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A novel approach to the production of NiCrAlY bond coat onto IN625 superalloy by selective laser melting
No full textInternational audienceThe present study investigated for the first time the feasibility of producing by Selective Laser Melting (SLM) a NiCrAlY bond coat material directly onto an IN625 substrate itself produced by SLM. A typical parameters optimization was conducted by varying laser power (P) and scanning speed (v). Single-line scanning tracks and two-layer coatings were carried out and analyzed for 15 different P/v conditions. Several criteria were defined for the selection of appropriate SLM parameters. The results showed significant remelting of the underlying substrate, which is a typical feature of SLM manufacturing. This led to the formation of an intermediate dilution zone characterized by substantial mixing between IN625 superalloy substrate and NiCrAlY bond coat suggesting excellent metallurgical bonding. Optimum processing conditions were found for P = 250 W and v = 800 mm/s. It produced a dense 242 µm thick bond coat including a 36% dilution zone. The SLMed system exhibited a smooth microhardness profile slightly increasing from 275 Hv in the bond coat to 305 Hv in the substrate. A progressive Al concentration distribution between the phases and low residual stress levels were found in the system. This suggested that SLM might be a valuable alternative manufacturing process for bond coat systems promoting excellent adhesion for high temperature applications
A physics-based theory to navigate across risks and opportunities in the performance space:Application to crisis management
No full textInternational audienceThis article presents an originaltheory for system management, based on physics principles. That theory considers that risks and opportunity can be seen as forces pushing orpulling a system with regards to its objective and its KPIs. Based on that proposal, this article presents the theory,based on (i) identification of susceptibility of systems to internal and external characteristics (danger, favorable conditions), thus creating forces (risks and opportunities),and (ii) evaluation of the sensibility of systems to these forces, thus creating consequences (damages or benefits). This article also presents the practical vision of that theory by detailing the way to observe the force-inducted trajectory of the considered system with regards to its KPIs. An illustrative example and discussions about the perspectives conclude the article
A Tool-Based Framework to Assess and Challenge the Responsiveness of Emergency Call Centers
No full textInternational audienceEmergency call centers (ECCs) are upstream of the prehospital emergency medical system and the life of many people depends on their effectiveness and responsiveness. This notwithstanding, the way their operations are organized and managed differs from one place to another. Also, depending on the number of incoming calls and available resources, they can operate differently. In the face of these heterogeneous situations, some ECCs do not always meet the expected performance levels: people still wait for too long before their call is answered. Moreover, they may have difficulties in managing an important upsurge of calls, especially in periods of crisis. Therefore, to support ECCs’ organizational improvement steps, this article aims to develop a tool-based framework that would enable to make clear and objective diagnoses, especially as regards responsiveness. Our proposal allows considering both nominal (normal days) and exceptional (crisis days) demands. It is based on data science, process mining, and discrete event simulation tools. By experimenting it on a French real case, the results show that such a tool-based framework can be very valuable for improving the performance of ECC organizational setups in both normal and disrupted situations
Proposition d'une démarche outillée d'analyse rétrospective du déroulement du programme au bloc opératoire : application à la régulation
No full textInternational audienceAu bloc opératoire, la réalisation du programme prévisionnel est ponctuée de perturbations aléatoires qui peuvent dégrader notablement la performance initialement visée. La régulation a pour mission de piloter l'activité du bloc au quotidien et de réduire les écarts de performance entre le prévisionnel et le réalisé. Pour y parvenir, nous proposons une démarche outillée d'amélioration continue basée sur une analyse rétrospective du déroulement du programme opératoire. Cette démarche a pour but (1) de mettre en évidence les écarts entre le prévisionnel et le réalisé et de déterminer leur(s) cause(s) racine(s) et (2) d'évaluer la pertinence des décisions prises par la régulation pour corriger les écarts. Elle se base sur deux outils : un journal de bord qui permet le recueil de données qualitatives sur la gestion des anomalies et un tableau de bord dont les indicateurs permettent d'objectiver la situation. La méthodologie de conception de cette démarche s'appuie d'abord sur une observation approfondie du terrain. Ensuite, un cycle itératif en trois phases : concevoir, construire et tester permet de construire progressivement la démarche et ses deux outils. Un exemple de l'analyse du déroulement du programme opératoire dans une salle interventionnelle du CH de Narbonne illustrera l'applicabilité de cette démarche outillée
Nouvelle fabrication de l'alliage 625 et du revêtement de liaison MCrAlY par la fusion laser sélective sur lit de poudre et contrôle des microstructures
No full textIn this study, Alloy 625 was fabricated by one of the most commonly used additive manufacturing (AM) methods, laser powder bed fusion (L-PBF), and its mechanical properties were evaluated at various temperatures. The L-PBF fabricated Alloy 625 showed high strength and relatively poor elongation. Thus, some heat treatments were applied to improve its performance. A solid-solution heat treatment with a temperature of more than 1000 °C was applied to the L-PBF Alloy 625, resulting in recrystallization because of high energy stored within the alloy attributed by high density of dislocations. This modified microstructure of the L-PBF Alloy 625 sample showed the required strength under tensile testing at room temperature (higher strength than wrought Alloy 625 and greater elongation than L-PBF as-built alloy). In view of enhancing mechanical properties at high temperature, a grain boundary serration (GBS) heat treatment was specifically designed for L-PBF Alloy 625. Because this was the first attempt to produce GBS in a high-Nb-content alloy, it was necessary to understand its mechanism first. To induce GBS, it is necessary for large solute atoms to move near the grain boundaries (GBs). Therefore, the GBS heat treatment was modified for application to the L-PBF Alloy 625. The specially designed GBS heat treatment successfully induced the zigzag patterns of serrated GBs for the first time. This GBS L-PBF Alloy 625 showed improved high-temperature mechanical properties in terms of increased ductility and elimination of the dynamic strain aging (DSA) effect at elevated temperatures. To further improve the high-temperature property of the L-PBF Alloy 625, NiCrAlY bond coat was applied to the Alloy 625 substrate by the same method (L-PBF) for the first time to improve the efficiency of the production process and increase the resistance to oxidation. Although their different thermal properties led to many trials and errors in the manufacturing of the material, the optimal parameters for applying NiCrAlY bond coat deposition by L-PBF were set and verified to assess the potential for the process to be commercialized. The remelting characteristic of L-PBF induced good metallurgical bonding between the substrate and coating, which indicates good stability. The oxidation behavior of the NiCrAlY-coated Alloy 625 was characterized by thermal gravimetric analysis (TGA) and thermal shock testing; the results indicated that the novel coated material had higher resistance to oxidation than bulk Alloy 625. Therefore, the GBS heat treatment together with efficient NiCrAlY coating can greatly improve the high-temperature mechanical properties of L-PBF manufactured Alloy 625.Dans cette étude, l'alliage 625 a été élaboré par l'une des méthodes de fabrication additive (AM) les plus couramment utilisées, la fusion laser sélective sur lit de poudre (L-PBF), et ses propriétés mécaniques ont été évaluées à différentes températures. L'alliage 625 fabriqué par L-PBF a montré une résistance élevée et un allongement à la rupture médiocre. Ainsi, des traitements thermiques ont été appliqués pour améliorer ses performances. Un traitement thermique de mise en solution à une température supérieure à 1000 °C a été appliquée à l'alliage L-PBF 625, ce qui a entraîné une recristallisation en raison de l’énergie stockée par le matériau attribuée à la forte densité de dislocations présentes dans l’alliage. Cette microstructure modifiée a montré une résistance satisfaisante lors des essais de traction à température ambiante (résistance plus élevée que l'alliage corroyé 625 et allongement supérieur à l'alliage L-PBF brut de fabrication). À l'étape suivante, l'alliage L-PBF 625 recristallisé a été soumis à un traitement thermique de Grain Boundary Serration (GBS, dentelure des joints de grains) pour améliorer ses propriétés mécaniques à haute température. Comme il s'agissait de la première tentative pour générer la GBS d'un alliage à haute teneur en Nb, il était d'abord important de comprendre le mécanisme GBS. Pour induire le GBS, il est nécessaire que les larges atomes de soluté se déplacent près des joints de grains (GB). Par conséquent, le traitement thermique GBS a été modifié pour être appliqué à l'alliage L-PBF 625. Le traitement thermique de GBS spécialement conçu a réussi à induire pour la première fois les motifs en zigzag des GB dentelés. Cet alliage GB-L-PBF dentelé 625 a montré des propriétés mécaniques améliorées à haute température en termes de ductilité accrue et d'élimination de l'effet de vieillissement dynamique (DSA). Pour améliorer davantage les propriétés à haute température de l'alliage L-PBF 625, un revêtement de liaison NiCrAlY a été nouvellement appliqué au substrat en alliage 625 par la même méthode (L-PBF) pour améliorer l'efficacité du processus de production et augmenter la résistance à l'oxydation/corrosion à haute température. Bien que leurs différentes propriétés thermiques aient conduit à de nombreux essais et erreurs dans la fabrication du matériau, les paramètres optimaux ont été définis et vérifiés pour évaluer le potentiel de commercialisation du procédé. La caractéristique de refusion du L-PBF a induit une bonne liaison entre le substrat et le revêtement, ce qui indique une bonne stabilité. Le comportement à l'oxydation de l'alliage 625 revêtu de NiCrAlY a été caractérisé par analyse thermo-gravimétrique (TGA) et des tests de chocs thermiques ; les résultats ont indiqué que le nouveau matériau avait une résistance à l'oxydation plus élevée que l'alliage 625 brut de fabrication. Par conséquent, le traitement thermique de GBS associé à un revêtement NiCrAlY efficace peut améliorer considérablement les propriétés mécaniques à haute température de l'alliage 625 fabriqué par L-PBF
Toward Assessing Physical Internet Potential Benefits for Humanitarian Supply Chains
No full textInternational audienceIn the view of the issues faced by humanitarian organizations to deliver beneficiaries in an effective, efficient and sustainable manner, the Physical Internet (PI) approach offers potential as an appropriate solution. Indeed, its high resilience, adaptability, efficiency and sustainability capabilities are attractive yet need to be proved as relevant and suitable for the humanitarian sector. Based on this consideration, it is judicious to assess the potential benefits of introducing Physical Internet concepts to humanitarian organizations and demonstrate the impact on performance. In this perspective, this paper proposes a methodology to organize such an investigation as well as some first experimental illustrations to present the approach and to highlight early positive insights
Inspection d'assemblages aéronautiques par vision 2D/3D en exploitant la maquette numérique et la pose estimée en temps réel
No full textThis thesis makes part of a research aimed towards innovative digital tools for the service of what is commonly referred to as Factory of the Future. Our work was conducted in the scope of the joint research laboratory "Inspection 4.0" founded by IMT Mines Albi/ICA and the company DIOTA specialized in the development of numerical tools for Industry 4.0. In the thesis, we were interested in the development of systems exploiting 2D images or (and) 3D point clouds for the automatic inspection of complex aeronautical mechanical assemblies (typically an aircraft engine). The CAD (Computer Aided Design) model of the assembly is at our disposal and our task is to verify that the assembly has been correctly assembled, i.e. that all the elements constituting the assembly are present in the right position and at the right place. The CAD model serves as a reference. We have developed two inspection scenarios that exploit the inspection systems designed and implemented by DIOTA: (1) a scenario based on a tablet equipped with a camera, carried by a human operator for real-time interactive control, (2) a scenario based on a robot equipped with sensors (two cameras and a 3D scanner) for fully automatic control. In both scenarios, a so-called localisation camera provides in real-time the pose between the CAD model and the sensors (which allows to directly link the 3D digital model with the 2D images or the 3D point clouds analysed). We first developed 2D inspection methods, based solely on the analysis of 2D images. Then, for certain types of inspection that could not be performed by using 2D images only (typically requiring the measurement of 3D distances), we developed 3D inspection methods based on the analysis of 3D point clouds. For the 3D inspection of electrical cables, we proposed an original method for segmenting a cable within a point cloud. We have also tackled the problem of automatic selection of best view point, which allows the inspection sensor to be placed in an optimal observation position. The developed methods have been validated on many industrial cases. Some of the inspection algorithms developed during this thesis have been integrated into the DIOTA Inspect© software and are used daily by DIOTA's customers to perform inspections on industrial sites.Cette thèse s'inscrit dans le contexte du développement d'outils numériques innovants au service de ce qui est communément désigné par Usine du Futur. Nos travaux de recherche ont été menés dans le cadre du laboratoire de recherche commun "Inspection 4.0" entre IMT Mines Albi/ICA et la Sté DIOTA spécialisée dans le développement d'outils numériques pour l'Industrie 4.0. Dans cette thèse, nous nous sommes intéressés au développement de systèmes exploitant des images 2D ou des nuages de points 3D pour l'inspection automatique d'assemblages mécaniques aéronautiques complexes (typiquement un moteur d'avion). Nous disposons du modèle CAO de l'assemblage (aussi désigné par maquette numérique) et il s'agit de vérifier que l'assemblage a été correctement assemblé, i.e que tous les éléments constituant l'assemblage sont présents, dans la bonne position et à la bonne place. La maquette numérique sert de référence. Nous avons développé deux scénarios d'inspection qui exploitent les moyens d'inspection développés par DIOTA : (1) un scénario basé sur une tablette équipée d'une caméra, portée par un opérateur pour un contrôle interactif temps-réel, (2) un scénario basé sur un robot équipé de capteurs (deux caméras et un scanner 3D) pour un contrôle totalement automatique. Dans les deux scénarios, une caméra dite de localisation fournit en temps-réel la pose entre le modèle CAO et les capteurs mis en œuvre (ce qui permet de relier directement la maquette numérique 3D avec les images 2D ou les nuages de points 3D analysés). Nous avons d'abord développé des méthodes d'inspection 2D, basées uniquement sur l'analyse d'images 2D puis, pour certains types d'inspection qui ne pouvaient pas être réalisés à partir d'images 2D (typiquement nécessitant la mesure de distances 3D), nous avons développé des méthodes d'inspection 3D basées sur l'analyse de nuages de points 3D. Pour l'inspection 3D de câbles électriques présents au sein de l'assemblage, nous avons proposé une méthode originale de segmentation 3D des câbles. Nous avons aussi traité la problématique de choix automatique de point de vue qui permet de positionner le capteur d'inspection dans une position d'observation optimale. Les méthodes développées ont été validées sur de nombreux cas industriels. Certains des algorithmes d’inspection développés durant cette thèse ont été intégrés dans le logiciel DIOTA Inspect© et sont utilisés quotidiennement chez les clients de DIOTA pour réaliser des inspections sur site industriel
Convergence issues in derivatives of Monte Carlo null-collision integral formulations: a solution
No full textInternational audienceWhen a Monte Carlo algorithm is used to evaluate a physical observable A, it is possible to slightly modify thealgorithm so that it evaluates simultaneously A and the derivatives ∂ς A of A with respect to each problem-parameter ς. The principle is the following: Monte Carlo considers A as the expectation of a random variable, this expectation is an integral, this integral can be derivated as function of the problem-parameter to give a new integral, and this new integral can in turn be evaluated using Monte Carlo. The two Monte Carlo computations (of A and ∂ς A) are simultaneous when they make use of the same random samples, i.e. when the two integrals have the exact samestructure. It was proven theoretically that this was always possible, but nothing ensures that the two estimators have the same convergence properties: even when a large enough sample-size is used so that A is evaluated very accurately,the evaluation of ∂ς A using the same sample can remain inaccurate. We discuss here such a pathological example:null-collision algorithms are very successful when dealing with radiative transfer in heterogeneous media, but they are sources of convergence difficulties as soon as sensitivity-evaluations are considered. We analyse theoreticallythese convergence difficulties and propose an alternative solution
Science Fiction: Past and Future Trends of Crisis Management
No full textInternational audienceThis paper is a position paper, presenting an original but very anticipative and mainly imaginative vision of the evolution of the crisis management domain. After analyzing the options to make the past evolutions of that domain somehow explainable (mainly by analyzing the data of all the articles of the last fifteen editions of the ISCRAM conference), the paper aims at providing a framework to assess and evaluate the maturity of the domain of crisis management. Moreover, this framework is also used to tentatively infer some future evolutions and some directions that could be relevant, dangerous, tricky or of great benefit for the crisis management domain. These future trends are mainly based on the current maturity of crisis management (according to the proposed framework) and current or future influential practices, technologies or threats. It will be necessary to wait for fifteen years to see if these bets should be considered as accurate
Characterization of char generated from solar pyrolysis of heavy metal contaminated biomass
No full textInternational audienceSolar pyrolysis of raw and heavy metals (HMs) impregnated willow was performed at different temperatures (600, 800, 1000, 1200, 1400 and 1600 °C) with heating rate of 50 °C/s. CHNS, ICP-OES, SEM-EDX and BET were employed to investigate the effects of temperature and HMs contamination on char properties. The results indicated that a more ordered and aromatic char was formed with increasing pyrolysis temperature. Char carbon contents increased from 70.0% to 88.4% while hydrogen and oxygen contents declined. Char BET surface area firstly increased from 5.3 to 161.0 m2/g with rising the temperature from 600 to 1000 °C, then decreased at higher temperatures due to plastic deformation. Pyrolysis caused alkali and alkaline-earth metals (A&AEMs) enrichment in char as temperature increased from 600 to 800 °C, then their content decreased at higher temperatures. The presence of Cu or Ni led to the decrease of hydrogen and oxygen contents and significant increase of Ni or Cu in char compared with those in raw willow char. Besides, Raman and BET analysis showed that contaminated willow char had a higher ratio of G band area to the integrated area (IG/IAll) and bigger BET surface area than raw material indicating a more organized and porous structure of the char