For several years, research work has been carried out at the University of Canterbury aimed at the development of a rapid prototyping and manufacturing process referred to as Robotic Foam Sculpting (RFS). This system uses a six-axis industrial robot and electrically-heated hot-wire and hot-blade tools to sculpt desired parts from blocks of polystyrene foam. The vision for this system is that it will be able to rapidly create large volume foam models at low cost, for a range of potential applications. Parts produced by the RFS system can potentially be used as investment casting patterns, cores for sculptures and architectural details, demonstration and testing models, wind tunnel test models, and many other potential applications. At the beginning of the work reported in this thesis, there was very little understanding of the nature of the surfaces produced by hot-tool cutting of foam, very little knowledge of the range of input cutting conditions that affected the surface quality, and almost no understanding of the relationships between the cutting strategy and the nature of the surfaces being produced. In addition, there was little evidence of published work on these subjects that was sufficiently robust to be applicable to the RFS system. This research was concerned with rectifying this gap in the existing knowledge. There were a number of different focal areas for this research. These included the surface texture of surfaces cut with hot tools, the effects of cutting strategy on the surface quality in single-pass cutting of foam, the effects of cutting strategy on the surface quality in multi-pass cutting, and the application of a current-control system to control the surface quality in real time during a cut. In each of the focal areas the goal was to develop a detailed understanding of the nature of the different aspects of surface quality, to map the factor interactions and dependencies that controlled these aspects of surface quality, to develop methods for predicting the expected surface quality based on cutting strategy (and vice versa) and to develop techniques for minimising the surface errors. The detailed investigation of the surface texture of surfaces produced with hot-tool cutting is presented in Chapter 4. This chapter explores the characteristic nature of foam surfaces, presents the development of a method of measuring the surface texture of foam, and investigates the usefulness of a range of standard texture parameters for assessing foam surface quality. It is concluded in this chapter that common texture parameters based on the relative heights of surface features are not capable of reliably discriminating between different foam surfaces, so a new texture parameter (the 10%-Height Contiguous Diameter) is developed and implemented. Using this parameter, it is possible to reliably predict the surface texture to be expected for a given set of cutting conditions. Investigations of the cutting strategy in single-pass cutting are presented in Chapter 5. This chapter identifies the two key aspects of surface quality in single-pass cutting, the kerfwidth and the surface barrelling. Experimental work is carried out to investigate the relationships between these errors and the cutting strategy, and the factors that influence each of them are identified. In addition, statistical models are developed for the kerf along the length of a cut so that the kerf can be predicted based on cutting conditions. This chapter also includes a study of the cutting force in single-pass cutting, and develops models that allow the prediction of the expected cutting force for a given cutting strategy. A detailed study of the cutting strategy for multi-pass cutting is presented in Chapter 6. This study identifies the most significant surface errors in multi-pass cutting and determines the causes of each of these errors and the factor interactions and dependencies that have to be considered when developing a multi-pass cutting strategy. Once again, statistical models that allow the prediction of these surface errors based on cutting strategy, or the evaluation of cutting strategy parameters to achieve a desired surface quality, are developed. The models for cutting force in single-pass cutting are applied to multi-pass cutting, and it is found that these models can accurately predict the force in multi-pass cutting as well. The characterisation of the acoustic output in hot-tool cutting forms the subject matter of Chapter 7. This study establishes that the magnitude of the acoustic output is proportional to the cutting force experienced during the cut, and is therefore potentially suitable for use as a trigger signal for feedback current control. This would allow an acoustic signal to be used instead of the current force signal, which has a number of drawbacks that will be discussed in Chapter 2, the Background Material chapter. The specific trigger signal identified as being of most use is the acoustic output in the 4 – 12 kHz band, where the presence of any non-zero acoustic output above background noise is a reliable and repeatable indicator of the presence of thermomechanical cutting. The work presented in this thesis provides a detailed, quantitative, evidence-based and reliable understanding of the nature of the cutting strategy in hot-tool cutting of foam. The key cutting strategy parameters and the important aspects of surface quality for different cutting types are identified, the relationships between all these parameters are mapped, and quantitative models are developed that allow the output metrics like the surface quality or the cutting force to be predicted with a high degree of accuracy based on the input cutting strategy conditions. Armed with this understanding, it is possible to determine the most suitable cutting strategy for sculpting a given part, and to assess whether a given part can be sculpted with the RFS system. As such, the research problem posed at the start of this thesis has been largely solved, and the stage is set for further research to optimise the cutting strategy for sculpting different parts and to correct the remaining drawbacks of the RFS system to complete the development of a commercially-useful manufacturing system.

En raison de sa stabilité microstructurale l'acier martensitique 'X10CrMoVNb9-1' est considéré comme un des candidats pour plusieurs futurs composants des réacteurs à hautes températures 'Very High Temperature Reactor' (VHTR). Ces épais composants (200 mm) sont assemblés par soudage TIG multi-passe. Ce procédé de soudage génère des cycles thermiques et thermomécaniques complexes au niveau de la Zone Affectée Thermiquement (ZAT). Cette thèse est la suite de celle de G.-M. Roux. Ce travail de six ans a pour but de prédire l'état microstructural après soudage dans la ZAT. G.-M. Roux a déjà développé une première version d'un modèle Thermo-Métallurgico-Mécanique (TMM) et a été validée en termes de contraintes résiduelles sur des essais de soudage simples mono-passe. Dans cette thèse une nouvelle version du modèle TMM est proposée, permettant d'améliorer les prévisions en termes de l'état microstructural post soudage dans la ZAT, et les contraintes résiduelles engendrées par l'opération de soudage.Cette thèse s¿appuie sur une approche de modélisation fine des transformations de phases, à savoir la modélisation de la transformation matériau de base - austénite lors d'un chargement anisotherme complexe, la modélisation de la transformation austénite - martensite et finalement la modélisation du revenu de la martensite. Sans oublier la caractérisation du comportement mécanique de chaque phase et l'étude du comportement multi-phasique. La simulation numérique avec le code éléments finis Cast3M de plusieurs procédés de soudage permet de comparer les modèles aux résultats expérimentaux. / Due to its microstructural stability, the martensitic steel 'X10CrMoVNb9-1 is considered a candidate for several future high temperatures reactor components. These thick components (200 mm) are assembled by GTA multi-pass welding. This welding process generates complex thermal and thermomechanical cycles in the Heat Affected Zone (HAZ). This thesis is following that of G.-M. Roux. This work of 6 years aims to predict the microstructural state after welding in the HAZ. A first version of a Thermo-Metallurgical-Mechanical model (TMM) has been developed and validated in terms of residual stresses on single-pass welding simple tests. In this thesis a new version of the TMM model is proposed to improve the forecasts in terms of the microstructural state and residual stresses post welding in the HAZ. The main improvements of this model TMM its capabilities to take into account the successive heating and cooling cycles, characterizing the multi-pass welding process. This thesis is based on a detailed modeling approach for phase transformations, namely modeling the transformation base material - austenite during anisothermal complex loadings, modeling transformation austenite - martensite and finally the martensite tempering modeling. Not to mention the characterization of the mechanical behavior of each phase and the study of multiphase behavior. Numerical simulation with the finite element code Cast3M of several welding processes was used to compare models with experimental results.

FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico / CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior / A soldagem multipasse de chapas grossas impÃe à junta soldada um estado de tensÃes residuais que pode ser muito prejudicial quando estas estÃo em serviÃo. Existem vÃrios fenÃmenos capazes de alterar os nÃveis de tensÃes residuais de soldagem nos materiais, um deles à a transformaÃÃo de fases. Este trabalho apresenta um estudo comparativo dos nÃveis de tensÃes residuais em trÃs juntas soldadas, produzidas com metais de adiÃÃo diferentes pelo processo arame tubular. Um arame eletrodo de aÃo inoxidÃvel martensÃtico Fe-12%Cr-5%Ni com baixa temperatura de transformaÃÃo foi o primeiro a ser utilizado, o segundo, um aÃo inoxidÃvel austenÃtico Fe-18,5%Cr-10%Ni, e finalmente, um aÃo baixa liga Fe-1,25%Cr-0,5%Mo. No processo de soldagem foi utilizada uma bancada robotizada com fonte multiprocesso para confecÃÃo das juntas, sendo o aÃo ABNT 4140 o metal de base. As tensÃes residuais foram medidas na superfÃcie das juntas soldadas atravÃs do mÃtodo de difraÃÃo de raios-X. TambÃm foram avaliadas as seguintes propriedades mecÃnicas; resistÃncia à traÃÃo, tenacidade e microdureza, bem como, as microestruturas resultantes na zona fundida, zona afetada pelo calor e metal de base. Os resultados mostraram que a junta produzida com arame eletrodo que sofreu transformaÃÃo martensÃtica a baixa temperatura apresentou nÃveis considerÃveis de tensÃo residual compressiva, ao contrÃrio das demais juntas que apresentaram tensÃo residual trativa na maioria dos pontos medidos. Nos ensaios de traÃÃo, a junta de baixa temperatura de transformaÃÃo martensÃtica apresentou elevados limites de escoamento e de resistÃncia à traÃÃo, e a sua ruptura ocorreu na interface entre o metal de base e o metal de solda. Nos ensaios de impacto da mesma junta, os valores de energia absorvida no metal de solda e zona termicamente afetada se apresentaram relativamente baixos. / The multi-pass welding of thick plates imposes to the welded joint a state of residual stresses that can be very harmful when they are in service. There are various phenomena that can alter the levels of residual stresses after materials welding; one of them is phase transformation. This work presents a comparative study of the levels of residual stresses in three welded joints, produced with different filler metals by Flux Cored Arc Welding (FCAW). A martensitic stainless steel wire Fe-12% Cr-5% Ni with low transformation temperature was the first to be used. After this an austenitic stainless steel Fe-18.5% Cr-10% Ni was used and finally a low alloy steel Fe -1.25% Cr-0.5% Mo. In the welding process, we used a workbench robot with multiprocess source for making joints, and the AISI 4140 the base metal.. Residual stresses were measured on the surface of welded joints using X-ray diffraction method. Tensile strength, toughness and hardness, as well as the resultant microstructure in weld metal, heat affected zone and base metal were evaluated. The results showed that the joint produced with wire electrode that has undergone low temperature martensitic transformation presents significant levels of compressive residual stress, unlike the other joints which present tensile residual stress at most of the measured points. In tensile tests, the joint of martensitic stainless steel showed high yield limits and tensile strength, and its rupture occurred at the interface between base metal and weld metal. Results of the impact tests of this joint showed relatively low absorbed energy values at the weld metal and heat affected zone.

S'il est indéniable que de nos jours la traduction automatique (TA) facilite la communication entre langues, et plus encore depuis les récents progrès des systèmes de TA statistiques, ses résultats sont encore loin du niveau de qualité des traductions obtenues avec des traducteurs humains.Ce constat résulte en partie du mode de fonctionnement d'un système de TA statistique, très contraint sur la nature des modèles qu'il peut utiliser pour construire et évaluer de nombreuses hypothèses de traduction partielles avant de parvenir à une hypothèse de traduction complète. Il existe cependant des types de modèles, que nous qualifions de « complexes », qui sont appris à partir d'informations riches. Si un enjeu pour les développeurs de systèmes de TA consiste à les intégrer lors de la construction initiale des hypothèses de traduction, cela n'est pas toujours possible, car elles peuvent notamment nécessiter des hypothèses complètes ou impliquer un coût de calcul très important. En conséquence, de tels modèles complexes sont typiquement uniquement utilisés en TA pour effectuer le reclassement de listes de meilleures hypothèses complètes. Bien que ceci permette dans les faits de tirer profit d'une meilleure modélisation de certains aspects des traductions, cette approche reste par nature limitée : en effet, les listes d'hypothèses reclassées ne représentent qu'une infime partie de l'espace de recherche du décodeur, contiennent des hypothèses peu diversifiées, et ont été obtenues à l'aide de modèles dont la nature peut être très différente des modèles complexes utilisés en reclassement.Nous formulons donc l'hypothèse que de telles listes d'hypothèses de traduction sont mal adaptées afin de faire s'exprimer au mieux les modèles complexes utilisés. Les travaux que nous présentons dans cette thèse ont pour objectif de permettre une meilleure exploitation d'informations riches pour l'amélioration des traductions obtenues à l'aide de systèmes de TA statistique.Notre première contribution s'articule autour d'un système de réécriture guidé par des informations riches. Des réécritures successives, appliquées aux meilleures hypothèses de traduction obtenues avec un système de reclassement ayant accès aux mêmes informations riches, permettent à notre système d'améliorer la qualité de la traduction.L'originalité de notre seconde contribution consiste à faire une construction de listes d'hypothèses par passes multiples qui exploitent des informations dérivées de l'évaluation des hypothèses de traduction produites antérieurement à l'aide de notre ensemble d'informations riches. Notre système produit ainsi des listes d'hypothèses plus diversifiées et de meilleure qualité, qui s'avèrent donc plus intéressantes pour un reclassement fondé sur des informations riches. De surcroît, notre système de réécriture précédent permet d'améliorer les hypothèses produites par cette deuxième approche à passes multiples.Notre troisième contribution repose sur la simulation d'un type d'information idéalisé parfait qui permet de déterminer quelles parties d'une hypothèse de traduction sont correctes. Cette idéalisation nous permet d'apporter une indication de la meilleure performance atteignable avec les approches introduites précédemment si les informations riches disponibles décrivaient parfaitement ce qui constitue une bonne traduction. Cette approche est en outre présentée sous la forme d'une traduction interactive, baptisée « pré-post-édition », qui serait réduite à sa forme la plus simple : un système de TA statistique produit sa meilleure hypothèse de traduction, puis un humain apporte la connaissance des parties qui sont correctes, et cette information est exploitée au cours d'une nouvelle recherche pour identifier une meilleure traduction. / Although communication between languages has without question been made easier thanks to Machine Translation (MT), especially given the recent advances in statistical MT systems, the quality of the translations produced by MT systems is still well below the translation quality that can be obtained through human translation. This gap is partly due to the way in which statistical MT systems operate; the types of models that can be used are limited because of the need to construct and evaluate a great number of partial hypotheses to produce a complete translation hypothesis. While more “complex” models learnt from richer information do exist, in practice, their integration into the system is not always possible, would necessitate a complete hypothesis to be computed or would be too computationally expensive. Such features are therefore typically used in a reranking step applied to the list of the best complete hypotheses produced by the MT system.Using these features in a reranking framework does often provide a better modelization of certain aspects of the translation. However, this approach is inherently limited: reranked hypothesis lists represent only a small portion of the decoder's search space, tend to contain hypotheses that vary little between each other and which were obtained with features that may be very different from the complex features to be used during reranking.In this work, we put forward the hypothesis that such translation hypothesis lists are poorly adapted for exploiting the full potential of complex features. The aim of this thesis is to establish new and better methods of exploiting such features to improve translations produced by statistical MT systems.Our first contribution is a rewriting system guided by complex features. Sequences of rewriting operations, applied to hypotheses obtained by a reranking framework that uses the same features, allow us to obtain a substantial improvement in translation quality.The originality of our second contribution lies in the construction of hypothesis lists with a multi-pass decoding that exploits information derived from the evaluation of previously translated hypotheses, using a set of complex features. Our system is therefore capable of producing more diverse hypothesis lists, which are globally of a better quality and which are better adapted to a reranking step with complex features. What is more, our forementioned rewriting system enables us to further improve the hypotheses produced with our multi-pass decoding approach.Our third contribution is based on the simulation of an ideal information type, designed to perfectly identify the correct fragments of a translation hypothesis. This perfect information gives us an indication of the best attainable performance with the systems described in our first two contributions, in the case where the complex features are able to modelize the translation perfectly. Through this approach, we also introduce a novel form of interactive translation, coined "pre-post-editing", under a very simplified form: a statistical MT system produces its best translation hypothesis, then a human indicates which fragments of the hypothesis are correct, and this new information is then used during a new decoding pass to find a new best translation.

The laser tool is predestined for automated manufacturing processes and has already proven its suit-ability in many areas. In particular, joining technologies in the field of hydrogen production, its storage and for bi-polar plates have to meet the highest requirements in terms of seam quality, reproducibility and manufacturing efficiency. By the examples  700 bar car H2 pressure tank with laser welded connection (welding depth 25 mm)  Laser Remote Welding of HT Fuel Cell Stacks  Laser-welded aluminum tube-ground heat exchanger for gas liquefaction the article presents the possibilities of modern laser beam welding technologies. Furthermore, it gives an outlook on future challenges, especially with regard to the requirements of welding bi-polar plates for upcoming applications in the field of mobility

京都大学 / 新制・課程博士 / 博士(エネルギー科学) / 甲第24926号 / エネ博第468号 / 新制||エネ||88(附属図書館) / 京都大学大学院エネルギー科学研究科エネルギー基礎科学専攻 / (主査)准教授 南 貴司, 教授 稲垣 滋, 教授 田中 仁 / 学位規則第4条第1項該当 / Doctor of Energy Science / Kyoto University / DFAM

The main goal of this master's thesis is to research different approaches of rendering geometries and spaces in virtual reality. Learn more about the terms, non-Euclidean geometry and non-Euclidean spaces, their origin and different principles used in video game industry to simulate such geometries or spaces. Based on the research, a selection of an optimal API is needed for the implementation of such application. Application is designed to run on desktop computers with Microsoft Windows operating system. Application, in it's core, is a video game and the main goal of the player is to successfully complete each and every level of the game. These levels are designed in a specific way so that they each individually represent some form of non-Euclidean geometry or space.

Additive manufacturing processes have been investigated for some years, and are commonly used industrially in the field of plastics for small- and medium-sized series. The use of metallic deposition material has been intensively studied on the laboratory scale, but the numerical prediction is not yet state of the art. This paper examines numerical approaches for predicting temperature fields, distortions, and mechanical properties using the Finite Element (FE) software MSC Marc. For process mapping, the filler materials G4Si1 (1.5130) for steel, and AZ31 for magnesium, were first characterized in terms of thermo-physical and thermo-mechanical properties with process-relevant cast microstructure. These material parameters are necessary for a detailed thermo-mechanical coupled Finite Element Method (FEM). The focus of the investigations was on the numerical analysis of the influence of the wire feed (2.5–5.0 m/min) and the weld path orientation (unidirectional or continuous) on the temperature evolution for multi-layered walls of miscellaneous materials. For the calibration of the numerical model, the real welding experiments were carried out using the gas-metal arc-welding process—cold metal transfer (CMT) technology. A uniform wall geometry can be produced with a continuous welding path, because a more homogeneous temperature distribution results.