Though continental magmatic arcs are factories for new continental crust, a significant proportion of continental arc magmas are recycled from supracrustal material. To evaluate the relative contributions of retroarc underthrusting and trench side partial sediment subduction for introducing supracrustal rocks to the middle and lower crust of continental magmatic arcs, we present results from the deeply exposed country rocks of the Coast Mountains batholith of western British Columbia. Prior work demonstrates that these rocks underwent widespread partial melting that contributed to the Coast Mountains batholith. We utilize U-Pb zircon geochronology, Sm-Nd thermochronology, and field-based studies to document the protoliths and early burial history of amphibolite and granulite-facies metasedimentary rocks in the Central Gneiss Complex. U-Pb detrital zircon data from the structurally highest sample localities yielded similar to 190Ma unimodal age peaks and suggest that retroarc rocks of the Stikine terrane constitute a substantial portion of the Central Gneiss Complex. These supracrustal rocks underwent thrust-related burial and metamorphism at >25km depths prior to similar to 80Ma. These rocks may also be underlain at the deepest exposed structural levels by Upper Cretaceous metasedimentary rocks, which may have been emplaced as a result of trench side underplating or intraarc burial. These results further our understanding of the mechanisms of material transport within the continental lithosphere along Cordilleran subduction margins.

L’AgCdO est l’un des matériaux de contact parmi les plus répandus dans le monde du fait de ses excellentes propriétés. Cependant, étant donné la présence de Cadmium dans celui-ci, il sera bientôt totalement interdit par des directives européennes d’ordre environnementales. Trouver un matériau ne contenant pas de Cadmium et ayant au moins d’aussi bonnes propriétés est donc la clé du projet. Le phénomène d’érosion du matériau de contact suite à l’impact d’un arc électrique joue un rôle de premier ordre dans la fiabilité et la durée de vie des dispositifs de commutation de puissance. Celui-ci influe en effet sur les propriétés du matériau et affecte ainsi le fonctionnement du dispositif de commutation de puissance. Dans ce contexte, nos axes de recherche ont été les suivants. Avant tout, et ce afin de mieux comprendre le comportement à l’érosion suite à l’impact d’un arc électrique de l’AgCdO (matériau de contact utilisé actuellement dans l’industrie aérospatiale) et celui de l’AgSnO2 (candidat potentiel au remplacement de l’AgCdO), des essais ont été réalisés en soumettant les dispositifs de commutation de puissance à différents nombres de décharges. Ensuite, un modèle macroscopique permettant de prédire l’érosion d’un matériau suite à l’impact d’un arc électrique, valable pour faibles et forts courants, a été développé. Ce modèle décrit le processus complet de coupure et donne la quantité totale de matériau érodé suite à une opération de commutation. En parallèle, des essais ont été réalisés sur des dispositifs de commutation de puissance AgCdO à forts courants (0 -> 1000 A) afin de valider ce modèle d’érosion. Les propriétés matériau les plus influentes sur le processus d’érosion ont ensuite été déterminées à l’aide de ce modèle. Enfin, une étude ab initio portant sur les effets d’un changement de composition locale du matériau sur ses propriétés identifiées comme influentes sur le processus d’érosion a été réalisée. Ainsi, l’ensemble de ces travaux permettront de conclure sur des directives dans l’élaboration du matériau de contact qui remplacera l’AgCdO, objectif principal de ces travaux de recherche / AgCdO is one of the most widely used contact materials in the world because of its outstanding performance. Nevertheless, due to environmental considerations, it will soon be completely forbidden by European environmental directives. Therefore, finding a good substitute is of crucial importance. Electrical arc erosion plays a crucial role in the reliability and life of power switching devices. Depending on the contact material’s behavior in response to an electrical arc, surface damage can induce severe changes in contact material properties that will impact the power switching device’s functioning. Consequently, electrical arc effects and consequences on the contact material surface are of first importance. In this context, we have focused our research activities on the following axes. First of all, in order to better understand AgCdO (Current contact material in aerospace industry) and AgSnO2 (Potential candidate to AgCdO substitution) arc erosion behaviors, arc erosion experiments, where the power switching devices have been subjected to different numbers of arc discharges, have been realized. Further, a general macroscopic electrical contact arc erosion model valid for low and high currents was developed. To compare model results to experimental data, this model describes the complete breaking process of electrical contacts and gives the total amount of material removed after one breaking operation. In parallel, arc erosion experiments on AgCdO power switching devices have been conducted at high currents (0 -> 1000 A) in order to validate the arc erosion model. Next, using the general arc erosion model, the properties having the greatest influence on the electrical arc erosion process have been determined through simulations on silver contact material. At this stage, ab initio calculations were needed to obtain ranges of variation of certain silver contact material properties. Finally, an investigation of the trends of changing local contact material composition of AgSnO2 on these identified material properties was performed. This study was based on ab initio calculations for two different oxide compositions of AgSnO2. These will allow us to give directions to aid the design of a good substitute for AgCdO, and therefore, to complete the main objective of this research work

No description available.

Scope and Contents: This thesis is concerned with the properties of arcs of cyclic order three in the conformal plane. It establishes necessary and sufficient conditions for the union of two arcs of cyclic order three to be again an arc of cyclic order three, and for an arc of cyclic order three to be extensible to a larger arc of cyclic order three. / Thesis / Master of Science (MSc)

Dans le procédé de refusion à l’arc sous vide, la structure et la dynamique de l’arc électrique conditionnent les distributions spatiales d’énergie et de courant au sommet du lingot refondu. Ces distributions impactent fortement les champs de température et de vitesse du métal liquide, qui gouvernent les conditions de solidification du lingot et donc la qualité finale du produit. Une étude par mesures optiques, de la dynamique de l’arc aux longues échelles de temps lors de refusions industrielles d’alliages de titane a été entreprise. Cette analyse a été effectuée par une méthode qualitative, à l’aide d’enregistrements vidéo, et par une nouvelle méthode de diagnostic quantitative développée spécifiquement dans ce travail, à base de photodiodes. L’analyse de la dynamique de l’arc confirme la présence d’un mouvement d’ensemble de l’arc électrique lors de refusions d’alliages de titane et montre une forte corrélation entre la dynamique observée et l’intensité du brassage électromagnétique imposé. Nos résultats ont de plus permis de prédire la dynamique probable de l’arc dans des conditions non étudiées et de proposer de possibles origines à la dynamique observée. Enfin, une première approche de modélisation de cette dynamique dans le logiciel de simulation RAVEL est proposée afin d’étudier son impact sur la solidification du lingot. Ce travail présente également une modélisation détaillée des rayonnements thermiques émis au sommet du lingot, basée sur la méthode des radiosités / In the vacuum arc remelting process, the structure and dynamics of the electric arc are responsible for the spatial distributions of energy and current at the top of the remelted ingot. Those distributions strongly impact the ingot temperature field and the liquid metal velocity field, which govern the ingot solidification conditions, hence the final product quality. A study based on the optical measurement of the electric arc dynamics at a long time-scale during vacuum arc remelting of titanium alloys was undertaken. This analysis was performed either qualitatively using melt video recordings, or quantitatively by a new specifically developed diagnostic technique based on the use of photodiodes. The analysis of the electric arc dynamics confirmed the presence of an ensemble arc motion during vacuum arc remelting of titanium alloys and showed a strong correlation between the observed dynamics and the magnitude of the imposed electromagnetic stirring. Furthermore, our results allow to predict the arc dynamics in non-studied conditions and to propose possible origins for the observed behaviors. Finally, a first simulation of the influence of the arc behavior is proposed in order to study its impact on the ingot solidification. This work comprises also a detailed modelling of the thermal radiation at the ingot top, based on the radiosity method

La sûreté de fonctionnement des batteries est un point clé pour la croissance de ce marché et le déploiement de solutions hybrides afin de réduire la consommation d’énergie. L’électrification croissante de ces systèmes ne fait qu’aggraver l’augmentation de l’occurrence de ce problème qui bien que connu depuis longtemps dans le domaine des applications DC ne fait l’objet de recherches intensives que depuis peu comme en témoigne le développement récent des premiers détecteurs d’arc pour l’aviation. L’arc dans les batteries représente aujourd’hui un risque potentiel pour l’intégrité du matériel et des personnes du fait de l’utilisation des batteries au sein d’applications industrielles de fortes puissances. Afin de caractériser ce risque et d’en évaluer la dangerosité, plusieurs bancs d’essais sont réalisés au niveau élément et système afin de reproduire le phénomène d’arc électrique. Les essais réalisés permettent d’extraire les caractéristiques intrinsèques de l’arc. En complément de cette caractérisation, un modèle d’arc permettant d’évaluer les paramètres et d’améliorer la compréhension de ce phénomène est réalisé. Des solutions de limitation, voire de suppression de l’arc issues de cette étude sont proposées. Parmi ces nombreuses solutions, l’utilisation de capteurs optiques, les méthodes numériques pour le traitement des signaux issus de l’arc, la modification de l’architecture batterie ainsi que l’augmentation du niveau de tension lors de l’amorçage de l’arc ouvrent la voie à la conception de systèmes de batteries innovants et plus sûrs en termes de fiabilité, sécurité et de robustesse. Les nombreuses perspectives de recherches proposées permettront également d’améliorer la couverture de ce risque. / The operational security of batteries is a key element in the growth of this market and the deployment of hybrid solutions to reduce energy consumption.The increasing electrification of these systems can only exacerbate the occurrence ratio increase of this problem. Although known for a number of years in the field of DC applications, electric arcs are the subject of intensive research for a short time as shown by the recent development of the first arc sensors for aviation. Electric arcs in batteries currently represent a potential risk to the integrity of the equipment and people because of the use of these batteries in industrial high power applications. To characterize this risk and assess its dangerousness, several test benches were designed at the cell and system level to reproduce the electric arc phenomenon. The tests carried out allow extracting the intrinsic characteristics of the arc. In addition to this characterization, an arc model to evaluate the parameters and improve the understanding of this phenomenon is realized. Limiting mitigation solutions or suppression of the arc resulting from this study are proposed. Among the many solutions, the use of optical sensors, the numerical methods for digital signal processing from the arc, the modification of the architecture as well as the increase of the arc ignition voltage pave the way for the design of innovative and safer batteries systems in terms of reliability, security and robustness. The numerous proposed research perspectives will also improve the coverage of this risk.

This master´s thesis si focused on determinig methodology of optical diagnostics of the switching arc using the high-speed camera Photron SA-X2. The thesis contains basic rules for proper setup of the measurement system and the rules to adjust the camera exposure. The experiments were performed on the prototype of a parametric switching chambre, while the majority of source materials was derived from the requirements of another study which was aimed on the movement of the electode spots. The process of the first adjustment of the camera, a record edit options for the presentation purposes and the process of the 3D model design of the switching arc in SketchUp software was stated. Paper contains a comparsion of the spectral filter effect and neutral density filter effect on the final record as well. The part of the work outputs are the 3D model of the switching arc and the supporting record editing software. The paper results show a degree of the inaccuracies in a optical diagnostics made from only one direction caused by the lack of the information about third dimension.

Aujourd’hui, l’étude des effets directs de la foudre sur les structures aéronautiques pourrait s’appuyer, au moins en partie, sur des outils de simulation. Néanmoins, le manque de données expérimentales sur la phase d’arc impulsionnelle ne permet pas de justifier le caractère prédictif des outils de simulation.L’objectif de cette thèse est de réaliser une base de données expérimentale en s’appuyant sur la caractérisation des arcs de foudre dans des situations standardisées. Ces données peuvent être utilisées à la fois pour la compréhension des phénomènes observés lors des essais, mais surtout comme référence comparable aux outils de simulation.Dans un premier temps, on s’intéresse à la colonne d'arc libre dans l’air, hors interaction avec les électrodes. Par ailleurs, les profils spatio-temporels de température et de pression sont évalués par spectroscopie d'émission. On montre ainsi que, pour un arc de 100 kA, la température maximale atteint 37400 K sur l'axe de la colonne à 2 μs après l’amorçage, avec une pression de l’ordre de 45 bars.Dans un second temps, on s’intéresse à l'interaction de l'arc foudre avec des matériaux aéronautiques. La dynamique du pied d'arc ainsi que les caractéristiques de l’onde de choc sont analysées sur différents matériaux aéronautiques tels que l’aluminium ou des composites à fibres de carbone. Les contraintes thermomécaniques subies par le matériau sont étudiées par thermographie infrarouge, et par des mesures de déflexion rapide au centre du matériau, conduisant à une évaluation de la pression exercée par l’arc au point d’impact. / Nowadays, the study of the direct effects of lightning on aeronautical structures could be based, at least in part, on simulation tools. Nevertheless, the lack of experimental data on the transient phase of the lightning arc does not allow us to justify the predictive nature of the simulation tools. The objective of this thesis is to produce an experimental database based on the characterization of lightning arcs in standardized situations. These data can be used both for the understanding of the phenomena observed during the tests, but especially as a reference comparable to the simulation tools.First, we are interested in the free arc column in air, without interaction with the electrodes. Furthermore, time- and space-resolved profilesof temperature and pressure are evaluated by emission spectroscopy. For a 100 kA arc, it is shown that the temperature reaches 37400 K in the arc axis at 2 μs after arc ignition, with a corresponding pressure of 45 bar.Second, we are interested in the interaction of the lightning arc with aeronautical materials. The dynamics of the arc roots and the characteristics of the shock wave are analyzed for different aeronautical materials such as aluminum or carbon fiber composites. The thermo-mechanical constraints applied on the material are studied by infrared thermography and by rapid deflection measurements at the center of panel, leading to an evaluation of the pressure exercised by the arc at the attachment point.

The protection of the electrical device is provided to prevent the electric shocks, protect the equipment and prevent a damage caused by electrical faults. The current protection for a small fault currents need not always have an effect. At the serious faults the current protections never work. The new type of device to protect against damage caused by electrical failure is an arc protection. The arc protection switches off safely all types of fault arc in different sizes. This work verifies its correct functionality in the case of electric circuit with deceptive signals from LED light sources. The output of the work is the measurement of the switching current of the LED light sources. The work is remarkable thanks the number of measurement for individual angles of switching on which have statistical meaning.

Welding is a common metal fabrication process within industry. Epidemiology suggests that welders as an occupational group demonstrate slight, but significant, increased risks of respiratory ill-health. This might be expected as welding processes often present high levels of occupational exposure to oxidising gasses and weld fumes which are often inadequately controlled through local exhaust ventilation or personal respiratory protection because of high costs and the burden of worker participation. Fundamental control strategies of occupational hygiene encourage development and use of engineering controls as the best means to optimally control occupational exposure. However, engineering controls have not yet been successfully developed to control occupational exposure to welding fume and gases. This thesis investigates the interrelationships between ultra-violet radiation (UV). ozone (0:;). and hexavalent chromium (CrVI) in metal inert gas (MIG) welding in order to investigate possible methods to control occupational exposure to welding fume and gases by engineering contro!' Past studies of occupational ill-health in welders are reviewed as is the currently understanding of the physico-chemical principles by which the various components of welding fume evolves. Experiments were designed to investigate the mechanisms of formation of UV, 0 3 and CrVI formation from which a number of possible control strategies were developed further. Among these results emerge two process modifications with exciting potential to reduce two toxic components. 0, and CrVI , in stainless steel welding fume and gas. The addition of trace amounts of Zinc to chromium containing steel wires virtually eliminates all 0, and significantly reduces hexavalent chromium within the weld plume. As Zn is a volatile metal, it does not contaminate weld quality but increases the zinc oxide le\els in the fume slightly. A second method developed in this thesis involves the addition of a dual shield gas shroud containing reducing gases such as C2H .. to remove 0, and consequently. reduce Cr(VI) levels. Preliminary results suggest that these methods can be used separately. or in combination, to provide a practical means of controlling occupational exposure to two of the more toxic components of welding fume and gases. This thesis describes in details the experiments and results culminating in successful preliminary development of engineering controls for 0 3 and CrVI through process modification of the stainless steel MIG welding process. Further work for further development of these methods is outlined and funding to extend this area of applied research is being actively pursued with the support of major UK industry.