Dissertations / Theses on the topic 'Torsion bar'

The Master’s thesis deals with the design of unconventional tractor cab suspension. It contains overview of current conceptions, mensions description of single components, takes closer look at torsion bar calculations and strength analysis. Subsequently, there is dynamic analysis of suspension in the thesis, performed with use of Adams View software aimed at ride over bump. Last section describes strength analysis of whole construction according to OECD methodics with use of numerical simulations in ANSYS Workbench software. Part of the thesis is also complete drawing documentation.

The presented master’s thesis is focused on the design of device for spring dismount from shock absorber and measuring of its spring characteristic. Then is the thesis focused on the design of device for measuring the spring characteristic of anti-roll and torsion bars. The introductory part of the thesis describes the basic distribution of springs and their properties and also design variants of wheel suspensions. Next part introduces devices already available on the market. The following sections aim to the design of stated devices itself, i.e. the description of their parts and functions, the definition of output parameters and stress-strain analysis. Both designs, including the analyses and technical drawings, were created in Autodesk Inventor software.

This master’s thesis is focused on a design of the formula student’s anti-roll bar. The beginning of the thesis is devoted to the introduction of the anti-roll bar function and the explanation of its effect on a vehicle including the analysis of various constructions. Second part deals with the Formula Student competition. There is the analysis of the formula Ford’s anti-roll bar as a starting point for our own design. In the section which deals with the anti-roll bar design several alternatives are designed, the stress analysis of components are made and multi body system models are developed for final solutions. These models serve for further analyses of driving characteristics of the vehicle.

A novel combined piezoelectric-composite actuator configuration is proposed and analytically modeled in this work. The actuator is a low complexity, active compliant mechanism obtained by coupling a modified star cross sectional configuration composite beam with a helicoidal bimorph piezoelectric actuator coiled around it. This novel actuator is a good candidate as a hinge tension-torsion bar actuator for a helicopter rotor blade flap or blade tip and mirror rotational positioning. In the wing tip case, the tip deflection angle is different only according to the aerodynamic moment depending on the hinge position of the actuator along the chord and applied voltage because there is no centrifugal force. For an active blade tip subject to incompressible flow and 2D quasi steady airloads, its twist angle is related not only to aerodynamic moment and applied voltage but also to coupling terms, such as the trapeze effect and the tennis racquet effect. Results show the benefit of hinge position aft of the aerodynamic center, such that the blade tip response is amplified by airloads. Contrary to this effect, results also show that the centrifugal effects and inertial effect cause an amplitude reduction in the response. Summation of these effects determines the overall blade tip response. The results for a certain hinge position of Xh=1.5% chord aft of the quarter chord point proves that the tip deflection target design range[-2,+2] can be achieved for all pitch angle configurations chosen.

Tato diplomová práce je zaměřená na stabilizátory u podvozku aut. První část popisuje všeobecné znalosti vlivu naklonění karosérie na jizdní vlastnosti auta a možnosti konstrukčních řešení používaných v praxi. Dále jsou v této části uvedeny nevýhody použití stabilizátoru a jejich náhrady. Nasledující téma se zaměřuje na soutěž Formule Student a její všeobecná pravidla. Hlavní částí této práce je analýza stabilizátoru Formule Ford, na kterou v poslední části této práce navazuje analýza předního a zadního stabilizátoru Formule Student. Byly vytvořené kompletní MBS modely pro přední a zadní zavěšení včetně stabilizátoru. Díky těmto modelům bylo možné provést výpočty klopných tuhostí a pevnostní výpočty. Z těchto výpočtů bylo možné určit vhodné nastavení stabilizátoru. Všechny modely mohou být dále použitelné pro analýzu jízdních vlastností příslušného vozidla.

De nos jours, les processus industriels se doivent d’être efficaces, en particulier au niveau de leur production et/ou consommation énergétique.Ce travail vise à améliorer l’efficacité des processus en analysant l’influence des perturbations sur leur comportement, de la phase de conception à la synthèse des contrôleurs/observateurs, ceci dans une approche intégrée.Le problème du Rejet de Perturbation est introduit ainsi que différents types de contrôles permettant d’atténuer et/ou rejeter ces perturbations. Le système de Barre de Torsion est présenté. Une loi de commande basée sur le concept d’état dérivé est présentée et ensuite validée avec comme application le rejet de perturbation. Il est nécessaire d’estimer les grandeurs physiques utilisées dans les différentes expressions de loi de commande. Un observateur à entrées inconnues basé sur la représentation bond graph est rappelé et ensuite étendu au cas multi-variable. C’est la première contribution théorique de ce travail de recherche.Nous comparons ensuite l’efficacité de différentes techniques de commandes pour le rejet de perturbation par simulation sur le système barre de torsion et analysons ainsi l’efficacité de la technique proposée. Une extension théorique au problème du découplage entrée-sortie nous permet de généraliser le problème du rejet de perturbation dans une même démarche intégrée d’analyse et de synthèse. Enfin, ces techniques sont exploitées et analysées sur le système réel. Nous validons ainsi expérimentalement nos résultats.Un modèle très simplifié de centrale hydroélectrique est développé afin d’appliquer les résultats de nos travaux. Un modèle bond graph simplifié est validé par simulation
Nowadays, industrial processes must be efficient, particularly at the production level and/or energy consumption.This research work aims at improving the process efficiency by analysing the influences of disturbances on their behaviour, from the conception phase to the synthesis of controller/observer, in an integrated approach.The disturbance rejection problem is first introduced as well as different control laws allowing attenuate/reject these disturbances. A control law based on the concept of derivative state variable is presented and validated while applied as disturbance rejection.In order to reject the disturbance, different physical variables must be estimated, such as state variables, derivative state variables as disturbance variables. An unknown input observer based on the bond graph representation is recalled and extended in the multivariable case. It is the first theoretical contribution of this work.We thus compare the efficiency of different so-called «modern control laws» for the disturbance rejection problems by simulation with the Torsion-Bar system example. We analyse the efficiency of our approach. One extension to the Input-Output decoupling problem allows us to extend the disturbance rejection problem to other control law type in an integrated approach. At least, these techniques are applied on the real Torsion-Bar system and compared. We validate our approach.Since this work aims at analysing and developing efficient control laws for industrial processes, a simplified model of a hydroelectric plant is developed, in order to apply our results. A simplified bond graph model is validated with simulations

Des barres en acier à section ouverte sont, dans la majorité des cas, soumises à une combinaison d’effort normal et de flexion bi-axiale. Cependant, en raison de leur utilisation elles peuvent également être soumises à un moment de torsion. Même si les barres à section ouverte peuvent être soumises à des charges de torsion en pratique, l’Eurocode 3, ne définit pas comment la résistance de la barre peut être déterminée dans ces conditions. Ce pourquoi, l’objectif principal de cette thèse est de remplir cette lacune. Pour atteindre cet objectif, le comportement des barres métalliques soumises à une combinaison complexe de charges est étudié par voie théorique, expérimentale et numérique. Tout d’abord, la résistance plastique des barres est étudiée. En cas de torsion, il a été montré que les barres à section ouverte possèdent une réserve plastique importante qui ne peut pas être mise en évidence à l’aide d’une simple analyse élastique. Afin de tenir compte de l’effet bénéfique de la réserve plastique en torsion, une méthode d’analyse simplifiée est développée et validée par des analyses numériques. Ensuite, l’interaction plastique entre les efforts internes est étudiée. Des essais en laboratoire ont été réalisés afin de caractériser l’interaction entre l’effort tranchant et le moment de flexion. L’étude est ensuite étendue à l’aide de simulations numériques sur des cas d’interaction plus complexes incluant notamment des moments de torsion. Les essais accompagnés par l’étude numérique ont permis de mettre au point un modèle de résistance basé sur la méthode « Partial Internal Force Method » développée dans le passé. La dernière partie de la thèse concerne la résistance des barres à l’instabilité. Un modèle de résistance incluant l’effet de l’instabilité élasto-plastique est développé pour les barres métalliques en présence de torsion. Cette méthode est basée sur une extension des formules d’interaction proposées dans l’Eurocode. Afin de franchir certaines limitations liées à cette méthode, un deuxième modèle de résistance est développé pour les barres en I dans le format du « Overall Interaction Concept »
Structural steel members with open cross-section are, in the majority of cases, subject to a combination of axial forces and mono- or bi-axial bending. Nonetheless, owing to specific use they may be subject to torsion as well. Even if torsional loads are of practical interest for steel members of open section, the European standard for the design of steel structures, Eurocode 3, does not contain a generally accepted design method addressing the resistance of these members. Consequently, the main objective of this thesis is to close the lack in the current standard. So as to attain this objective the behaviour of members of open section subject to a complex load combination has been studied theoretically, experimentally and numerically. First, the plastic resistance of steel members has been analysed. It has been shown that members subject to torsion may possess a high plastic system reserve that cannot be predicted by simple elastic analysis. So as to account for the beneficial effect of the plastic reserve, a simplified analysis method has been developed and validated with numerical simulations. After this, the plastic interaction between all internal forces and moments has been studied. Several laboratory tests have been performed to characterise the interaction between bending moments and the shear force. The study is then extended to more complex interaction cases including torsion by means of numerical simulations. The laboratory test and the numerical simulations allowed the development of a precise resistance model based on the “Partial Internal Force Method” developed in the past. The last part of this thesis was dedicated to the member resistance including instability. A resistance model has been developed based on the Eurocode 3 interaction equations. So as to overcome some of the limitations linked to this method, a second design approach is developed based on the “Overall Interaction Concept”

碩士
國立成功大學
土木工程學系碩博士班
96
End effects in circular bar and tube under torsion, compare with different boundary conditions, anisotropic, functionally graded material and multilayersproblem, the usability of Saint-Venant’s principle, in what situation, the end effect can be neglected. The shear stress formula in “Material Machenics” only including the non-decay term, and lateral boundary condition is traction free. According to elasticity theory, in using state space method, compare with homogeneous material problem and the shear stress formula in “Material Machenics”, then consider the functionally graded material and multilayers under torsion, the region of the end effect.

碩士
國立臺灣大學
工程科學及海洋工程學研究所
100
Wind turbine blade pitch angle control system can generally divided into two types : active control system and passive control system. This paper will focus on passive control system. The main concept is a metal torsion bar device. Let torsion bar connect with the axis of wind turbine blades that can make blades has torsion characteristic. When the wind speed goes up, the torsion bar will change the attack angle of blades. It would not only improve overall efficiency but also reduce the damage of blade structure. There are two parts of this research：experiment measurements and computer simulation. Experiment measurement will made by small wind tunnel equipment, the testing blade had been optimize design. Testing items are include：pitch angle changes, different wind speed, different stiffness of torsion bar and the torsion direction. In the other hand, computer simulation is using MATLAB-simulink for 2D emotional simulation and ANSYS-Workbench CFX for 3D simulation. The results of experiment, the torsion bar device could work in high wind speed situation. It not only protected blade structure but also improved about 18% efficiency. Compare to computer simulation, whether 2D dynamic simulation and 3D-CFD simulation are really fit to experimental results. To sum up, this torsion bar device is really suit for small wind turbine blades in the high wind speed situation. This research could improve the design of small wind turbine blade.

碩士
國立臺灣海洋大學
河海工程學系
104
In this thesis, the null-field integral equation approach in conjunction with the degenerate kernel is used to solve the torsion problems of a circular bar with coated fibers or cracks. The degenerate kernel is employed to substitute the closed-form fundamental solution in the integral equations. In order to fully capture the geometry property, the boundary densities are expanding by Fourier series and eigenfunction expansion for circular boundary and elliptical boundary, respectively. For a circular bar with coated fibers, there are some difficulties on directly analyzing the bar since it has different materials in the bar. By using the technique of taking free body, the bar could be decomposed into three parts. One is a circular bar with circular holes, another is multiple individual circular-ring coatings, and the other is multiple circular fibers. After collocating points on each boundary and satisfying the continuity of displacement and equilibrium of force between interfaces, the unknown coefficients of Fourier series or eigenfunction can be determined by a linear algebraic system. For the problem of cracks in a bar, we adopt the limiting process of approaching the semi-minor axis of elliptical hole to be zero to simulate cracks. Finally, several numerical examples are employed to verify the feasibility and validity of the proposed approach. Besides, the partially and totally neutral behaviors for the composite bars are numerically analyzed.

In the last decades, the multi-scale approach has gained wide attention for studying and understanding the mechanisms affecting the performance of asphalt mixtures. According to such approach, the asphalt mixture could be seen as an assemblage of components of different length scales, each with its own mechanical properties, and thanks to the investigation on these lower scales a scale-wise insight can be gained and used to capture phenomena not considered in continuum approaches. This Thesis is focused on the interrelation between the Fine Aggregate Matrix (FAM) the asphalt mixtures. Fine aggregates, filler, binder and air voids compose the FAM, which represents the intermediate scale between mastic and asphalt mixture. This phase has a critical role in the overall performance evaluation of asphalt mixture and the simplicity, efficiency and the lower costs/times required to study the FAM make it a very attractive specification-type approach. However, despite the growing interest on FAM testing, there are some concerns about proper FAM mix design. Moreover, there are many lacks in predicting the performances of asphalt mixtures from the FAM phase. The primary objective of this Thesis was the identification of a design method for FAM, which allows recreating the FAM phase, as it exists within the asphalt mixture. The selected design method has shown promising results and seems quite accurate in reproducing the FAM within the asphalt mixture. The second issue which is pursued in this Thesis, is a multi-scale approach based on the rheological 2S2P1D model, allowing to interrelate the four material scales (from binder to asphalt mixture). Firstly, it was verified that the 2S2P1D model remains valid for FAM in the Linear ViscoElastic (LVE) range and that it could adequately fit experimental data of FAM. Then, it was possible to relate the different phases thanks to the definition of interrelationships between one model parameter. The interrelation between the asphalt mixture and the corresponding FAM could be used to predict the rheological properties of the asphalt mixtures starting from FAM tests. This methodology allows making reliable forecasts of the LVE behaviour of the asphalt mixtures, as demonstrated by the results of validation tests. Future developments will investigate other volumetric compositions of mixes, to study the influence of microstructural and volumetric characteristics on the model parameters.

Tese no âmbito do Doutoramento em Engenharia Civil na Especialidade de Estruturas apresentada à Faculdade de Ciências e Tecnologia da Universidade de Coimbra
The main body of the thesis is divided into two largely self-contained parts. The first one is devoted to the development of a continuous one-dimensional linear model for the stretching, bending and twisting of tapered thin-walled bars with open cross-sections under general quasi-static loading conditions. These bars are treated as two-dimensional Kirchhoff-Love shells, exhibiting both membrane and flexural behaviours. To achieve the necessary dimensional reduction, the classical assumptions of Vlasov and Kirchhoff-Love are regarded systematically as internal constraints, that is, a priori restrictions, of a constitutive nature, on the possible deformations of the bars (alternatively, they may also be viewed as holonomic-scleronomic constraints). Moreover, the internal forces are decomposed additively into active and reactive parts and this is shown to lead to a dual one-dimensional description of kinematics and statics. Two examples illustrate the application of the developed one-dimensional model, shed light on its physical aspects and demonstrate the shortcomings of piecewise prismatic models, regardless of the number of prismatic segments used (indeed, even in the limit when the length of these segments tends to zero). The main original contributions in this first part of the thesis may be summarized as follows: (i) The second fundamental form of the middle surface of a bar and the change of curvature tensor are established in general form. (ii) The displacement field of a whole bar (not just of its middle surface) is completely characterized, thus including the so-called through-the-thickness (or secondary) warping deformation. (iii) In the characterization of the internal forces in the bar, the shell bending and twisting moments and the transverse shear forces are taken into account, in addition to the membrane forces. (iv) The Saint-Venant contribution to the strain energy and the corresponding component of the total torque are derived consistently. (v) A set of fundamental inequalities concerning the cross-sectional properties is established. The second part of the thesis is restricted to the important special case of depth-tapered singly symmetric I-section bars and deals with one-dimensional models of the Hencky bar-chain type, whose nature is intrinsically discrete. Indeed, a Hencky bar-chain model consists of a finite number of rigid units linked by elastic springs (or, more generally, by rheological elements) – it can be thought of not only as an idealization of a (continuous) member, but also as an actual mechanical structure in its own right, the inherent simplicity and transparency of which make its qualitative behaviour more easily grasped. Two types of problem are addressed in successive chapters: (i) the linear mechanical behaviour in three-dimensional space under general quasi-static loading conditions and (ii) the linearized flexural-torsional buckling behaviour under bending (in the plane of symmetry, which is also the plane of greatest flexural rigidity) and compression, including the so-called Wagner effect associated with the asymmetry of the flanges. Particular attention is paid to the calibration of the spring stiffnesses and to the appropriate definition of boundary conditions. It is shown that the bar-chain models are consistent with (but not subordinate to or in any away dependent on) previously developed Vlasov-type continuum models, in the sense that the local truncation errors tend to zero as the length of the rigid units approaches zero. Several illustrative examples, including prismatic and flangeless members (i.e., members with narrow rectangular cross-sections), are solved in order to verify the discrete Hencky bar-chain models and to assess their convergence rates.
Contributos para a Modelação Unidimensional do Comportamento Tridimensional de Barras Não Prismáticas com Secção de Parede Fina Aberta A tese encontra-se dividida em duas partes em larga medida independentes. A primeira é dedicada ao desenvolvimento de um modelo linear unidimensional contínuo para a flexão e torção de barras com secção aberta de paredes finas, continuamente variável, submetidas a carregamentos quase-estáticos genéricos. Estas barras são tratadas como cascas de Kirchhoff-Love (bidimensionais), considerando tanto o comportamento de membrana como o de flexão. Para levar a cabo a necessário redução dimensional, as hipóteses clássicas de Vlasov e Kirchhoff-Love são tratadas sistematicamente como constrangimentos internos, isto é, restrições de natureza constitutiva às possíveis deformações de uma barra (alternativamente, aquelas hipóteses podem também ser vistas como constrangimentos holonómicos-escleronómicos). Assim, as forças internas são decompostas em parcelas activa e reactiva, o que conduz a uma descrição dual (unidimensional) da cinemática e da estática. São apresentados dois exemplos que ilustram a aplicação do modelo unidimensional desenvolvido, esclarecem os seus aspectos físicos e atestam as limitações dos modelos seccionalmente prismáticos (ou “em escada”), independentemente do número de segmentos prismáticos utilizados (de facto, estas limitações mantêm-se mesmo no processo de passagem ao limite quando o comprimento dos segmentos tende a para zero). Os principais contributos originais nesta primeira parte da tese podem ser resumidos da seguinte forma: (i) Obtêm-se expressões gerais para a segunda forma fundamental da superfície média de uma barra e para o tensor de mudança de curvatura (ii) Generaliza-se a definição do campo de deslocamentos da superfície média para todo a barra, incluindo assim a caracterização do empenamento na espessura das paredes (também designado por empenamento secundário). (iii) Na caracterização dos esforços internos, são tidos em consideração não apenas os esforços de membrana, mas também os momentos flectores e de torção e as forças de corte transversais “de casca”. (iv) A contribuição de Saint-Venant para a energia de deformação e a componente correspondente do momento torsor total são obtidas de forma consistente. (v) Estabelece-se um conjunto de desigualdades fundamentais relativas às propriedades mecânicas das secções transversais. A segunda parte da tese, cujo âmbito se restringe ao importante caso particular de barras com secção em I monossimétricas e altura variável, trata de modelos unidimensionais do tipo Hencky, cuja natureza é intrinsecamente discreta. De facto, um modelo de Hencky consiste num número finito de unidades rígidas ligadas por molas elásticas (ou, mais geralmente, por elementos reológicos) e pode ser encarado não apenas como uma idealização de um elemento estrutural contínuo, mas também como uma estrutura real por direito próprio. A sua simplicidade e transparência faz com que o seu comportamento, de um ponto de vista qualitativo, seja mais facilmente apreendido. São abordados dois tipos de problema em capítulos sucessivos: (i) o comportamento linear no espaço tridimensional, sob acções quase-estáticas genéricas e (ii) a encurvadura por flexão-torção (linearizada) de vigas e colunas-viga solicitadas à flexão no seu plano de simetria (que é também o plano de maior rigidez à flexão), incluindo o chamado efeito Wagner associado à assimetria dos banzos. É dada uma especial atenção à calibração das rigidezes da mola e à definição apropriada das condições de fronteira. Mostra-se que os modelos de Hencky, se bem que desenvolvidos de forma totalmente independente, são consistentes com modelos contínuos do tipo Vlasov previamente desenvolvidos, na medida em que os erros de truncatura locais tendem para zero à medida que o comprimento das unidades rígidas também se aproxima de zero. Apresentam-se vários exemplos ilustrativos, que incluem elementos prismáticos e elementos de secção rectangular fina, de forma a verificar os modelos discretos de Hencky e avaliar as suas taxas de convergência.