En France, 460000 nourrissons âgés d’un moins à deux ans, sont affectés par la bronchiolite aiguë chaque hiver. Cette infection virale, qui a pour conséquence une inflammation des voies respiratoires, est généralement traitée par des séances de kinésithérapie respiratoire (KR). Afin d’améliorer l’apprentissage des techniques de KR pédiatriques, un simulateur, représentatif d’un nourrisson de six mois présentant un encombrement moyen, a été réalisé au laboratoire SYMME. Ce premier simulateur permet aux kinésithérapeutes novices d’apprendre les gestes de base de la KR dans un environnement didactique et protégé. Ce travail s’inscrit dans la continuité de cette étude, et devra permettre à terme d’améliorer la formation, en proposant des situations didactiques variées. Dans un premier temps, un système permettant de reproduire sur le simulateur le mouvement de respiration du nourrisson a été réalisé. Puis nous avons travaillé sur la conception d’un mécanisme permettant d’obtenir un comportement mécanique variable au niveau du thorax, afin de permettre à l’apprenant de s’entrainer sur différents cas cliniques. Pour la réalisation d’un tel dispositif, nous nous sommes orientés vers des systèmes classiquement utilisés pour dissiper de l’énergie en modifiant la raideur et/ou l’amortissement de la structure. Deux dispositifs semi-actifs basés sur l’utilisation d’un vérin hydraulique ont été principalement étudiés. Ils se différencient par la façon dont l’écoulement du fluide entre les deux chambres du vérin est modifié : le premier par un changement de section de la canalisation, le deuxième par une modification des propriétés d’écoulement d’un fluide magnétorhéologique. La première solution a été validée partiellement par un kinésithérapeute référent mais n’est pas tout à fait satisfaisante. La seconde a été testée sur un banc d’essai spécifique et semble être une voie prometteuse pour la réalisation du simulateur à propriétés variables / In France, 460000 infants between one month and two years are affected by the acute bronchiolitis each winter. This viral infection which leads to an inflammation of the respiratory tract is generally treated during a respiratory physiotherapy(RP) session. In order to improve the technical learning of the paediatric RP, a simulator which represents a six month old infant with an average type of bronchiolitis was developed in the laboratory SYMME. This first simulator allows the physiotherapist students to learn the basic gestures of the RP in a didactic and safe environment. This research work follows the frame work of this study and should allow an improvement of the training by proposing various didactic situations. As a first step, a system that allows reproducing the breathing movement of an infant on the simulator was developed. Then we worked on the design of a mechanism that allows obtaining a variable mechanical behaviour of the thorax in order to enable the student to practice on different clinical cases. For the realisation of such a device, we focused on systems which are conventionally used to dissipate energy by modifying the stiffness and/or the damping of the structure. Two semi-active devices based on the usage of a cylinder/piston system were examined. They differ in the way the pressure difference between the two chambers of the cylinder is generated : first, by changing the flow geometry and second, by a modification of the fluid flow characteristics of a magnetorheological fluid. The first solution was partially validated by a physiotherapist but was not completly satisfying. The second solution was tested on a specific test bench and seems to be a promising way to realise a simulator with variable properties.

Resumo: Neste trabalho é apresentado uma proposta de absorvedor de vibrações ajustável tipo viga sanduíche utilizando fluido Magnetoreológico no centro. Para o desenvolvimento deste projeto foi realizada uma revisão sobre os vários tipos de absorvedores e algumas aplicações. Em seguida foi realizado um estudo sobre o comportamento do fluido magnetoreológico, mostrando como este material inteligente varia suas propriedades quando submetido a um campo magnético. O objetivo do estudo foi verificar as propriedades do sistema para realização de um futuro controle, que é realizado através da variação do campo magnético. Avaliou-se, também, a relação com a corrente elétrica, quais os parâmetros que o influenciam e como podemos produzir um campo magnético com a intensidade desejada. Para avaliar as características do sistema foi utilizado o modelo no programa Ansys, com o objetivo de se verificar o comportamento do sistema. Para encontrar as características reais do sistema foi utilizado o modelo na forma de espaço de estados modais, identificado através do método PEM, Método de Predição de Erros (do inglês Prediction Error Methods ���� PEM). Os testes experimentais foram realizados para se adquirir conhecimento do comportamento dinâmico deste tipo de fluido e, verificar se há repetibilidade nas medidas / Abstract: This work presents a proposal of a tunable vibrations absorber type sandwich beam, using the Magnetorheologic fluid in the intermediate layer. For the development of this study a revision of some types of absorber with some applications was carried out. After that, a study of the behavior of the magnetorheologic fluid was carried through, showing as this intelligent material tunable its properties when submitted to a magnetic field. The objective of this analysis was to verify the properties of the system for implementation of a future control, which is based on the variation of the magnetic field. It was realized an analysis of the relation of the electric current and the parameters that influence it, in order to produce a magnetic field with the desired intensity. The characteristics of the system were verified through a mathematical model obtained with the software Ansys. The real characteristics of the system were found through the identification method PEM, Prediction Error Methods, using modal space states formulation. Experimental tests were carried out in order to obtain know how of the dynamic behavior of this type of material / Orientador: Vicente Lopes Junior / Coorientador: Michael J. Brennan / Banca: Hermes Adolfo de Aquino / Banca: Edson Antonio Capello Sousa / Mestre

This master's thesis deals with an engineering design of an external reservoir for hydraulic shock absorbers with combined filling of oil and magnetorheological fluid. The first part describes existing designes of magnetorheological shock absorbers and characteristics of magnetorheological fluid. Next part describes a design of an experimental external reservoir and a test of its functionality on a prototype. This is followed by an optimalized engineering design of the experimental external reservoir.

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Made available in DSpace on 2014-06-11T19:27:13Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-02-29Bitstream added on 2014-06-13T19:35:06Z : No. of bitstreams: 1 mesquitaneto_c_me_ilha.pdf: 1673109 bytes, checksum: 0f8131abf5fc45715c92abece81e6a7a (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Neste trabalho é apresentado uma proposta de absorvedor de vibrações ajustável tipo viga sanduíche utilizando fluido Magnetoreológico no centro. Para o desenvolvimento deste projeto foi realizada uma revisão sobre os vários tipos de absorvedores e algumas aplicações. Em seguida foi realizado um estudo sobre o comportamento do fluido magnetoreológico, mostrando como este material inteligente varia suas propriedades quando submetido a um campo magnético. O objetivo do estudo foi verificar as propriedades do sistema para realização de um futuro controle, que é realizado através da variação do campo magnético. Avaliou-se, também, a relação com a corrente elétrica, quais os parâmetros que o influenciam e como podemos produzir um campo magnético com a intensidade desejada. Para avaliar as características do sistema foi utilizado o modelo no programa Ansys, com o objetivo de se verificar o comportamento do sistema. Para encontrar as características reais do sistema foi utilizado o modelo na forma de espaço de estados modais, identificado através do método PEM, Método de Predição de Erros (do inglês Prediction Error Methods PEM). Os testes experimentais foram realizados para se adquirir conhecimento do comportamento dinâmico deste tipo de fluido e, verificar se há repetibilidade nas medidas / This work presents a proposal of a tunable vibrations absorber type sandwich beam, using the Magnetorheologic fluid in the intermediate layer. For the development of this study a revision of some types of absorber with some applications was carried out. After that, a study of the behavior of the magnetorheologic fluid was carried through, showing as this intelligent material tunable its properties when submitted to a magnetic field. The objective of this analysis was to verify the properties of the system for implementation of a future control, which is based on the variation of the magnetic field. It was realized an analysis of the relation of the electric current and the parameters that influence it, in order to produce a magnetic field with the desired intensity. The characteristics of the system were verified through a mathematical model obtained with the software Ansys. The real characteristics of the system were found through the identification method PEM, Prediction Error Methods, using modal space states formulation. Experimental tests were carried out in order to obtain know how of the dynamic behavior of this type of material

Sedimentation in magnetorheological (MR) fluids is undesirable for many technological applications. For this reason, several ways have been proposed to prevent sedimentation instability. This thesis deals specifically with the addition of a suitable additive. The topic was examined based on available literature and according to it was suggested a procedure for the experimental part. Two types of MR liquids with different composition and preparation method were prepared. The first suspensions included a water-in-oil emulsion as a carrier liquid and Span 80 and Tween 80 as additives. For the second MR fluids, the continuous phase was a blend of bearing oils and the suspension was stabilized with organoclay. In both cases, carbonyl iron particles with a diameter of 1,8–2,3 µm were used. The kinetic stability of the prepared MR fluids was monitored and compared using an analytical centrifuge.

In this thesis was designed, manufactured and tested the fourth evolution of a slit-flow rheometer with another necessary parts, eg. rheometer`s holder, drive frame and important jig tools. The rheometer is able to measure rheological properties of magnetic and non-magnetic fluids at very high shear rates, which commercial rheometers can not reach. It is designed for 200 bar pressure and maximum load 15 kN. The construction of the slit-flow rheometer with it`s holder and drive frame improves user friendliness, accelerates change of the fluid sample and expands research opportunities thanks to a big space for additional adjustments. It is possible to use different length of the slit and thanks to a changeable inserts it is possible to change parameters of the slit (roughness of the walls, wall material, thickness of the slit). A part of this thesis was focused on illation of necessary equations for planning calibration measurements. Aim of these measurements is to obtain minor pressure losses dependence on Reynolds number for specific slit.

This work deals with the research of degradation of magnetorheological (MR) fluid during long-term loading under conditions that correspond to the real load in the linear MR devices such as dampers. The behaviour of MR fluid is described by a Bingham model of viscoplastic fluid. The parameters of this model are the yield stress and viscosity. Their values are determined by the shear rate from 1 to 2,8104 s-1. Results of durability tests show a significant decrease in viscosity of MR fluid, a gradual increase in yield stress in the off-state and a significant decrease in MR effect. The paper also described the effect of temperature on these parameters and there is also designed a method of non-assembly diagnostic of the MR fluid state in the damper using the "rate of pulsation."

This study of adaptable vibration isolating mounts sets out to capture the uniqueness of magnetorheological (MR) fluid's variable viscosity rate, and to physically alter the damping and stiffness when used inside an elastomeric mount. Apparent variable viscosity or rheology of the MR fluid has dependency on the application of a magnetic field. Therefore, this study also intends to look at the design of a compact magnetic field generator which magnetizes the MR fluid to activate different stiffness and damping levels within the isolator to create an adaptable and tunable feature. To achieve this adaptable isolator mount, a mold will be fabricated to construct the mounts. A process will then be devised to manufacture the mounts and place MR fluid inside the mount for later compatibility with the magnetic field generator. This process will then produce an MR fluid-elastic mount. Additionally for comparative purposes, passive mounts will be manufactured with a soft rubber casing and an assortment of metal and non-metal inserts. Next, the design of the magnetic field generator will be modeled using FEA magnetic software and then constructed. Stiffness or force/displacement measurements will then be analyzed from testing the isolator mount and magnetic field generator on a state-of-the-art vibration dynamometer. To vary the magnetic flux through the mount, an electro-magnet is used. To analyze the results, a frequency method of the stiffness will be used to show the isolators adaptation to various increments of magnetic flux over the sinusoidal input displacement frequencies. This frequency response of the stiffness will then be converted into a modeling technique to capture the essence of the dynamics from activating the MR fluid within the isolator mount. With this methodology for studying the adaptability of an MR fluid-elastic mount, the stiffness increases are dependent on the level of magnetic field intensity provided from the supplied electro-magnet. When the electro-magnet current supply is increased from 0.0 to 2.0 Amps, the mount stiffness magnitude increase is 78% in one of the MR fluid-elastic mounts. Through comparison, this MR fluid-elastic mount at off-state with zero magnetic field is similar to a mount made of solid rubber with a hardness of 30 Shore A. With 2 Amps of current, however, the MR fluid-elastic mount has a higher stiffness magnitude than a rubber mount and resembles a rubber casing with a steel insert. Moreover, when the current in the electro-magnet is increased from 0.0 to 2.0 Amps the equivalent damping coefficient in a MR fluid-elastic mount increases over 500% of the value at 0 Amps at low frequency. Through damping comparisons, the MR fluid-elastic mount with no current is similar to that of a mount made of solid rubber with a hardness of 30 Shore A. At full current in the electromagnet, however, the damping in the MR fluid-elastic mount is greater than any of the comparative mounts in this study. Therefore, the results show that the MR fluid-elastic mount can provide a wide range of stiffness and damping variation for real-time embedded applications. Since many aerospace and automotive applications use passive isolators as engine mounts in secondary suspensions to reduce transmitted forces at cruise speed, the MR fluid-elastic mount could be substituted to reduce transmitted forces over a wider range of speeds. Additionally, this compact MR fluid-elastic mount system could be easily adapted to many packaging constraints in those applications. / Master of Science