La fatigue à nombre de cycles élevé (HCF) est un mode de défaillance courant et dangereux pour les aubages de turbomachines. Elle est induite par les efforts dynamiques élevés générés lors de résonances présentes dans la plage de fonctionnement de ces machines. Les dispositifs amortisseurs basés sur l'utilisation du frottement sec, tels que les nageoires ou les frotteurs sous-plateformes, permettent de réduire les amplitudes vibratoires, voire de repousser les fréquences de résonance hors des zones de fonctionnement. Cependant la conception de ces dispositifs reste encore largement basée sur l'empirisme et ils peuvent être la source d'un effet de désaccordage potentiellement nuisible. L'objectif ici est de développer des modélisations adaptées au traitement du problème de vibration des aubages en présence de frottement sec, ceci afin de mieux maîtriser les comportements physiques mis en jeu et donc, de mieux maîtriser leur processus de conception. Plusieurs modélisations numériques sont testées et confrontées à des résultats de référence. Une comparaison entre procédures de résolution temporelle et fréquentielle est menée et montre l'efficacité des méthodes fréquentielles. La méthode fréquentielle de la balance harmonique à plusieurs harmoniques est adaptée au problème et exploitée dans le cadre d'une étude énergétique. Cette étude conduit à une meilleure compréhension des phénomènes mis en jeu lors de l'aplatissement des pics en fonctionnement ; elle permet de démontrer que l'alternance des états de contact glissant et bloqué est à l'origine de cet aplatissement et non la dissipation d'énergie comme souvent avancé dans la littérature. Enfin, la méthode est exploitée pour décrire le comportement des disques aubés désaccordés. La méthode de Monte Carlo est utilisée pour obtenir les caractéristiques statistiques de la réponse forcée d'un système discret, en tenant compte des variations stochastiques des paramètres du contact notamment, la charge normale, la raideur du contact et le coefficient de frottement. Les résultats obtenus permettent de mieux comprendre les effets de la nature variable de ces paramètres fondamentaux sur la dynamique d'ensemble du système non linéaire.

Baigiamajame darbe nagrinėjamos visureigio automobilio dinaminės charakteristikos bei pagrindiniai jas lemiantys parametrai, ieškoma būdų šių parametrų pagerinimui. Taip pat darbe apžvelgiamos automobilį veikiančios jėgos, apžvelgiama automobilio masės bei įkrovos lygio įtaka automobilio dinamikai, priekabos įtaka automobilio stabilumui bei valdomumui. Atlikus eksperimentinius visureigio automobilio kėbulo svyravimų bandymus priklausomai nuo: priekabos įkrovos, kelio dangos, bei transporto priemonės ir transporto priemonių junginio greičio gauti rezultatai išanalizuoti ir palyginti tarpusavyje. Pateikiami skaitinius bandymų rezultatus atitinkantys grafikai. Išvadose apibendrinami tyrimo rezultatai. / This master thesis analysis dynamic characteristics of all – terrain vehicle, main parameters having impact on them, searches for ways to improve them. The paper also reviews the forces operating on the vehicle, reviews the impact of the vehicle’s weight and the level of load on the dynamics of the vehicle, the influence of a trailer on the stability and controllability of the vehicle. The results of the experimental tests of all – terrain vehicles body’s swinging were analyzed and compared. The charts depicting numeric results of tests are provided. The conclusions summarize the results of the research.

Baigiamajame magistro darbe atliekamas sklandytuvo atakos ir slydimo kampo matavimo metodų tyrimas. Pirmoje darbo dalyje apžvelgiami atakos kampo matuokliai: virvutė, pritvirtinta ant stiklinio gaubto, atakos – slydimo kampo matuoklis su vėjarodžiu ir Pitoto vamzdelio tipo daviklis. Davikliai palyginami, aprašomi jų privalumai ir trūkumai lyginant su kitais davikliais. Antroje dalyje aprašomi alfa ir beta kampų matavimo metodai: matavimas vamzdelio tipo davikliu ir metodas, kai nenaudojami specialūs atakos, slydimo kampo davikliai. Toliau apžvelgiami veiksniai, turintys įtakos matavimo tikslumui. Pateikiamos kelių vamzdelio tipo daviklių kalibravimo kreivės. Paskutinėje dalyje programa Matlab kuriamas matematinis-dinaminis sklandytuvo modelis. Modeliu, pagal nustatytas sąlygas, skaičiuojami atakos ir slydimo kampai, analizuojami grafikai. / The thesis made the glider’s attack and slip angle measurement methods for the investigation. The first part gives an overview of measuring devices of angle of attack and slip angle: The side string, attached to the side of the canopy, vane mounted AOA sensor, Pitot-tube type sensor. The sensors are compared, describes their advantages and disadvantages compared with other sensors. The second part describes the alpha and beta angle measurement methods: measurement with the tube-type sensor, and the method without using the specific attack, slip angle sensors. The following gives an overview of factors affecting the measurement accuracy. Several tube-type sensor calibration curves are presented. The last part of thesis presents development of mathematical – dynamic model of the glider using Matlab software. The model calculates the angle of attack and slip using set conditions of flight.

The main objective of this thesis is to study the fundamental behaviour of multi-component gas mixture flows in micro/nano-channels undergoing catalytic chemical reactions on the walls. This work is primarily focused on nano-scale reacting flows seen in related applications; especially, miniaturized energy sources such as micro-fuel cells and batteries. At these geometries, the order of the characteristic length is close to the mean free path of the flowing gas, making the flow highly rarefied. As a result, non-equilibrium conditions prevail even the bulk flow and therefore, continuum assumptions are not held anymore. Hence, discrete methods should be adopted to simulate molecular movements and interactions described by the Boltzmann equation. The Direct Simulation Monte Carlo (DSMC) method was employed for the present research due to its natural ability for simulating a broad range of rarefied gas flows, and its flexibility to incorporate surface chemical reactions. In the first step, fluid dynamics and the heat transfer of H₂/N₂ and H₂/N₂/CO₂ gas mixture slip flows in a plain micro-channel are simulated. The obtained results are compared to the corresponding data achieved from Navier-Stokes equations with slip/jump boundary conditions. Generally, very good agreements are observed between the two methods. It proves the ability of DSMC in replicating the fluid properties of multi-component gas mixtures even when high mass discrepancies exist among the species. Based on this comparison, the proper parameters are set for the prepared DSMC code, and the appropriate intermolecular collision model is identified. It is also found that stream variables should be calculated more accurately at flow boundaries in order to simulate the intense upstream diffusion emerging at low velocity flows frequently seen in micro/nano-applications. Therefore, in the second step, a novel pressure boundary condition is introduced for gas mixture flows by substituting the commonly used Maxwell velocity distribution with the Chapman-Enskog distribution function. It is shown that this new method yields better results for lower velocity and higher rarefaction level cases. In the last step, a new method is proposed for coupling the flow field simulated by DSMC and surface reactions modelled by the species conservation ODE system derived from the reaction mechanism. First, a lean H₂/air slip flow subjected to oxidation on platinum coated walls in a flat micro-channel 4μm in height is simulated as a verification test case. The results obtained are validated against the solutions of the Navier-Stokes equations with slip/jump boundary conditions and very good conformity is achieved. Next, several cases undergoing the same reaction with Reynolds numbers ranging from 0.2 to 3.6 and Knudsen numbers ranging from 0.025 to 0.375, are simulated using the verified code to investigate the effects of the channel height ranging from 0.5μm to 2μm , the inlet mass flow rate ranging from 5 kg/m².s to 25 kg/m².s, the inlet temperature ranging from 300K to 700K, the wall temperature ranging from 300K to 1000K, and the fuel/air equivalence ratio ranging from 0.28 to 1.5. Some of the findings are as follows: (1) increasing the surface temperature from 600K to 1000K and/or the inlet temperature from 300K to 700K results in negligible enhancement of the conversion rate, (2) the optimum value of the equivalence ratio is on the fuel lean side (around 0.5), (3) the efficiency of the reactor is higher for smaller channel heights, and (4) increasing the inlet mass flux elevates the reaction rate especially for the smaller channels; this effect is not linear and is more magnified for lower mass fluxes.

Advances in hardware design have made wheeled mobile robots (WMRs) exceptionally mobile. To fully exploit this mobility, WMR planning, control, and estimation systems require motion models that are fast and accurate. Much of the published theory on WMR modeling is limited to 2D or kinematics, but 3D dynamic (or force-driven) models are required when traversing challenging terrain, executing aggressive maneuvers, and manipulating heavy payloads. This thesis advances the state of the art in both the formulation and calibration of WMR models We present novel WMR model formulations that are high-fidelity, general, modular, and fast. We provide a general method to derive 3D velocity kinematics for any WMR joint configuration. Using this method, we obtain constraints on wheel ground contact point velocities for our differential algebraic equation (DAE)-based models. Our “stabilized DAE” kinematics formulation enables constrained, drift free motion prediction on rough terrain. We also enhance the kinematics to predict nonzero wheel slip in a principled way based on gravitational, inertial, and dissipative forces. Unlike ordinary differential equation (ODE)-based dynamic models which can be very stiff, our constrained dynamics formulation permits large integration steps without compromising stability. Some alternatives like Open Dynamics Engine also use constraints, but can only approximate Coulomb friction at contacts. In contrast, we can enforce realistic, nonlinear models of wheel-terrain interaction (e.g. empirical models for pneumatic tires, terramechanics-based models) using a novel force-balance optimization technique. Simulation tests show our kinematic and dynamic models to be more functional, stable, and efficient than common alternatives. Simulations run 1K-10K faster than real time on an ordinary PC, even while predicting articulated motion on rough terrain and enforcing realistic wheel-terrain interaction models. In addition, we present a novel Integrated Prediction Error Minimization (IPEM) method to calibrate model parameters that is general, convenient, online, and evaluative. Ordinarily system dynamics are calibrated by minimizing the error of instantaneous output predictions. IPEM instead forms predictions by integrating the system dynamics over an interval; benefits include reduced sensing requirements, better observability, and accuracy over a longer horizon. In addition to calibrating out systematic errors, we simultaneously calibrate a model of stochastic error propagation to quantify the uncertainty of motion predictions. Experimental results on multiple platforms and terrain types show that parameter estimates converge quickly during online calibration, and uncertainty is well characterized. Under normal conditions, our enhanced kinematic model can predict nonzero wheel slip as accurately as a full dynamic model for a fraction of the computation cost. Finally, odometry is greatly improved when using IPEM vs. manual calibration, and when using 3D vs. 2D kinematics. To facilitate their use, we have released open source MATLAB and C++ libraries implementing the model formulation and calibration methods in this thesis.

Heat transfer analysis of two-dimensional, incompressible, constant property, hydrodynamically developed, thermally developing, single phase laminar flow in microtubes and microchannels between parallel plates with negligible axial conduction is performed for constant wall temperature and constant wall heat flux thermal boundary conditions for slip flow regime. Fully developed velocity profile is determined analytically, and energy equation is solved by using finite difference method for both of the geometries. The rarefaction effect which is important for flow in low pressures or flow in microchannels is imposed to the boundary conditions of the momentum and energy equations. The viscous dissipation term which is important for high speed flows or flows in long pipelines is included in the energy equation. The effects of rarefaction and viscous heating on temperature profile and local Nusselt number are discussed. The results of the numerical method are verified with the well-known analytical results of the flow in macrochannels (i.e. Kn =0, Br =0) and with the available analytical results of flow in microchannels for simplified cases. The results show significant deviations from the flow in macrochannels.

Quantifying the velocity field near the wall in microfluidic devices is important because surface effects become significant at micro- to nanometer scales. Recent studies have suggested that the "no-slip" boundary condition breaks down in microscale flows of Newtonian liquids, where the amount of slip is usually extrapolated from velocity components measured far from the wall. This doctoral thesis presents a new technique, multilayer nano-particle image velocimetry (MnPIV), for measuring the tangential velocity components at different distances from and within about 500 nm of the wall and its application to measuring slip. The feasibility of MnPIV was demonstrated using synthetic images of plane Couette flow incorporating Brownian diffusion and imaging noise. The errors in MnPIV data were then quantified with Brownian dynamics simulations. Calibration experiments were used to correlate the image intensity of the tracer to its distance from the wall z. Multilayer nPIV was then used to determine the z-positions and distribution of the particles for z < 500 nm in experimental studies of microscale Poiseuille flow. The tracers were divided into three distinct layers based on their image intensities, and the average velocity of each layer was placed at the average z-position sampled by the particles in that layer. The resultant velocity gradients were within 6% on average of analytical predictions for 2D Poiseuille flow. Finally, the results of MnPIV studies of aqueous solutions flowing through microchannels with hydrophilic and hydrophobically-coated fused silica surfaces suggest that if the slip lengths are nonzero for both of these surfaces, they are less than the uncertainty in these results, or 27 nm and 31 nm for the hydrophilic and hydrophobic channels, respectively.

Thèse (M.Sc.T.) -- Université du Québec à Chicoutimi, 2005. / Bibliogr.: f. 124-134. Document électronique également accessible en format PDF. CaQCU

Η παρούσα διατριβή ασχολείται με την καμπτική ενίσχυση δοκών οπλισμένου σκυροδέματος με στρώσεις σκυροδέματος στο εφελκυόμενο ή στο θλιβόμενο πέλμα τους. Ιδιαίτερα ασχολείται με τον προσδιορισμό της ολίσθησης στη διεπιφάνεια τους. Συγκεκριμένα στο 1ο Κεφάλαιο γίνεται βιβλιογραφική ανασκόπηση για τις διεπιφάνειες σκυροδέματος. Παρουσιάζονται όλα τα προσομοιώματα που προτείνονται είτε σε Κανονισμούς, είτε από διάφορους ερευνητές, για τον προσδιορισμό της διατμητικής αντοχής της διεπιφάνειας, καθώς και για τον προσδιορισμό της σχέσης διατμητικής τάσης – ολίσθησης στη διεπιφάνεια σκυροδέματος. Στο 2ο Κεφάλαιο, παρουσιάζεται βιβλιογραφική ανασκόπηση για τις διεπιφάνειες σκυροδέματος με χάλυβα ή σύνθετα υλικά, σε σύμμικτες κατασκευές και σε μέλη ενισχυμένα με ελάσματα χάλυβα ή από ινοπλισμένα πολυμερή (ΙΟΠ), καθώς και πειραματικά αποτελέσματα κατανομής ολίσθησης σε διεπιφάνεια δοκών οπλισμένου σκυροδέματος ενισχυμένες με στρώση σκυροδέματος. Στο 3ο Κεφάλαιο παρουσιάζεται η πειραματική διερεύνηση δοκών οπλισμένου σκυροδέματος (Ο.Σ.) ενισχυμένων με στρώσεις σκυροδέματος. Εξετάστηκαν δύο ομάδες δοκιμίων. Στην πρώτη ομάδα εξετάστηκαν τέσσερα πρισματικά δοκίμια σκυροδέματος που ενισχύθηκαν με στρώση σκυροδέματος και στη συνέχεια δοκιμάστηκαν με φόρτιση τριών σημείων. Η δεύτερη ομάδα αναφέρεται σε πέντε δοκούς Ο.Σ. ενισχυμένες επίσης με στρώση σκυροδέματος, καθώς και σε αντίστοιχες μονολιθικές δοκούς που όλες δοκιμάστηκαν με φόρτιση τεσσάρων σημείων. Σε όλα τα δοκίμια και των δύο ομάδων μετρήθηκε η αντοχή τους καθώς και η ολίσθηση στη διεπιφάνεια τους. Στο 4ο Κεφάλαιο προτείνεται αναλυτική διαδικασία για τον υπολογισμό της ολίσθησης στη διεπιφάνεια σκυροδέματος και η εφαρμογή της στα πειραματικά δοκίμια που παρουσιάστηκαν στο Κεφάλαιο 3 καθώς και σε κάποια άλλα δοκίμια της βιβλιογραφίας που παρουσιάστηκαν στο 1ο Κεφάλαιο. Το 5ο Κεφάλαιο της παρούσας διατριβής, εξετάζει την επιρροή της συστολής ξήρανσης στο μέγεθος της ολίσθησης. Στο κεφάλαιο αυτό, παρουσιάζονται πειραματικές μετρήσεις της παραμόρφωσης και ολίσθησης λόγω συστολής ξήρανσης στα δοκίμια και των δύο ομάδων πειραματικών δοκιμίων που παρουσιάζονται στο Κεφάλαιο 3 και προτείνεται αναλυτικός τρόπος υπολογισμού της ολίσθησης και της διατμητικής τάσης στη διεπιφάνεια, συνυπολογίζοντας την επιρροή της συστολής ξήρανσης. Τέλος, παρουσιάζονται τα συνολικά συμπεράσματα που προέκυψαν στα πλαίσια της παρούσας διατριβής, καθώς και προτάσεις για μελλοντική έρευνα. / The present thesis concerns the flexural strengthening of reinforced concrete (RC) beams by placing a new concrete layer on their compressive or tensile side. The main objective of the thesis is to evaluate interface slip. The first chapter is a literature review on concrete interfaces. Theoretical models, suggested by design codes or other researchers, for the calculation of the shear resistance and the relationship between the shear stress and the slip at the interface are presented. Moreover, experimental results for the shear stress against slip relationship at the concrete interface are given. The second chapter presents a literature review on the shear stress and slip distribution at concrete to steel or concrete to fibre reinforced polymer (FRP) interfaces. Theoretical and experimental results for the value of shear stress at the interface of concrete beams strengthened with steel or FRP plates and shear stress and slip distribution at the interface of composite steel and concrete beams are presented. The third chapter concerns an experimental investigation of RC beams strengthened with concrete layers. Two types of specimens are examined. The first group are prismatic RC specimens strengthened with a concrete layer and tested by three point bending. The second group contains 10 RC beams. Five are strengthened with a concrete layer on their compressive or tensile side, four are respective monolithic specimens and the final one is a control beam without any strengthening. These beams are tested under four point bending. In all tests, for both groups of specimens, load against deflection curves are determined and the slip along the interface is measured. An analytical evaluation of the slip at the interface of RC beams strengthened with concrete layers and the verification of the method comparing the analytical results with respective experimental results presented in Chapters one and three is presented in Chapter four. The shrinkage effect on interface slip and shear stress is examined in Chapter five. Experimental measurements of shrinkage strains and slip on specimens of both experimental groups presented in Chapter three are presented. An analytical evaluation of the extra slip and shear stress at the interface caused by shrinkage effect is also suggested. Finally, all results of the thesis and suggestions for future work are given.

Je me focalise sur trois grands systèmes de failles transformantes obliques au Tibet et en Californie du Sud, et ce, afin de mieux comprendre et quantifier les relations entre les différentes structures qui les définissent. L'interférométrie radar à Synthèse d'Ouverture (InSAR) dispose du potentiel pour cartographier et localiser précisément la déformation sur des zones étendues et ainsi contraindre la géométrie des structures profondes. Cependant son utilisation en milieu naturel se trouve fortement entravée par la décorrelation due à la végétation, au relief, et aux cycles de gel et dégel, mais aussi par les délais troposphériques et les rampes orbitales résiduelles. J'ai développé des méthodes pour palier ces limitations. Au Tibet, j'ai ainsi traité les archives du satellite Envisat au niveau de deux zones de lacune sismique, à la bordure Nord du plateau, se présentant comme des zones intéressantes pour étudier le partitionnement de la convergence: le système de faille de Haiyuan au north-est Tibet et la faille sénestre de l'Altyn Tagh, au nord-ouest du plateau. Une attention spécifique sur les déformations liées au pergélisol m'a permis de (1) retrouver la continuité du signal sur de grandes zones, (2) de quantifier le comportement temporel des cycles de gel et dégel des sédiments recouvrant le pergélisol, (3) d'isoler les zones stables des sédiments se déformant. Je montre que les déformations saisonnières sont fortement dépendantes des unités géomorphologiques et que la fonte du pergélisol est plus important à faible qu'à haute altitude. J'analyse aussi le signal saisonnier au travers la marche topographique et je définie un proxy pour les incertitudes de la correction atmosphérique. J'observe un gradient de déformation au travers la faille de l'Altyn Tagh de l'ordre de 11-15 mm/an et un alignement claire de la déformation dans le Tarim, parallèle à la faille de l'Altyn Tagh, ainsi que des soulèvements de l'ordre de 1 mm/an associés à des chevauchements. Ce travail montre aussi un gradient de déformation associé à la terminaison ouest de la faille du Kunlun, re-définissant ainsi la géométrie des blocs tectoniques dans cette région. Parallèlement à cette acquisition de données, je développe des outils d'inversion basés sur des algorithmes de Monte Carlo afin d'explorer l'ensemble des géométries en accord avec les observations et d'estimer la compatibilité de la déformation actuelle avec des modèles tectoniques long-termes. Je montre ainsi une convergence uniforme de 8.5-11.5 mm/an et d'orientation N81-98E à travers le système de faille d'Haiyuan et quantifie son partitionnement le long des différentes structures. Par ailleurs, j'applique mon approche en Californie du Sud, au niveau du « Big Bend » de la faille de San Andreas où, en analogie avec des modèles structuraux géologiques, j'utilise des lois de conservations du mouvement pour contraindre la géométrie des chevauchements aveugles. Je montre la compatibilité du champs de déformation actuel avec un décollement grande échelle et quantifie une accumulation de contrainte de 2.5 mm/an le long de la structure majeure sous Los Angeles. / I focus on three major oblique transform faults in Tibet and in Southern California, in order to better measure and quantify the present-day strain accumulation on these structures. Interferometric synthetic Aperture Radar (InSAR) has the potential to map and localize precisely the deformation over wide areas and thus constrain the deep geometry of these structures. However, its application in natural environments in hindered by strong decorrelation of the radar phase due to vegetation, relief, and freeze and thaw cycles, but also due to variable tropospheric phase delays across topographic feature and long-wavelength residual orbital ramps. Here, I develop methodologies to circumvent these limitations and separate tectonic from other parasite signals. In Tibet, I process data from the Envisat satellite archives, at the boundary of the Tibetan plateau, in two seismic gaps, which appear interesting to study the partitioning of the convergence: the Haiyuan Fault system in northeastern Tibet and the left-lateral Altyn Tagh Fault, in northwestern Tibet. A specific focus on the permafrost related deformation signal allows us to: (1) correctly unwrap interferograms from north to south, (2) quantify the temporal behavior of the freeze/thaw cycles, and (3) isolate bedrock pixels that are not affected by the permafrost signal for further tectonic analysis. I show that the seasonal subsidence depends greatly on the geological land unit and that lower elevations are thawing faster than higher elevations. I analyze the atmospheric signal across the high plateau margin and estimate proxy for the uncertainty on atmospheric corrections. I observe a strike-slip deformation of around 11-15 mm/yr across the Altyn Tagh fault, a clear line of concentrated strike-slip deformation of around 3 mm/yr within the Tarim basin, trending parallel to the Altyn Tagh Fault trace, as well as thrust signal uplifting terraces at a rate of 1 mm/yr. This work also shows a strain accumulation around the west extension of the south trace of the Kunlun Fault, redefining the block boundaries in northwestern Tibet. In parallel this data acquisition, I develop Monte Carlo inversion tools in order to explore the various geometries in agreement with observations and estimate the compatibility of actual surface displacements with long-term slip partitioning models. I thus show a uniform convergence rate of 8.5-11.5 mm/yr with a N81-98E across the Haiyuan fault system and quantify the partitioning along the various structures. I also apply my approach in Southern California, across the « Big Bend » of the San Andreas Fault, where, in analogy with structural geological models, I use conservation of motion to help constraining the geometry and the kinematics of blind thrust faults. I show the compatibility of surface displacements with a large-scale décollement and quantify a loading rate of 2.5 mm/yr along the major thrust structure developing under Los Angeles.