Thèses : « Mechanism vibration »

1

George, Lynnane E. « Active vibration control of a flexible base manipulator ». Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/17115.

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Rahman, M. Shafiqur. « A Hybrid Technique of Energy Harvesting from Mechanical Vibration and Ambient Illumination ». ScholarWorks@UNO, 2016. http://scholarworks.uno.edu/td/2220.

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Hybrid energy harvesting is a concept applied for improving the performance of the conventional stand-alone energy harvesters. The thesis presents the analytical formulations and characterization of a hybrid energy harvester that incorporates photovoltaic, piezoelectric, electromagnetic, and electrostatic mechanisms. The initial voltage required for electrostatic mechanism is obtained by the photovoltaic technique. Other mechanisms are embedded into a bimorph piezoelectric cantilever beam having a tip magnet and two sets of comb electrodes on two sides of its substructure. All the segments are interconnected by an electric circuit to generate combined output when subjected to vibration and solar illumination. Results for power output have been obtained at resonance frequency using an optimum load resistance. As the power transduced by each of the mechanisms is combined, more power is generated than those obtained by stand-alone mechanisms. The synergistic feature of this research is further promoted by adding fatigue analysis using finite element method.

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Magee, David Patrick. « Optimal arbitrary time-delay filtering to minimize vibration in elastic manipulator systems ». Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/15891.

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Loper, Jeffrey Cameron. « Vibration cancellation an disturbance rejection in serially linked micro/macro manipulators ». Thesis, Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/15873.

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Novosád, Ivan. « Šestiválcový řadový vznětový motor s vypínáním válců ». Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-417519.

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Master 's thesis deals with design of a drivetrain of six cylinder inline engine with cylinder deactivation for heavy agricultural vehicles. In this thesis were devised various possibilities of crankshaft balancing, the best design solution of counterweight was based on optimization in software Catia. Further, the crankshaft was analysed for force and momentum loading and torsional vibration, based on which, the torsional vibration damper was designed. There were considered several options for cylinder deactivation, which were analysed for finest run of engine and the best thermal distribution. Based on these criteria, the best option was to deactivate 2nd and 5th cylinder. The crankshaft was analysed for the fatigue failure by finite element method. The fatigue failure is the most dangerous case for the crankshaft, the resulting safety factor for this limit state is 3,05.

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Unsal, Memet. « Semi-active vibration control of a parallel platform mechanism utilizing magnetorheological damping ». [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0013824.

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7

Huey, John. « Dynamics and vibration control of large area manipulators ». Thesis, Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/16469.

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8

Huang, Ya. « Mechanism of nonlinear biodynamic response of the human body exposed to whole-body vibration ». Thesis, University of Southampton, 2008. https://eprints.soton.ac.uk/64575/.

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When the human body is exposed to mechanical vibration, the resonance frequencies of the frequency response functions, such as apparent mass and transmissibility, decrease with increasing magnitude of excitation. For the past two decades, this biodynamic ‘nonlinearity’ has been reported with vertical and horizontal excitation of the body in a wide variety of static sitting and standing postures that require activity from muscles to maintain the stability of the body. There has been speculation, but no experimental evidence, as to the mechanism causing the non-linearity. A review of the literature suggested that either active muscular activity or passive thixotropy of soft tissues is the primary cause of the nonlinearity. The principal objective of this thesis is to identify, and provide experimental evidence of, the primary causal mechanism for the biodynamic nonlinearity. With 0.5 to 20 Hz broadband random vertical vibration at 0.25 and 2.0 ms-2 r.m.s., the first experiment investigated the effect of voluntary periodic upper-body movement and vibration magnitude on the apparent masses of 14 seated subjects. Some movements of the body, such as ‘back-abdomen bending’, significantly reduced the difference in resonance frequency at the two vibration magnitudes compared with the difference during upright static sitting. Without voluntary periodic movement, the median apparent mass resonance frequency was 5.47 Hz at the low vibration magnitude and 4.39 Hz at the high vibration magnitude. With voluntary periodic movement (e.g. back-abdomen bending), the resonance frequency was 4.69 Hz at the low vibration magnitude and 4.59 Hz at the high vibration magnitude. It was concluded that voluntary or involuntary muscular activity, or passive thixotropy of soft tissues, or both muscle activity and thixotropy, could explain the reduction in nonlinearity evident during voluntary periodic movement. The effect of shear history and vibration magnitude on the apparent mass was investigated using 12 subjects in a relaxed semi-supine posture assumed to involve less muscle activity than static sitting and standing. The semi-supine subjects were exposed to two types of vertical (in the x-axis of the semi-supine body) and longitudinal horizontal (z-axis) vibration: (i) continuous random vibration (0.25–20 Hz) at five magnitudes (0.125, 0.25, 0.5, 0.75, and 1.0 ms-2 r.m.s.); (ii) intermittent random vibration (0.25–20 Hz) alternating between 1.0 and 0.25 ms-2 r.m.s. With continuous random vibration, the dominant primary resonance frequency in the median normalised apparent mass decreased from 10.35 to 7.32 Hz as the magnitude of vertical vibration increased from 0.125 to 1.0 ms-2 r.m.s., and from 3.66 to 2.44 Hz as the magnitude of horizontal vibration increased from 0.125 to 1.0 ms-2 r.m.s. With the intermittent vibration, the resonance frequency was higher at the higher magnitude (1.0 ms-2 r.m.s.) and lower at the lower magnitude (0.25 ms-2 r.m.s.) than during continuous vibration at the same magnitudes. The response was typical of thixotropy being the primary cause of the nonlinearity. Harmonic distortions in the dynamic force of semi-supine subjects exposed to sinusoidal excitation showed similar dependence on the frequency and magnitude of vibration as previously reported for seated subjects, again suggesting thixotropy as a primary cause of the nonlinearity. In a group of 12 subjects, the apparent mass and transmissibility to the sternum, upper abdomen, and lower abdomen were measured in three supine postures (relaxed semi-supine, lying flat, and constrained semi-supine) during vertical random vibration (0.25 to 20 Hz) at seven vibration magnitudes (nominally 0.0313, 0.0625, 0.125, 0.25, 0.5, 0.75 and 1.0 ms-2 r.m.s.). The motion transmission path that included more soft tissues exhibited a greater nonlinear response. The substantial nonlinearities found in transmissibilities to both the sternum and the abdomen of supine subjects, and previously reported for the transmissibilities of seated and standing subjects, imply that soft tissues at the excitation-subject interface contribute to the nonlinearity. It is concluded that the thixotropy of soft tissues, rather than voluntary or involuntary muscular activity, is the primary cause of the biodynamic nonlinearity seen with varying magnitudes of excitation.

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Endo, Jun. « Mechanism and function of synchronized hatching in Pentatomidae (Insecta : Heteroptera) ». Kyoto University, 2018. http://hdl.handle.net/2433/232287.

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Čep, David. « Klikový mechanismus plynového vidlicového šestnáctiválce ». Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2010. http://www.nusl.cz/ntk/nusl-229090.

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Diploma thesis is trying to analyze crank mechanism of a gas V-sixteen engine. Kinematics and balance crank mechanism are analyzed, dynamic model parameters are dermined, natural frequency of the torsional system are calculated, coupling parameters are designed and torsional problem with attached electric generator is analyzed.

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Tegge, Samuel. « The Mechanism of Biotremor Production in the Veiled Chameleon (Chamaeleo calyptratus) ». TopSCHOLAR®, 2018. https://digitalcommons.wku.edu/theses/2336.

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Vibratory communication has evolved in numerous animal groups, including insects, spiders, fishes, mammals, and was recently discovered in veiled chameleons (Chamaeleo calyptratus). I examined the mechanism by which C. calyptratus produce these biotremors. Muscle activity data were gathered during simulated anti-predator responses via electromyography (EMG) with simultaneous recordings of biotremor production using an accelerometer. I correlated EMG data with the accelerometer data to implicate the muscles responsible for the production of the biotremors. Mixed-effect linear regression models described the mechanism, and a model selection framework determined which model fit the data best. I then used an analysis of variance to partition the variance to each variable to determine which muscles were most important in the biotremor producing mechanism. The Mm. sternohyoideus superficialis et profundus, Mm. mandibulohyoideus, and M. levator scapulae were active during the production of biotremors. Mean latency calculations revealed that the M. levator scapulae and Mm. mandibulohyoideus activated prior to the vibration onset, and the Mm. sternohyoideus superficialis et profundus activated after the vibration onset. The M. sternohyoideus superficialis then ceased activity prior to vibration cessation, and the M. sternohyoideus profundus, Mm. mandibulohyoideus, and M. levator scapulae ceased activity after the vibration had ended. The description of the biotremor producing mechanism further supports that C. calyptratus can produce biotremors, possibly for communication.

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Holzinger, Felix [Verfasser]. « Coupling of tip leakage flow and blade vibration in transonic compressors : Mechanism and countermeasures / Felix Holzinger ». Aachen : Shaker, 2018. http://d-nb.info/1159835063/34.

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13

Rose, Kyle. « Synthesis, Phase Development, and the Mechanism for Negative Thermal Expansion in Aluminum Tungstate ». Thesis, University of North Texas, 2020. https://digital.library.unt.edu/ark:/67531/metadc1703275/.

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An in-depth study of Al2W3O12 negative thermal expansion (NTE) ceramic was performed, focused on synthesis, phase mappings, and the underlying mechanisms shown to be responsible for NTE. Review of the literature has shown inconsistencies in reported values of the dilatometry measured coefficients of thermal expansion, and the temperature for the known monoclinic to orthorhombic phase transition. Two synthesis techniques are introduced: an ionic-liquid non-hydrolytic sol-gel synthesis route; and a low temperature solid state reaction synthesis for Al2W3O12. X-ray diffraction, Raman spectroscopy, and attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR) were used to verify the techniques. Two differential scanning calorimetry (DSC) experiments (high and low temperature) were performed on the material showing the transition between -5 and -20 °C and no other phase changes until a reported degradation above 1100 °C. Extensive dilatometry on the material led to the discovery of elastic transitions occurring in the polycrystalline sample capable of explaining the inconsistencies in reported dilatometry results. This is further developed into a proposed model defining the regions between these transitions. Each region has a different thermal expansion as well as a direct effect on the reaction of the material upon cooling. This proposed model may allow more consistent reporting of dilatometry results for NTE materials. Raman spectroscopy was performed from 25-725 °C on the material showing both a joining in the tungsten-oxygen bending modes as well as a broadening in the tungsten-oxygen stretching modes. This is consistent with Al-O-W angle changes along the same temperature range reported in literature as well as the transverse vibrational modes responsible for NTE.

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Vignotto, Davide. « Analysis of the in-Flight Performance of a Critical Space Mechanism ». Doctoral thesis, Università degli studi di Trento, 2021. http://hdl.handle.net/11572/323575.

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Gravitational waves detection is a challenging scientific objective, faced by scientist in the last 100 years, when Einstein theorized their existence. Despite multiple attempts, it was only in 2016 that the first observation of a gravitational wave was officially announced. The observation, worth a Nobel Prize, was made possible thanks to a worldwide collaboration of three large ground-based detectors. When detecting gravitational waves from ground, the noisy environment limits the frequency bandwidth of the measurement. Thus, the type of cosmic events that are observable is also limited. For this reason, scientists are developing the first gravitational waves detector based in space, which is a much quieter environment, especially in the sub-Hertz bandwidth. The space-based detector is named laser interferometer space antenna (LISA) and its launch is planned for 2034. Due to the extreme complexity of the mission, involving several new technologies, a demonstrator of LISA was launched and operated between 2015 and 2017. The demonstrator mission, called LISA Pathfinder (LPF), had the objective to show the feasibility of the gravitational waves observation directly from space, by characterizing the noise affecting the relative acceleration of two free falling bodies in the milli-Hertz bandwidth. The mission was a success, proving the expected noise level is well below the minimum requirement. The free-falling bodies of LPF, called test masses (TMs), were hosted inside dedicated electrode housings (EH), located approximately 30 cm apart inside the spacecraft. When free falling, each TM stays approximately in the center of the EH, thus having milli-meter wide gaps within the housing walls. Due to the presence of such large gaps, the TMs were mechanically constrained by dedicated mechanisms (named CVM and GPRM) in order to avoid damaging the payload during the launch phase and were released into free fall once the spacecraft was in orbit. Prior to the start of the science phase, the injection procedure of the TMs into free-fall was started. Such a procedure brought each TM from being mechanically constrained to a state where it was electro-statically controlled in the center of the EH. Surprisingly, the mechanical separation of the release mechanism from the TM caused unexpected residual velocities, which were not controllable by the electrostatic control force responsible for capturing the TM once released. Therefore, both the TMs collided with either the surrounding housing walls or the release mechanism end effectors. It was possible to start the science phase by manually controlling the release mechanism adopting non-nominal injection strategies, which should not be applicable in LISA, due to the larger time lag. So, since any release mechanism malfunctioning may preclude the initialization of LISA science phase, the GPRM was extensively tested at the end of LPF, by means of a dedicated campaign of releases, involving several modifications to the nominal injection procedure. The data of the extended campaign are analyzed in this work and the main conclusion is that no optimal automated release strategy is found for the GPRM flight model as-built configuration that works reliably for both the TMs producing a nominal injection procedure. The analysis of the in-flight data is difficult since the gravitational referencesensor of LPF is not designed for such type of analysis. In particular, the low sampling frequency (i.e., 10 Hz) constitutes a limiting factor when detecting instantaneous events such as collisions of the TM. Despite the difficulties of extracting useful information on the TM residual velocity from the in-flight data, it is found that the main cause of the uncontrollable state of the released TM is the collision of the TM with the plunger, i.e., one of the end-effectors of the GPRM. It is shown that the impact is caused by the oscillation of the plunger or by the elastic relaxation of the initial preload force that holds the TM. At the end of the analysis, some improvements to the design of the release mechanism are brie y discussed, aimed at maximizing the probability of performing a successful injection procedure for the six TMs that will be used as sensing bodies in the LISA experiment.

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Ye, Zhou. « Mechanism and the Effect of Microwave-Carbon Nanotube Interaction ». Thesis, University of North Texas, 2005. https://digital.library.unt.edu/ark:/67531/metadc4919/.

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A series of experimental results about unusual heating of carbon nanotubes by microwaves is analyzed in this dissertation. Two of vibration types, cantilever type (one end is fixed and the other one end is free), the second type is both ends are fixed, have been studied by other people. A third type of forced vibration of carbon nanotubes under an alternating electromagnetic field is examined in this paper. Heating of carbon nanotubes (CNTs) by microwaves is described in terms of nonlinear dynamics of a vibrating nanotube. Results from the model provide a way to understand several observations that have been made. It is shown that transverse vibrations of CNTs during microwave irradiation can be attributed to transverse parametric resonance, as occurs in the analysis of Melde's experiment on forced longitudinal vibrations of a stretched elastic string. For many kinds of carbon nanotubes (SWNT, DWNT, MWNT, ropes and strands) the resonant parameters are found to be located in an unstable region of the parameter space of Mathieu's equation. Third order wave equations are used to qualitatively describe the effects of phonon-phonon interactions and energy transfer from microwaves to CNTs. This result provides another way to input energy from microwaves to carbon nanotubes besides the usual Joule heating via electron-phonon interaction. This model appears to be the first to point out the role of nonlinear dynamics in the heating of CNTs by microwaves.

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Yun, Yuan. « Kinematics, dynamics and control analysis for micro positioning and active vibration isolation using parallel manipulators ». Thesis, University of Macau, 2011. http://umaclib3.umac.mo/record=b2542954.

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Ducheček, Martin. « Čtyřválcový řadový vznětový motor s excentrickým klikovým mechanismem pro užitková vozidla ». Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-232116.

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The purpose of this thesis is to evaluate the influence of eccentricity of crank mechanism to the force between the piston and the cylinder liner for appointed crank mechanism. Furthermore the influence of eccentricity to balancing crankshaft is verified and for selected value of eccentricity is realized balance. For the construction check was realized stress analysis of crank mechanism included torsion vibration.

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Jöcker, Markus. « Numerical Investigation of the Aerodynamic Vibration Excitation of High-Pressure Turbine Rotors ». Doctoral thesis, KTH, Energy Technology, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3416.

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The design parameters axial gap and stator count of highpressure turbine stages are evaluated numerically towards theirinfluence on the unsteady aerodynamic excitation of rotorblades. Of particular interest is if and how unsteadyaerodynamic considerations in the design could reduce the riskofhigh cycle fatigue (HCF) failures of the turbine rotor.

A well-documented 2D/Q3D non-linear unsteady code (UNSFLO)is chosen to perform the stage flow analyses. The evaluatedresults are interpreted as aerodynamic excitation mechanisms onstream sheets neglecting 3D effects. Mesh studies andvalidations against measurements and 3D computations provideconfidence in the unsteady results. Three test cases areanalysed. First, a typical aero-engine high pressure turbinestage is studied at subsonic and transonic flow conditions,with four axial gaps (37% - 52% of cax,rotor) and two statorconfigurations (43 and 70 NGV). Operating conditions areaccording to the resonant conditions of the blades used inaccompanied experiments. Second, a subsonic high pressureturbine intended to drive the turbopump of a rocket engine isinvestigated. Four axial gap variations (10% - 29% ofcax,rotor) and three stator geometry variations are analysed toextend and generalise the findings made on the first study.Third, a transonic low pressure turbine rotor, known as theInternational Standard Configuration 11, has been modelled tocompute the unsteady flow due to blade vibration and comparedto available experimental data.

Excitation mechanisms due to shock, potential waves andwakes are described and related to the work found in the openliterature. The strength of shock excitation leads to increasedpressure excitation levels by a factor 2 to 3 compared tosubsonic cases. Potential excitations are of a typical wavetype in all cases, differences in the propagation direction ofthe waves and the wave reflection pattern in the rotor passagelead to modifications in the time and space resolved unsteadypressures on the blade surface. The significant influence ofoperating conditions, axial gap and stator size on the wavepropagation is discussed on chosen cases. The wake influence onthe rotorblade unsteady pressure is small in the presentevaluations, which is explicitly demonstrated on the turbopumpturbine by a parametric study of wake and potentialexcitations. A reduction in stator size (towards R≈1)reduces the potential excitation part so that wake andpotential excitation approach in their magnitude.

Potentials to reduce the risk of HCF excitation in transonicflow are the decrease of stator exit Mach number and themodification of temporal relations between shock and potentialexcitation events. A similar temporal tuning of wake excitationto shock excitation appears not efficient because of the smallwake excitation contribution. The increase of axial gap doesnot necessarily decrease the shock excitation strength neitherdoes the decrease of vane size because the shock excitation mayremain strong even behind a smaller stator. The evaluation ofthe aerodynamic excitation towards a HCF risk reduction shouldonly be done with regard to the excited mode shape, asdemonstrated with parametric studies of the mode shapeinfluence on excitability.

Keywords:Aeroelasticity, Aerodynamics, Stator-RotorInteraction, Excitation Mechanism, Unsteady Flow Computation,Forced Response, High Cycle Fatigue, Turbomachinery,Gas-Turbine, High-Pressure Turbine, Turbopump, CFD, Design

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Bills, Kyle. « Mechanoreceptor Activation in the Treatment of Drug-Use Disorders : Mechanism and Outcome ». BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/8627.

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The therapeutic benefits attributed to activation of peripheral mechanoreceptors are poorly understood. There is growing evidence that mechanical stimulation modulates substrates in the supraspinal central nervous system (CNS) that are outside the canonical somatosensory circuits. This work demonstrates that activation of peripheral mechnoreceptors via mechanical stimulation (MStim) is sufficient to increase dopamine release in the nucleus accumbens (NAc), alter neuron firing rate in the ventral tegmental area (VTA) and increase membrane translocation of delta opioid receptors (DORs) in the NAc. Further, we demonstrate that these effects are dependent on DORs and acetylcholine receptors. Additionally, MStim can block neuronal markers of chronic ethanol dependence including ethanol-induced changes to VTA GABA neuron firing during withdrawal, and DA release profiles after reinstatement ethanol during withdrawal. These are presented in tandem with evidence that MStim also ameliorates behavioral indices of ethanol withdrawal. Finally, exercise, a modality that includes a mechanosensory component, is shown to alter expression of kappa opioid receptors (KORs) in the NAc. This change substantively depresses KORs influence over evoked DA release in direct contraversion to the effects of chronic ethanol. These changes translate into reduced drinking behavior.

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Černohous, Tomáš. « Dvouválcový řadový vznětový motor s excentrickým klikovým mechanismem pro užitková vozidla ». Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-232050.

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The goal of this master’s thesis is to examine the influence of eccentricity on the behaviour of forces between the piston and cylinder liner and on balancing of the crank mechanism for given parameters of the diesel engine. Another aim of this paper is to propose an appropriate balancing of the crank mechanism followed by stress analysis considering torsional vibration for a chosen value of eccentricity.

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Moghaddas, Mohamad Amin. « On the Mechanism of the Ultrasonic-Assisted Drilling Process ». The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1534723108853497.

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Qiu, Donghai. « Theoretical and experimental study of tuned nonlinear energy sink : application to passive vibration control ». Thesis, Toulouse, INSA, 2018. http://www.theses.fr/2018ISAT0029/document.

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: Les travaux présentés dans cette thèse traitent du contrôle de systèmes dynamiques soumis à des excitations harmoniques et transitoires en utilisant des absorbeurs de type Nonlinear Energy Sink (NES). Plusieurs aspects ont été développés : la conception et la réalisation d'un nouveau design pour le NES cubique, l'étude de la location et du transfert irréversible d'énergie sur un NES bistable et le développement d'un critère de conception pour un NES à Vibro-Impact (VI). Dans un premier temps, un critère de conception est proposé pour le NES à raideur cubique. Le design proposé est basé sur des ressorts coniques ou des ressorts à pas variable. Un mécanisme à raideur négative est aussi introduit pour supprimer la partie linéaire et avoir une raideur cubique pure. Dans un deuxième temps, le concept du NES est validé expérimentalement par des essais statiques et des essais dynamiques. Une analyse de sensibilité est aussi menée sur la longueur des ressorts précontraints, elle dénote parfois un état bistable de l'oscillateur. Ensuite, le NES bistable ainsi obtenu est étudié plus en détail. Ce type d'absorbeur s'avère être très robuste pour différents types d’excitation. Des études expérimentales sont aussi menées afin d'explorer le comportement dynamique. Enfin, un critère de conception est proposé pour le NES à Vibro-Impact. Des calculs analytiques détaillés sont proposés pour contrôler les vibrations sous différentes excitations. L'étude expérimentale montre une bonne cohérence avec les résultats théoriques
The work presented in this thesis deals with the passive control of dynamics systems subjected to harmonic and transient excitations using a Nonlinear Energy Sink (NES). Several research aspects have been developed: design theory and experimental study of a novel NES, efficient Targeted Energy Transfer (TET) of bistable NES and design criteria for optimally tuned Vibro-Impact (VI) NES. Firstly, a design criterion intended to provide optimal nonlinear stiffness is proposed. Then a novel design of NES system yielding cubic stiffness with conical springs or variable pitch springs and negative stiffness mechanism is developed. Secondly, the experimental procedures for static and dynamic test are presented and applied to validate the concept of NES system. Then a sensitivity analysis is performed with respect to the pre-compressed length of springs. Thirdly, the optimal design of the above device with negative stiffness (termed as bistable NES) is studied. This type of NES is proved to work robustly for different types of excitation, and experimental study of semi-active control are explored. Finally, design criteria for optimally tuned VI NES are studied. Detailed analytical calculations of clearance to control the vibration under different excitations are proposed. A good correspondence between theoretical and experimental results is observed

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Izuka, Jaime Hideo 1974. « Modelo e teste experimental para o controle de vibração de vigas longas deformadas ». [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/264567.

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Orientador: Paulo Roberto Gardel Kurka
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
Made available in DSpace on 2018-08-23T11:40:22Z (GMT). No. of bitstreams: 1 Izuka_JaimeHideo_D.pdf: 4550690 bytes, checksum: d283c500cecbc7a038784ba35f0f73df (MD5) Previous issue date: 2013
Resumo: A utilização de braços manipuladores flexíveis em veículos de exploração foi o motivador deste trabalho. Estas estruturas têm como vantagens a sua massa reduzida e a capacidade de suportar grandes deformações sem que o limite de elasticidade seja excedido. O controle das vibrações de sua extremidade livre é essencial para uma aplicação prática. Neste contexto, este trabalho tem como objetivo a determinação de um modelo dinâmico para uma estrutura longa e flexível, visando o seu controle de vibração. A estrutura considerada possui seção variável, semelhante a uma viga telescópica. Considera-se ainda que a estrutura esteja sujeita a uma grande deformação causada pelas ações de tendão de tração, peso próprio e cargas concentradas. O modelo dinâmico consiste na adaptação de uma malha de elementos finitos de baixa ordem à configuração da linha de deformação estática da viga. A vibração a ser controlada consiste das pequenas oscilações que ocorrem em torno da posição de equilíbrio da viga deformada. O modelo dinâmico encontrado para a estrutura é utilizado no projeto de um controlador de vibrações, ativado por forças exercidas no tendão de tração, responsável pela deformação estática da própria viga. Comparações com a literatura, bem como resultados experimentais comprovam a validade do modelo empregado para a caracterização do sistema. Simulações numéricas mostram o sucesso de uso do modelo no projeto de um controlador ativo de vibrações
Abstract: The use of flexible manipulator arms in exploration vehicles was the motivation of this work. The advantages of such structures are their light weight and the capability to withstand large displacements without exceeding their specified elastic limit. The control of vibrations of its free end is essential for a practical application. In this context, the objective of this study is to determine a dynamic model for a long and flexible structure, aiming its vibration control. The structure has a variable section, similar to a telescopic beam. Large deformation behavior of the structure is considered. Concentrated loads, self-weight of the structure and tendon traction are the loads applied to the structure. The model dynamics is described by a low order finite element mesh, which is adapted to the geometry defined by the static deformation of the beam. The vibrations to be controlled are the small oscillations about the equilibrium position of the deformed beam. The dynamic model found for the structure is applied to design an active vibration controller. The controller forces are applied though the tendon traction cables, which is also responsible for the static deformation of the beam itself. Comparison with literature as well as experimental results prove the validity of the model used to characterize the system. Numerical simulations show the success of using the model in the design of an active vibration controller
Doutorado
Mecanica dos Sólidos e Projeto Mecanico
Doutor em Engenharia Mecânica

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Dragoun, Jan. « Dvouválcový čtyřdobý plochý zážehový motor ». Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2013. http://www.nusl.cz/ntk/nusl-230626.

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This thesis deals with the possibilities for realization of the crankshaft-cylinder four-stroke gasoline engine is flat, usable in the urban vehicle. In the work described stresses exerted on the crank mechanism can balance the crankshaft, torsional stress and strength calculation method of control. In the final part of this work is outlined proposal for implementation of the crankshaft.

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Steigl, Vladimír. « Čtyřválcový zážehový motor s vypínáním válců ». Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2017. http://www.nusl.cz/ntk/nusl-318839.

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The aim of this diploma thesis is design of configuration and balancing of crankshaft which is determined for four-cylinder gasoline engine. The thesis investigates kinematics, dynamics and possible ways of balancing the inertial forces and moments of the rotating and sliding parts of the central crank mechanism. Subsequently, the 3D CAD model is designed according to the presented drawing. It is transformed into a spare torsion system, from which the calculations of its own and forced torsional vibrations are based. The proposed 3D CAD model is then spatially transmitted in the FEA software Ansys Workbench and modified (boundary conditions, etc.) in the FEA software Ansys Mechanical APDL so that it can be calculated according to the selected LSA method. From the selected results of the LSA method, the crankshaft safety factor against fatigue damage is calculated.

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Bertrandias, Aude. « Understanding drop generation mechanisms in transversally vibrating membrane emulsification ». Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLC094/document.

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Dans certaines conditions, une baisse significative de la taille des gouttes se produit en émulsification membranaire avec vibrations transversales. Pour comprendre les mécanismes impliqués, nous avons développé deux dispositifs expérimentaux, dans lesquels une goutte unique est formée à travers un capillaire dans une phase externe, qui est soit stationnaire, soit en écoulement. Le capillaire peut être mis en vibration parallèlement à son axe.Lorsque la phase externe est stationnaire, au-delà d’une amplitude seuil de forçage, la taille des gouttes formées diminue significativement. La goutte entre en résonance quand sa fréquence propre coïncide avec la fréquence de forçage et elle se détache si elle atteint une élongation critique. La goutte est modélisée comme un oscillateur harmonique linéaire forcé. Un terme d’amortissement additionnel décrit la dissipation visqueuse entre la goutte et la surface du capillaire. Ce modèle prédit bien les amplitudes seuils et les diamètres de gouttes.Lorsque la phase externe s’écoule, nous avons étudié deux régimes de formation de gouttes, en goutte à goutte (dripping) ou à partir d’un jet (jetting). Expérimentalement, la transition du dripping au jetting se produit à un nombre de Weber interne seuil, dont la valeur dépend des nombres capillaire et d’Ohnesorge externes. Le jet se rétrécit (narrowing) ou s’élargit (widening) selon le rapport de vitesses des phases choisi. En dripping, les diamètres de gouttes sont bien prédits par un bilan des moments. En jetting, un modèle basé sur l’équation du mouvement permet d’estimer la vitesse critique permettant la transition au jetting et les diamètres de gouttes résultants
In transversally vibrating membrane emulsification, significantly smaller drops are generated in certain conditions. We aim to explain the mechanisms involved. To do so, two experimental setups were developed. A single drop is formed from a nozzle into an outer phase, which is either stationary or cross-flowing. The nozzle can be submitted to axial vibrations.For a drop formed into a stationary phase, a transition in drop generation occurs above a critical forcing amplitude. Below the threshold, a large drop forms by dripping. Above the threshold, a drop detaches when its first eigenfrequency and the forcing frequency coincide. The drop then resonates and detaches once a critical elongation ratio is reached. We model a drop as a linearly forced harmonic oscillator and add an extra damping term to account for the viscous dissipation between the drop and nozzle surface. We well reproduce the threshold amplitudes and drop diameters.We also study drops generated into cross-flow. In dripping mode, drop diameters are described by a torque balance. At a critical inner Weber number function of the outer capillary and Ohnesorge numbers, a transition to jetting occurs. Jet widening or narrowing takes place depending on the phase velocity ratio. We propose a model to account for the transition to jetting based on the drop equation of motion. Overall, we adequately account for the jetting velocity and drop diameters, with discrepancies which were explained

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Ehrenberger, Pavel. « Modální vlastnosti klikového ústrojí čtyřválcového traktorového motoru ». Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2010. http://www.nusl.cz/ntk/nusl-228988.

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This diploma thesis contains a summary of the general information about the torsion vibration of the crankshaft. The main task is to prepare a flexible model of the crankshaft in the FEM program ANSYS and the subsequent export into the MBS ADAMS / Engine. According to parameters the model of four-cylinder line tractor engine with flexible crankshaft is built. Crank mechanism is analyzed to determine the natural frequencies and natural modes. Finally the results are evaluated and compared with analytical calculations.

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Kučera, Ondřej. « Čtyřválcový řadový zážehový letecký motor ». Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-444959.

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The thesis deals with the structural design of a steel connecting rod for the aircraft engine Walter Mikron III, which is currently still manufactured and developed by company PARMA-TECHNIK, s.r.o. The proposed connecting rod would replace the current duralumin connecting rod. The work also contains a strength analysis of the designed component, in which it was aimed to verify the stress on the connecting rod, based on which the fatigue safety factor was performed. This is crucial for dynamically stressed parts of internal combustion engines. Furthermore, was investigated the effect of the change of the connecting rod on the torsional vibration of the crank mechanism. For this purpose, was built a discrete torsion model. The output of the whole work is the drawing documentation of the new connecting rod, meeting the requirements for application in an aircraft engine.

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Süttő, Daniel. « Pětiválcový řadový vznětový motor s excentrickým klikovým mechanismem ». Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2014. http://www.nusl.cz/ntk/nusl-231456.

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The aim of this thesis is to find out the influence of eccentricity of crank mechanism on the duration of the force between the piston and the cylinder liner. At the same time I wanted to find out its influence on the balance of the whole system. It is important to design the balance for the selected value of the eccentricity and subsequently put through the crank shaft to stress analysis with torsional vibrations. I got so interested in this problem that in addition to the whole topic I designed a torsional vibration damper.

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Ting-Kong, Christopher. « Design of an adaptive dynamic vibration absorber ». Title page, contents and abstract only, 1998. http://thesis.library.adelaide.edu.au/adt-SUA/public/adt-SUA20010220.212153.

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Pulava, Oleksandr. « Šestiválcový vznětový motor pro užitková vozidla ». Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2018. http://www.nusl.cz/ntk/nusl-378397.

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The aim of this diploma is to design a crankshaft for a six-cylinder commercial vehicle, which is one of the unified motors. The main parts are the design of the crankshaft configuration, the crankshaft balancing method for forces and moments, the crankshaft design documentation, and the crankshaft strength verification. The design of torsional vibration damping characteristics is also made and its effect on torsional vibration and crankshaft strength is determined.

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Monteil, Mélodie. « Comportement vibratoire du steelpan : effet des procédés de fabrication et dynamique non linéaire ». Phd thesis, Palaiseau, École nationale supérieure de techniques avancées, 2013. http://pastel.archives-ouvertes.fr/pastel-00913650.

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Cette étude porte sur le steeldrum, aussi appelé steelpan, percussion mélodique de Trinidad et Tobago, fabriquée à partir de bidons métalliques dont une des faces subit un ensemble de déformations irréversibles afin d'obtenir une cuve principale à l'intérieur de laquelle sont façonnées les différentes notes de l'instrument. Cette thèse s'organise autour de deux axes. D'une part les processus de fabrication sont étudiés afin de mieux comprendre le travail du facteur et de proposer une modélisation de la première étape de fabrication. D'autre part, des études vibratoires sont menées sur l'instrument fini, pour comprendre la dynamique complexe responsable de son timbre. La première partie rend compte de l'évolution des caractéristiques vibratoires au cours de la fabrication. On remarque une forte localisation vibratoire au moment de la création des notes, des évolutions marquées des amortissements et des fréquences propres lors du chauffage, et des relations harmoniques après l'accordage final. La seconde partie se concentre sur la première étape de fabrication au cours de laquelle le haut du bidon est martelé pour obtenir une calotte sphérique concave. Ce processus de plasticité est modélisé analytiquement sous les hypothèses de von Karman par une structure mince soumise à des contraintes initiales. L'influence du changement géométrique et celle de l'état de contraintes résiduelles sont alors quantifiées sur les paramètres dynamiques de la structure dans son nouvel état d'équilibre. Enfin la dernière partie s'intéresse aux vibrations de l'instrument terminé qui présente un comportement dynamique caractéristique des systèmes non linéaires géométriques. En mode de jeu usuel, des échanges d'énergie entre les modes sont clairement audibles. Cette richesse de timbre provient des résonances internes dues à l'accordage, si bien que des couplages complexes sont mesurés pour des amplitudes vibratoires très faibles. Des modèles originaux de résonances internes sont proposés.

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Leon, Armando. « Non-Linear Vibration and Dynamic Fracture Mechanics of Bridge Cables ». Licentiate thesis, Karlskrona : Blekinge Institute of Technology, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-00488.

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In the present work, the non-linear vibrations and the corresponding dynamic fracture mechanics of cables of cable-stayed bridges are studied. The cables are among the most critical components in cable-stayed bridges and there are different damage sources such as corrosion, vibration, fatigue and fretting fatigue that can significantly affect them, thereby reducing the cable’s service life and even producing their failure. Cable-Parametric Resonance is the specific non-linear vibration studied in this research. This type of vibration occurs due to displacements presented at the cable supports. These displacements are induced by the wind and traffic loads acting on the pylon and deck of the bridge. Under certain conditions, unstable cable-vibration of significant amplitude can be registered. Therefore, numerical and experimental analyses are carried out in order to describe this phenomenon and to determine the corresponding instability conditions. Two non-linear models of cable-parametric resonance are studied to predict the cable response. In the simulation method, the non-linear components are treated as external forces acting on the linear systems, which are represented by Single Degree of Freedom systems and described by digital filters. A clear non-linear relationship between the excitation and the cable response is observed in the simulations and the experiments. The corresponding experimental analysis is based on a scaled model (1:200) of the Öresund bridge and a good agreement between the numerical and experimental results is found. After obtaining the relationship between the cable response and the excitation, the cable instability conditions are determined. This is done by finding the minimum displacement required at the cable supports in order to induce nonlinear cable vibration of considerable amplitude. The instability conditions are determined within a wide range of excitation frequencies and conveniently expressed in a simplified and practical way by a curve. The determination process is rather fast and offers the possibility to evaluate all bridge cable stays in a rather short time. Finally, the dynamic fracture mechanics of the cable is considered by studying the fracture toughness characteristics of the material under dynamic conditions. Finite Element simulations on a pre-cracked three-point bending specimen under impact loading are performed. The observed cable instability is equivalently considered as the associated response to impact load conditions, and a crack as a defect on the wires of a cable stay. The simulations are based on an experimental work by using the Split Hopkinson pressure bar (Jiang et al). The dynamic stress intensity factor KI(t) up to crack initiation is then obtained by different methods. The numerical estimations based on the specimen’s crack tip opening displacement (CTOD) and mid-span displacement were closest to the experimental results. It is observed that a better estimation of the dynamic stress intensity factor relies on a proper formulation of the specimen’s stiffness.
Lic March 2011

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Freisleben, Pavel. « Dvouválcový zážehový motor s excentrickým klikovým mechanismem pro osobní vozidla ». Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-232115.

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This thesis deals with forces of the crank mechanism. The aim of this work is to find the right value of the eccentricity of the crank mechanism, which will have a positive effect on the size and course of forces that cause friction losses in the crank mechanism. Next solves this balancing eccentric unit. The last part deals with the design and strength check of the crankshaft considering torsional vibration.

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Nolte, Rainer. « Formatabhängige hochdynamische Bewegungen mit Servoantrieben ». Universitätsbibliothek Chemnitz, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-226132.

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OPTIMUS MOTUS (R) ist ein grafischer Editor, um komplexe Bewegungsabläufe zu modellieren, zu optimieren, zu testen und schließlich als Funktionsbausteine für die SPS-Welt zu exportieren. So können SPS-Bewegungsprogramme erheblich schneller entwickelt und geändert werden als bei manueller Programmentwicklung. Die aus der Kurventechnik bekannte Bewegungsqualität kommt damit auch bei Servoantrieben zum Tragen. Das Debugging entfällt, weil die Quelltexte maschinell erzeugt werden.

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James, Ashley Jean. « Vibration induced droplet ejection ». Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/17337.

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Munera, Ramirez Marcela. « Analyse vibro-biomécanique et dynamique en sport/santé. Cas du cyclisme ». Thesis, Reims, 2014. http://www.theses.fr/2014REIMS016/document.

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Le phénomène de vibration offre deux facettes dans le monde sportif. Bien maîtrisé, il peut être bénéfique pour le renforcement musculaire, pour la rééducation mais dans le cas contraire ce phénomène engendre des effets délétères pour le corps humain. Ces effets délétères dépendent de la nature de la vibration mais aussi de son environnement de propagation, structural ou humain. Les vibrations ressenties par l'homme ne peuvent pas, le plus souvent, être découplées de l'analyse de mouvement et de l'analyse de la fatigue musculaire. Ainsi cette thèse s'inscrit autour de trois notions : la vibration, le mouvement et la physiologie. L'objectif est de définir les caractéristiques de performance et de santé à travers l'étude de la réponse vibro dynamique et physiologique du corps humain
Vibration phenomenon presents two faces in the sports world. Got under control ; it can be useful in body and muscle building and muscle re-education ; otherwise this phenomenon leads deleterious consequences for the human body. These deleterious effects depend on the vibration nature but also of its propagation background : structural or human. Usually, the vibration suffered by the human body cannot be decoupled either the motion analysis or the analysis of muscular fatigue. This topic research is based in three notions : vibration, motionand the physiologie. The aim of this work will be to define the characteristics of performance and health through the study of the dynamical and physiological response of the human body

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Ehnes, Charles W. « Damping in stiffener welded structures ». Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03Jun%5FEhnes.pdf.

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Graves, Kynan E., et kgraves@swin edu au. « Electromagnetic energy regenerative vibration damping ». Swinburne University of Technology, 2000. http://adt.lib.swin.edu.au./public/adt-VSWT20060307.120939.

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This thesis documents a PhD level research program, undertaken at the Industrial Institute Swinburne, Swinburne University of Technology between the years of 1997 and 2000. The research program investigated electromagnetic energy regenerative vibration damping; the process of recovering energy from damped, vibrating systems. More specifically, the main research objective was to determine the performance of regenerative damping for the application of vehicle suspension systems. This question emerged due to the need for continuous improvement of vehicle efficiency and the potential benefits possible from the development of regenerative vehicle suspension. It was noted, at the outset of this research, that previous authors had undertaken research on particular aspects of regenerative damping systems. However in this research, the objective was to undertake a broader investigation which would serve to provide a deeper understanding of the key factors. The evaluation of regenerative vibration damping performance was achieved by developing a structured research methodology that began with analysing the overall requirements of regenerative damping and, based on these requirements, investigated several important design aspects of the system. The specific design aspects included an investigation of electromagnetic machines for use as regenerative damping devices. This analysis concentrated on determining the most promising electromagnetic device construction based on its damping and regeneration properties. The investigation then proceeded to develop an 'impedance-matching' regenerative interface, in order to control the energy flows in the system. This form of device had not been previously developed for electromagnetic vibration damping, and provided a significant advantage in maximising energy regeneration while maintaining damping control. The results from this analysis, when combined with the issues of integrating such a system in vehicle suspension, were then used to estimate the overall performance of regenerative damping for vehicle suspension systems. The methodology and findings in this research program provided a number of contributing elements to the field, and provided an insight into the development of regenerative vehicle systems. The findings revealed that electromagnetic regenerative vibration damping may be feasible for applications such as electric vehicles in which energy efficiency is a primary concern, and may have other applications in similar vibrating systems.

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Assi, Gustavo R. S. « Mechanisms for flow-induced vibration of interfering bluff bodies ». Thesis, Imperial College London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.508992.

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Jane, Kuo Chang. « Buckling, postbuckling deformation and vibration of a delaminated plate ». Diss., Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/19975.

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Howard, Carl. « Active isolation of machinery vibration from flexible structures ». Title page, abstract and table of contents only, 1999. http://web4.library.adelaide.edu.au/theses/09PH/09phh8478.pdf.

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Thesis (Ph. D.)--University of Adelaide, Dept. of Mechanical Engineering, 1999?
Copy 2 does not have a CD-ROM. Includes bibliographical references (p. 317-330). Also available in an electronic version.

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Zhou, Li. « Vibration control of buildings using smart magnetorheological dampers / ». View Abstract or Full-Text, 2002. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202002%20ZHOU.

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Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2002.
Includes bibliographical references (leaves 163-177). Also available in electronic version. Access restricted to campus users.

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Baldassarri, Mirko. « Review of Vibration Energy Harvester ». Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2021.

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This work presents a state-of-the-art on vibration energy harvesting that is one of the hottest topics addressed by a big part of the scientific community to minimize the requirement of external power source. A lot of transduction mechanisms have been investigated and designed by researchers, based on different mechanical systems and transduction principles, in order to recover energy coming from environmental vibrations. This dissertation is intended to illustrate and analyse the main findings in order to highlight the critical aspects of this technology and the key challenges for further developments. Firstly, a classification of vibration energy harvesters (VEHs) based on their "oscillating structures" and "transduction mechanisms" is provided, corresponding to the most widely used mathematical reference model and transduction devices, respectively. Then, the most common examples of application of such devices is presented to illustrate how vibrations of the surrounding environment can be converted into electrical energy exploited for different intended uses. Based on this survey, the limitations of the simplest devices are discussed, the most important of which is the ineffectiveness of VEHs when prompted by vibrations with a frequency even slightly different from the device resonance frequencies, (which is a common scenario, since environmental vibrations are often random and broadband). To solve this problem, researchers are currently focusing on developing efficient VEHs by adopting new materials and optimising the harvesting devices. The recent prototypal devices appear promising, but the achievement of robust solutions for real practical applications still seems a long-term goal, due to the limited capability of current technology to harvesting meaningful levels of electrical energy.

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Holdhusen, Mark Horner. « Experimental validation and the effect of damping on the state-switched absorber used for vibration control ». Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/16688.

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Huang, Yao-Hsin. « Some fundamental issues of constrained layer damping treatments / ». Thesis, Connect to this title online ; UW restricted, 2000. http://hdl.handle.net/1773/7046.

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Yellin, Jessica M. « An analytical and experimental analysis for a one-dimensional passive stand-off layer damping treatment / ». Thesis, Connect to this title online ; UW restricted, 2004. http://hdl.handle.net/1773/7030.

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Neukirch, Sebastien. « Enroulement, contact et vibrations de tiges élastiques ». Habilitation à diriger des recherches, Université Pierre et Marie Curie - Paris VI, 2009. http://tel.archives-ouvertes.fr/tel-00667562.

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Ce mémoire présente plusieurs études sur l'équilibre, la stabilité et les vibrations de poutres élastiques en grande rotation. Le modèle utilisé est d'abord présenté de deux manières différentes : les équations de Kirchhoff sont introduites (i) comme une théorie directe de Cosserat, (ii) par une approche asymptotique 3D->1D. Une étude relativement complète des équilibres avec et sans auto-contact d'une poutre sous contrainte de tension et torsion et encastrée en ses deux extrémités est ensuite exposée. Le modèle est d'autre part appliqué au sur-enroulement de la molécule d'ADN et aux expériences sur molécule individuelle. Le cas d'une poutre naturellement courbe enroulée autour d'un obstacle cylindrique est ensuite traité. Les équations d'équilibre obtenues sont appliquées au cas d'une plante grimpante autour d'un tuteur ainsi qu'aux conﬁgurations dimériques de la protéine kératine. Enﬁn la dynamique d'une poutre plane est analysée sous deux angles différents : (i) le relâchement d'une poutre console qui donne lieu au phénomène de renforcement de courbure, et (ii) les vibrations d'une poutre post-ﬂambée, encastrée en ses deux extrémités, avec comparaison des cas extensibles et inextensibles. La conclusion mentionne quelques problèmes d'intérêt qui seront l'objets d'études futures.

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Desplanche, Sarah. « De l'étude fondamentale d’hydrates d’acide fort par spectroscopie de vibration et de relaxation à l'application de leur super-conductivité protonique pour le développement d'une micropile à combustible ». Thesis, Bordeaux, 2018. http://www.theses.fr/2018BORD0171/document.

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Les piles à combustible (PAC) utilisant l’hydrogène comme vecteur, possèdent de bons rendements énergétiques et ne produisent aucun gaz à effet de serre. Elles se présentent donc aujourd’hui comme une solution propre et efficace. Cette alternative pourrait ainsi devenir un substitut possible aux hydrocarbures et pallier l’intermittence de certaines énergies renouvelables.Il existe différents types de PAC se distinguant principalement par la nature de l’électrolyte qui compose leur membrane échangeuse de protons. Utiliser les clathratehydrates d’acide fort comme électrolyte solide représente une alternative peu explorée à ce jour. Ces systèmes sont des solides cristallins nanoporeux constitués d’un réseau hôte de molécules d’eau formant des cavités nanométriques et encapsulant des molécules invitées.Dans le cas de clathrate hydrates d’acide fort, le confinement d’acides au sein des cages aqueuses génère des excès de protons délocalisés le long de leur réseau aqueux. A température ambiante, ces clathrate hydrates présentent alors une excellente conductivité protonique, plus élevée que celle des membranes de PACs actuellement utilisées. L’objectif de ce doctorat a été d’élaborer un électrolyte à base de clathrate hydrate d’acide hexafluorophosphorique (un des meilleurs conducteurs connus de cette classe de systèmes)sur la base d’une approche physico-chimique fondamentale, et de développer un montage miniaturisé de PAC intégrant ce nouvel électrolyte.A un niveau fondamental, il a été nécessaire de comprendre les facteurs régissant la conductivité protonique élevée de ces systèmes et en particulier, le lien existant entre la conductivité et le nombre d’hydratation (rapport molaire eau/acide dans le clathrate). Les mécanismes microscopiques mis en jeu ont été étudiés en s’appuyant sur la spectroscopie et l’imagerie Raman, complétées par des expériences de résonance magnétique nucléaire, de diffraction des rayons X et de spectroscopie d’impédance électrochimique. Un ensemble d’informations structurales (type de clathrate formé, transition de phase et stabilité thermodynamique), dynamiques (modes de vibration, diffusion des protons et cinétique) et chimiques (inclusion d’impuretés fluorées) a ainsi été obtenu. En tant que sonde sélective et locale, la technique de diffusion Raman a apporté des informations uniques. Elle a permis de sonder les interactions acides-cages, de proposer un protocole expérimental permettant de contrôler le nombre d’hydratation et également, de révéler pour la première fois une microstructuration du clathrate hydrate observée uniquement au-dessus d’un seuil d’hydratation. Ces propriétés physico-chimiques ont été corrélées aux mesures de conductivité, permettant de comprendre l’impact du nombre d’hydratation et des impuretés chimiques sur les performances de l’électrolyte solide. L’ensemble de ces résultats a permis d’aboutir à un développement technologique original. Une nouvelle micropile à combustible utilisant des clathrate hydrates d’acide hexafluorophosphorique comme électrolyte a été conçue. Ce développement offre ainsi une PAC aux performances comparables aux PACs actuellement disponibles et fonctionnant de la température ambiante à des températures négatives
Fuel cells (FC) using hydrogen possess very good energy performance and produce no greenhouse gases. It presents itself today as a clean and efficient solution. This alternative could then become a possible substitute for fossil fuels and palliate for the intermittency ofcertain renewable energies.There are various types of FC, mainly distinguished by the nature of the electrolyte that composes their proton exchange membrane. Using strong acid clathrate hydrates as solid electrolyte represents an alternative for which very little is known nowadays. These systems are nanoporous crystalline solids consisting of a water host network forming nanometric cavities encapsulating guest molecules. In the case of strong acid clathrate hydrates, the confinement of acidic species within the aqueous cages generates proton excess that isdelocalized along their aqueous network. At room temperature, these clathrate hydrates have then excellent proton conductivity, which is higher than that of the FCs membranes currently used. The objective of this PhD was to develop an electrolyte based on hexafluorophosphoricacid clathrate hydrate (one of the best-known conductors of this class of system) on the basisof a fundamental physico-chemical approach, and to develop a miniaturized FC assemblyincorporating this new electrolyte.At a fundamental level, it was necessary to understand the driving factors responsible for the super-protonic conductivity of these systems and in particular, the relationship between the conductivity and the hydration number (i.e. water to acid molar ratio in the clathrate). The microscopic mechanisms have been studied by means of Raman spectroscopy and imaging, supplemented by nuclear magnetic resonance, X-ray diffraction and electrochemical impedance spectroscopy experiments. A set of results concerning the structure (clathrate type, phase transition and thermodynamic stability), the dynamics (vibrational modes, proton diffusion and kinetics) and the chemistry (inclusion of fluorinated impurities) has thus been obtained. As a selective and microscopic probe, the Raman scattering technique provided unique information. It allowed to probe the acid-cages interactions, to propose an experimental protocol monitoring the hydration number and also,to reveal, for the first time, a microstructuration of the clathrate hydrate only observed abovea hydration threshold. These physico-chemical properties have been correlated with the conductivity measurements, making it possible to understand the impact of the hydration number and of the chemical impurities onto the electrochemical performances of the solid electrolyte. All these results led to an original technological development. A new micro-fuel cell using hexafluorophosphoric acid hydrates as the electrolyte has been designed. This development offers a FC with performances comparable to the FCs currently available and operating from room temperature to negative temperatures

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Blom, Peter. « Exploring the vibration control potential of magneto-sensitive rubber ». Licentiate thesis, Stockholm, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-241.

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Thèses sur le sujet « Mechanism vibration »

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