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Assessing the homogeneity of an alumina/zircon powder mixture at various scales by scanning electron microscopy
No full textInternational audiencePowder mixing is a fundamentally important unit operation in industries handling powders. The purpose ofsuch an operation is to reach a given homogeneity, which has to be defined at a certain scale, theobservation scale, in order to be relevant. This scale is defined by the final product’s requirements.Moreover, the homogeneity of a mixture can hardly be known exactly, and its assessment is always ascientific issue due to theoretical and practical limitations
Kissing Bonds Gezielte Herstellung und Detektion mit Ultraschall
No full textInternational audienceKissing Bonds stellen bei der Verklebung von Faserverbundkomponenten speziell im Luftfahrtbereich eine bisher nicht zufriedenstellend gelöste Fragestellung dar. In dieser Forschungsarbeit wurde versucht, Proben mit Kissing Bonds durch Variation des Mischungsverhältnisses der Komponenten eines Zweikomponentenklebers gezielt herzustellen, wobei als Kriterium galt, dass diese Klebeverbindungen im C-Scan unauffällig sind, aber deutlich schlechtere Scherfestigkeiten als Proben mit einwandfreier Verklebung aufweisen. Anschließend wurden die Proben hinsichtlich der Änderung der Mittenfrequenz mittels Featurescans (F-Scans) geprüft. Als Ultraschallgerät stand hierfür eine USPC 3040S AIRTECH 4000 Tauchtankanlage vom Ingenieurbüro Dr. Hillger mit einem Frequenzbereich von 0,5 30 MHz zur Verfügung. Es war möglich, frequenzbasiert Kissing-Bond-Proben von Gut-Proben zu unterscheiden. Im Folgenden wurde ein Blindtest mit zehn Proben durchgeführt, bei dem mit der entwickelten Methode eine fehlerfreie Selektion in Gut- und Schlechtklebungen möglich war
Toward an agile adaptation of supply chain planning : a situational use case
No full textPart 9: Digital Transformation of Supply ChainInternational audienceThe project CAASC “Cloud Adaptation for an Agile Supply Chain” (French ANR project) aims to develop monitoring services in multi actors supply chain, by integrating uncertainties in supply chain planning and developing adaptation functions to environment changes. In this paper we present a use case in the form of a serious game that aim to emerge and validate the required functionalities for the project. The game simulates a collaborative rolling horizon mid-term planning process. By analyzing its processes and results, we identify the central role of deviations analysis of plans to qualify uncertainties, assess robustness and propose response strategies
Étude de la mise en oeuvre de composites thermostables cyanate-ester pour pièces structurales aéronautiques tièdes
No full textAeronautical parts which operate in high temperature area (300-400°C) are currently made of titanium (aircraft pylon) or composite materials based on epoxy matrix (plenum). In which extent the weight of these pieces could be reduced as well as avoiding their degradation when operating at these working temperature ranges? TACT project (Technologie pour Aérostructures composites Tièdes), overseen by Nimitech Innovation® (Groupe LAUAK), suggests an innovative solution based on the development of high performance composites parts reinforced by carbon fibers (CF) and cyanate ester matrix (CE) through RTM process. The CE resin belongs to the class of high-performance thermosetting polymers and is mainly chosen in this project due to its thermal stability when operating at high temperatures (with a glass transition Tg>300°C), as well as epoxy-like processability. However, the cross-linking reaction exhibits highly exothermic process, resulting in non-linear increase in internal temperature, which may cause a temperature overshoot. The scientific work carried out within this thesis focuses on the problem of overheating of the resin during the highly exothermic polymerization process in the RTM mold. The objective would thus be to control the curing cycle of the composite in order to avoid problems of runaway or degradation during the crosslinking of the matrix. Hence, the thesis is organized as follows: firstly, thermokinetic behavior of CE resin is analyzed during the crosslinking process in order to optimize the curing cycle. Secondly, thermal properties (heat capacity, conductivity, diffusivity) are identified as a function of the conversion degree in order to evaluate the thermal gradient covered by the heat equation making it possible to control the curing along the thickness of the composite. Moreover, the vitrification of the cyanate ester matrix is studied by monitoring the glass transition temperature Tg as a function of the temperature and conversion degree using different methods (DSC, DMA, TMA). Finally, Di-Benedetto model, a vitrification model, is chosen in order to identify the glass transition temperature Tg∞ of a full crosslinked resin.Les pièces situées dans des zones chaudes/tièdes (300-400°C) de l'avion sont actuellement en titane (mât moteur) ou en composite à matrice époxy (plenum). Comment pourrait-on diminuer la masse de ces pièces tout en évitant leur dégradation à hautes températures de fonctionnement ? Le projet TACT (Technologie pour Aérostructures composites Tièdes), porté par Nimitech Innovation® (Groupe LAUAK), propose une solution innovante consistant à mettre en oeuvre par voie RTM des pièces structurales tièdes à base de renfort en fibres de carbone (FC) et de matrice Cyanate ester (CE). Le choix de la matrice thermodurcissable CE est justifié par son caractère thermostable, c'est-à-dire sa capacité d'opérer en continu à de hautes températures de fonctionnement (avec une température de transition vitreuse Tg>300°C). Par ailleurs, elle possède la facilité de mise en oeuvre des époxydes du fait qu'elle s'adapte généralement bien aux paramètres du procédé RTM. Toutefois, l'exothermie élevée de la matrice CE lors de la réticulation implique un gradient de température dans la pièce composite et peut ainsi engendrer des problèmes de surchauffe. Les travaux scientifiques menés dans le cadre de cette thèse se focalisent sur la problématique de surchauffe de la résine pendant le processus de polymérisation très exothermique dans le moule RTM. L'objectif serait ainsi de maîtriser le cycle de cuisson du composite afin d'éviter tout problème d'emballement ou de dégradation pendant la réticulation de la matrice. Dès lors, la thèse s'organise de la manière suivante : dans un premier temps, le comportement thermocinétique de la matrice CE (pure et catalysée) est analysé pendant l'étape de réticulation, et ceci dans l'optique de contribuer à l'optimisation de cycle de cuisson lors de la mise en oeuvre du composite FC/CE par procédé RTM. Ensuite, les propriétés thermiques (capacité calorifique, conductivité, diffusivité) en fonction du degré d'avancement de la résine CE sont menés afin d'évaluer le gradient thermique régi par l'équation de la chaleur permettant de maîtriser la cuisson de la résine dans l'épaisseur. Par ailleurs, la vitrification de la matrice CE est étudiée par le suivi de la température de transition vitreuse Tg en fonction de la température et du taux d'avancement à l'aide de différents techniques de mesure (DSC, DMA, TMA). Enfin, une modélisation de la vitrification à l'aide du modèle Di-Benedetto permettra l'estimation de la température de la transition vitreuse Tg ∞ pour le réseau tridimentionnel entièrement réticulé
Estimer le nombre de solutions sur les contraintes de cardinalité
No full textThe main asset of constraint programming is its wide variety of algorithms that comes from the major areas of artificial intelligence, logic programming and operational research. It offers specialists a limitless range of possible configurations to tackle combinatorial problems, but it becomes an obstacle to the wider diffusion of the paradigm. The current tools are very far from being used as a black-box tool, and it assumes a good knowledge of the field, in particular regarding the parametrization of solvers.In this thesis, we propose to analyze the behavior of cardinality constraints with probabilistic models and counting tools, to automatically parameterize constraint solvers: heuristics of choice of variables and choice of values and search strategies.La richesse de la programmation par contraintes repose sur la très large variété des algorithmes qu’elle utilise en puisant dans les grands domaines de l’Intelligence Artificielle, de la Programmation Logique et de la Recherche Opérationnelle. Cependant, cette richesse, qui offre aux spécialistes une palette quasi-illimitée de configurations possibles pour attaquer des problèmes combinatoires, devient une frein à la diffusion plus large du paradigme, car les outils actuels sont très loin d’une boîte noire, et leur utilisation suppose une bonne connaissance du domaine, notamment en ce qui concerne leur paramétrage. Dans cette thèse, nous proposons d’analyser le comportement des contraintes de cardinalité avec des modèles probabilistes et des outils de dénombrement, pour paramétrer automatiquement les solveurs de contraintes : heuristiques de choix de variables et de choix de valeurs et stratégies de recherche
High temperature micromechanical testing for meso/macroscale characterizations under controlled atmospheres
No full textInternational audienceThe evaluation of the thermomechanical properties within high temperature coated systems for aeronautical turbine applications motivated the concomitant developments of (i) preparation techniques to extract tens-of-micrometre-thick with centimetre-size specimens, and (ii) dedicated mechanical test rigs under highly controlled atmospheres to test them at elevated temperatures. Owing to the high “surface/volume” ratio of micromechanical specimens, a particular attention has be paid on the testing atmospheres in order to limit surface reactivity at high temperature. Freestanding coatings, interdiffusion zones and substrates constitutive of turbine blades were thus tested up to 1100°C to document the gradient of meso/macroscopic mechanical and thermal properties, and in particular, the brittle-to-ductile transition behaviour of the coating material. This recent high temperature micromechanical development enables a better evaluation of the plastic behaviour of coating materials in comparison with previous microtensile devices. Such a database is necessary for materials selection and for feeding numerical models predicting both the high temperature mechanical behaviour and the service life of coated structural components. Furthermore, size effects approach in reactive environments were also explored. Using ultrathin specimens amplify the contribution of the environment due to high “surface/volume” ratio and offer a limited content of reactive elements. The progressive consumption of the reactive element during oxidation allows breakaway phenomenon, also called “reservoir effect”, for short exposures at elevated temperature. The investigation of environmental degradation on the debit in mechanical performance of structural materials is thus possible using large but ultrathin specimens
Revisiting Counting Solutions for the Global Cardinality Constraint
No full textInternational audienceCounting solutions for a combinatorial problem has been identified as an important concern within the Artificial Intelligence field. It is indeed very helpful when exploring the structure of the solution space. In this context, this paper revisits the computation process to count solutions for the global cardinality constraint in the context of counting-based search. It first highlights an error and then presents a way to correct the upper bound on the number of solutions for this constraint
Automatic inspection of aeronautical mechanical assemblies using 2D and 3D computer vision
No full textInternational audienceQuality control is of key importance in the aerospace industry. This paper deals with the automatic inspection of mechanical aeronautical assemblies. For that purpose, we have developed a computer-vision-based system made of a robot equipped with two 2D cameras and a 3D scanner. The 3D CAD model of the mechanical assembly is available. It is used as a reference and it describes the assembly as it should be. The objective is to verify that the mechanical assembly conforms with the CAD model. Several types of inspection are required. For instance, we must check that the needed elements of the assembly are present, and that they have been mounted in the correct position. For this kind of inspection we use the 2D cameras and we have developed inspection solutions based on 2D image analysis. We have found that some types of inspection cannot be performed by using only 2D image analysis. A typical example of such types is detecting the interference between elements. It requires to check if two flexible elements (e.g. cables,harnesses) or a flexible and a rigid element (e.g. pipe, support) are at a safe distance from each other. For this type of situations, we use the 3D data provided by the 3D scanner and we have developed an inspection solution based on 3D point cloud analysis. We have also developed a method to compute the best viewpoints for the sensor held by the robot, in order to obtain an optimal view of each component to be inspected. The view-point selection is performed off-line (before the on-line inspection) and it exploits the CAD model of the mechanical assembly. The proposed automatic computer-vision-based inspection system has been validated in a context of industrial applications. Our software solution for 2D image analysis has been deployed on the robot platform as well as in a hand-held tablet. Since it requires a 3D sensor, our approach based on 3D point cloud has been tested in the robotic context only
Influence du désensimage par traitement thermique sur les propriétés mécaniques de fibres de basalte
No full textNational audienceThis study deals with the effects of desizing by heat cleaning on the mechanical properties of basalt fibers. The heattreatment at 350°C for 10h, considered in this work, leads to a complete desizing of the fibers. The mechanical propertiesof basalt fibers before and after desizing were investigated by single fiber tensile tests. The tensile strength is reduced of34% after desizing while no evolution of the Young’s modulus is observed. SEM micrographs reveals that the defectslocated on the fibers surface are at the origin of the failure. Moreover, since the basalt structure is not modified during thetreatment, the strength loss is only ascribed to sizing layer removal. In fact, the desizing reveals the surface flaws of thefibers and increases their criticality. Tensile specimens of unidirectional composite materials were produced with an epoxymatrix and tested by considering both fibers states. The differences of mechanical properties observed for the compositeparts corresponds to those observed for single fibers. As a consequence, in the composite, the matrix is not able to playthe protective role of the sizing.Cette étude s’intéresse à l’influence du désensimage par traitement thermique sur les propriétés mécaniques de fibres de basalte. Le traitement thermique à 350°C pendant 10 h, considéré dans ces travaux, permet d’obtenir un désensimage complet des fibres. Les propriétés mécaniques des fibres de basalte avant et après désensimage ont été évaluées par essais de traction sur monofilaments. Une diminution de 34% de la résistance mécanique a été observée suite au désensimage tandis qu’aucune différence significative n’a été constatée sur le module d’Young. L’observation au MEB des faciès de rupture montre que les défauts présents à la surface des fibres sont responsables de la rupture. La structure du basalte n’étant pas modifiée au cours du traitement, la perte de résistance mécanique est exclusivement attribuée au désensimage. Celui-ci a révélé les défauts surfaciques des fibres et aggravé leur criticité. Des éprouvettes en matériaux composites unidirectionnels ont été fabriquées avec une matrice époxy et testées en considérant les deux états de fibres. Les différences de propriétés mécaniques observées sur les composites correspondent à celles observées sur les monofilaments. Autrement dit, la présence de la matrice ne permet pas de « protéger » les défauts surfaciques des fibres révélés par le désensimage, comme pouvait le faire l’ensimage
How to overcome the main challenges of SPS technology: Reproducibility, multi-samples and elaboration of complex shapes
No full textInternational audienceThe spark plasma sintering process (SPS) permits the densification of a wide variety of materials [1–2] (metals, alloys, ceramic, polymer, and composites). This breakthrough sintering technique is able to create highly dense materials with micro-structural control and a very short processing time [3–5]. Although it has experienced a very strong growth in the last three decades in terms of publications and patents, its industrialization is still in its infancy. This is mainly due to the fact that only pieces of simple geometries have been densified so far, and that this technology is considered to suffer from a lack of reproducibility and productivity. We will try to show in this chapter how to overcome three of the main challenges of SPS technology: reproducibility, multi-samples, and elaboration of complex shapes