In the automotive industry uniaxial vibration testing is a common method used to predict the lifetime of components. In reality truck components work under multiaxial loads meaning that the excitation is multiaxial. A common method to account for the multiaxial effect is to apply a safety margin to the uniaxial test results. The aim of this work is to find a safety margin between the uniaxial and multiaxial testing by means of virtual vibration testing and statistical methods. Additionally to the safety margin the effect of the fixture’s stiffness on the resulting stress in components has been also investigated.

Les vibrations main-bras sont spécifiquement reconnues pour être la cause du syndrome des vibrations, une maladie atteignant les doigts et la main à des niveaux vasculaires, musculo-squelettiques et neurosensoriels. De longues durées et de fortes intensités de vibration peuvent accélérer l'apparition des symptômes. De plus, des muscles soumis à la vibration ont tendance se contracter involontairement de façon plus intense que sans vibration : c'est le réflexe tonique vibratoire. Or, une plus grande rigidité musculaire est associée à une plus grande transmission de vibration aux structures corporelles. Le but de cette étude était de mesurer la transmission de vibration et mesurer le taux de contraction des muscles par électromyographie en fonction de différents paramètres de force de poussée, de moment de force, de fréquence et d'amplitude de vibration. De plus, les somatotypes ectomorphes et mésomorphes ont été comparés afin de déterminer si des gens de avec plus ou moins de masse musculaire obtenaient des résultats différents. Douze participants (six ectomorphes et six mésomorphes) ont participé à cette expérimentation. Cette expérimentation durait environ 3h et comportait 81 essais en fonction d'une combinaison des trois niveaux de chacune des quatre variables (poussée, moment de force, amplitude de vibration et fréquence de vibration). Le somatotype n'a pas eu d'effet notable ni sur la vibration et peu sur le réflexe tonique vibratoire. Les variables biomécaniques (moment de force, force de poussée) ont généralement eu pour effet d'augmenter la transmission de vibration ainsi que les scores d'EMG. Les variables de vibration ont permis de déceler la présence d'un réflexe tonique vibratoire significatif mais de faible importance. ______________________________________________________________________________ MOTS-CLÉS DE L’AUTEUR : Électromyographie, outils vibrants, réflexe tonique vibratoire, somatotype, moment de force.

In this thesis, a novel robust estimation strategy for observing the system state variables of robotic manipulators with distributed flexibility is established. Motivation for the derived approach stems from the observation that lightweight, high speed, and large workspace robotic manipulators often suffer performance degradation because of inherent structural compliance. This flexibility often results in persistent residual vibration, which must be damped before useful work can resume. Inherent flexibility in robotic manipulators, then, increases cycle times and shortens the operational lives of the robots. Traditional compensation techniques, those which are commonly used for the control of rigid manipulators, can only approach a fraction of the open-loop system bandwidth without inducing significant excitation of the resonant dynamics. To improve the performance of these systems, the structural flexibility cannot simply be ignored, as it is when the links are significantly stiff and approximate rigid bodies. One thus needs a model to design a suitable compensator for the vibration, but any model developed to correct this problem will contain parametric error. And in the case of very lightly damped systems, like flexible robotic manipulators, this error can lead to instability of the control system for even small errors in system parameters. This work presents a systematic solution for the problem of robust state estimation for flexible manipulators in the presence of parametric modeling error. The solution includes: 1) a modeling strategy, 2) sensor selection and placement, and 3) a novel, multiple model estimator. Modeling of the FLASHMan flexible gantry manipulator is accomplished using a developed hybrid transfer matrix / assumed modes method (TMM/AMM) approach to determine an accurate low-order state space representation of the system dynamics. This model is utilized in a genetic algorithm optimization in determining the placement of MEMs accelerometers for robust estimation and observability of the system’s flexible state variables. The initial estimation method applied to the task of determining robust state estimates under conditions of parametric modeling error was of a sliding mode observer type. Evaluation of the method through analysis, simulations and experiments showed that the state estimates produced were inadequate. This led to the development of a novel, multiple model adaptive estimator. This estimator utilizes a bank of similarly designed sub-estimators and a selection algorithm to choose the true value from a given set of possible system parameter values as well as the correct state vector estimate. Simulation and experimental results are presented which demonstrate the applicability and effectiveness of the derived method for the task of state variable estimation for flexible robotic manipulators.

Equipment failure and well deviations are prevailing contributors to production delays within the petroleum industry. Particular monetary focus is given to the drilling operations of wells to overcome these deficits, in order to extract natural resources as efficiently, and as safely, as possible. The research presented here focuses on minimizing vibrations of the drill string near the bottom-hole assembly (BHA) by identifying the cause of external forcing on the drillstring in vertical and horizontal wells and measuring the effects of various factors on the stability of perturbations on the system. A test rig concept has been developed to accurately measure the interaction forces and torques between the bit, formation and fluids during drilling in order to clearly define a bit/formation interface law (BFIL) for the purpose vibrational analysis. As a secondary function, the rig will be able to measure the potential inputs to a drilling simulation code that can be used to model drillstring vibrations. All notable quantities will be measured including torque on bit (TOB), weight on bit (WOB), lateral impact loads (LIL), formation stiffness, bit specific properties, fluid damping coefficients and rate of penetration (ROP). The conceptual design has been analyzed and refined, in detail, to verify its operational integrity and range of measurement error. The operational envelope of the rig is such that a drill bit of up to 8 ½ inches in diameter can be effectively tested at desired operational parameters (WOB: 0-55,000 lbf, RPM: 60-200) with various rock formations and multiple fluid types. Future use and design possibilities are also discussed to enhance the functionality of the rig and the potential for further research in the area of oil and gas drilling and vibrational modeling.

Vortex-induced vibrations of a pivoted circular cylinder and control of these vibrations were investigated experimentally. A novel experimental setup was employed to reproduce orbiting response observed in some engineering applications. An adaptive pendulum tuned-mass damper (TMD) was integrated with the cylindrical structure in order to control the vortex-induced vibrations. All experiments were performed at a constant Reynolds number of 2100 for a range of reduced velocities from 3.4 to 11.3 and damping ratios from 0.004 to 0.018. For the experiments involving TMD, the TMD mass ratio was 0.087 and the TMD damping ratios investigated were 0 and 0.24. The results of the experiments performed without the TMD show that, in the synchronization region, the frequencies of transverse and streamwise vibrations lock onto the natural frequency of the structure. The cylinder is observed to trace elliptic trajectories. A mathematical model is introduced to investigate the mechanism responsible for the occurrence of the observed elliptic trajectories and figure-8 type trajectories reported in previous laboratory investigations. The results show that the occurrence of either elliptic trajectories or figure-8 type trajectories is governed primarily by structural coupling between vibrations in streamwise and transverse directions. Four types of elliptic trajectories were identified. The results show that the occurrence of the different types of elliptic trajectories is linked to phase angle between the streamwise and transverse vibrations of the structure, which depends on structural coupling. The results of the experiments performed to investigate effectiveness of the TMD in controlling vortex-induced vibrations show that tuning the TMD natural frequency to the natural frequency of the structure decreases significantly the amplitudes of transverse and streamwise vibrations of the structure. Specifically, the transverse amplitudes of vibrations are decreased by a factor of ten and streamwise amplitudes of vibrations are decreased by a factor of three. The results show that, depending on the value of the TMD damping ratio, the frequency of transverse vibrations is either characterized by the natural frequency or by two frequencies: one higher and the other lower than the natural frequency of the structure, referred to as fundamental frequencies. Independent of TMD damping and tuning frequency ratios, the frequency of streamwise vibrations matches that of the transverse vibrations in the synchronization region, and the cylinder traces elliptic trajectories. The phase angle between the streamwise and transverse vibrations is nearly constant when the pendulum is restrained. However, with the TMD engaged and tuned to the natural frequency, the phase angle fluctuates significantly with time. A mathematical model was utilized to gain insight into the frequency response of the structure. The results of the modeling show that the frequency of transverse vibrations is characterized by the fundamental frequency or frequencies of the structure and the frequency of streamwise vibrations is characterized by the fundamental frequency or frequencies as well as the first harmonic of the fundamental frequency or frequencies of the structure.

Tuned mass dampers (TMDs) are auxiliary damping devices installed within tall structures to reduce undesirable wind-induced vibrations and to enhance the overall system damping and hence, the dissipative capacity. The design of TMDs involves the selection of optimal auxiliary mass, frequency, and damping, based on the main structure's mass, natural frequency and damping properties. TMDs are inherently susceptible to detuning, where the auxiliary parameters are no longer optimal due to deterioration or changes within the system, resulting in a degradation in their performance. In order to correct for this detuning, it is necessary to perform a condition assessment while the TMDs are in service. The main goal of this thesis is to present a methodology to conduct condition assessment while the TMDs are in service. The proposed methodology does not involve either restraining the TMD or providing controlled external excitation to the structure, and relies on ambient measurements only. The first phase in the condition assessment is to estimate the bare structure's modal properties using acceleration measurements obtained from the structure while the TMDs are unrestrained. The present work accomplishes this goal within the framework of parametric identification using Kalman filtering, where the unknown parameters (bare modal properties) are appended to the state vector and estimated. Unlike most of the literature on this subject, the noise statistics for the filter are not assumed to be known a priori. They are estimated from the measurements and incorporated into the filter equations. This filter involves direct feedthrough of the process noise in the measurement equation and the appropriate filter is derived and used following the noise covariance estimation step. In the next phase, criteria to assess the condition of the TMD are developed. They include optimal tuning parameters established using simulated experiments and measured equivalent viscous damping. The research considered pendulum tuned mass dampers (PTMDs), which presently account for a large fraction of full-scale applications. Results were demonstrated using numerical investigations, a bench-scale model equipped with an adaptive mechanism for adjusting auxiliary damper parameters, and a full-scale PTMD-equipped structure. The main contributions of this thesis are: (a) a broader understanding of the coupled biaxial behaviour of PTMDs has been developed; (b) a systematic procedure for estimating the underlying modal characteristics of the structure from ambient vibration measurements within the framework of Kalman filtering has been achieved; (c) a comprehensive framework to undertake condition assessment of TMDs has been presented, integrating parametric identification from measured response data and performance prediction for design period wind events using boundary layer wind tunnel studies. The work provided new insight into the design and behaviour of PTMDs and presented a comprehensive approach to quantify their performance. The Kalman filtering framework also provides an efficient platform to build adaptive passive tuned mass dampers that can be tuned in place and adjusted to correct for detuning and accommodate various operating conditions.

In both aviation and power generation, gas turbines are used as key components. An important driver of technological advance in gas turbines is the race towards environmentally friendly machines, decreasing the fuel burn, community noise and NOx emissions. Engine modifications that lead to propulsion efficiency improvements whilst maintaining minimum weight have led to having fewer stages and lower blade counts, reduced distance between blade rows, thinner and lighter components, highly three dimensional blade designs and the introduction of integrally bladed disks (blisks). These changes result in increasing challenges concerning the structural integrity of the engine. In particular for blisks, the absence of friction at the blade to disk connections decreases dramatically the damping sources, resulting in designs that rely mainly on aerodynamic damping. On the other hand, new open rotor concepts result in low blade-to-air mass ratios, increasing the influence of the surrounding flow on the vibration response.   This work presents the development and validation of a numerical tool for aeromechanical analysis of turbomachinery (AROMA - Aeroelastic Reduced Order Modeling Analyses), here applied to an industrial transonic compressor blisk. The tool is based on the integration of results from external Computational Fluid Dynamics (CFD) and Finite Element (FE) solvers with mistuning considerations, having as final outputs the stability curve (flutter analysis) and the fatigue risk (forced response analysis). The first part of the study aims at tracking different uncertainties along the numerical aeromechanical prediction chain. The amplitude predictions at two inlet guide vane setups are compared with experimental tip timing data. The analysis considers aerodynamic damping and forcing from 3D unsteady Navier Stokes solvers. Furthermore, in-vacuo mistuning analyses using Reduced Order Modeling (ROM) are performed in order to determine the maximum amplitude magnification expected. Results show that the largest uncertainties are from the unsteady aerodynamics predictions, in which the aerodynamic damping and forcing estimations are most critical. On the other hand, the structural dynamic models seem to capture well the vibration response and mistuning effects.   The second part of the study proposes a new method for aerodynamically coupled analysis: the Multimode Least Square (MLS) method. It is based on the generation of distributed aerodynamic matrices that can represent the aeroelastic behavior of different mode-families. The matrices are produced from blade motion unsteady forces at different mode-shapes fitted in terms of least square approximations. In this sense, tuned or mistuned interacting mode families can be represented. In order to reduce the domain size, a static condensation technique is implemented. This type of model permits forced response prediction including the effects of mistuning on both the aerodynamic damping as well as on the structural mode localization. A key feature of the model is that it opens up for considerations of responding mode-shapes different to the in-vacuo ones and allows aeroelastic predictions over a wide frequency range, suitable for new design concepts and parametric studies. / QC 20111125 / Turbopower, AROMA

Le crissement des freins des Trains à Grande Vitesse (TGV) est un bruit aigu particulièrement gênant émis lors de l'arrivée du train en gare. Ce travail a pour but de comprendre le phénomène en vue de réduire voire de supprimer l'émission du bruit. Ce phénomène acoustique est d'origine vibratoire : le crissement des freins à disque résulte des vibrations auto-entretenues des différents constituants induites par le frottement des garnitures sur le disque. Le phénomène de frottement étant lié aux aspérités de surface, il met en évidence un problème à deux échelles où un phénomène apparaissant à l'échelle microscopique crée des vibrations dans un disque à l'échelle macroscopique (amplitude de vibration du disque de l'ordre de quelques micromètres). Les phénomènes de bruits de freinage dont le crissement fait partie sont complexes, variés et ont des origines diverses selon les points de fonctionnement du mécanisme. Un état de l'art sur les différents travaux de modélisation montre qu'une instabilité de l'équilibre stationnaire dite géométrique ou par couplage de mode permet de mobiliser les modes de vibration responsables du crissement et ceci à coefficient de frottement constant.<br /><br />D'un point de vue modélisation, ces constatations nous orientent vers un modèle de mécanique des milieux continus déformables dans l'hypothèse de petites transformations. Beaucoup de travaux sur les vibrations auto-entretenues s'intéressent à la stabilité de l'équilibre mais font un raccourci rapide entre fréquences des modes instables et solution transitoire. Les travaux numériques traitant de la caractérisation de ces évolutions transitoires mettent en évidence des événements fortement non linéaires sous la zone de contact (comme de 'adhérence ou du décollement à cause de l'unilatéralité du contact). Un premier objectif de ce travail est l'étude de l'évolution des perturbations proches de l'équilibre vers la solution transitoire. Cette étude permet de mettre en évidence les liens entre les fréquences caractéristiques de cette solution transitoire (fréquences de crissement) et les fréquences des modes de stabilité. Le cas particulier d'un mécanisme de frein à disque TGV simplifié tridimensionnel est choisi. La transition entre l'évolution des perturbations proches de l'équilibre et l'évolution transitoire est étudiée grâce à une méthode originale de projection sur les modes de stabilité. Elle permet une étude spatiale et temporelle des champs vibratoires solutions. Son application sur le modèle simplifié de frein à disque est rendue possible grâce à une formulation eulérienne du problème. D'un point de vue calcul de structures, les solutions transitoires ont été déterminées grâce à des algorithmes et des stratégies numériques adaptés permettant de tenir compte du caractère non régulier du comportement du contact unilatéral frottant dans le cadre dynamique (tel que les situations de choc).<br /><br />L'instabilité de l'équilibre par couplage de mode est le mécanisme générateur de vibrations auto-entretenues privilégié dans la littérature. Qu'en est-il sur le mécanisme de freinage TGV? Cette question nous a conduit dans un premier temps à observer le comportement du mécanisme réel grâce à des campagnes d'essais. Dans un deuxième temps, elle nous a conduit à proposer un modèle de frein TGV réaliste. L'étude de la stabilité de l'équilibre a permis de prédire les fréquences de crissement mesurées. Elle a aussi permis de préciser le mécanisme physique de couplage de mode ainsi que sa dépendance vis à vis des caractéristiques physiques des garnitures. La connaissance de ce mécanisme physique est un fil conducteur robuste dans la recherche de solutions de réduction du bruit.

Made available in DSpace on 2014-10-09T12:31:04Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:56:16Z (GMT). No. of bitstreams: 1 01377.pdf: 3916698 bytes, checksum: ed6e95533001fb610ab17e41a058b984 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

The increase of greenhouse gas emission is commonly accepted to largely contribute to global warming, in part due to the massive use of non-renewable fossil energy sources. It is a reason why recently, beside other industrial sectors, electric mobility has been considered as the next generation for transportation systems. But the electrification of a vehicle introduces new challenges in its design since it involves different domains of expertise than the ones from Internal Combustion Engine (ICE) vehicles. In particular, Noise, Vibration and Harshness (NVH) comfort is significantly affected by powertrain changes, i.e. from ICE to electric machine. High and unpleasant acoustic noise from resonances may occur but can be addressed numerically to support decision making processes early enough in the design stages. The accurate prediction of its radiated acoustic noise then requires a thorough multi-physical understanding, from the system-level (electric machine) to the component-level (stator and rotor cores).First from a system-level point of view, two multi-physical modeling frameworks that use different model simplifications were implemented. By comparing simulated results to experimental measurements at each physical step of the modeling flow (electromagnetic, vibration, acoustic), it was shown that both models are accurate enough for pre-designing phases. It was also shown that considering only the stator core to contribute to the vibro-acoustic behavior of electric machines is a valid assumption.Second from a component-level point of view, the rotor and the stator core were investigated. The rotor influence on the complete machine structural dynamics was assessed. Beside the validated effects of different rotor topologies on the radiated noise, an analytical model was successfully developed to explain the occurrence of a particular vibration mode; whose explanation was still not offered in literature. In parallel, the stator core was studied, essentially because it is composed of hundreds of thin laminations stacked together which introduce difficulties in understanding its structural behavior. The effects of the laminations on the structural behavior of the stator core were studied numerically and experimentally as well. Two modeling guidelines were thus provided depending on the mode shape of interest and the computational resources available. The experimental studies comforted these two modeling approaches, and also permitted to highlight the importance of looking at the damping properties. Therefore it was shown that different lamination stacking techniques could affect significantly this damping.Finally the influence of the stacking technique (gluing, welding) on the structural behavior of the laminated compound motivated the implementation of an alternative solution to the mitigation of resonance phenomenon responsible for large acoustic noise. By using a skewed distribution of welding or glue lines, the technique aims at forcing laminations to vibrate with different phases which generates friction between them. The induced damping increases and then depends on the introduced asymmetry and on the mode shape considered. This innovative technique was validated experimentally and showed up to 7 times higher structural damping and 10 dB reduction in structural transfer function amplitudes. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished