L'objectif du projet ITER est de démontrer la faisabilité scientifique et technique de la fusion nucléaire à des fins énergétiques. Pour obtenir les réactions de fusion, un plasma chauffé à 150 millions de degrés doit être confiné par un champ magnétique de plusieurs teslas en quasi-continu. Pour obtenir ces températures, des antennes radiofréquences (RF) injectent des ondes électromagnétiques de forte puissance dans le plasma, en particulier entre 40 et 55 MHz aux fréquences de résonance cyclotron des ions. L'assemblage et la dilatation thermique en fonctionnement de ces antennes sont rendus possibles par des contacts électriques glissants. Ces contacts doivent supporter un courant RF crête de 2.25 kA en régime stationnaire, dans un environnement sous vide et pendant toute la durée de fonctionnement de l'antenne. De plus, les matériaux de ces contacts doivent être compatibles avec la température de 250°C utilisée pour l'étuvage de la machine pendant plusieurs milliers d'heures cumulées. Ces contacts RF sont donc des composants critiques pour les performances de l'antenne. Aucun contact électrique du commerce n'a jusqu'à présent été qualifié pour ces spécifications et un effort particulier a donc été porté dans le cadre de ce travail de thèse afin de développer une solution satisfaisante. Le choix des matériaux et des revêtements utilisés pour ces contacts a fait l'objet de la première partie de cette étude. Pour ce faire, un modèle multi-physique tenant compte des paramètres RF, mécaniques et thermiques a été développé. À la suite de cette étude, des premiers couples de matériaux et de revêtements ont été sélectionnés. Les propriétés d'échantillons représentatifs ont été caractérisées par des mesures réalisées au laboratoire CIRIMAT avant et après un vieillissement thermique simulé. Afin d'évaluer le comportement électrique et tribologique de ces paires de matériaux dans les conditions de fonctionnement d'ITER, un tribomètre sous vide a été spécifiquement conçu et utilisé pendant ce travail de thèse.[...] / Ion Cyclotron Resonance Heating (ICRH) is one of the most important plasma heating methods in magnetically confined fusion experiments. In ITER, two ICRH antennas are designed to supply 20 MW of Radio-Frequency (RF) power at 40-55 MHz to heat the plasma. RF sliding contacts are used in the antennas to allow their remote handling assembly and to improve their maintainability, as well as to absorb the thermal expansion of the RF conductors during operations. One of the RF contacts is designed to be operated at 2.25 kA in steady-state (1200 s), with a current density of 4.8 kA/m. With such current levels, high heating occurs at the contact area which threatens the structural and material safety of the RF contacts and constrain their life time. In addition, before operation of the ITER ICRH antennas, all the in-vessel structures will be baked at 250°C during thousands of cumulated hours for outgassing. In CEA, R&D work on RF contact development has been carried out for 10 years. Recently, Ag-coated CuCrZr louvers RF contact prototype based on Multi-Contact LA-CUT commercial contact configuration was tested on TITAN test-bed. 1500 A, 1200 s steady-state operation was achieved. However, due to burn failure, the RF contact prototype couldn't reach 1200 s steady-state under 2 kA as expected. In order to improve the performances of the RF sliding contacts to match ITER requirements, failure mechanisms of RF contacts during RF operations were analyzed and possible materials or coated systems that can be used for RF sliding contacts compatible with the ITER environment have been studied in detail within this thesis work. The effects of material selection, cooling parameter and contact resistance on louvers temperature have been modelled and simulated through finite element methods. Moreover, functional coatings like Ag, Au, Rh and their alloys were manufactured by electroplating on 316L and CuCrZr, which are commonly used as base materials on tokamak. By mimicking the ITER baking conditions, the coated samples were thermal aged under vacuum at 250ºC for 500 h, after which the materials properties evolution such as hardness, grain size and adherence was characterized. In addition, the coating life time has been evaluated through cross-sectional diffusion characterizations.[...]

No description available.

Metal on metal wear at high sliding speeds and high contact pressures results in the melting of one or both of the sliding solid bodies due to heat generated at the contact interface. Understanding the influence of sliding speeds, contact pressures and material properties on wear rates is important in developing predictive models for designing more efficient and effective engineering system components. Typical engineering applications subjected to these extreme conditions include ultrahigh speed machining, rocket sleds, large caliber cannon, and electromagnetic launchers. Sliding speeds on the order of 1,000 m/s and contact pressures in excess of 100 MPa are common in these applications and difficult to replicate in a laboratory environment. A unique wedge experiment using a minor caliber electromagnetic launcher has been developed and implemented to characterize wear deposition of a 6061-T6 aluminum sliding body on several different guider materials of varying mechanical and thermal properties at sliding speeds from 0 – 1,200 m/s and contact pressures from 100 – 225 MPa. Optical microscopy and 3D profilometry were used to characterize and quantify the slider wear. Three distinct wear regions, plasticity dominated, severe plastic deformation and melt lubrication were observed. Test results provided evidence that the aluminum slider contact interface was molten. Modeling of the experimental wear data showed a dependence on pressure and velocity and guider material properties, density and specific heat. A predictive wear model was developed for the melt lubrication region as a tool for designing components subjected to similar operating conditions.

The aim of this study is to evaluate a methodology for modeling the influence of crystallographic grain orientation on key parameters in normal and sliding contacts. The simulations of interfering cylindrical asperities, using finite element analysis, were conducted using two different plasticity models for copper: a conventional isotropic, homogeneous J2 plasticity model and a continuum crystal plasticity model. A normal contact study was conducted in which crystallographic orientation effects on different parameters were investigated. The model was then adapted for sliding contacts, which allowed other parameters such as energy dissipation to be investigated. Using crystal plasticity, the dependence of crystallographic orientation on plastic deformation and energy dissipation can be determined. The relative trends predicted using crystal plasticity are consistent with experiments that show friction depends on crystallographic orientation when plastic deformation is one of the primary energy dissipation mechanisms.

This master thesis deals with study of properties pick-up generators for wind power. First part of thesis studies wind turbines, its structure, generators and describes advantages and disadvantages of ashore and offshore location. The next part presents description of parts of sliding contact. The main part assesses the impact of sea environment on sliding contact in generators at offshore wind turbines.

This thesis is devoted to the topic of kluzný kontakt and its diagnostic, especially to the type of diagnostic using the method of -- of dust particles. The author presents an example of applying this method and deals with the topic of development of a laboratory template that will give access to bigger variability in studying this method.

The thesis is devoted to assessing the concept of a new solution to the sliding contact in electrical machines. The work is focused mainly on the issue of collector engines, which are almost exclusively used in electric hand tools. Much of the work is devoted to angle grinders, which are usually used in extreme conditions and demands for seamless operation are enormous. In order partial insight into the problems in the introduction are studied phenomena acting on the sliding contact, wear and durability. Then further materials and diagnostic methods for increasing the transfer efficiency brush - commutator brush - ring. The following sections of this thesis is also considered a proposal innovated brush along with the practical verification and evaluation of the suitability of the use of innovative sliding contact.

Para transmitir o torque gerado pelo motor de combustão interna para a caixa de transmissão por meio da embreagem, seja em automóveis ou caminhões, é necessário que haja contato por deslizamento entre um material polimérico multifásico e um contracorpo metálico de ferro fundido cinzento. Além disso, os níveis do coeficiente de atrito entre esses materiais têem que ser suficientemente alto e estável, para proporcionar uma transmissão de torque regular e eficiente. Porém, durante o deslizamento, materiais são transferidos de uma superfície para outra, e alterações microestruturais e fisico-químicas ocorrem. Como consequência, uma nova superfície (denominada de tribofilme) se desenvolve, influenciando o desempenho funcional da embreagem. Dessa forma, compreender as suas características tem se tornado essencial para desenvolver sistemas de embreagens cada vez mais eficientes. No entanto, muitos ensaios são necessários para que se possa entender como uma ou várias matérias primas se comportam em relação aos aspectos tribológicos. Isso faz com que surja a necessidade de repetir os ensaios inúmeras vezes, para que se façam as escolhas mais assertivas tanto das matérias primas quanto dos processos envolvidos. Como alternativa, para reduzir tempo e custos, e ter um maior controle sobre as variáveis de ensaio, busca-se simular em laboratório, com equipamentos mais simples, a reprodução das interações tribológicas em condições reais. A primeira fase deste trabalho tem como objetivo apresentar os mecanismos de desenvolvimento do tribofilme para três níveis de severidade em condições reais de aplicação (ensaios mais demorados, complexos e mais caros, devido à necessidade da confecção completa dos protótipos), e posteriormente correlacionar esses mecanismos com os que foram simulados por meio de ensaios conduzidos num tribômetro de laboratório do tipo pino-disco (ensaios mais rápidos e mais simples, consequentemente menos complexos), variando o PV de 3,08 até 11,08 MPa ms-1. Foi constatado que as características do tribofilme dependem da severidade da aplicação. Além do que, o tribômetro pino-disco (amostra de 13 mm de diâmetro externo) consegue reproduzir os mecanismos identificados em campo, pois houve paridade na transferência das características do tribossistema do modelo de ensaio para o da condição real (430 mm de diâmetro externo). Na segunda fase, diferentes séries de ensaios tribométricos foram realizadas para investigar a influência do tribossistema no desempenho funcional do par tribológico (atrito e desgaste). Para os ensaios tradicionais, foi constatada um aumento na taxa de desgaste para temperaturas superiores a 250°C, revelando uma transição no regime moderado de desgaste para o severo. Quando os debris de desgaste foram removidos do meio interfacial, o nível do coeficiente de atrito aumentou e a taxa de desgaste reduziu. Já a adição de debris de desgaste ao meio interfacial contribuiu para aumentar a taxa de desgaste e reduzir drasticamente o nível do coeficiente de atrito. No entanto, quando os ensaios foram realizados empregando discos pré-condicionados, a taxa de desgaste e o nível do coeficiente de atrito foram otimizados, principalmente em níveis de severidade mais elevados (PV 10,09 MPa ms-1) indicando potencial ganho na eficiência do sistema embreagem. / Torque from an internal combustion-engine to a gear box, either in automobiles or trucks, is transmitted by a clutch system. In order to transmit torque from one side to the other, sliding contact between a multiphase friction material and a gray iron rotor is necessary. Torque transmission depends on the friction level among the tribological couples, and it have to be relatively high and most importantly stable to allow an efficient and regular performance. During the sliding between the coupling surfaces, material is transferred from one surface to the other causing microstructure and chemical changes. As consequence, a new surface, also known as tribofilm, is developed. This surface governs the clutch system performance and understanding the tribofilm characteristics is very important to improve the development of efficient clutch systems. For this, a large number of tests are necessary to understand the tribological behavior of the raw materials. Such investigation is highly empirical and in order to have a consistent data it\'s necessary to carry out several friction tests repetitions. Alternatively, to save time and money, and have better control over the test variables, the real tribological interactions can be simulated in laboratory by using simple equipment, pin-on-disc tribometer. The simplicity of this device allows evaluating a larger number of alternative materials. The first part of this work aims to investigate the tribofilm development mechanisms in three severity levels on the field application (those tests are more time-consuming, complex and expensive, because it is necessary to produce the entire prototype), and then correlate these mechanisms with those simulated in a pin-on-disc tribometer (faster and simpler test) by changing the PV level from 3.08 to 11.08 MPa ms-1. It was found that the tribofilm characteristics depend on the severity of application. In addition, the pin-on-disc tribometer (sample of 13 mm outside diameter) can reproduce the same mechanisms that were identified on the field, due to the parity between the tribosystem characteristics of test model and field condition (430 mm external diameter). In the second part of this work, different series of tribometer tests were performed to investigate the influences of tribosystem on tribological couple performance (friction and wear). Standard tribometer tests presented an increasing in the wear rate at temperatures of 250°C, revealing a transition from moderate to severe wear regime. When wear debris were removed from the interfacial contact, the friction coefficient level increased and wear rate reduced. On the other hand, when the wear debris were added, it contributed to increase the wear rate and to reduce the friction level dramatically. However, when the experiments were performed by using pre-conditioned discs, the wear rate and friction coefficient level has been optimized, particularly at higher severity levels (PV 10.09 MPa ms-1).

Para transmitir o torque gerado pelo motor de combustão interna para a caixa de transmissão por meio da embreagem, seja em automóveis ou caminhões, é necessário que haja contato por deslizamento entre um material polimérico multifásico e um contracorpo metálico de ferro fundido cinzento. Além disso, os níveis do coeficiente de atrito entre esses materiais têem que ser suficientemente alto e estável, para proporcionar uma transmissão de torque regular e eficiente. Porém, durante o deslizamento, materiais são transferidos de uma superfície para outra, e alterações microestruturais e fisico-químicas ocorrem. Como consequência, uma nova superfície (denominada de tribofilme) se desenvolve, influenciando o desempenho funcional da embreagem. Dessa forma, compreender as suas características tem se tornado essencial para desenvolver sistemas de embreagens cada vez mais eficientes. No entanto, muitos ensaios são necessários para que se possa entender como uma ou várias matérias primas se comportam em relação aos aspectos tribológicos. Isso faz com que surja a necessidade de repetir os ensaios inúmeras vezes, para que se façam as escolhas mais assertivas tanto das matérias primas quanto dos processos envolvidos. Como alternativa, para reduzir tempo e custos, e ter um maior controle sobre as variáveis de ensaio, busca-se simular em laboratório, com equipamentos mais simples, a reprodução das interações tribológicas em condições reais. A primeira fase deste trabalho tem como objetivo apresentar os mecanismos de desenvolvimento do tribofilme para três níveis de severidade em condições reais de aplicação (ensaios mais demorados, complexos e mais caros, devido à necessidade da confecção completa dos protótipos), e posteriormente correlacionar esses mecanismos com os que foram simulados por meio de ensaios conduzidos num tribômetro de laboratório do tipo pino-disco (ensaios mais rápidos e mais simples, consequentemente menos complexos), variando o PV de 3,08 até 11,08 MPa ms-1. Foi constatado que as características do tribofilme dependem da severidade da aplicação. Além do que, o tribômetro pino-disco (amostra de 13 mm de diâmetro externo) consegue reproduzir os mecanismos identificados em campo, pois houve paridade na transferência das características do tribossistema do modelo de ensaio para o da condição real (430 mm de diâmetro externo). Na segunda fase, diferentes séries de ensaios tribométricos foram realizadas para investigar a influência do tribossistema no desempenho funcional do par tribológico (atrito e desgaste). Para os ensaios tradicionais, foi constatada um aumento na taxa de desgaste para temperaturas superiores a 250°C, revelando uma transição no regime moderado de desgaste para o severo. Quando os debris de desgaste foram removidos do meio interfacial, o nível do coeficiente de atrito aumentou e a taxa de desgaste reduziu. Já a adição de debris de desgaste ao meio interfacial contribuiu para aumentar a taxa de desgaste e reduzir drasticamente o nível do coeficiente de atrito. No entanto, quando os ensaios foram realizados empregando discos pré-condicionados, a taxa de desgaste e o nível do coeficiente de atrito foram otimizados, principalmente em níveis de severidade mais elevados (PV 10,09 MPa ms-1) indicando potencial ganho na eficiência do sistema embreagem. / Torque from an internal combustion-engine to a gear box, either in automobiles or trucks, is transmitted by a clutch system. In order to transmit torque from one side to the other, sliding contact between a multiphase friction material and a gray iron rotor is necessary. Torque transmission depends on the friction level among the tribological couples, and it have to be relatively high and most importantly stable to allow an efficient and regular performance. During the sliding between the coupling surfaces, material is transferred from one surface to the other causing microstructure and chemical changes. As consequence, a new surface, also known as tribofilm, is developed. This surface governs the clutch system performance and understanding the tribofilm characteristics is very important to improve the development of efficient clutch systems. For this, a large number of tests are necessary to understand the tribological behavior of the raw materials. Such investigation is highly empirical and in order to have a consistent data it\'s necessary to carry out several friction tests repetitions. Alternatively, to save time and money, and have better control over the test variables, the real tribological interactions can be simulated in laboratory by using simple equipment, pin-on-disc tribometer. The simplicity of this device allows evaluating a larger number of alternative materials. The first part of this work aims to investigate the tribofilm development mechanisms in three severity levels on the field application (those tests are more time-consuming, complex and expensive, because it is necessary to produce the entire prototype), and then correlate these mechanisms with those simulated in a pin-on-disc tribometer (faster and simpler test) by changing the PV level from 3.08 to 11.08 MPa ms-1. It was found that the tribofilm characteristics depend on the severity of application. In addition, the pin-on-disc tribometer (sample of 13 mm outside diameter) can reproduce the same mechanisms that were identified on the field, due to the parity between the tribosystem characteristics of test model and field condition (430 mm external diameter). In the second part of this work, different series of tribometer tests were performed to investigate the influences of tribosystem on tribological couple performance (friction and wear). Standard tribometer tests presented an increasing in the wear rate at temperatures of 250°C, revealing a transition from moderate to severe wear regime. When wear debris were removed from the interfacial contact, the friction coefficient level increased and wear rate reduced. On the other hand, when the wear debris were added, it contributed to increase the wear rate and to reduce the friction level dramatically. However, when the experiments were performed by using pre-conditioned discs, the wear rate and friction coefficient level has been optimized, particularly at higher severity levels (PV 10.09 MPa ms-1).

Lors d'une opération d'usinage, l'intégrité de la surface usinée et l’optimisation du procédé sont conditionnées par les paramètres de coupe (vitesses de coupe et d’avance, géométrie et matériau de l'outil...). Certaines conditions de coupe peuvent induire des effets indésirables tels que des vibrations importantes, des efforts de coupe excessifs et une usure prématurée de l'outil, conduisant à des qualités de surfaces médiocres. Dans l’industrie, l’utilisation d'approches empiriques pour opérer ce choix se révèle couteux et difficilement exploitable. Le développement d’outils de simulation basés sur des modèles prédictifs s’avère nécessaire. Ces modèles permettent de maitriser et de comprendre les phénomènes thermomécaniques aux interfaces outil-copeau et outil-pièce qui conditionnent l'intégrité de la surface usinée ainsi que la durée de vie de l'outil de coupe. L'objectif de la thèse est la modélisation des effets thermomécaniques en usinage avec des approches hybrides 'Analytique-c. Ceci permet d'analyser l'interaction entre les conditions de coupe du procédé d'usinage, le comportement du matériau et les conditions tribologiques aux interfaces outil-copeau et outil-pièce (contact collant-glissant, partage de la source de chaleur due au frottement). Le travail comporte également une validation expérimentale pour la coupe orthogonale à sec. Le modèle proposé est basé sur les développements suivants: (i) mise en place d'une 'Approche 1D par Tranche' pour la prise en compte de l'écoulement de la matière dans la zone primaire de cisaillement du copeau, (ii) modélisation du problème thermique transitoire non linéaire dans le système 'copeau-outil-pièce' en couplant une formulation EF de type Petrov-Galerkin avec la méthode de Newton-Raphson et une intégration implicite dans le temps, (iii) une nouvelle formulation de la distribution de pression le long de la face de coupe de l'outil, (iv) une nouvelle approche pour gérer le partage de la source de chaleur par friction à l'interface outil-copeau. La démarche proposée permet de mettre en place une modélisation thermomécanique de l'interaction outil-matière applicable aux procédés industriels comme le perçage très utilisé dans le domaine aéronautique. Comparée aux simulations basées sur la méthode des Éléments Finis, l'approche développée requiert un temps de calcul de l'ordre de quelques minutes avec une précision comparable / In dry machining, the thermomechanical process of chip formation, the tool wear and the surface integrity depend strongly on the tribological conditions along the tool rake face. Besides, the friction conditions at the tool-chip interface and along the round cutting edge are very complex. It should be noted that to understand the friction effects in machining, we have to analyse the inherent relationship among, the cutting conditions (cutting and feed velocities, tool geometry), the workpiece material behaviour, the thermomechanical characteristics of the tool material, the frictional heat partition in the sliding zone and the friction conditions at the tool-chip and tool-workpiece interfaces. Due to the problem complexity, it appears that despite many works on machining, the understanding of the effect of friction conditions requires further investigations. In the present work, to identify the interaction between the thermomechanical phenomena at the tool-chip interface and the material flow in the primary shear zone; an analytical model has been coupled with a finite element approach. For the tool rake face, a new pressure model was developed. The transient nonlinear thermal problem in the workpiece-tool-chip system has been solved by using a FE model based on the Petrov-Galerkin formulation. The coupling between the primary shear zone (PSZ) (chip formation), the secondary shear zone (SSZ) (sticking zone) and the frictional heat at the sliding zone has been taking into account. The model allows to determine in a fast and simple way several significant machining parameters as: (i) the cutting forces, (ii) the temperature distribution in the tool-chip-workpiece system, (iii) the heat flux from the PSZ to the workpiece, (iv) the tool-chip contact length, (v) the frictional heat partition and (vi) the apparent friction coefficient. The proposed model allows to analyze different industrial machining processes such as drilling and milling