructuras ferroviarias a través del método de los Elementos Finitos (EF) para cubrir el rango de las altas frecuencias. La Tesis adopta un modelo de eje montado rotatorio que toma ventaja computacional de su simetría rotacional. También desarrolla un modelo de carril flexible y cíclico que fija la fuerza de contacto en un punto espacial de la malla mediante el método de los Elementos Móviles (EM). Se utiliza un enfoque modal para reducir significativamente el número de grados de libertad del problema global; las ecuaciones de movimiento resultantes en coordenadas modales se desacoplan mendiante una técnica de diagonalización para aumentar la velocidad computacional del integrador temporal. Las simulaciones en condiciones de curva en el dominio del tiempo se llevan a cabo en condiciones de fricción constante con el objetivo de estudiar si el modelo de interacción propuesto puede reproducir las características del chirrido en curva para diferentes radios de curva y coeficientes de fricción. / [CAT] L'objectiu de la present Tesi és desenvolupar models per a l'estudi de fenòmens de molt alta freqüència associats amb la dinàmica acoblada d'un vehicle ferroviari amb la via. Aquests models permeten simular el soroll de rodament encara que, en particular, aquest treball es proposa abordar el fenomen del soroll grinyolant produït quan el tren negocia un radi de curvatura estret. La interacció roda/carril és la font predominant de l'emissió de soroll en les operacions ferroviàries. El contacte acobla la roda i el carril a través d'una àrea molt reduïda que es caracteritza per una dinàmica fortament no lineal i no estacionària. El problema de contacte roda/carril s'estudia mitjançant la teoria variacional de Kalker i el descens local del coeficient de fricció s'introdueix per mitjà d'una regularització de la llei de Coulomb, què demostra que la seua influència en les corbes de fluència es pot suposar insignificant. Per tant, s'utilitza un coeficient de fricció constant per a modelar el contacte. La flexibilitat s'introdueix en les subestructures de ferrocarril a través del mètode d'Elements Finits (EF) per tal de cobrir el rang d'alta freqüència. La present tesi adopta un model d'eix muntat rotatori que s'aprofita de la seua la simetria rotacional per a augmentar la eficiència computacional. També desenvolupa un model de carril flexible i cíclic que fixa la força de contacte en un punt espacial de la malla a través del mètode dels Elements Mòbils (EM). S'empra un enfocament modal per reduir significativament el nombre de graus de llibertat del problema global, al temps que s'implementa una tècnica diagonalització que permet desacoblar les equacions modals de moviment per a augmentar la velocitat computacional de l'integrador temporal. Les simulacions en les condicions de corba en el domini del temps es duen a terme per a condicions de fricció constant per tal d'estudiar si el model d'interacció proposat pot reproduir les característiques del soroll grinyolant per a diferents radis de corba i coeficients de fricció. / Giner Navarro, J. (2017). Advances Techniques for Time-Domain Modelling of High-Frequency Train/Track Interaction [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/90637 / TESIS

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