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Evaluation des performances des modèles thermodynamiques pour le dimensionnement du procédé de lixiviation HP/HT
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Experimental and numerical investigations of structural inhomogeneity of pharmaceutical compacts
No full textSession W2, Symposium S14Mechanics of porous and granular materialsInternational audiencePowder compaction is widely used in several industrial fields. This forming process is particularly useful to produce complex net shaped compacts. However, the final structural homogeneity of the compact is, among others, dependent on the material behavior, the complex geometry of the punches used, and the wall friction. Understanding of the development of stress and relative density fields in compaction process is thus a crucial step for improving product quality.The aim of this study was to develop a continuum modelling of pharmaceutical powder compaction process to predict structural inhomogeneity of the compact not only due to wall friction but also to the non-uniform applied pressure linked to the embossed punch surface. The development was applied to special configurations in which the upper and lower punch are identically designed with two or multiple deep trapezoidal grooves. The modelling ambition was to capture the density gradient in between opposite grooves, which was suspected as responsible of the compact damage during the unloading. The powder behavior was described in the framework of porous mechanics using the phenomenological model of Drucker Prager Cap (DPC) in which material parameters are density dependent and have been determined by means of diametral and uniaxial failure tests and compaction trials in instrumented die. Simulations of the loading and unloading were performed in 2D plane strain using a finite element method and an explicit integration incorporated in the Abaqus software. Predictions of the density gradient between the opposite grooves were validated using X-ray tomography analyses. Results showed a good agreement between predictions and X-ray tomography measurements. They showed also that the multiple grooves promoted more the structural homogeneity of the compact
Intensification du procédé de mélange des poudres en continu par étagement de l'alimentation (thèse sous embargo)
No full textToday, powder mixing is increasingly considered as a continuous operation, as it offers a number of advantages, including the limitation of certain sources of segregation. However, continuous operation implies the presence of transient regimes, for example at start-up, during which the mixture produced is generally considered out-of-specification. The aim of this thesis is to study ways of intensifying a continuous powder mixing process, for the purpose of reducing the mass of mixture produced during start-up, while maintaining acceptable output homogeneity. To achieve this, a method for determining the time required to reach steady-state was first developed, followed by a study of different feed configurations with the aim of delivering the “right” amount of powder to the “right” place at the “right” time. Shifting the powder feeding to the middle or end of the mixer alters the composition profile within the mixer, enabling several of the segregation mechanisms involved to be identified, and produces a slightly lower mass of mixture produced during the start-up phase than with a conventional feeding. Staging or distributing the feeding over the entire length of the mixer, starting the feeding of one of the powders after the beginning of the experiment, significantly reduces the mass of mixture produced during start-up compared with a conventional feeding, as well as improving the homogeneity of the mixture at the mixer outlet. A Markov chain model based on experimental observations has been developed to predict the mass of mixture produced during start-up for various feed configurations, taking into account certain segregation mechanisms.Aujourd'hui, l'opération de mélange de poudres est de plus en plus souvent envisagée en continu car elle présente de nombreux avantages dont la limitation de certaines sources de ségrégation. Toutefois, le fonctionnement continu implique la présence de régimes transitoires, par exemple au démarrage, pendant lequel le mélange produit est généralement considéré hors-spécification. Cette thèse a pour but d'étudier des moyens d'intensification d'un procédé de mélange de poudres en continu dans l'objectif de réduire la masse de mélange produite au démarrage, tout en conservant une homogénéité de sortie acceptable. Pour cela, une méthode de détermination du temps d'établissement du régime permanent a d'abord été développée puis différentes configurations d'alimentation ont été étudiées dans l'idée d'apporter la « bonne » quantité de poudre au « bon » endroit et au « bon » moment. Décaler l'alimentation d'une poudre au milieu ou à la fin du mélangeur modifie le profil de composition à l'intérieur du mélangeur permettant d'identifier plusieurs mécanismes de ségrégation mis en jeu, et de produire une masse de mélange pendant la phase de démarrage légèrement plus faible qu'avec une alimentation conventionnelle. Etager ou distribuer l'alimentation sur toute la longueur du mélangeur, en démarrant l'alimentation d'une des poudres après le début de l'expérience permet de réduire significativement la quantité de mélange produite au démarrage par rapport à une alimentation conventionnelle, ainsi que d'obtenir une meilleure homogénéité du mélange en sortie de mélangeur. Un modèle markovien basé sur les observations expérimentales a été développé et permet de prédire la masse de mélange produite au démarrage pour diverses configurations d'alimentation en prenant en compte certains mécanismes de ségrégation
Building a collaborative manufacturing system’s network resilience through an adaptability potential analysis
No full textInternational audiencePurpose This research aims to investigate how adaptability potential analysis in collaborative manufacturing networks can be used to enhance resilience when addressing innovative production challenges that require change initiatives. Design/methodology/approach A literature review on collaborative adaptive systems showed a lack of solutions to adapt production to an unpredicted product within a network. A framework is proposed for evaluating the adaptability of collaborative networks and providing inter-system adaptation recommendations. We demonstrate the applicability of this approach through an illustrative experimentation involving a cosmetic company seeking to produce a new product, hydroalcoholic gels in the context of collaborative networks. Findings The experimentation demonstrates that the adaptability analysis based on ontology can help different manufacturing systems make decisions based on their state and limits of capabilities. Also, our adaptation recommendations may help understand the economic impacts of collaboration for different scenarios before launching. Research limitations/implications The research scope does not extend to the consideration of quantity and operational aspects. Additionally, the reconfigurability aspects within each manufacturing system, such as the reordering of layout sequences, have not been addressed yet. Practical implications The results allow organizations to compare resilience states from an individual and collaborative perspective, enabling them to make informed decisions about new production opportunities and effectively navigate the changing manufacturing landscape. Originality/value This research combines capability-based analysis and a collaborative network perspective to streamline decision-making for systems facing new production demands. It provides new insights into effectual decision-making, empowering organizations to skilfully manage unexpected challenges and identify suitable partners accordingly
Solid refuse fuel-derived biocarbons for coal replacement in an industrial process: combustion performances and environmental assessment
No full textInternational audienceAbout 75% of global CO2 emissions (38.8Gt, in 2022) come from the combustion of fossil fuels. In this context, there is an urgent need in the short term to replace coal with biofuel derived from renewable resources such as biomass and waste. Biochar (named biocarbon) is a promising sustainable alternative to replace fossil fuels in industrial energy processes due to its properties closer to those of coal but its biosourced origin. In this context, the objective of this work is assessing coal replacement in an industrial process by biocarbon obtained from solid refuse fuel (SRF) pyrolysis, both in terms of combustion performance and emissions associated
Configuration of Heterogeneous Agent Fleet: a Preliminary Generic Model
No full textInternational audienceA multitude of autonomous agents – encompassing a range of technologies, including robots and drones – represent a crucialmodern tool for the execution of a multitude of tasks, including surveillance, delivery and the saving of lives. In order tooptimally utilise these agents, it is vital to configure each agent, the composition of the entire fleet of agents and the missionplan associated with each agent in the most effective manner possible. The following article presents a knowledge model for theconfiguration of a fleet of heterogeneous agents, encompassing the three levels of configuration: agent configuration, agent fleetconfiguration, and mission plan configuration. It explicitly delineates the relationships between these three configuration levels,thereby facilitating rapid, efficient, robust, and simultaneous configuration. A toy problem illustrates our first proposals
Gas permeability of thermoplastic films at low temperature: effect of glass transition and crystallinity
No full textInternational audienceRecent interest in hydrogen technologies has led to many questions, including how to store hydrogen. Some fields, such as aeronautics, are considering storing hydrogen in the liquid state, i.e. at cryogenic conditions (T<120K) and atmospheric pressure. Polymers and composite materials are good candidates for these storage tanks (high mechanical performance/weight ratio), but the phenomena of gas transport at these temperatures are still poorly understood. This study therefore aimed to characterize the permeability, diffusion and solubility of polymers materials at cryogenic temperatures. A specific experimental permeability test setup was developed for this purpose, which temperature can be controlled down to 55K (-220°C). This original device was used to study the effect of glass transition and crystallinity of semi-crystalline thermoplastic materials on permeability temperature-dependence.The results show that the glass transition reduces the barrier effect of PVDF, while the crystallinityimproves PEKK impermeability at low temperature. Comparison of these two polymer families shows that PVDF has an excellent helium impermeability property that is better than PEKK’s
Grain size effect on strain localization, slip-grain boundary interaction and damage in the Alloy 718 Ni-based superalloy at 650 °C
No full textInternational audienceGrain size effects on the early plastic strain localization and slip transfer at grain boundaries were investigated for the Alloy 718 Ni-based superalloy at 650 °C. Three microstructures with different grain sizes underwent monotonic tensile tests at 650 °C, both in air and under vacuum, until rupture. All the microstructure variants exhibit fully intragranular fracture under vacuum and partially intergranular fracture in air. In this latter case, predominant intergranular fracture mode was found in the fine-grain microstructures. Interrupted tensile tests were also conducted under vacuum with ex-situ SEM high-resolution digital image correlation (HR-DIC) measurements to assess in-plane kinematics fields at the microstructure scale. Out-of-plane displacement jumps were obtained using laser scanning confocal microscopy. Both crystallographic slip within grains and near twin boundaries (TBs) and morphological sliding happening at grain boundaries (GBs) were documented. Statistical analysis of all plastic events aimed at quantifying strain localization distribution as a function of the microstructure. The fine-grain microstructure was found to have extensive strain localization at grain boundaries, while the coarse-grain microstructure is more prone to intragranular slip development and slip localization near TBs. Different scenarios of slip band/grain boundary interactions were evidenced
Influence of semi-crystalline microstructure on gas permeability of Poly(Ether-Ketone-Ketone)
No full textInternational audienceIn a context of ecological transition, aeronautics is moving towards the development of hydrogen-powered aircraft for which lightweight, long-lasting and tough storage tanks must be developed. Among other properties, the tightness of tanks made of polymer and composite materials is of prime importance. This study thus aims at understanding the permeation phenomena through Poly-Ether-Ketone-Ketone (PEKK), which is one of the thermoplastic polymers considered for tank manufacture. In order to better understand the phenomena governing gas permeability, tests were carried out on different PEKK grades of different T/I ratios and degree of crystallinity. The results show that the crystallinity ratio is not the only factor that governs gas diffusion and solubility, but that permeability also depends on PEKK semi-crystalline microstructure. Even if considering crystallites organization through a tortuosity factor improves permeability predictions, permeability can be better understood using a 3 phases description of PEKK microstructure considering distinct contributions of the rigid and mobile amorphous fractions (RAF and MAF). It appears that the MAF permeation does not depend on PEKK T/I ratio, but that gas diffusion and solubility increase for RAF when increasing T/I ratio, thus counterbalancing the blocking effect of crystallites
Un modèle de programmation par contraintes pour la maintenance opérationnelle aéronautique
No full textInternational audienceLes compagnies aériennes cherchent à optimiser leur maintenance pour maximiser le potentiel opérationnel de leur flotte. Leurs objectifs est réduire les coûts de maintenance et d’optimiser la gestion des ressources. Le problème de planification de la maintenance opérationnelle aéronautique est décrit comme un Resource Constrained Project Scheduling Problem (RCPSP). Un modèle de Programmation Par Contraintes (PPC) est utilisé pour résoudre le problème. Une comparaison avec un solveur industriel est proposée sur des instances réelles