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Soudage par ultrasons de composites thermoplastiques à matrice PAEK
No full textThe latest advancements in PAEK matrix composite parts have brought to light assembly issues. Ultrasonic welding represents a promising issue for the largescale use of such parts. Indeed, the process is fast and easy to use. During their development, a polymer film was integrated on the surface of PEEK and AE 250 matrix composites. This film is called an energy director and is necessary for optimizing the assembly. Different energy directors have been used for welding, such as PEEK, PEI and AE 250. Crystallization and rheological analysis have been carried out to characterize the behavior of the new Victrex PAEK AE 250 matrix. In the case of bi-material welding, rheological analysis of PEEK/PEI mixtures has been conducted, giving information about the thermomechanical behaviors during welding. Moreover, a non-intrusive procedure of thermocouple integration allowed measurements of temperature profiles at the interface for different welding conditions. These data were used to develop a finite element model that gives information about the thermal diffusion in the specimen thickness. Finally, single lap shear tests were used to evaluate the influence of different welding conditions on the quality of the weld. The analysis of fracture surfaces allowed a deeper understanding of the physical phenomena occurring during welding. Finally, a parametric study of AE 250 composites welding was compared with the results obtained for PEEK composites joints.Les dernières avancées sur l’application des pièces composites à matrice PAEK ont mis en avant des problématiques d’assemblages. Le soudage par ultrasons représente un enjeu prometteur pour l’utilisation à grande échelle de telles pièces. En effet, il s’agit d’un procédé très rapide et facile d’utilisation. Au cours de l’élaboration des éprouvettes de soudage, un film polymère a été intégré à la surface des composites à matrice PEEK et AE 250. Ce film est appelé directeur d’énergie et est nécessaire pour optimiser l’assemblage. Différents directeurs d’énergie ont été utilisés pour le soudage, tels que le PEEK, le PEI et l’AE 250. Des analyses rhéologiques et de cristallisation ont été réalisées pour caractériser le comportement de la nouvelle matrice Victrex PAEK AE 250. Dans le cas du soudage bi-matériau, une analyse rhéologique de mélanges PEEK/PEI a été réalisée, donnant des informations sur le comportement thermo-mécanique pendant le soudage. En complément, une procédure non-intrusive d’intégration de thermocouples a donné lieu à des mesures de profils de températures à l’interface pour différentes conditions de soudage. Ces données ont permis de développer un modèle par élément finis pour étudier la diffusion thermique dans l’épaisseur des éprouvettes. Enfin des essais mécaniques de cisaillement simple recouvrement ont permis d’évaluer l’influence de différentes conditions de soudage sur la qualité de la soudure. L’analyse des faciès de rupture a permis une compréhension plus approfondie des phénomènes physiques se déroulant pendant le soudage. Enfin, une étude paramétrique du soudage de composites à matrice AE 250 a été réalisée et comparée avec les résultats obtenus pour du soudage de composites à matrice PEEK
Handling Uncertainties with and Within Digital Twins
No full textInternational audienceThe Digital Twin (DT) is often used in environments characterized by uncertainty and complexity, where operating conditions are prone to variability based on external and internal factors. Thus, the literature about DT emphasizes the importance, limitations, and absence of uncertainty quantification. However, there is no explicit review discussing uncertainty in complex systems and within the digital twin model. Such an explicit review could improve the conception, construction, and utilization of DT in environments that are both dynamic and stochastic. Thus, this article aims to (1) describe how a DT can help manage uncertainties in a dynamic system, and (2) explain how DT should deal with uncertainties inside the model
Purification de jus extraits de feuilles de Stevia rebaudiana parprécipitation de sels
No full textInternational audienceStevia rebaudiana is a perennial herbaceous plant, part of the Asteraceae family and native of Paraguay [1]. It has been cultivated in China and Southeast Asia for several decades [2] and more recently in France, in the Occitanie region. More commonly known as “Stevia”, it is a new source of natural sweetener, since it contains steviol glycosides with a sweet taste. The objective of the work carried out is to develop a method of purification of juice extracted from Stevia rebaudiana leaves, pre-purified by various membrane filtration operations, supplied by the company OVIATIS. The objective is to increase the purity of steviol glycosides in these juices, by precipitating impurities such as quinic acid. These juices initially have a purity of 23 ± 2.5 g of glycosides/100 g of dry matter (ie 23%). The tests presented in this study make it possible to assess the impact of the addition of ethanol, whether or not combined with the addition of potassium or calcium hydroxide. The addition of ethanol to the juices leads to an increase in purity and makes it possible to reach a value of 32 ± 3%. By combining the addition of ethanol with the addition of calcium hydroxide, a purity greater than 50% is obtained. Indeed, for a calcium hydroxide ratio of 0.06, the purity reached a level of 56 ± 5% during the test.Stevia rebaudiana est une plante herbacée vivace, faisant partie de la famille des Asteraceae et originaire du Paraguay [1]. Elle est cultivée en Chine et en Asie du sud-est depuis plusieurs décennies [2] et plus récemment en France, en région Occitanie. Plus communément appelée « Stévia », c’est une nouvelle source d’édulcorant naturel, puisqu’elle contient des glycosides de stéviol ayant un goût sucré. Le travail mené a pour objectif de développer une méthode de purification de jus extraits de feuilles de Stevia rebaudiana , pré-purifiés par différentes opérations de filtration membranaire, fournis par la société OVIATIS. L’objectif est d’augmenter la pureté des glycosides de stéviol dans ces jus, en faisant précipiter les impuretés tel que l’acide quinique. Ces jus possèdent initialement une pureté de 23 ± 2,5 g de glycosides/100 g de matières sèches (soit 23 %). Les essais présentés dans cette étude permettent d’évaluer l’impact de l’ajout d’éthanol, combiné ou non à un ajout d’hydroxyde de potassium ou calcium. L’ajout d’éthanol dans les jus entraine une augmentation de la pureté et permet d’atteindre une valeur de 32 ± 3 %. En combinant, l’ajout d’éthanol avec l’ajout d’hydroxyde de calcium, une pureté supérieure à 50 % est obtenue. En effet, pour un ratio d’hydroxyde de calcium de 0,06 la pureté a atteint, au cours de l’essai, un palier à 56 ± 5 %
Stand-alone obstacle avoidance controller for image-based navigation
No full text"© 2023 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.”International audienceIn this paper we present a stand-alone reactive avoidance controller inspired by the spirals described by insects during their flights. Unlike state-of-the-art obstacle avoidance methods, it only focuses on circumventing hazardous elements and can be coupled to navigation controllers working in different state space, such as the image one. We describe the obstacle avoidance problem by following a set of spirals, the spiral parameters computation to deal with convex/concave obstacles, and the spiral following controller design. Finally, a set of simulations obtained with ROS/Gazebo show the efficiency of the proposed approach to navigate in a cluttered environment
A Simulation Framework Dedicated to Characterizing Risks and Cascading Effects in Collaborative Networks
No full textPart 12: Risk and resilience in collaborative networksInternational audienceCascading effects describe risk interdependencies, whereby the occurrence of one risk may trigger one or more risks with potential propagation chains in complex systems. In this study, on the basis of a formalized model namely danger-risk-consequence chain, a generic simulation framework is proposed to characterize risk causal processes and cascading effects within collaborative networks. Risk-related components and the causal relationships between them are visualized by abstractly representing the instantaneous state of the considered collaborative network as a directed graph. Furthermore, the simulation of trajectories of the state evolution over time is realized by knowledge-driven automatic inference of causal chains and propagation chains, thus enabling the tracing of cascading effects within complex systems. The presented simulation framework provides a solid foundation for a systemic understanding of risks, which implies an innovative tool that helps decision-makers to identify, prevent and mitigate cascading effects within collaborative networks (e.g., supply chains)
Persistent physics-based crisis management framework: A case study of traffic in the Nantes city due to flood exposure
No full textInternational audienceIn the context of crisis, the characteristics of the crisis area and the operational measures of the community play key roles in managing the crisis. The Nantes ring road in France is always exposed to flooding and its disruptions. To anticipate the disruptions and timely preventive actions for this frequent phenomenon, the main challenges are (i) forecast of vehicles' flows, (ii) capacity of the ring road to handle the traffic (iii) evaluate the performance of alternate routes during the flooding. The flooded area as a system has components of (i) the flood (e.g. time of onset, magnitude, intensity, etc.), (ii) the area (e.g. geographical features, temporary perimeter barriers, dam, diversion canals), and (iii) the community (e.g. reaction time, emergency strain, evacuation delay). The approach chosen to conduct this anticipative study consists of collecting data about forecasts and using simulation models to work simultaneously on evaluating the performance of the ring road and its alternative routes
Tailoring the Hydroxyl Density of Glass Surface for Anionic Ring-Opening Polymerization of Polyamide 6 to Manufacture Thermoplastic Composites
No full textInternational audienceReactive thermoplastics matrices offer ease of processing using well-known molding techniques (such as Resin Transfer Molding) due to their initially low viscosity. For Polyamide 6 (PA6)/glass composites, the hydroxyl groups on the glass surface slow down the anionic ring-opening polymerization (AROP) reaction, and can ultimately inhibit it. This work aims to thoroughly control the hydroxyl groups and the surface chemistry of glass particulates to facilitate in situ AROP-an aspect that has been barely explored until now. A model system composed of a PA6 matrix synthesized by AROP is reinforced with calcinated and silanized glass microparticles. We systematically quantify, by TGA and FTIR, the complete particle surface modification sequence, from the dehydration, dehydroxylation and rehydroxylation processes, to the silanization step. Finally, the impact of the particle surface chemistry on the polymerization and crystallization of the PA6/glass composites was quantified by DSC. The results confirm that a careful balance is required between the dehydroxylation process, the simultaneous rehydroxylation and silane grafting, and the residual hydroxyl groups, in order to maintain fast polymerization and crystallization kinetics and to prevent reaction inhibition. Specifically, a hydroxyl concentration above 0.2 mmol OH·g−1 leads to a slowdown of the PA6 polymerization reaction. This reaction can be completely inhibited when the hydroxyl concentration reaches 0.77 mmol OH·g−1 as in the case of fully rehydroxylated particles or pristine raw particles. Furthermore, both the rehydroxylation and silanization processes can be realized simultaneously without any negative impact on the polymerization. This can be achieved with a silanization time of 2 h under the treatment conditions of the study. In this case, the silane agent gradually replaces the regenerated hydroxyls. This work provides a roadmap for the preparation of reinforced reactive thermoplastic materials
Rôle du procédé SLM sur la microstructure, la santé métallurgique et les propriétés de superélasticité de l’alliage NiTi
No full textSince the 1990s, endodontic tools used by dentists have evolved from steel to NiTi to exploit the superelastic properties of this shape memory alloy. These very thin tools are quickly damaged and out of order by complex cyclic stresses (tensile/compression fatigue, torsion, wear, etc.). Currently, these tools are manufactured by machining drawn wires (diameter 0.1 to 2 mm) causing a large number of rejects and limiting the freedom on the manufactured geometries. Selective laser melting process (SLM) on a metal powder bed is an advanced process allowing the fabrication of complex geometries with micrometric dimensions and could be suitable to manufacture such tools, by bringing more liberty in their design. This thesis will focus on understanding the relationships between SLM process parameters, microstructure and mechanical properties of as-cast NiTi-SLM sample, in order to identify optimal manufacturing parameters. An "acceptable" melting range, described by volume energy density, was identified using detailed analyses of grain size, microbath depths and porosity rate in the material. An analytical approach considering thermal conduction of heat is used to estimate the depth of these baths and predict the optimal melting parameters. The influence of the manufacturing parameters on the phases, phase transformations and precipitations present in the material is also studied. It reveals 6 main crystallographic structures: NiTiB2, Ni3Ti > Ni4Ti3, NiTiB19’, Ni3TiO5 et NiTi2. The significant peak broadening in XRD and DSC is explained by the presence of oxides associated with these 6 phases, the generation of thermomechanical distortions/stresses during fabrication, and a chemical composition distribution throughout the material. The laser scanning speed has revealed that it generates a strong distortion on the mesh parameters. Finally, the cyclic tensile mechanical properties of the NiTi-SLM samples are found to be much lower than those of the NiTi-drawn samples. Indeed, the NiTi-SLM microstructure generates a low damping rate and a strong plastic damage by micro shear bands through the sample and leading to a mixed brittle-ductile failure.Depuis les années 90, les outils endodontiques utilisés par les dentistes ont évolué de l’acier vers le NiTi pour exploiter les propriétés superélastiques de cet alliage à mémoire de forme. Ces outils très fins sont rapidement endommagés et mis hors d'usage par des sollicitations cycliques complexes (fatigue en traction/compression, torsion, usure, etc.). Actuellement, ces outils sont fabriqués par usinage de fils tréfilés (diamètre 0.1 à 2 mm) provoquant un grand nombre de rebuts et limitant la liberté sur les géométries fabriquées. Le procédé de fusion laser (SLM) sur lit de poudre métallique est un procédé avancé permettant de réaliser des géométries complexes aux dimensions micrométriques et pourrait convenir à la fabrication de tels outils, en apportant plus de liberté dans leur conception. Cette thèse s’attache à comprendre les relations entre les paramètres du procédé SLM, la microstructure et les propriétés mécaniques du NiTi-SLM à l'état brut de fabrication, afin d’identifier des paramètres de fabrication optimaux. Un intervalle de fusion dit "acceptable", décrit par des termes d'énergies volumiques, a été identifié à l'aide d'analyses détaillées de la taille des grains, des profondeurs des micro-bains de fusion et du taux de porosité dans le matériau. Une approche analytique considérant la conduction thermique de la chaleur a été utilisée pour estimer la profondeur de ces bains et prédire les paramètres optimaux de fusion. L’influence des paramètres de fabrication sur les phases, les transformations de phases et les précipitations présentes dans le matériau a aussi été étudiée. Elle a mis en évidence 6 structures cristallographiques principales : NiTiB2, Ni3Ti > Ni4Ti3, NiTiB19’, Ni3TiO5 et NiTi2. L'élargissement important des pics en DRX et DSC a été expliqué par la présence d'oxydes associés à ces 6 phases, à la génération de distorsions/contraintes thermomécaniques lors de la fabrication et à une distribution de composition chimique sur l'ensemble du matériau. La vitesse de balayage laser a révélé qu'elle génère une forte distorsion sur les paramètres de maille. Enfin, les propriétés mécaniques en traction cyclique des échantillons NiTi-SLM se sont révélées très inférieures à celles des NiTi-tréfilés. En effet, la microstructure NiTi-SLM engendre un faible taux d'amortissement et un fort endommagement plastique par des microbandes de cisaillement à travers l'échantillon et menant à une rupture mixte fragile-ductile
The Integration of Risk Aspects into Business Process Management: The e -BPRIM Modeling Method
No full textInternational audienceRisk consideration in enterprise engineering is gaining attention since the business environment is becoming more and more competitive, complex, and unpredictable. Risk-aware Business Process Management (R-BPM) is a recently emerged management paradigm, which assists organizations in addressing this concern. R-BPM strives to integrate two traditionally isolated areas: risk management and business process management. This chapter will present recent achievements of our long-term research devoted to this field. It consists in developing an integrated process-risk management methodological framework, named BPRIM, and its related multi-view modeling method, called e -BPRIM, which promotes and supports risk-aware process management with AdoBPRIM, a computer-assisted modeling environment based on ADOxx. A case study related to the management of the COVID-19 pandemic in France shall illustrate the usage of the e -BPRIM method with the AdoBPRIM modeling environment