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1
Hack, Thorsten. "Stick-slip piezoelectric actuators." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624403.
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Манько, Наталія Миколаївна, Наталья Николаевна Манько, and Nataliia Mykolaivna Manko. "Stick-slip mode of boundary friction." Thesis, Сумський державний університет, 2013. http://essuir.sumdu.edu.ua/handle/123456789/33545.
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The study of the boundary friction processes that develop in nanosized tribosystems has drawn active interest of many researchers. One of the perspective directions is the investigation of the friction of atomically smooth solid surfaces in the presence of an ultrathin film of a homogeneous lubricant between them. The interest is partially due to the applied significance of these systems, as they are used in increasing frequency to design precise devices and instruments.
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3
Breguet, Jean-Marc Breguet Jean-Marc. "Actionneurs "stick and slip" pour micro-manipulateurs /." [S.l.] : [s.n.], 1998. http://library.epfl.ch/theses/?display=detail&nr=1756.
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Smith, Jonathan Hurndall. "Stick-slip vibration and is constitutive laws." Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304168.
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Mak, Hong-man Herman, and 麥匡文. "Effective slip due to Stokes flow through channels with patterned stick-slip walls." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B47153970.
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This thesis comprises studies of two problems on Stokes flows through (i) a plane microchannel, and (ii) a microscale circular capillary tube, of which the walls are superhydrophobic surfaces featuring micro- or nano-patterns. In the first problem, an analytical study on longitudinal and transverse flows through a plane microchannel, which is made up of a periodic array of ribs and grooves on the upper and lower walls, is performed. This study focuses not only on the Cassie state, but also on the state whereby the liquid is allowed to penetrate the grooves between the ribs. These grooves are filled with inviscid gas and this periodic array gives rise to heterogeneous boundary conditions for the flow. Partial-slip and shear-free conditions are applied on the solid–liquid interface and the liquid–gas interface, respectively. Using the methods of eigenfunction expansions and domain decomposition, semi-analytical models are developed for four different settings. Two of them correspond to longitudinal flow with in-phase and 180-out-of-phase alignments of ribs between the upper and lower walls. The other two are for transverse flow with the in-phase and out-of-phase wall alignments. These models enable the effective slip lengths, normalized by half the pitch of the pattern, to be deduced as functions of the channel height, the microscopic or intrinsic partial slip length, the depth of liquid penetration, and the width of the grooves or the shear-free area fraction of the liquid-gas interface. Numerical calculations are performed to examine effects of these parameters on the effective slip length. The effect of the phase of alignment of ribs is appreciable when the surface is in the Cassie state and the channel height is sufficiently small. In-phase alignment yields a larger effective slip length in longitudinal flow. In sharp contrast, out-of-phase alignment is preferable in transverse flow. In the case involving penetration, a larger liquid penetration can give rise to a larger slip length in a thin channel.
In the second problem, an analytical study on flow through a microscale circular tube, of which the wall is patterned with a periodic array of spots or holes, is performed. Void region is filled with inviscid gas and patterns of circular and square shapes are considered. For simplicity, liquid penetration into the cavities is not considered, and hence the focus is on the Cassie state. No-slip and shear-free conditions are applied on the solid–liquid interface and the liquid–gas interface, respectively. By the methods of eigenfunction expansions and point collocation, a semi-analytical model is established. The effective slip length, normalized by the tube radius, is found as a function of the pitch of the pattern in the streamwise direction, the number of periodic units in the circumferential direction, and the solid fraction. Comparisons with some proposed scaling laws, varying pitch, solid fraction and tube size are performed. Large slip length is produced by arranging small circular no-slip spots with large separation in the streamwise direction. In some situations, spots and holes can be replaced by parallel stripes to increase the slip length.published_or_final_version
Mechanical Engineering
Master
Master of Philosophy
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Grunewald, Natalie. "Mathematische Analyse einer Stick-Slip-Bewegung in zufälligem Medium." Bonn : Mathematisches Institut der Universität, 2004. http://catalog.hathitrust.org/api/volumes/oclc/62767423.html.
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Dalbe, Marie-Julie. "Instabilité de Stick-Slip lors du pelage d’un adhésif." Thesis, Lyon 1, 2014. http://www.theses.fr/2014LYO10236.
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Cette thèse de doctorat présente une étude essentiellement expérimentale de l'instabilité de stick-slip lors du pelage d'adhésifs. Nous avons développé différents dispositifs expérimentaux permettant d'observer directement la dynamique de rupture saccadée du pelage. Les expériences sont réalisées à vitesse imposée dans différentes géométries : l'adhésif est pelé directement depuis son rouleau, ou depuis un substrat plan à angle imposé. D'une part, nous avons mis en évidence d'importants effets dynamiques, que les modèles théoriques actuels ne permettent pas d'expliquer. D'autre part, nous avons montré l'effet crucial de l'angle de pelage sur l'instabilité, qui est fortement réduite (en amplitude et en gamme d'existence) pour de grands angles. De plus, une nouvelle approche théorique, prenant en compte l'inertie du ruban, permet de comprendre en partie ces résultats expérimentaux. Enfin, nous démontrons que l'instabilité de stick slip est multi-échelle, en mettant en évidence la présence d'une instabilité secondaire, à des échelles temporelles et spatiales plus faibles que le stick-slip observé habituellement. Alors que l'instabilité principale est causée par des variations d'énergie élastique d'élongation, cette instabilité secondaire est pilotée par un relâchement de l'énergie de courbure du rubanThis thesis presents a mainly experimental study of the stick-slip instability during the peeling of adhesive tape. We developed different experimental set-ups, allowing us to observe directly the jerky dynamics during peeling. The experiments are conducted at an imposed velocity and different geometries : the adhesive is peeled directly from a roller, or from a flat substrate at a fixed angle. On the one hand, we highlight the existence of strong dynamical effects, which cannot be understood with the existing theoretical models. On the other hand, we show the crucial effect of the peeling angle on the instability, which is strongly reduced at large angles (both its amplitude and range of existence decrease). Besides, a new theoretical approach, taking into account the ribbon inertia, can allow us to understand partially the experimental observations. Finally, we show that the stick-slip instability is multi-scale : a secondary instability can occur at spatial and temporal scales smaller than the usually observed stick-slip. While the main instability is due to variations of the stretching elastic energy, this secondary instability is driven by the release of the bending energy stored in the ribbon
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Tariku, Fitsum. "Simulation of dynamic mechanical systems with stick-slip friction." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0011/MQ38415.pdf.
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Verwijs, Marinus Jacobus. "Stick-slip in powder flow a quest for coherence length /." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0013049.
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Baptist, Olu. "Powder cohesion and stick-slip failure in a shear cell." Thesis, University of Surrey, 2007. http://epubs.surrey.ac.uk/843467/.
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The overriding aim of this project is to gain an understanding of the flowability of powders. Industrial interest for this study was provided by Centura Foods, U.K. who supplied three samples for study. These powder samples are starch, maltodextrin and hydrolysed vegetable protein (HVP). The first half of this project addresses the influence of adsorbed moisture on the flowability of these powders with strong emphasis on the value of cohesion. There is evidence in the literature suggesting that the prevailing relative humidity has an influence on powder cohesion. The general trend indicates an increase in cohesion with an increase in relative humidity. Some attempts have been made in the literature to relate this humidity dependence to powder properties notably the propensity for water sorption. Material characterisation studies revealed the morphological and surface characteristics of the samples through Scanning Electron Microscopy (SEM). It revealed the angular and amorphous appearances of the maltodextrin and HVP particles respectively. The starch particles appear to have distinct groups of larger and smaller particles. The larger particles are ellipsoidal and the smaller particles are near perfectly spherical. Water sorption studies using a gravimetric analyzer showed that the starch and maltodextrin powders had on average 19 and 25 % mass increase respectively when subjected to a relative humidity change from 0 % to 90 %. However, the HVP powders had the largest percentage mass uptake of over 100 %. This was supported by in-situ humidity microscopy results that showed significant swelling with dissolution when exposed to saturated air. Comparatively but to a lesser degree, similar behaviour was observed for maltodextrin powders. Starch particles also exhibited swelling under saturation conditions. Powder flowability studies were carried out using a Jenike-type shear cell. Commissioning of the shear cell was conducted using limestone powders. Measurements were carried out at dry, ambient and saturated conditions. This was facilitated by a newly designed in-situ humidity control system. Values of cohesion were obtained by constructing a family of yield loci for each material. HVP powders showed a significant increase in cohesion with humidity. Maltodextrin and starch powders showed no significant change in cohesion with humidity. However, both powders were more difficult to stir with changes to the relative humidity thereby highlighting that the shear cell in this study is not sensitive enough to detect the changes in fiowability. The phenomenon of stick-slip failure was observed for starch at all humidities, and for maltodextrin but only at 0 %RH. Published information implies that stick-slip behaviour is linked to the rate of stored elastic energy and frictional dissipation. A study of stick-slip observed with starch powder was conducted under four levels of consolidation over four different velocities. A mathematical model has been applied which describes the various stages of stick-slip and consequently identifying the parameters that influence stick-slip. A comparison of the model with experimental values highlighted the effectiveness of the model. Results from this study identified the levels of consolidation and drive velocities as the governing parameters influencing stick-slip, with the level of consolidation argued to have a greater impact. It was anticipated that the study would identify conditions to eliminate stick-slip. Although this was not achieved, the study however presents O, a measureable which represents the extent of stick-slip. On this basis, stick-slip is argued to be minimized under a combination of high consolidation loads and velocities. The study has identified possible areas for future work. Firstly, some irregular trends were observed when comparing some results under the two intermediate consolidation levels (4 kN/m2 and 12.5 kN/m2). It is possible to further investigate stick-slip failure with smaller increments to the level of consolidation. It is possible to add to the work done in this study by investigating the effects of higher consolidation and velocities and testing on other materials. Finally, a parallel study repeating the work done in this study (and incorporating the proposed ideas for future work) using a different type of shear tester remains a good candidate for research.
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Darby, A. P. "Active control of flexible structures using inertial stick-slip actuators." Thesis, University of Cambridge, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.598276.
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Future space mission proposals include many large optical structures which must be capable of maintaining high shape accuracy. Typically, dimensional stability of the order of microns must be maintained over distances of tens of meters. In the past, this stability has been achieved by the use of organic composite materials, such as carbon fibre reinforced plastic (CFRP), which are thermally unresponsive, lightweight and stiff. These materials, however, are both expensive and subject to unknown changes in their properties during their space exposure lifetime. Hence, active control allows the use of more conventional engineering materials and the construction of larger and more ambitious structures. In a typical application the two main effects to be controlled are vibrations, due mainly to on-board disturbances, such as torque wheels, and quasi-static disturbances, caused by effects such as temperature gradients or initial lack-of-fit of structural members. This dissertation describes a system which provides 6DOF alignment correction of a payload mounted at the tip of a flexible structure, subject to dynamic and quasi-static disturbances, using a Stewart platform arrangement. The six legs of the platform are formed by a new type of actuator. The actuator uses a stick-slip motion, driven by an inertial mass. The dynamics of the actuator are described and its ability to control both dynamic and quasi-static disturbances is examined, experimentally. The inherently non-linear input-output response of the actuator is quantified and modelled. The flexible structure, used for experimental tests, consists of a pantographic mast. The modal parameters are identified through the use of a numerical model verified by modal tests that have been carried out on the actual structure. Important joint effects are examined and modelled. The modal model is combined with a rigid body model of the Stewart platform to produce a non-linear analytical model of the interaction between the structure and the actuators. This is used to estimate the performance and examine the stability of the closed-loop controlled system.
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Andersson, Jacob, Fredrik Danielsson, and Wilhelm Löwen. "Screaming screw tightenings." Thesis, KTH, Maskinkonstruktion (Inst.), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-209544.
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This paper is a bachelor thesis in machine design where screaming screw tightenings are discussed. The research was initiated with a preliminary study in screw mechanics and the tightening process, as well as the stick-slip phenomenon. Furthermore, interviews were conducted with people at Scania and Atlas Copco who have relevant experience in screaming screw tightenings. These interviews strengthened the theory that screaming is caused by stick-slip. The natural frequency of a screw joint with a M8 x 60 mm screw and M8 M6M nut were approximated with FEM-analysis in Ansys. This in order to provide data for comparison with measured screams in future practical tests. The initial hypothesis that stick-slip causes scream was considered plausible since the natural frequency for the screw joint’s torsional oscillation is within the audible range.Denna rapport är ett kandidatexamensarbete i maskinkonstruktion där skrikande skruvdragningar undersöks. Undersökningen inleddes med en förstudie i skruvens mekanik och åtdragningsprocessen. Stick-slip-fenomenet har även undersökts i förstudien. Vidare har intervjuer gjorts med personer som har erfarenhet inom området på Scania och Atlas Copco. Dessa intervjuer stärker teorin om att skrikfenomenet orsakas av stick-slip. Egenfrekvenser för ett skruvförband med dimensionerna M8 x 60 mm för skruven och M8 M6M för muttern togs fram genom en FEM-analys i Ansys. Detta för att i framtida praktiska tester kunna jämföra dessa frekvenser med uppmätta skrik. Den ursprungliga hypotesen om att stick-slip orsakar skrik bedömdes rimlig då egenfrekvensen för skruvförbandets torsionssvängning faller inom det hörbara intervallet.
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Arcieri, Michael Angel Santos. "Controle de vibrações mecânicas tipo "stick slip" em colunas de perfuração." Pós-Graduação em Engenharia Elétrica, 2013. https://ri.ufs.br/handle/riufs/5011.
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Mechanical vibrations are inevitable in drilling operations. Torsional stick-slip vibrations are vibrations that occur in drilling columns, which are produced by periodic variations of torque and characterized by large fluctuations in the speed of the drill bit. These vibrations are dangerous, primarily by the cyclical characteristic of the phenomenon that by the amplitude of the same, which can cause fatigue of the pipe, failures in the components of the drill string, deformations in the walls of the well, excessive wear of the drill, low rate of penetration, and collapse of the drilling process. The frequency of these unwanted oscillations can be reduced by the application of automatic control techniques. The objective of this study is to evaluate through numerical simulations, the application of conventional control techniques, such as proportional-integral control (PI), and nonlinear, as the sliding mode control (SMC) and the input-output linearization control (IOLC), to eliminate the presence of stick-slip oscillation in drilling columns. The controllers are designed primarily to maintain a constant speed of rotation system, by manipulating engine torque, thereby inferentially control the speed of the drill, thus providing optimum operation conditions, beyond preserving system stability. Results of simulations using drill string torsional models of two degrees of freedom (2-DOF) and four degrees of freedom (4-DOF) show the performance of the proposed control systems, which are analyzed and qualitatively compared.Vibrações mecânicas são inevitáveis nas operações de perfuração. Vibrações torcionais stick-slip são vibrações que ocorrem em colunas de perfuração, as quais são produzidas pelas variações periódicas de torque e caracterizadas por grandes oscilações da velocidade da broca. Estas vibrações são prejudiciais, mais pela característica cíclica do fenômeno que pela amplitude da mesma, podendo originar fadiga da tubulação, falhas nos componentes da coluna de perfuração, deformações nas paredes do poço, desgaste excessivo da broca, baixa taxa de penetração e, inclusive, colapso do processo de perfuração. A frequência destas oscilações indesejadas pode ser reduzida pela aplicação de técnicas de controle automático. O objetivo deste trabalho é avaliar, mediante simulações numéricas, a aplicação de técnicas de controle convencional, como o controle proporcional-integral (PI), e não linear, como o controle por modos deslizantes (SMC) e o controle por linearização entrada-saída (IOLC) para eliminar a presença de oscilações stick-slip em colunas de perfuração. Os controladores são desenvolvidos principalmente para manter constante a velocidade do sistema de rotação, mediante a manipulação do torque do motor, para assim controlar inferencialmente a velocidade da broca, fornecendo desta maneira condições ótimas de operação, além de preservar a estabilidade do sistema. Resultados das simulações, usando modelos torcionais de uma coluna de perfuração de dois graus de liberdade (2-DOF) e de quatro graus de liberdade (4-DOF), mostram o desempenho dos sistemas de controle propostos, os quais são analisados e comparados qualitativamente.
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Suetti, André Garcia Lima. "Estudo do fenômeno "stick-slip" aplicado às vibrações de freios automotivos." [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265209.
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Orientador: Robson PederivaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
Made available in DSpace on 2018-08-19T13:48:38Z (GMT). No. of bitstreams: 1 Suetti_AndreGarciaLima_M.pdf: 20585864 bytes, checksum: 84c85d26b6df77562a52c8ca3aa2aedf (MD5) Previous issue date: 2011
Resumo: O interesse da indústria automobilística em projetar freios menos ruidosos vem incentivando pesquisas na área de acústica e vibração. A compreensão de um dos principais fenômenos de excitação de vibração em sistemas com atrito, o stick-slip, é de grande importância para o aprofundamento desses estudos, que muitas vezes não consideram uma fonte de excitação bem definida e realimentada, recorrendo a excitações impulsivas ou com frequências aleatórias. O stick-slip é uma vibração auto-excitada que pode ocorrer em um corpo fixo que se atrita com outro corpo que está em movimento, fundamentada na diferença entre o coeficiente de atrito estático e dinâmico. Tendo em vista a aplicação da excitação por stick-slip em vibrações em sistemas de freio, equacionamentos analíticos são propostos nesse trabalho tendo a dificuldade incrementada gradualmente. Um estudo dos efeitos do amortecimento em sistemas com stick-slip é também proposto, apresentando um comportamento que difere de sistemas mecânicos sem realimentação. Com o objetivo de se avaliar esses métodos, realizam-se simulações numéricas e um experimento, que se utiliza de materiais de atrito e disco empregados em freios. Os resultados demonstram a compatibilidade das simulações numéricas e os dados obtidos experimentalmente, o que comprova que os métodos podem ser usados na simulação do problema
Abstract: Interest of the automotive industry in designing quieter brakes has encouraged the researches in the fields of acoustics and vibration. Understanding one of the main phenomena of vibration excitation in systems with friction, stick-slip, is crucial to a deeper study. Many a time these studies do not consider a well-defined and fed back source, falling back on impulsive and random excitations. The stick -slip is a self-excited vibration that may occur when a static body rubs against a dynamic one. It is based on the difference between the static and dynamic friction coefficients. Considering the stick-slip excitation in the braking system vibration, analytical equations with continuous incremental difficulties are proposed herein. A study of the effects of damping in stick -slip systems is also proposed, presenting a kind of behavior that is different from that of mechanical systems without feedback. In order to evaluate these methods, an experimental or sometimes numerical simulation is conducted using friction material and discs used in braking systems. The results are in agreement with the experimental data, proving that the methods can be used in simulations of problems
Mestrado
Mecanica dos Sólidos e Projeto Mecanico
Mestre em Engenharia Mecânica
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Manko, N. N., and I. A. Lyashenko. "Stochastic Oscillations at Stick-Slip Motion in the Boundary Friction Regime." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35148.
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In this paper, the further development of the synergetic model describing the ultrathin lubricant film state
clamped between two atomically smooth solid surfaces operating under boundary friction mode has been done
based on the Lorentz model for the approximation of a viscoelastic medium. In all cases, the phase portraits have
been built. It has been found that the friction surfaces' temperature increasing leads to the growth of stochasticity
in the investigated system. In the phase plane the stochastic oscillation mode can be described as a strange attractor.
Also, the behavior of two different types of tribosystems were described using current model. The first
was the system with the unidirectional shear of the surfaces and, and the second was the system under an alternating
external effect. Obtained results agree qualitatively with known experimental data.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35148
16
De, Zotti Vincent. "Instabilité de pelage d'un ruban adhésif : effet de l'inertie sur la dynamique multi-échelle du front de détachement." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEN012/document.
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Cette thèse concerne l'étude de la dynamique instable du front de détachement d'un ruban adhésif lors de son pelage à vitesse constante depuis un substrat plan. Nous avons en particulier mis en évidence le rôle essentiel de l'inertie du ruban sur cette instabilité.Dans un premier temps, nous avons réalisé une étude expérimentale des différentes dynamiques macroscopiques du front, observé par imagerie rapide, en fonction de la vitesse et de l'angle de pelage. Un régime constitué d'oscillations sinusoïdales en vitesse a alors été mis en évidence à la transition entre le pelage régulier et l'instabilité de stick-slip. Un modèle théorique, prenant en compte l'inertie du ruban, et sa résolution numérique ont permis de retrouver les différentes dynamiques observées, ainsi que les caractéristiques de ces oscillations.D'autre part, l'instabilité de stick-slip microscopique, récemment découverte, a également été étudiée. Nous avons caractérisé l'amplitude des avancées saccadées en fonction de la vitesse et de l'angle de pelage, mais également des propriétés physiques du ruban (masse et module de flexion). Son évolution avec ces différents paramètres est en accord avec une modélisation dynamique du front de détachement, couplant énergie de courbure et énergie cinétique du rubanThis thesis presents the study of the unstable dynamics of the detachment front of an adhesive tape peeled at constant velocity from a flat surface. We could specifically highlight the essential role of the ribbon inertia on this instability.On one hand, we have performed an experimental study of the different front dynamics at macroscopic scales, observed by fast imaging, as a function of the peeling velocity and peeling angle. We could find a novel dynamical regime with sinusoidal oscillations of the detachment front velocity at the transition between regular peeling and stick-slip motion. A theoretical model taking into account the ribbon inertia, and its numerical resolution allow to explain the different dynamics observed, and furthermore, the characteristics of those velocity oscillations.On the other hand, the recently discovered microscopic stick-slip instability has also been studied. We have characterized the amplitude of the corresponding slips as a function of the peeling velocity and peeling angle, but also, as a function of the ribbon properties (mass and bending modulus). We show that a dynamical model coupling bending and kinetic energy of the ribbon can explain its evolution with these different parameters
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Fernandes, Raul de Sousa. "Modelagem e simulação do processo de aparafusamento/." reponame:Biblioteca Digital de Teses e Dissertações da FEI, 2018. https://doi.org/10.31414/EM.2018.D.130285.
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Wu, Wendy Xiaohui. "The corrugation of railway track." Thesis, London South Bank University, 1997. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245157.
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Headings, Leon Mark. "Modeling, characterization, and design of smart material driven stick-slip actuation mechanisms." Connect to resource, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1141700440.
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Hamilton, Tony. "An analogue model for the simulation of earthquake rupture and stick-slip." Thesis, University of Ulster, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326325.
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Lyashenko, I. A., Олексій Віталійович Хоменко, Алексей Витальевич Хоменко, Oleksii Vitaliiovych Khomenko, Антон Миколайович Заскока, Антон Николаевич Заскока, Anton Mykolaiovych Zaskoka, and K. S. Zhmaka. "Hysteresis Phenomena in the Stick-Slip Motion at the Boundary Friction Mode." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35072.
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The tribological system is considered, which consists of two atomically smooth solid surfaces separated
by an ultrathin lubricant film. The thermodynamic model based on the Landau theory of phase transitions
is built, which describes behavior of this system in the boundary friction mode. The free energy density for
an ultrathin lubricant film is given in the form of expansion into series by the powers of order parameter
that is reduced to the shear modulus of lubricant. The kinetics of the system is studied on the basis of
model describing first-order phase transitions between kinetic modes of friction. It is shown that in the
presence of spring between the external drive and block the width of temperature hysteresis increases versus
fixed coupling.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35072
22
Schneck, Christian [Verfasser]. "Simulation von Stick-Slip-Effekten an einem elastischen Dichtringmodell im Mehrkörpersystem / Christian Schneck." Magdeburg : Universitätsbibliothek Otto-von-Guericke-Universität, 2018. http://d-nb.info/1220035165/34.
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Hatipogullari, Metin. "Modelling of contact lines on heterogeneous substrates :stick-slip and contact angle hysteresis." Doctoral thesis, Universite Libre de Bruxelles, 2020. https://dipot.ulb.ac.be/dspace/bitstream/2013/304847/5/contratMH.pdf.
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This thesis highlights generic aspects of contact angle hysteresis and stick-slip motion,encountered in most practical wetting situations.First, we study the scaling relation between the heterogeneity strength and the amplitudeof the contact angle hysteresis it induces in the model configuration of a chemicallyheterogeneous microchannel. A key parameter which determines the qualitativefeatures is the heterogeneity wavelength. In particular, we identify a near-thresholdbehavior where the quadratic scaling between the heterogeneity amplitude and the resultinghysteresis, already known for a dilute system of wetting defects, is explainedby the closeness to the threshold, and a macroscopic limit without observable stick-slipwhere this scaling is linear.In the second part, we adapt the description to the configuration of a meniscusaround a wavy fibre. This adaptation brings the generic results of the first part in thereach of experiments. A comparison with experiments is achieved at the level of theindividual topography-induced jumps.In the third part, we expand the formulation to treat the quasi-steady interface shapecontact line dynamics and study how the the presence of stick-slip motion at the observableor unobservable scale modifies the scaling relation between the contact linevelocity and contact angle. We recover the known result that the scaling exponent dependson the nature of the externally controlled parameter, identify the causes of thisdependency in the corresponding static limits, and predict the disappearance of this dependencyabove a critical velocity which decreases with the heterogeneity wavelength.Finally, we show trough examples how the modelling framework which permitscapturing contact angle hysteresis and stick-slip motion in a minimalistic way can beadopted to treat configurations with a finite amount of contact points, or the 3D problemof a drop with a deformed contact line. We discuss the arising configuration-specificeffects, also in configurations of biomimetic interest.Doctorat en Sciences de l'ingénieur et technologie
info:eu-repo/semantics/nonPublished
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Wu-Bavouzet, Fangnien. "Friction sur surfaces à plots." Paris 6, 2008. http://www.theses.fr/2008PA066383.
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L'objet de cette thèse est l'adhésion et la friction de lentilles millimétriques d'élastomères sur un substrat décoré de plots micrométriques de hauteur variable. A cette fin, nous avons utilisé un AFM géant permettante mesurer les forces normales et tangentielles appliquées à la lentille et d'observer le contact. Il permet d'explorer des vitesses de glissement de l'ordre de 100 µm/s, et des forces de l'ordre de 10-3 N. Nous avons observé deux types de contact selon la hauteur h des plots : intime (h
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Boone, Jacob Dee. "Design, Construction and Evaluation of Universal Friction Tester." OpenSIUC, 2010. https://opensiuc.lib.siu.edu/theses/307.
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AN ABSTRACT OF THE THESIS OF Jacob Boone, for the Master of Science degree in Mechanical Engineering, presented on 10/28/2010, at Southern Illinois University Carbondale. TITLE: DESIGN, CONSTRUCTION, AND EVALUTAION OF UNIVERSAL FRICTION TESTER MAJOR PROFESSOR: Dr. Peter Filip Many different types of friction testers are currently available for testing specific frictional applications. Of these machines very few have versatility, and of the ones that do, the amount of versatility is limited. Since friction is a property specific to each system, all operating parameters need to match the specific application as closely as possible in order to obtain accurate data. This requires many research facilities to have several specific friction testers in order to provide the necessary testing capabilities. The goal of this project was to design a Universal Friction Tester (UFT) with enough versatility to reproduce most types of sliding friction situations. This was accomplished by providing a wide range of testing capabilities through the use of interchangeable system components. Results show that the UFT provides quality data over its entire operating range. It was shown that normal pressure, sliding speed, temperature and system stiffness all have drastic effects on frictional performance. By using a borosilicate glass disc, the friction surface was viewed in-situ during testing. This allowed insights into true surface temperature and contact area. In conclusion, the UFT can successfully take the place of several friction testers and thus provide many friction research capabilities while requiring fewer resources. The wide range of testing capabilities will allow the UFT to be used as a research tool for many types of advanced friction studies. Some of these may include true surface temperatures, true contact area, influence of conditions on stick-slip phenomenon, and thermo-elastic instabilities.
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Edeler, Christoph [Verfasser]. "Modellierung und Validierung der Krafterzeugung mit Stick-Slip-Antrieben für nanorobotische Anwendungen / Christoph Edeler." München : Verlag Dr. Hut, 2011. http://d-nb.info/1018982469/34.
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Adjémian, Florence. "Stick-slip et transition de broutage dans les essais triaxiaux sur billes de verre." Châtenay-Malabry, Ecole centrale de Paris, 2003. http://www.theses.fr/2003ECAP0907.
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Ce travail expérimental a consisté à caractériser le comportement particulier de stick-slip observé dans des empilements 3D de billes de verre soumis à une compression uni-axiale verticale. Ce comportement de stick-slip diffère du comportement classique d'un sol, qui est généralement régulier et lisse, et quasi-statique; ici les échantillons de billes étudiés engendrent par intermittence des chutes de force (stick-slip) et ils sont rhéo-fluidifiants. Les nombreux essais réalisés à différentes valeurs des paramètres extérieurs ont permis de définir les variables intrinsèques principales, qui sont l'amplitude. 1f et l'intermittence M;, et les paramètres de contrôle, qui sont la vitesse de compression et le nombre de grains formant l'empilement. L'analyse statistique des données a démontré que la forme des distributions des variables. 1f etM: variait au passage entre un petit échantillon (distribution exponentielle) et un grand échantillon (distribution gaussienne) de telle sorte que le comportement d'erratique devient quasi-périodique. La périodicité obtenue dans les grands échantillons est caractéristique d'un comportement gouverné par une loi macroscopique. En diminuant le nombre de grains, lesfluctuations locales deviennent non négligeables et déclenchent des instabilités provoquant un stick-slip erratique. L'étude de la régression des fluctuations observées dans des échantillons à comportement régulier en fonction de la taille de l'échantillon et l'application du théorème central limite ont permis de redéfinir la notion de volume élémentaire représentatif (VER) et de montrer que ce VER est de (1 à 3)3 grains en temps normal. Par contre, le VER des échantillons avec "stick-slips" est beaucoup plus grand (>107 grains) car il correspond au comportement quasi-périodique. Le comportement rhéo-fluidifiant met en évidence l'importance de la physico-chimie au contact grain-grain, et des effets de mémoire associée. On propose donc enfin une expérience de diffusion multiple d'ondes ultrasonores pour obtenir des informations sur le mouvement des contacts au cours de la compression; et on montre sa faisabilité.
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Silva, James Emanuel. "PNIPAM hydrogel micro/nanostructures for bulk fluid and droplet control." Thesis, Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/54252.
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Poly(N-isopropylacrylamide) (PNIPAM) belongs to a class of stimuli-responsive materials known as “smart” polymers. When cast in the form of a hydrogel, PNIPAM’s lower critical solution temperature (LCST) of 32°C serves as a threshold for volumetric change. For solution temperatures below LCST, PNIPAM hydrogels exist as swollen, hydrophilic networks of polymer and water, spontaneously expelling the bound water molecules to shrink (and become increasingly hydrophobic) as temperature increases beyond LCST.
This thesis centers on PNIPAM hydrogel layers grafted along the inner diameter of glass capillaries in order to form a temperature-responsive gating mechanism that spontaneously seals for solution temperatures below LCST. Surprisingly, very thin layers (10-20µm) of PNIPAM have dramatic effects on bulk fluid flow through the capillary due to complex interactions at the swelling interface. Specifically, for the case of capillary pressure driven flow, the swelling PNIPAM interface gives rise to "stick-and-slip" motion for bulk flow. Experiments explore the extent of this phenomenon, while a theoretical framework is proposed to model how the evolving gel interface pins the contact line.
Additionally, an exploratory segment of this work examines the ways in which PNIPAM hydrogel nanoarrays can be synthesized via scalable template methods. Nanostructured PNIPAM films exhibit dramatic changes in surface properties with temperature, characterized by very low contact angles (~10°) below LCST, and very high ones (~160°) above LCST. Results for several methods are presented with lessons learned to guide future development of surfaces with temperature-responsive wetting properties.
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Deleau, Fabrice. "Comportement tribologique acoustique d'un contact élastomère / verre : Contribution à la compréhension de l'éssuyage : Application aux systèmes automobiles d'essuie glace." Ecully, Ecole centrale de Lyon, 2009. http://www.theses.fr/2009ECDL0003.
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L'essuyage d'un pare-brise est assuré par le mouvement alternatif d'une lèvre en caoutchouc qui permet l’évacuation de l’eau par un contact linéique de très petite dimension (40 µm). Cette interface exige une meilleure connaissance de son comportement tribologique et vibratoire et ces travaux de thèse proposent donc de simuler ce contact caoutchouc/verre en fonction d’une quantité d’eau et avec une instrumentation qui analyse son comportement tribologique dans des conditions sèche, lubrifiée et de séchante. L'épaisseur du film d'eau à l'interface est estimée par une technique d’interférométrie optique. Les instabilités de frottement, lorsqu’elles sont observées, sont caractérisées par des capteurs dédiés et à l’aide d’une visualisation rapide du contact à l'échelle micrométrique. Cinq situations peuvent être différenciées selon l'évolution du frottement. Le premier est observé en condition sèche et trois autres en condition mouillée et ceci en fonction de la vitesse de glissement. La contribution relative des aires sèches et humides de la surface de contact est discutée en fonction de la vitesse de glissement, de la charge normale et des matériaux. Dans un contact sec, les expériences donnent un accès direct à la zone de contact solide donc à sa contribution au frottement. En condition humide, les performances en essuyage sont observées et l'évolution du niveau de frottement par rapport à la vitesse est corrélée à une réduction de l’aire réelle de contact. Le plus haut coefficient de frottement définit un 5ième régime de frottement qui apparaît lorsque la quantité d’eau au sein du contact est réduite à quelques nano litres, ce régime est appelé «séchante». Des ménisques d’eau restent confinés dans la zone de contact et cette "zone humide" augmente le niveau de frottement par une action capillaireThe wiping of a car windshield is carried out with the reciprocating motion of a rubber blade on glass which allows the water removal. This function is realized by a contact between rubber and glass of very small dimension (40 µm). The analysis of rubber lip sliding on a smooth surface requires a better understanding of both their frictional response and its stability. This work analyses the tribological behaviour of micrometer rubber spots sliding on a smooth surface (nanometer surface roughness) with a controlled amount of water. Our experiment proposes to simulate the rubber/glass contact with a complete instrumentation to analyse the sliding steady state behaviour within different conditions: dry, lubricated and tacky and the unstable one. The friction instabilities are characterised with dedicated sensors and a fast camera record system. These aspects have been investigated at the nanometer scale using the resources of a modified elasto hydrodynamic tribometer in order to measure the water film thickness at the interface by interferometric technique. Five tribological situations can be differentiated by the evolution of friction stress, the real contact area and the section strain. One is observed in dry condition and three in wet one according to the sliding velocity. The relative contribution of both dry and wet contact area on frictional response according to sliding velocity, normal load and slider’s material, is discussed. In a dry contact, the experiments give direct access to the solid contact area contribution to friction stress. In wet condition, the wiping performance is observed and the evolution of the friction stress versus the sliding speed is correlated to a reduction of the real contact area. The highest friction coefficient appears when the quantity of liquid is reduced to few nanoliters, this fifth regime is called “tacky”. Droplets are confined in the contact zone and this “lubricated zone” increases the friction stress
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Johannessen, Morten Krøtøy, and Torgeir Myrvold. "Stick-Slip Prevention of Drill Strings Using Nonlinear Model Reduction and Nonlinear Model Predictive Control." Thesis, Norwegian University of Science and Technology, Department of Engineering Cybernetics, 2010. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-9112.
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The main focus of this thesis is aspects in the development of a system for prevention of stick-slip oscillations in drill strings that are used for drilling oil wells. Stick-slip is mainly caused by elasticity of the drill string and changing frictional forces at the bit; static frictional forces are higher than the kinetic frictional forces which make the bit act in a manner where it sticks and then slips, called stick-slip. Stick-slip leads to excessive bit wear, premature tool failures and a poor rate of penetration. A model predictive controller (MPC) should be a suitable remedy for this problem; MPC has gained great success in constrained control problems where tight control is needed. Friction is a highly nonlinear phenomenon and for that reason is it obvious that a nonlinear model is preferred to be used in the MPC to get prime control. Obviously it is of great importance that the internal model used in the MPC is of a certain quality, and as National Oilwell Varco (NOV) has developed a nonlinear drill string model in Simulink, it will be useful to check over this model. This model was therefore verified with a code-to-code comparison and validated using logging data provided from NOV. As the model describing the dynamics of the drill string is somewhat large, a nonlinear model reduction is needed due to the computational complexity of solving a nonlinear model predictive control problem. This nonlinear model reduction is based on the technique of balancing the empirical Gramians, a method that has proven to be successful for a variety of systems. A nonlinear drill string model has been reduced and implemented to a nonlinear model predictive controller (NMPC) and simulated for different scenarios; all proven that NMPC is able to cope with the stick-slip problem. Comparisons have been made with a linear MPC and an existing stick-slip prevention system, SoftSpeed, developed by National Oilwell Varco.
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Busse, Leif [Verfasser]. "Investigation, prediction and control of rubber friction and stick-slip : experiment, simulation, application / Leif Busse." Hannover : Technische Informationsbibliothek und Universitätsbibliothek Hannover (TIB), 2013. http://d-nb.info/1032719249/34.
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Franceschini, Joel. "Avaliação do fenômeno de Stick-Slip em materiais de fricção com utilização de um tribômetro." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2014. http://hdl.handle.net/10183/96294.
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Nos sistemas de freio automotivo, o principal componente que determina seu desempenho é o material de fricção, pois um bom material de fricção deve garantir estabilidade no atrito em diferentes condições de uso, além de possuir resistência à corrosão, longa vida útil, baixa taxa de desgaste, boa relação custo versus desempenho e baixo ruído. Desde que o conforto dos veículos tornou-se um fator importante para indicar sua qualidade, eliminar ou reduzir os ruídos e vibrações de seus componentes passou a ser uma vantagem competitiva no mercado automotivo, e, o problema de ruído nos sistemas de freios vem sendo um dos maiores causadores de reclamações de clientes nos últimos anos. O ruído de freio é na maioria das vezes o resultado de uma vibração auto excitada induzida pela fricção ou uma instabilidade dinâmica do sistema de freio. O processo de stick-slip é um típico exemplo de oscilação induzida por atrito, observada em baixas velocidades de deslizamento e geralmente resulta em vibrações, que geram ruídos graves e rangidos. Com o objetivo de verificar a viabilidade da utilização das medições de vibração durante a ocorrência do fenômeno do stick-slip para a caracterização de materiais de fricção utilizando um tribômetro, foram preparados seis materiais de fricção produzidos pela empresa Fras-le, fabricante de materiais de fricção para freios automotivos. Os ensaios foram realizados no Laboratório de Tribologia (Latrib) da Escola de Engenharia da Universidade Federal do Rio Grande do Sul (UFRGS). No tribômetro utilizado nos ensaios foi instalado um acelerômetro sobre o suporte onde é fixada a pastilha do material de fricção a ser ensaiado. Vários ensaios foram realizados, cada um sob ação de força normal e velocidade de giro do disco constantes. Os resultados dos ensaios demonstraram que o tribômetro apresenta excelente desempenho para caracterização de materiais de fricção, possibilitando o desenvolvimento de novos materiais a partir de ensaios realizados neste equipamento. A avaliação da resposta da aceleração da vibração obtida nos ensaios demonstrou que a resposta da vibração é dependente dos diversos parâmetros medidos, como deslocamento, velocidade e variação de torque, e para melhor prever a propensão de um determinado material em apresentar vibração de stick-slip deve-se levar em consideração, além da variação de torque, o torque máximo de cada ciclo de stick-slip. Além disso, o uso do acelerômetro para avaliação de ensaios de stick-slip mostrou-se viável e seu uso deve ser estimulado em trabalhos futuros.In automotive brake systems, the main component that determines their performance is the friction material, because good friction material must ensure stability in friction under different conditions of use, as well as corrosion resistance, long life, low wear rate, good relation between cost and performance, and low noise. Since the comfort of vehicles has become important factor to indicate its quality, eliminate or reduce the noise and vibration of its components has become a competitive advantage in the automotive market, and the problem of noise in brake systems has been a cause of customer complaints in recent years. The brake noise is most often the result of a self-excited vibration induced friction or dynamic instability of the brake system. The stick-slip phenomenon is a typical example of oscillation induced by friction observed at low sliding speeds and generally results in vibrations which generate noise. In order to check the feasibility of using vibration measurements during the occurrence of the stick-slip phenomenon in the characterization of friction materials using a tribometer, were prepared six friction materials produced by the company Fras-le, manufacturer of friction materials for automotive brake. The tests were performed in the Laboratory of Tribology (Latrib) of the School of Engineering at Federal University of Rio Grande do Sul (UFRGS). In tribometer used for testing an accelerometer was installed on the support of the pad of friction material to be tested. Several tests were conducted, each under constant normal force and speed of rotation of the disk. The test results showed that the tribometer shows excellent performance for characterization of friction materials, enabling the development of new materials from tests performed on this equipment. The evaluation of the response of vibration acceleration obtained in the tests demonstrated that the response of vibration is dependent on various measured parameters, such as displacement, velocity and torque variation, and to better predict the propensity of a material to present vibration stickslip must take into account both the variation of torque and the maximum torque of each cycle of stick-slip. Furthermore, the use of accelerometer for assessing stick-slip tests was viable and its use should be encouraged in future work.
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Lu, Tianming. "Design and Realization of a Desktop Micro-Manipulation Cobotic Platform." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066009/document.
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La microrobotique est un domaine de recherche en croissance rapide et les microsystèmes sont très demandés par un large éventail de notre vie. Aujourd’hui, des solutions d'automatisation massive sont déjà disponibles pour la production en série des microsystèmes, tandis que la production de petites quantités s'appuie principalement sur des processus manuels en l'absence de système de micro-manipulation flexible. Un processus manuel impose des contraintes à la productivité et la précision, ce qui accroît les difficultés pour les petites et moyennes entreprises à conquérir leur place sur le marché international. Dans ce contexte, la société pionnière pour la microrobotique Percipio Robotics a proposé une plate-forme cobotique Chronogrip, qui vise à gérer la micro-manipulation flexible. Toutefois, la solution n'est pas encore complète et il y a trois principaux défis à résoudre :• la dynamique de l'actionneur piézo-électrique stick-slip n'est pas entièrement comprise, ce qui retarde le développement des stratégies de suivi de trajectoire;• les interfaces haptiques ont peu de bande passante en raison des propriétés mécaniques, par conséquent il n'y a aucune option disponible qui soit capable de reproduire des informations haptiques de haute dynamique depuis le micromonde;• pour la micro-manipulation à la pince dans l'horlogerie, aucune interface haptique existante n'est en mesure d'assurer un fonctionnement intuitif et efficace.L’objectif de la thèse consiste à répondre à ces trois défis. La première partie de la thèse est consacrée à l'élaboration d'un modèle dynamique non linéaire de l'actionneur piézo-électrique stick-slip. Le résultat montre qu'il est le premier modèle dynamique qui puisse décrire la dynamique de l'actionneur dans des domaines temporels et fréquentiels, pour les fonctionnements en sous-pas et en grand déplacement, et à la fois pour les directions vers l'avant et l’arrière. La deuxième partie de la thèse est consacrée à développer une méthode pour étendre la bande passante d’une interface haptique en double étage en utilisant la technique de signal crossover. Le résultat montre que la bande passante est uniformément étendue à 1 kHz, ce qui rend possible la reproduction des phénomènes de haute dynamique depuis le micromonde. La troisième partie de la thèse vise à concevoir une interface haptique intuitive dédiée aux opérations d’horlogerie à la pince. Le design est également compatible avec l'utilisation conventionnelle d’une pince. Il est prévu d'intégrer tous les résultats de ces trois sujets de recherches dans la plate-forme de cobotique Chronogrip afin d’améliorer la productivité et l'efficacité de la micro-manipulationMicrorobotics is a fast growing field of research and microsystems are in high demand from across a wide spectrum of our life. Nowadays, mass automation solutions are already available for large batch production of microsystems, while small batch production mainly relies on handmade processes due to the lack of flexible micro-manipulation system. Handmade processes have limited productivity and accuracy, which makes it more and more difficult for small and medium-sized enterprises to conquer their place on the international market. Under such circumstances, pioneer microrobotics company Percipio Robotics has proposed a desktop cobotic platform, Chronogrip, which aims to handle flexible micro-manipulation. However, the solution is not yet complete and there are three main challenges to resolve:• the dynamics of the piezoelectric stick-slip actuator is not fully understood, which delays the development of trajectory tracking strategies;• existing haptic interfaces have limited bandwidth due to their mechanical properties, consequently there is no available option that is able to render high dynamic haptic information from the microworld;• for tweezers-based micro-manipulation in watchmaking process, no existing haptic interface is able to provide intuitive and effective operation.The objective of thesis is to address these three issues. The first part of the thesis is dedicated to the development of nonlinear dynamic model of the piezoelectric stick-slip actuator. The result shows that it is the first dynamic model which can describe the actuator dynamics in time and frequency domain, for stepping and scanning mode, and for both forward and backward motion. The second part of the thesis is devoted to develop a method to extend the bandwidth of dual-stage haptic interface by using the signal crossover technique. The result shows that the bandwidth is uniformly extended to 1 kHz, which makes it possible to reproduce high dynamic phenomena from the microworld. The third part of the thesis aims to design an intuitive haptic interface for tweezers-based watchmaking operations. The design is also compatible with conventional tweezers-based usage. It is expected to integrate all of the three research results into the cobotic platform Chronogrip to enhance the productivity and effectiveness of micro-manipulation
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Sayed, Baraa Al. "Comportement dynamique des ensembles tournants de turbomachines : Maîtrise des effets des dispositifs de liaisonnement amortisseurs." Thesis, Lyon, INSA, 2011. http://www.theses.fr/2011ISAL0022/document.
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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 linéaireFatigue with high number of cycles (HCF) is a current and dangerous mode of failure for the blades of turbo shaft engines. It is induced by the high dynamic stresses generated at resonance in the operating range of these machines. The rubbing devices based on use of dry friction, such as shrouds or under-platform dampers, make it possible to reduce the vibratory amplitudes, to even push back the resonance frequencies out of the operation zones. However the design of these devices remains still largely based on empiricism and they can be the source of a potentially harmful effect of mistuning. The goal is to develop adapted modelling for the treatment of blades vibration problem in the presence of dry friction, this in order to better control the concerned physical behaviours and thus, to better control their process of design. Several numerical modelling are tested and confronted with reference results. A comparison between procedures of time and frequency domains resolution is carried out and shows the effectiveness of frequential methods. The frequential method of the Harmonic Balance including several harmonics is adapted to the problem and is used within an energy study. This study leads to a better comprehension of the phenomena of peaks flattening and it shows that the alternation of the states of slipping and sticking contact is the real cause of this flattening and not energy dissipation like often advanced in the literature. Lastly, the method is exploited to describe the behaviour of mistuned bladed disks. The Monte Carlo method is used to obtain the statistical characteristics of the forced response for a lumped system, by taking account of the stochastic variations of parameters in the contact, specifically the normal load, the stiffness of the contact and the coefficient of friction. Results obtained make it possible to better include/understand the effects of the variable nature of these fundamental parameters on dynamics of nonlinear system
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Gadenne, Leslie. "Processus de déformation et diagenèse dans les zones de subduction : impact sur les propriétés mécaniques des roches : Approche expérimentale." Thesis, Orléans, 2015. http://www.theses.fr/2015ORLE2001/document.
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La partie superficielle des zones de subduction (0-10 km de profondeur) a longtemps été considérée comme asismique. Cependant la découverte de séismes très basses fréquences dans cette zone, ainsi que la propagation très superficielle de la rupture cosismique lors du séisme de Tohoku-Oki (Japon) remettent en question cette hypothèse jusqu’alors largement admise. L’une des raisons pour lesquelles le potentiel sismogénique de cette zone est mal contraint réside dans le fait que les processus qui y règnent sont complexes, mêlant déformation et diagenèse (principalement la transformation des argiles de type transition smectite vers illite), et ainsi difficilement reproductibles en laboratoire. Au cours de cette thèse, des expérimentations en presse triaxiale sur échantillons smectitiques (représentatifs des matériaux accrétés dans les prismes d’accrétion) et illitiques ont été réalisées sous différentes conditions de pression de confinement (de 50 à 200 MPa) et de température (20°C et 300°C). Ces expériences ont été menées afin d’identifier les modes de déformation de ces échantillons, et de déterminer les effets couplés de cette déformation et de la diagenèse sur la rhéologie de ces roches et notamment leur potentiel à générer des instabilités de glissement. Dans ces expériences, le style de déformation est à chaque fois similaire, avec, tout d’abord, une localisation progressive de la déformation le long d’une zone de cisaillement, puis formation d’une fracture. Malgré cette constance dans le style de déformation, le comportement rhéologique des échantillons, lui, est drastiquement opposé entre les expériences à 20 et à 300°C, avec un comportement exclusivement durcissant à 20°C (i.e. stable) quel que soit la minéralogie, et un comportement qui évolue systématiquement vers du stick-slip (i.e. instable) à 300°C (pour les échantillons smectitiques). Ces résultats montrent que la réactivité chimique des smectites au cours de la diagenèse (activée dans les expériences à 300°C) conditionne la formation d’instabilités de glissement. Nous proposons que la réactivité chimique des smectites dans les zones de subduction pourrait promouvoir la propagation de la rupture cosismique vers la surfaceThe shallow portion of subduction zones (0-10 km depth) has long been considered as unable to store and release seismic energy. However, the detection of very-low frequency earthquakes in this zone, as well as the propagation of the coseismic rupture to the trench during the Tohoku-Oki earthquake, question this hypothesis. The difficulty to assess the seismogenic potential of this shallow portion lies principally in the complexity of the processes that occur in this zone, combining deformation and diagenesis (especially the smectite-to-illite transition), and hence not easily reproducible in laboratory. In order to analyse the mechanical properties of the shallow portion of subduction zones, triaxial tests have been performed with smectitic and illitic samples, under confining pressure between 50 and 200 MPa and at temperature of 20 and 300°C. The aim of these experiments was to identify the deformation modes of such sedimentary material and to determine the effects of deformation and diagenesis on rheology of these materials and on the rock potential to exhibit instable failure. In the experiments, deformation operates under the same pattern with a progressive localisation from shear band to fracturation. Even if the deformation style does not differ much between experiments, the rheology of the samples tested at 20°C and at 300°C contrasts drastically. Indeed, while the samples (smectitic and illitic) tested at 20°C show exclusively a strengthening behaviour (i.e. stable), the smectitic samples tested at 300°C exhibit a rheology that systematically evolves from strengthening to stick-slip behaviour (i.e. unstable). These results indicate that the chemical reactivity of smectite under diagenetic conditions (diagenesis is activated in the experiments conducted at 300°C) constitutes a weakening mechanism promoting unstable sliding. Finally, we propose that, at the subduction zone scale, the chemical metastability of smectite could promote the propagation of the coseismic rupture to the very shallow portion of accretionary prisms
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SANTOS, ADRIANO DOMENY DOS. "DYNAMICS OF A SLENDER ROTATING COLUMN SUBJECT TO THE STICK-SLIP ACTION IN TWO DISTINCT REGIONS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2015. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=26272@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
Este trabalho apresenta um estudo do comportamento dinâmico de uma bancada de testes representativa do sistema real de perfuração, composta por um motor CC acoplado a um sistema físico torcional, sujeita a fontes de atrito que induzem um regime de stick-slip no sistema em duas regiões distintas. O estudo incluiu a identificação de parâmetros da bancada de testes por meio de uma série de ensaios experimentais; e a caracterização do atrito, por meio do levantamento experimental da curva do coeficiente de atrito, em função da velocidade angular dos rotores principais. O intuito inicial foi a obtenção de um modelo numérico que fosse o mais simples possível e que representasse bem a bancada de testes. Uma vez obtido o modelo numérico, prosseguiu-se com uma série de simulações que permitissem uma caracterização indireta do regime de atrito ao qual estivessem submetidos os rotores principais, partindo-se apenas de medições de parâmetros no motor. Esse estudo é de grande relevância para a compreensão qualitativa da dinâmica do sistema real de perfuração, uma vez que ainda hoje não há técnicas totalmente confiáveis para caracterização do comportamento da coluna no fundo do poço a partir de dados da superfície somente.
This paper presents a study of the dynamic behavior of a representative test bench of a real rotary drilling system, comprising a DC motor coupled to a very exible torsional system subjected to sources of friction which can induce self-excitation into two distinct regions of the system. The study includes the identification of parameter settings from the test bench by means of a series of experimental tests and characterization of friction, by obtaining the experimental curve of the friction coefficient as a function of the angular speed of the main rotor. The initial aim was to obtain a numerical model as simple as possible, capable of representing the test bench. Once obtained the numerical model, a series of numerical simulations were done, which allow an indirect characterization of the friction condition to which main rotors were subjected, starting only with the parameters measured at the drive. This study is of great importance for a qualitative understanding of the dynamics of the real drilling system, since today there is no fully reliable techniques to characterize the behavior of the column in the deep from surface data only.
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Oubellil, Raouia. "Modeling and control of a SEM-integrated nano-robotic system driven by piezoelectric stick-slip actuators." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAT117.
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La capacité de réaliser des tâches robotiques dextres à l'échelle nanométrique dans un microscope électronique à balayage (MEB) est un enjeu crucial pour les nanotechnologies. Les systèmes nano-robotiques dédiés à des applications sous MEB ont ainsi émergé dans de nombreux laboratoires de robotique. Ils peuvent être composés d'un ou de plusieurs actionneurs intégrés à des plateformes nano-robotiques avec un ou plusieurs effecteurs. L’actionneur Piézoélectrique Stick-Slip (PSS) est l'un des meilleurs candidats pour actionner les systèmes nano-robotiques dédiés à des applications sous MEB car il est capable d'effectuer un positionnement grossier avec une plage de déplacement millimétrique et un positionnement précis avec une plage de déplacement de quelques micromètres. La modélisation des actionneurs PSS est complexe notamment en raison de leur mode de fonctionnement hybride. La commande est également difficile à cause de plusieurs caractéristiques liées aux actionneurs PSS, soient le frottement, l’hystérésis et les vibrations non-amorties, qui dégradent leur performances en termes de précision et de vitesse. Ce travail porte sur la modélisation et la commande d'un système nano-robotique à 3 axes dédié à des applications sous MEB et actionné par des actionneurs piézoélectriques de type stick-slip. Chaque élément et caractéristique des actionneurs PSS ont été analysés et modélisés afin d’établir par la suite un modèle dynamique complet capable de décrire les deux modes de fonctionnement, à savoir le mode balayage et pas à pas. Pour chacun de ces deux modes, des lois de commande ont ainsi été développées pour les actionneurs PSS. Des stratégies de commande robuste ont été synthétisées pour des objectifs de positionnement rapide et à haute résolution en mode balayage. De telles performances sont fondamentales dans plusieurs tâches micro-/nano-robotique tels que le nano-assemblage rapide et précis et la nano-caractérisation des matériaux. Une commande proportionnelle en fréquence et en amplitude est synthétisée pour effectuer un déplacement millimétrique en mode pas à pas. Ceci est motivé par les applications robotiques pour lesquelles une large plage de déplacement est requise, tels que le scan de grandes surfaces et les phases d’approche d’une sonde d’un échantillon à manipuler. Une stratégie de commutation qui combine les modes balayage et pas à pas, est alors proposée pour remédier au manque de précision en mode pas à pas, lors de passage d’un grand à un petit déplacement. Ce travail a donné lieu à des résultats qui ouvrent de nouvelles perspectives pour l'utilisation des actionneurs PSS dans les systèmes nano-robotiques dédiés à des applications sous MEBThe capability of doing dexterous robotic tasks at the nanometer scale inside a Scanning Electron Microscope (SEM) is a critical issue for nanotechnologies. SEM-integrated nano-robotic systems have consequently emerged in many robotics laboratories. They can be composed of one or more actuators assembled into nano-robotic platforms with one or several effectors. Piezoelectric Stick-Slip (PSS) actuators is one of the best candidate to actuate SEM-integrated nano-robotic systems because it is able to perform coarse positioning with millimeter displacement range and fine positioning with travel range of few micrometers. Modeling of PSS actuators is complex and difficult mainly because of their hybrid operating mode. Furthermore, control is challenging due to several characteristics related to PSS actuators, namely friction, hysteresis and undamped vibrations, which degrade their performance in terms of precision and speed. This work deals with modeling and control of a 3-axes SEM integrated nano-robotic system driven by piezoelectric stick-slip actuators. Each element and characteristic of PSS actuators are analyzed and modeled to thereafter establish a complete dynamic model able to describe the two functioning modes, namely the scanning and the stepping modes. PSS actuators are then controlled in each of these modes. Robust control strategies are developed to achieve high-resolution and fast positioning in scanning mode. Such performance is fundamental in several micro/nano-robotic tasks such as fast and accurate nano-assembly and nano-material characterization. A frequency/amplitude proportional controller is designed to perform millimeter displacement in stepping mode. This is motivated by robotic tasks where large motion is required, such as large surfaces scan and bringing a probe close to a sample to manipulate. A switched strategy, which combines scanning and stepping motion modes, is then proposed to remedy to the lack of precision in stepping motion, when passing from a large to a small displacement. This work has given rise to results which open new perspectives to the use of PSS actuators in SEM integrated nano-robotic systems
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PAULA, GUILHERME RODRIGUES SAMPAIO DE. "DYNAMICS AND CONTROL OF STICK-SLIP AND TORSIONAL VIBRATIONS OF FLEXIBLE SHAFT DRIVEN SYSTEMS APPLIED TO DRILLSTRINGS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2017. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=31846@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE EXCELENCIA ACADEMICA
Sistemas rotativos atuados através de um eixo flexível apresentam um grande desafio para estratégias de controle, uma vez que o atuador não está conectado diretamente ao sistema principal, causando efeitos de propagação de ondas e acúmulos e dissipações de energia no eixo. Este trabalho apresenta um estudo sobre uma das mais notórias aplicações deste problema, sistemas de perfuração de petróleo. Habitualmente, o sistema de perfuração é composto por um motor de topo conectado à broca através de milhares de metros de tubos de aço que transmitem o toque. Diversos tipos de vibrações podem ser observadas: Axiais, de flexão e torcionais, estas últimas ligadas ao fenomeno stick-slip. Para um completo conhecimento do problema, é necessário conhecer cada uma delas. Esta tese trata especificamente das vibrações torsionais através de uma análise com dois diferentes modelos, um primeiro mais simples de fois graus de liberdade (inércia, mola torcional, amortecedor), e um segundo mais completo discretizado em 20 graus de liberdade capaz de considerar a masssa do eixo e efeitos de propagação de ondas mecânicas no eixo. Este trabalho inclui aidna a construção de uma bancada em escala reduzida para observar os fenômenos associados as vibraçoes torcionais. São apresentados ainda estudos numéricos e experimentais de técnicas de controle de minimizar os efeitos do atrito na dinâmica torcional do sistema. Duas estrututas de controle são estudadas nesta tese a fim de reduzir vibrações torcionais em colunas de perfuração. A primeira é um controle simples, de malha aberta, baseado no comportamento do sistema. A segunda é o controle adaptativo L1, que faz uso de um modelo de refeência do sistema em sua estrutura.
Systems actuated trough a highly flexible shaft poses a big challenge to control strategies as the actuator is not connected directly to the end effector, causing propagation effects as well as an energy accumulation and dissipation in the shaft. This thesis focuses the study of one of the most investigated application of this type, the top driven drilling system used in the oil and gas industry. Usually, the drilling system is composed by a top drive linked to the drill bit trough hundreds or even thousands of meters of steel pipes. All kind of vibrations will be found: longitudinal deformations will be associated to the bit bouncing, flexional with rubbing, and torsional with stick-slip effects. A better understanding is only possible when each of these situations is carefully investigated. This thesis focuses on the torsional deformation of the highly flexible string and presents two different models for the drill string, the first is the most common single spring single damper model. The second one is a 20 DOF Lumped parameters that has the advantage of being able to consider the mass of the drill string and propagation of torsional waves in the shaft. The investigation includes the development of a test rig adequate for torsional vibrations under damping that may induce stick-slip in the system. Two control techniques are studied to reduce the torsional vibrations in drill strings with numerical and experimental results presented. The first is a behavior based open loop scheme control, which is very simple and effective to reduce stick-slip oscillations. The second one is the L1 adaptive control that uses a reference model on its structure.
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Abdulgalil, Farag. "Commande non linéaire dans les systèmes de forage pétrolier : contribution à la suppression du phénomène de "stick-slip"." Phd thesis, Université Paris Sud - Paris XI, 2006. http://tel.archives-ouvertes.fr/tel-00272937.
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Le travail présenté dans cette thèse porte sur la modélisation et la commande non linéaire le système du forage pétrolier. La problématique principale consiste à proposer un modèle de forage non linéaire et à élaborer un ensemble de stratégies de commande avancées pour améliorer les performances du trépan.A l'heure actuelle, les commandes des systèmes de forage pétroliers sont réalisées à l'aide de régulateurs classiques PI ou PID. Leurs performances se dégradent notablement lors de vibration de torsion causée par le « stick- slip », phénomène qui peut provoquer des couples non linéaires et donc endommager le trépan et le train de tiges. Par conséquent, il est nécessaire de disposer de systèmes de commande plus performants afin de mieux répondre aux exigences et aux performances demandées.
En dépit des diverses lois de commandes linéaires tentatives pour commander ce système mais qui ne garantissent pas la stabilité vis-à-vis des incertitudes. Ceci nous a conduits à proposer une modèle non linéaire en prenant en compte la totalité de l'information du phénomène du stick-slip, ce qui a conduit à une modélisation globale du forage rotary approchant donc au mieux le comportement réel de la plate-forme pétrolière. Pour cela, nous avons suggéré deux approches pour améliorer les performances du système de forage rotary:
• Commande par la technique de linéarisation par bouclage.
• Développement d'une commande par la technique des modes glissant associé à la commande linéarisation par Bouclage.
Comme le système de forage est généralement, est un système soumis aux incertitudes paramétriques, nous avons proposé, de plus, une nouvelle loi de commande non linéaire par Backstepping permettant de mieux améliorer la réponse de la vitesse de rotation du trépan.
Ces trois stratégies de commandes apparaissent la première fois dans ce domaine et la approche de Backsteping s'avère la meilleure. Les résultats de simulations obtenus dans les trois cas sont concluants et la synthèse par Backstepping montré la supériorité de, où la question de robustesse a pu être considérée.
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Cavalcante, de Sousa José Mácio. "Analyse der Ursachen des Stick-Slip-Effekts an Bahnenerzeugnissen für die Anwendung im Fahrzeuginnenraum am Beispiel von PVC." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2009. http://nbn-resolving.de/urn:nbn:de:bsz:105-9990928.
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Die Erzeugung von Störgeräuschen im Fahrzeuginnenraum stellt eine wichtige und kostenspielige Frage für die Automobilindustrie dar. Das physikalische Phänomen Stick-Slip (zu Deutsch Ruckgleiten) wird als die Hauptursache betrachtet. Als eine Erscheinungsform der Reibmerkmale eines Materials steht der Stick-Slip-Effekt (SSE) bekanntlich in Zusammenhang mit Oberflächeneigenschaften, wie z.B. Rauheit und Adhäsionskräften. Untersuchungen an Automobilledern zeigten zusätzlich, dass eine Beziehung zwischen dem SSE und dem Deformationsverhalten besteht. Der natürliche Charakter von Naturleder beeinträchtigte die Erstellung weiterer schlüssiger Aussagen. Ein synthetisches Material - PVC - wurde daher ausgewählt. Die Fortführung der Forschungsarbeit beruhte darauf, das Deformationsverhalten von PVC-Folie, die im Fahrzeuginnenraum Anwendung findet, in Bezug zu deren Stick-Slip-Neigung zu bringen. Dafür wurde der Einfluss unterschiedlicher Modifizierungen und Behandlungen untersucht.
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Svernestam, Jonas. "En studie av en industrirobots beteende vid borrning." Thesis, Linköping University, Department of Mechanical Engineering, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-4603.
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In the assembly process of airframe structures there are many drilled holes and on some parts the holes are mainly drilled manually with pneumatic handheld drilling machines. During conventional drilling in metal, burrs appear. To remove these burrs the parts of the structure must be separated and deburred before they can be put together for fastening. This is a time consuming measure and therefore expensive. To facilitate this process and lower production costs some parts of the process needs to be automated.
A part of this thesis was a project in co-operation with Saab, Novator, Specma Automation and the University of Linköping. The purpose of this project was to investigate the ability of an industrial robot to drill holes in aeroplane structures using orbital drilling.
How the project tests were carried out and the results of these tests are presented in the first part of this thesis. The tests showed that slip-stick appeared when a force was applied on the working object by the robot. Because of the movement of the pressure foot the drilled hole will be in the wrong position and if the movement appears during drilling the quality of the hole is being poor.
Several different tests were performed using different amounts of forces and different pressure feet trying to prevent slip-stick from appearing. Finally tests were performed with good results concerning the quality of the holes.
In the second part of this thesis the proceeding tests that were carried out are presented. The purpose of these tests was to find out how the robot acts when a static pressure is applied on a work object by the robot and try to find out what the cause of the slip-stick was. Several tests were done where the robot applied a force on several different points on the fixture and the slip-stick was measured.
The tests that were carried out during this thesis showed that an industrial robot can be used to drill holes in aeroplane structures. To make sure that the quality of the drilled holes is sufficient for the high demands of the aeroplane industry the working area of the robot is limited to a small area in front of the robot. The slip-stick that appears when the robot is extended into a position on the far side of the robot is too large for the robot to drill the hole in an accurate position.
Vid flygplansmontering borras det många olika hål och på vissa delar borras större delen av dessa hål manuellt med pneumatiska handborrmaskiner. Vid konventionell borrning i metall bildas oönskade grader. Strukturen plockas därför isär så att graderna kan tas bort innan strukturens delar kan passas samman igen för att sammanfogas. Detta är en tidskrävande åtgärd och därmed dyr och i ett steg att förenkla denna process och få en billigare produktion vill man automatisera vissa steg i denna process.
En del av detta examensarbete var ett projekt i samarbete med Saab, Novator, Specma Automation och Linköpings Universitet vars syfte var att klargöra en robots förmåga att borra hål i flygplansmaterial med orbitalborrningsteknik.
I första delen av detta examensarbete redovisas genomförande och resultat av projektets tester. Testerna visade att tryckfoten gled på testmaterialets yta när roboten lade en tryckkraft på testplåten, så kallad slip-stick uppkom. Denna glidning gör att det borrade hålet inte hamnar på rätt position och sker glidningen under borroperationen så försämras hålets kvalité. Flera olika tester gjordes med varierad tryckkraft och med olika tryckfötter för att försöka förhindra att slip-stick uppkom. Tester genomfördes där hål borrades med bra kvalité.
I den andra delen av denna rapport redovisas fortsättningen på examensarbetet som var en vidareundersökning av de tidigare genomförda testerna. Syftet med denna del var att undersöka hur en industrirobot beter sig när den används för att lägga på en tryckkraft mot ett material samt att försöka ta reda på vad som är orsaken till slip-sticken. Fler tester gjordes där roboten tryckte på olika punkter på en fixtur och de uppkomna slip-sticken mättes upp.
Testerna under detta examensarbete har visat att det går att använda en industrirobot till att borra hål i flyglansmaterial. För att kvaliteten på de borrade hålen ska klara de höga krav som ställs inom flygplansindustrin är robotens arbetsområde begränsat till ett litet fönster mitt framför roboten. De glidningar som uppkommer när robotarmen är utsträckt långt åt sidan om roboten är alldeles för stora för de positioneringskrav som är på hålens placering på flygplansstrukturen.
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Tonazzi, Davide. "Macroscopic frictional contact scenarios and local contact dynamics : At the origins of “macroscopic stick-slip”, mode coupling instabilities and stable continuous sliding." Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0110/document.
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Le comportement local au contact et son interaction avec la dynamique globale du système sont à l'origine d’innombrables problèmes de contact concernant plusieurs disciplines telles que la tribologie, la géophysique, la mécanique de vibration ou la mécanique de la rupture. Lorsque deux corps élastiques sont en mouvement relatif avec une interface de frottement, des vibrations induites se produisent dans le système. Dans un point de vue macroscopique, le scénario macroscopique de stick-slip survenant pendant le mouvement relatif est caractérisé par la chute soudaine de la force de frottement (état de glissement), séparées par des périodes d'accumulation d'énergie élastique (état d’adhérence). Autrement, une instabilité dynamique se produit quand un mode de vibration du système mécanique devient instable en raison des forces de frottement. Ces types d'instabilités, générées par des forces de frottement, ont été principalement objet de publies traitant de problèmes spécifiques dans différents domaines. Dans ce contexte, des analyses expérimentales et numériques ont été ici mis en place pour comprendre comme le comportement de l'interface locale affecte la réponse macroscopique du système et vice-versa, au cours de scénarios d'instabilité. Les scénarios macroscopiques (instabilité de « stick-slip macroscopique », instabilité modale, glissement continu stable), survenant entre deux milieux élastiques simples en mouvement relatif, ont été étudiés numériquement et expérimentalement. Un dispositif expérimental dédié (TRIBOWAVE) a été développé et a permis de reproduire et examiner les différents scénarios de frottement dans des conditions aux limites bien contrôlées. Les mêmes scénarios de frottement ont été reproduits par des simulations numériques transitoires. Une loi de frottement en fonction du temps d’adhérence (stick) a été définie à partir des essais expérimentaux. La loi de frottement obtenue a été mise en œuvre dans le modèle numérique, conduisant à une validation quantitative des scénarios de frottement par les expériences. Les simulations transitoires non linéaires, l’analyse aux valeurs propres complexes et les tests expérimentaux ont permis de dessiner des cartes de scénarios d'instabilité en fonction des paramètres clés du système. Validé par la comparaison avec les mesures des signaux expérimentaux globaux (forces, accélérations / vitesse), le modèle numérique a permis d'étudier le couplage entre le comportement du contact local (distribution de l'état du contact, propagation des ondes et des ruptures, précurseurs) et la réponse dynamique du système au cours du « stick-slip macroscopique », de l’instabilité due au couplage modale et du glissement continu stable. La compréhension du couplage entre le contact et la dynamique des systèmes apportera de nouvelles améliorations sur le contrôle des instabilités de contact et les problèmes d'usure connexesLocal contact behavior and its interaction with the global dynamics of the system are at the origin of innumerable contact issues concerning several different disciplines like tribology, geophysics, vibration mechanics or fracture mechanics. When two elastic media are in relative motion with a frictional interface, friction induced vibrations arise into the system. By a macroscopic point of view, the “macroscopic stick-slip” scenario occurring during relative motion is characterized by sudden friction force drops (sliding state) along the time, separated by periods of elastic energy accumulation (stick state). Instead, the mode dynamic instability occurs when a vibration mode of the mechanical system becomes unstable, due to frictional contact forces. This kind of instabilities, generated by frictional forces, have been mainly object of papers dealing with specific issues in different domains. In this context, experimental and numerical analyses have been focused here on understanding how the local interface behavior affects the macroscopic frictional response of the system, and, conversely, during instability scenarios. The macroscopic frictional scenarios (macroscopic stick-slip instability, mode coupling instability, stable continuous sliding) arising between two simple elastic media in relative motion have been investigated numerically and experimentally. A newer experimental setup (TRIBOWAVE) has been developed and it allowed to reproduce and to investigate the different scenarios under well-controlled boundary conditions. The same frictional scenarios have been reproduced by transient numerical simulations. A dedicated friction law as a function of adherence (sticking) time has been recovered by means of experimental tests. The obtained friction law has been implemented in the numerical model, leading to a quantitative validation of the simulated scenarios by the experiments. Nonlinear transient simulations, complex eigenvalue analyses and experimental tests allowed for drawing instability maps as a function of system key parameters. The numerical model, validated by the comparison with the experimental global measurements (forces, accelerations/velocity), allowed for investigating the coupling between the local contact behavior (contact status distribution, wave and rupture propagation, precursors) and the system dynamic response during macroscopic stick-slip instability, mode coupling instability and stable continuous sliding. The understanding of the coupling between contact and system dynamics will bring to further improvements on the control of contact instabilities and related wear issues
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Amri, Mohamed. "Étude expérimentale et théorique de l’effet de la vitesse de coupe sur la forabilité des roches sous pression de boue." Thesis, Paris Sciences et Lettres (ComUE), 2016. http://www.theses.fr/2016PSLEM095.
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L'optimisation des systèmes de forage nécessite une meilleure compréhension des vibrations indésirables comme le stick-slip. Ce phénomène vibratoire, qui affecte principalement les outils PDC (Polycristalline Diamond Compact), met en péril l'intégrité des équipements de forage et réduit considérablement la vitesse de pénétration de l'outil. Plusieurs travaux ont été menés ces dernières années pour déterminer ses origines. Les observations réalisées en fond de puits montrent que ces oscillations s'accompagnent systématiquement d'une baisse du couple à l'outil en fonction de sa vitesse de rotation. De nombreux groupes de recherche attribuent cette baisse de performance à l'occurrence du stick-slip.L'objectif de ce travail est de développer un modèle élémentaire de coupe qui permet d'analyser l'effet de la vitesse de coupe sur la forabilité des roches dans des conditions opératoires réalistes. Dans le cadre de cette thèse, nous avons réalisé une série d'essais de coupe en utilisant des taillants et des outils à échelle réelle dans trois roches de propriétés hydromécaniques différentes, et ceci à pression atmosphérique et sous pression de fluide. Les essais réalisés à pression atmosphérique montrent que les efforts élémentaires de forage augmentent avec la vitesse de coupe. Sous pression de boue, cet effet dépend largement de la perméabilité de la roche. En effet, nous avons observé que l'effet de la vitesse est relativement faible dans les formations de faible et de moyenne perméabilité sous pression de boue de 20 MPa. En revanche, cet effet augmente d'un ordre de grandeur dans les roches très perméables.Afin de comprendre ces observations, nous avons développé un modèle hydromécanique d'interaction taillant-roche construit à partir de la théorie de la poroélastoplasticité. D'abord, le problème est résolu analytiquement en s'inspirant des travaux existants. Par la suite, nous avons apporté une résolution numérique aux éléments finis des équations de la promécanique appliquées à la coupe des roches sous pression de boue. Les deux modèles montrent que le phénomène de dilatance génère une baisse de la pression de pore qui augmente la résistance de la roche au forage. Cette chute de pression dépend de la vitesse de coupe ainsi que des caractéristiques hydrodynamiques de la roche. Les résultats théoriques ont été comparés aux nombreux résultats expérimentaux obtenus dans le cadre de ce travailThe optimization of the drilling practice requires a better understanding of drillstring harmful vibrations such as stick-slip. This form of torsional vibrations is a typical problem of PDC (Polycristalline Diamond Compact) drillbits. It can reduce the rate of penetration drastically and can raise fatigue of the drilling devices. Many attempts were carried out in the last years in order to determine the causes of stick-slip phenomenon. Field observations show that torque on bit decreases as a function of bit velocity during stick-slip oscillations. Hence, it is widely believed that this decreasing relationship is the root cause of stick-slip.The purpose of this work is to examine cutting speed influence on rock drillability as a function of operating conditions and hydromechanical properties of the drilled formation. For this, a set of drilling tests was performed in three sedimentary rocks of different permeability using a full scale PDC drillbit and a single PDC cutter. In the first step, dry tests were carried out at atmospheric pressure. As previously observed in literature, single-cutter tests showed that drilling forces increase with cutting velocity. In a second step, we performed the same experiments at 20 MPa bottom-hole pressure. It appears that rate effect on cutting forces in the medium and low-permeability rocks is relatively low. By contrast, rate effect in the highly permeable rock increases by one order of magnitude in comparison with dry experiments.In order to understand this phenomenon, a steady state solution of the cutting model is derived in the framework of the theory of poroelastoplasticity. The problem is firstly solved analytically using some assumptions derived from previous works. Then, a numerical resolution based on finite element method is presented to solve the fully coupled problem ensuring the satisfaction of poro-material physics basic equations. Using these two different approaches, we show that pore pressure in shear-dilatant rocks decreases as a function of cutting velocity depending on rock permeability and interstitial fluid properties. This change has a hardening effect resulting in an increase of rock drilling resistance. Comparison between theory and experience shows good agreements
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Aubry, Jérôme. "Séismes au laboratoire : friction, plasticité et bilan énergétique." Thesis, Paris Sciences et Lettres (ComUE), 2019. http://www.theses.fr/2019PSLEE053.
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Au sein de la lithosphère, la transition entre déformations fragile et plastique des roches s’effectue dans le régime semicassant. Comprendre le comportement des failles naturelles dans le régime semi-cassant est fondamental puisque d’importants séismes nucléent à la base de la zone sismogénique, à des conditions de pression et température proches de celles de la transition fragile-plastique. Pendant un séisme, l’énergie élastique accumulée lors de la période intersismique est dissipée au sein de l’interface de glissement par des processus frictionnels et de fracture, le reste étant relâché sous forme d’ondes sismiques. Ce budget énergétique est influencé par la déformation des surfaces de failles pendant des glissements lents à rapides, et plus particulièrement par des processus de chauffage, invisibles aux yeux de la sismologie. Afin d’étudier la déformation semi-cassante des roches et le budget énergétique des séismes, nous avons effectué des expériences de reproduction de séismes au laboratoire, en conditions triaxiales, à l’aide de failles expérimentales de différentes lithologies. Nous avons étudié l’influence de la pression, de la vitesse de déformation, de la température et de la rugosité sur la stabilité des failles le long de la transition fragile-plastique et exploré la dynamique des séismes au laboratoire en mesurant la quantité de chaleur produite sur une faille durant un cycle sismique. Deux conclusions principales émanent de ces travaux. D’abord, les séismes au laboratoire peuvent se déclencher au sein de roches déformées plastiquement dans le régime semi-cassant. Les glissements observés sont majoritairement contrôlés par la rugosité de la faille. Pour finir, lors d’un cycle sismique, les failles opèrent une transition depuis un stade avec de multiples aspérités radiant peu d’énergie, à un stade où elles évoluent comme une aspérité unique, radiant un maximum d’énergieIn the lithosphere, the transition from brittle to plastic rock deformation corresponds to the semi-brittle regime. Understand how natural faults behave in the semi-brittle regime is fundamental to explain why large earthquakes generally nucleate at the base of the seismogenic zone, found at pressure and temperature conditions close to the predicted brittle-plastic transition. During an earthquake, part of the released elastic strain energy stored during the interseismic period is dissipated within a fault slip zone by frictional and fracturing processes, the rest being radiated away via elastic waves. This energy balance is influenced by the deformation of fault surfaces during slow or fast sliding, especially by frictional heating processes which could not be resolved by seismology. To investigate semi-brittle deformation and the energy balance of natural earthquakes, we performed laboratory earthquakes in triaxial conditions on experimental faults of various lithologies. We studied the influence of the confining pressure, axial loading rates, temperature and fault roughness on fault stability across the brittle-plastic transition and investigate the dynamics of laboratory earthquakes by measuring frictional heat dissipated during the propagation of shear instabilities. The main conclusions are twofold. First, laboratory earthquakes may nucleate on inherited fault interfaces at brittle-plastic transition conditions and fault slip behavior is mainly influenced by roughness. Second, we conclude that during sliding, faults exhibit a transition from a weak stage with multiple strong asperities and little overall radiation, to a highly radiative stage during which the fault behaves as a single strong asperity
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Di, Bartolomeo Mariano, and Bartolomeo Mariano Di. "Wave generation and propagation at tribological interfaces." Phd thesis, INSA de Lyon, 2011. http://tel.archives-ouvertes.fr/tel-00715732.
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This thesis is addressed to the understanding of the mechanisms at the origin of the contact wave fields at frictional interfaces and its relationship with the local characteristics of the surfaces in contact, as well as with the global dynamics and macroscopic frictional behaviour of the system. The aim of this work is to provide insights on the generation and propagation of the waves through the contact both to avoid instabilities and to control their effect on friction. The work is organized in two main parts. The first part presents the development of a non-linear finite element analysis in large transformations of the dynamic rupture at the interface with contact friction separating two bodies (isotropic and elastic) without relative motion. A rupture is considered when an initially sticking zone shifts in sliding state. The properties of the obtained ruptures are analyzed for a flat interface between dissimilar materials in function of the nucleation energy; then the effect of the interface roughness is analyzed. The differentiated rupture inside the asperities and the conditions for coupling and uncoupling between the waves radiating in the two bodies have been also investigated. In the second part, the analysis deals with the sliding onset between two bodies in contact. The sliding between two bodies made of different isotropic elastic materials and separated by a frictional interface is simulated. The evolution along the time of the global normal and tangential forces is analyzed, relating it to the local phenomena occurring at the interface. This part tries to investigate how micro-slips at the interface, acting as distributed ruptures, trigger the macro-slips between the two bodies. The interaction between local and global dynamics is also studied. Finally a numerical parameter space study is carried out, as a function of several system parameters (contact law, friction coefficient, material damping, normal load, translational velocity and regularization time). The results show the key role of the micro-slips and precursors (detectable wave propagations that occur at tangential global force well below the critical value expected by the friction law) in triggering the macro-slip between the two bodies. Depending on their distribution and magnitude the evolution of the contact forces passes from stick-slip-like behaviour to continuous sliding. The local dynamics at the contact (wave and rupture propagation) is linked to the global behaviour of the system (stick-slip, continuous sliding, induced vibrations); the effect of the contact and system parameters on the transfer of vibrational energy between the sliding contact and the system is investigated. The numerical results obtained by the two parts of the work show a good agreement with experimental results in literature.
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Benkassem, Sâd. "Propriétés mécaniques et modélisation multiéchelle de l'effet de taille dans les polycristaux nanométriques." Metz, 2007. http://docnum.univ-lorraine.fr/public/UPV-M/Theses/2007/Benkassem.Sad.SMZ0729.pdf.
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La contrainte d'écoulement des matériaux cristallins dépend de la taille des grains selon la loi de Hall-Petch. Dans ce travail, une modélisation multiéchelle de l'effet de taille utilisant la méthode autocohérente généralisée sera présentée en vue de prédire le comportement viscoplastique d'un matériau nanocristallin cubique à face centrée. Dans notre démarche, on modélise séparément les mécanismes supposés actifs dans les nanomatériaux ce qui permet d'augmenter graduellement le raffinements de nos approches. Dans les modèles ainsi élaborés, l'inclusion représente le coeur du grain et la matrice représente le joint du grain et les triples jonctions réunis. Différentes approches seront discutées et étudiées afin de modéliser le comportement dit anormal des nanomatériaux. Nous verrons en particuliers le mécanisme de déformation plastique basée sur le glissement des dislocations, la diffusion de lacunes, le mécanisme d'émission et de pénétration de dislocations par les joints de grains et enfin le mécanisme de glissement des joints de grains où l'interface grain/joint de grains joue un rôle considérable lors du glissement pouvant engendrer la décohésion de l’interface par le mécanisme de stick-slipThe yield stress of crystalline materials depends on the grain size accordhg to the Hall-Petch relationship. In this work, a multi scale modeling of the effect of size using the generalized self-cbnsistent method will be presented in order to predict the viscoplastic behavior of nanocrystalline materials. In our step, one,models the supposed active mechanisms separately in the nanomatenals. In the models thus worked out, inclusion iegresents the grain core and the matrix represents the grain boundaries and triple junctions. Various approaches will be discussed and studied in order to mode1 the abnormal behavior of the nanocrystalline materials. 'We will study the dislocation glide mechanism as well as Coble creep the emission and penetration mechanism of dislocations by the grain boundaries and finally the grain boundaries sliding mechanism where the interface grain corelgrain boundary plays a considerable part of the slip which can generate the damage of the interface by stick-slip mechanism
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Fulleringer, Benjamin. "Semi-analytical modeling of complex mechanical contacts : application to inclusions and swear of coated surfaces." Phd thesis, INSA de Lyon, 2011. http://tel.archives-ouvertes.fr/tel-00684944.
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Les pieds d'aubes de soufflantes de turboréacteurs font face à des sollicitations de type fretting. Il en résulte deux types d'endommagements: (i) l'amorçage et la propagation de fissures, (ii) l'usure des surfaces en contact. OBJECTIF: Afin de fournir les outils permettant de répondre à la problématique industrielle, une méthode semi-analytique permettant de traiter des problèmes de contacts élasto-plastiques revêtus et/ou hétérogènes est développé à partir d'éléments existants et de solutions analytiques et numériques novatrices. METHODE: La structure est simplifiée en supposant un contact entre deux massifs élastiques semi-infinis. Des solutions analytiques donnant pour: + les contributions élémentaires de chargements normaux et tangentiels constants sur une surface rectangulaire + les contributions élémentaires de déformations plastiques supposées constantes sur un volume parallélépipédique + les contributions élémentaires de déformations d'incompatibilité liées à un problème hétérogène (inclusions, revêtements, endommagement,...) supposées constantes sur un volume parallélépipédique. >> les déplacements en surface ou les contraintes dans le volume. Les déplacements en surface ou les contraintes dans le volume sont alors exprimés en utilisant des produits de convolution discrets entre des coefficients d'influence et la source surfacique (chargements en surface) ou volumique (déformations plastiques ou d'incompatibilité). Le problème normal et le problème tangentiel en glissement total ou en glissement partiel peuvent alors être résolus, en prenant en compte les effets plastiques et hétérogènes. L'algorithme d'optimisation sous contrainte utilisé (contact elastique) est celui développé par L.Gallego tandis que la base du solver plastique utilisé a été développé par C. Jacq (contact elasto-plastique sans frottement) RESULTATS: De nouvelles solutions analytiques sont obtenues pour le calcul des déplacements résiduels tangentiels.
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Ferreira, Jeferson. "Fatores atuantes no aperto de fixadores roscados de aço com tratamentos superficiais que influem no surgimento do fenômeno stick-slip/." reponame:Biblioteca Digital de Teses e Dissertações da FEI, 2014. http://sofia.fei.edu.br:8080/pergamumweb/vinculos/00000b/00000b14.pdf.
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Toumi, Samir. "Contribution à la suppression du phénomène stick slip et à la construction d'un observateur de dimension infinie en forage pétrolier." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLE034/document.
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Les différents types de vibrations des garnitures de forage jouent un rôle important dans le dysfonctionnement des opérations de forage car celles-ci conduisent à la rupture prématurée des trains de tiges, par conséquent, à la perte de l'outil au fond du trou et aussi à l'endommagement de la machine. En s'intéressant au forage de type rotary, cette thèse étudie le phénomène des vibrations de torsion de point de vu, modélisation par une EDP (modèle distribué) dont on établi les conditions aux limites adéquats. Une large partie de notre analyse dans ce mémoire concerne la commande du phénomène de vibration de torsion conduisant à une vitesse de rotation contrôlée sur le bord. La modélisation du phénomène de torsion affectant le train de tiges lors d'un forage pétrolier a été représentée par une équation aux dérivées partielles (1D) d'ordre deux: type linéaire intégrant le phénomène de frottement. Deux entrées apparaissent dans les conditions aux limites en termes de vitesse de rotation du train et de la réaction avec le sol. Il s'agit donc de designer la commande en vitesse qui assure la rotation adéquate pour le forage et qui n'excite pas le phénomène du torsion en tenant en compte l'interaction de la formation avec le sol. La stabilité de la garniture de forage dépend d'un système de boue du fluide qui doit injecté. Nous traitons une connexion entre le système de forage rotary et le système du fluide. Nous obtenons un système couplé sous la forme EDP-EDO. Egalement, nous avons transformé le système couplé à un système neutre avec retard. Nos achevons ce mémoire par la construction d'une loi de contrôle pour l'observateur du système de forage rotary avec une seule mesure aux limites dans le haut de la colonne pour estimer les paramètres de l'outil de forage qui sont accessibles à mesurerThe different types of drilling vibrations play an important role in the malfunctioning of the drilling operations because the lead to the premature rupture of the trains, consequently, to the Loss of the tool at the bottom hole and also damage to the machine. Much of our analysis in this specification relates to the control of the phenomenon of vibration of twisting leading to a controlled rotational speed on the edge. The mathematical aspects and simulation results will be detailed. The modeling of the torsion phenomenon affecting the drill string during was represented by a second order partial differential equation : linear type integrating the phenomenon of friction. Two entries appear in the boundary conditions in terms of the speed of the train and the reaction with the soil. It is therefore a matter of designating the speed which ensures adequate rotation for drilling and which avoid the torsional phenomenon of twist taking into account the interaction of formation with the soil. The dynamic of the drill string stability depends on a system of fluid which should be injected to bring cuttings out of the well bore and amplify the torsional vibrations phenomena. To suppress fracturing collapse or influx of fluids surrounding the well, it is important to integrate the dynamic of the pressure in this study : PDE-ODE control problem. Finally, we are concerned with the problem of boundary observer stabilization for a system of hyperbolic PDEs which describes the drilling systems. The design relies on the top boundary measurements only
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Elmaian, Alex. "Méthodologies de simulation des bruits automobiles induits par le frottement." Phd thesis, Université du Maine, 2013. http://tel.archives-ouvertes.fr/tel-00839253.
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Les bruits automobiles induits par le frottement sont à l'origine de nombreuses plaintes clients et occasionnent des coûts de garantie considérables pour les constructeurs automobiles. Les objectifs de la thèse consistent à comprendre la physique à l'origine de ces bruits et proposer des méthodologies de simulation afin de les éradiquer. Un système générique est tout d'abord étudié. Ce système discret met en jeu un contact entre deux masses et une loi de frottement de Coulomb présentant une discontinuité à vitesse relative nulle. Des calculs de valeurs propres complexes de ce système linéarisé autour de sa position d'équilibre glissant sont menés et montrent la présence d'instabilités par flottement voire par divergence. Les simulations temporelles montrent quant à elles que les non-linéarités de contact permettent de stabiliser les niveaux vibratoires en cas d'instabilité selon quatre régimes distincts. De plus, malgré ses trois degrés de liberté, ce système est capable de reproduire les mécanismes de stick-slip, sprag-slip et couplage modal ainsi que les bruits de crissement, grincement et craquement rencontrés sur les systèmes automobiles. Des études paramétriques sont également présentées et mettent en avant des bifurcations de Hopf ainsi que l'effet déstabilisant potentiellement induit par l'amortissement. Des méthodologies permettant de catégoriser les réponses en termes de bruit et de mécanisme sont par la suite proposées. Les occurrences et risques de ces derniers sont alors analysés et des tendances sont dégagées. Enfin, la relation entre les bruits et les mécanismes est établie. L'attention est ensuite portée sur un système automobile particulier. Afin d'étudier son comportement crissant, les analyses de stabilité et les simulations temporelles sont désormais menées sur des modèles éléments-finis. Les simulations temporelles permettent d'observer l'établissement de vibrations auto-entretenues et d'identifier, parmi tous les modes instables prédits lors des analyses de stabilité, celui qui est réellement à l'origine de l'instabilité. L'effet du coefficient de frottement sur les motifs de coalescence et les cycles limites est également investigué. Le risque de crissement est ensuite évalué pour des conditions d'utilisation variées du système. La méthodologie, basée sur des analyses de stabilité, permet de retrouver les principaux constats expérimentaux obtenus sur banc d'essai. Le rôle des géométries et des matériaux constituant le système est également discuté. Enfin, une solution permettant de réduire de façon significative le risque de crissement est proposée.