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Modeling of streamer in gas by FEM and semi-Lagrangian method
No full textInternational audienceDetermining the likelihood of occurrence, growth and extinction of partial discharges between two conductors is a key point when designing electrical devices such as transformers, electrical machines or busbars. The continuity equations governing both timeand position-dependence of charged particle densities makes it possible to build the most comprehensive model of partial discharge development in gas. Known in the literature as fluid model, plasma model or even electrohydrodynamic model, it consists of a set of advection-diffusion-reaction type equations strongly coupled to Poisson's equation that still remains challenging to solve by means of FEM due to numerical instability. This paper deals with the modeling of spatio-temporal growth of partial discharge inside gas using FEM and stabilized by a semi-Lagrangian method. The main contribution lies in the development of the weak formulation of the state problem in the general case for the electro-hydrodynamic problem. The simulation based on this formulation of the POSS method is validated for a streamer discharge
Liquid metal embrittlement of Cu-30%Zn by EGaIn: Microscale fracture toughness by in situ SEM testing
No full textInternational audienceLiquid Metal Embrittlement (LME) of Cu-30 %Zn brass induced by liquid Ga-In eutectic (EGaIn) is investigated through a novel approach that combines in situ scanning electron microscopy (SEM) and micromechanical testing. Unlike macroscopic measurements, at a small scale, the crack initiation process can be sufficiently monitored such that a crack initiation fracture toughness can be derived using Finite Element Modeling (FEM) both at the continuum level or within a Crystal Plasticity framework (CPFEM). Using this new analysis methodology, the measured fracture initiation toughness values, K ½ Jc = 2.00 (FEM) and 2.36 MPa⋅m (CPFEM), are found to be considerably lower than the ones previously measured in the LME literature, thanks to the minimization of plastic zone size effects. These results highlight the critical role of real-time observations in capturing crack nucleation and open a pathway for direct comparison with atomistic fracture models
Le maintien de la cohérence du jumeau numérique par rapport aux évolutions de son jumeau physique physique
No full textThis thesis proposes a generic and modular Digital Twin architecture centred around a Digital Twin Data Structure (DTDS). The DTDS abstracts the implementation details of physical entities, enabling standard interfaces for Digital Twin services, such as a Decision Support System (DSS). The proposed architecture includes a historical data management module, featuring a data transformation pipeline and an asynchronous data queue to ensure real-time performance. Additionally, coherence maintenance methodologies leverage the DTDS and DSS to synchronise the Digital Twin with its physical twin. The proposed system was validated through experiments using manufacturing equipment in the ENSAM platform and the platform of an academic partner. The evaluation assessed the architecture’s genericity, real-time performance, and effectiveness in integrating Digital Twin services. Results demonstrate the feasibility of a modular, scalable, and fully integrated Digital Twin architecture that incorporates historical data management and supports decision-making. This research contributes to the broader goal of developing a standardised Digital Twin architecture for Industry 4.0 applications in the manufacturing domain.Cette thèse propose une architecture générique et modulaire de jumelage numérique centrée sur une structure de données de jumelage numérique (DTDS). La DTDS fait abstraction des détails de mise en œuvre des entités physiques, permettant des interfaces standard pour les services de jumelage numérique, tels qu'un système d'aide à la décision (DSS). L'architecture proposée comprend un module de gestion des données historiques, avec un pipeline de transformation des données et une file d'attente asynchrone pour obtenir des performances en temps réel. En outre, les méthodologies de maintien de la cohérence s'appuient sur le DTDS et le DSS pour synchroniser le jumeau numérique avec son jumeau physique. Le système proposé a été validé par des expériences utilisant l'équipement de production de la plateforme de l'ENSAM et de la plateforme d'un partenaire universitaire. L'évaluation a vérifié la généricité de l'architecture, les performances en temps réel et l'efficacité de l'intégration des services de jumeau numérique. Les résultats démontrent la faisabilité d'une architecture de jumeau numérique modulaire, évolutive et entièrement intégrée qui incorpore la gestion des données historiques et soutient la prise de décision. Cette recherche contribue à l'objectif plus large de développer une architecture de jumeau numérique normalisée pour les applications de l'industrie 4.0 dans le domaine de la fabrication
Une meilleure circularité des composants d'Electronique de Puissance grâce au passage de l'industrie 4.0 à la circularité 4.0
No full textInternational audienceUne meilleure circularité des composants d'Electronique de Puissance grâce au passage de l'industrie 4.0 à la circularité 4.
Vers un environnement numérique collaboratif pour l'analyse multimodale du comportement de structures
No full textEvaluating the stability of built structures and understanding their structural behavior are critical for shaping their resilience. Heritage buildings present unique challenges in structural diagnosis due to the complexity and diversity of techniques employed throughout their lifecycle. However, interdisciplinary collaboration between Cultural Heritage and Architecture, Engineering, and Construction fields faces obstacles from the heterogeneity of produced information. This often results in linear, disconnected diagnostic processes instead of iterative and integrated ones.This study proposes linking structural diagnostic information and processes using a knowledge graph built on Semantic Web technologies. Its development follows a dual methodological approach: reusing the CIDOC CRM ontology via ontological patterns and defining a system architecture to manage and preserve this information.The study focuses on combining visual inspection data, such as masonry deterioration, with mechanical simulation results using the Discrete Element Method to support decision-making during diagnosis and restoration strategy design. This approach is applied to the structural diagnosis of Notre-Dame de Paris' buttressing system, demonstrated through a proof-of-concept.L'évaluation de la stabilité d'un ouvrage bâti et une bonne compréhension du comportement de sa structure sont des enjeux cruciaux pour construire leur résilience. Parmi eux, les ouvrages patrimoniaux sont autant de cas uniques, présentant des enjeux de diagnostic structurel dont la complexité n'équivaut qu'à la diversité des techniques mises en oeuvre au long de leur cycle de vie. Toutefois, l'effort interdisciplinaires entre les disciplines du Patrimoine Culturel et celles de l'Architecture, Ingénierie et Construction nécessaires à la création du corpus de connaissances adéquat se heurte à l'hétérogénéité des informations produites. Il en résulte des processus de diagnostic linéaires et disjoints, plutôt que cycliques et connectés.Cette étude propose de connecter les informations et processus du diagnostic structurel à travers un graphe de connaissances, basé sur la pile technologique du Web Sémantique. Sa construction repose sur une démarche méthodologique duale: la réutilisation de l'ontologie CIDOC CRM par des motifs ontologiques, et la définition d'un système et de son architecture pour pérenniser et manipuler ces informations.Le point focal de l'étude porte sur la combinaison des informations de l'inspection visuelle, notamment les altérations de la maçonnerie, et les résultats de simulation mécanique par la Méthode des Éléments Discrets, afin d'informer la prise de décision en phase de diagnostic et pour la conception de stratégies de restauration. Cette approche est appliquée au diagnostic structurel du système de contrebutement de la cathédrale Notre-Dame de Paris, et démontrée par une preuve de concept
Automotive battery pack standards and design characteristics: a review
No full textInternational audienceThe latest advancements and near-future trends in automotive battery packs, underlying regulatory compliance, and performance requirements are presented in this paper. In response to these specifications, high-level solutions that converge towards a standard architecture for passenger cars are provided. Transitioning to high-voltage systems (400 V-800 V), which support charging power levels above 350kW, reduces the required current. This, in turn, lowers the weight and volume of cell/module connectors and high-voltage cables in the drivetrain. Additionally, optimization strategies are crucial for enabling fast charging in all conditions, especially in cold climates, while ensuring safe operation, preventing thermal runaway, and reducing charging times to under 20 minutes. Also, advances in energy density (up to 300 Wh/kg) and battery capacities make advancements in enhancing the electric vehicle's range beyond 1000 km per charge. Key factors such as electrical performance, safety, mechanical integrity, reliability, endurance, environmental conditions, and diagnostics are examined. This study explores the next generation of cost-effective and high-performance battery systems and discovers near-future battery technologies, including sodium-ion chemistry and rare-earth-free alternatives, as well as battery applications in aviation
Entre réalité semi-mécanisée et esprit artisanal, la tonnellerie française, une activité économique millénaire
No full textInternational audienceCooperage is the production of wooden barrels of different sizes and volumes. Historically hand-crafted by one person, these containers are now made in semi-mechanised workshops that do not require operator technical skills. Here, we explore how this age-old profession has enough competitors to be of commercial interest.La tonnellerie est la désignation par laquelle on entend la production de tonneaux et de barriques en bois, de différentes hauteurs et volumes. La réalisation de ces contenants, historiquement réalisée à la main par une unique personne, s’opère aujourd’hui dans des ateliers semi-mécanisés où la technicité de l’opérateur n’est pas nécessaire. Enfin, cette profession millénaire présente un nombre suffisant de concurrents pour présenter un intérêt commercial que nous proposons de mettre en lumière. Messages clés :- La tonnellerie produit des barriques et tonneaux en bois dénommés vaisseaux vinaires. - Des procédures spécifiques historiquement artisanales mais actuellement semi-mécanisées sont impliquées dans son fonctionnement.- La formation de ses opérateurs apparaît comme étant inadaptée.- L’activité bénéficie d’une forte concurrence mondialisée
Extending the Lifespan of Garments Globally through Local Upcycling : A Multimethod Approach
No full textInternational audienceExtending the lifespan of garments is considered a solution to counteract a culture that views them as disposable objects. However, how this is to be done in practice remains unclear. Using a multimethod approach, this study aims to investigate how garments can adapt to their local environment(s) and user(s) so that they can go through different life cycles. To this end, the authors combined data from semi-structured interviews conducted in five different countries and enriched them through triangulation with available literature. We discovered that the durability of garments is dynamic in nature, and that upcycling is a method to extend their lifespans. Furthermore, how the materials of the garment are perceived locally, influences if it is considered eligible for upcycling. As local conditions have not been considered in the definition of the concept so far, we have defined local upcycling as: a process in which materials and garments that are considered worth discarding in their current state are transformed into a product of higher value that is suitable for the local environment, eliminating the need for a new product. Although the lack of field research at the organizational level is a limitation of this study, the authors view this as a potential avenue for future research
MemorIA, an Architecture for Creating Interactive AI Historical Agents in Educational Contexts
No full textInternational audienceThis article presents the architecture of MemorIA, an integrative system that combines existing AI technologies into a coherent educational framework for creating interactive historical agents, with the aim of fostering students' learning interest. MemorIA generates animated digital portraits of historical figures, synchronizing facial expressions with synthesized speech to enable natural conversations with students. The system leverages NVIDIA Audio2Face for real‐time facial animation with first‐order motion model for portrait manipulation, achieving fluid interaction through low‐latency audio‐visual streaming. To assess our architecture in a field situation, we conducted a pilot study in middle school history classes, where students and teachers engaged in direct conversation with a virtual Julius Caesar during Roman history lessons. Students asked questions about ancient Rome, receiving contextually appropriate responses. While qualitative feedback suggests a positive trend toward increased student participation, some weaknesses and ethical considerations emerged. Based on this assessment, we discuss implementation challenges, suggest architectural improvements, and explore potential applications across various disciplines
A comparison of process damping modelling as local flank face interaction and as macroscopic modal feature in a time domain machining simulation
No full textInternational audienceDissipative components of tool-workpiece interaction are of major importance in cutting-related vibrations. At the macroscopic vibration scale, such dissipation is usually accounted for by additional generalized damping forces in the equation of motion of the system’s elastodynamics. A finer consideration at cutting edge scale would bring up a line-distributed force mostly of ploughing nature. These two scales are usually linked by analytical integration, involving simplifying kinematical assumptions. In the present work a comparative investigation is proposed, for a machining operation, considering both representations in a detailed time domain modeling framework. Tool’s cutting edges are represented in a discretized manner, i.e. split into numerous elementary cutters allowing for detailed tool-workpiece interaction force distribution. The matter removal process is modeled via dexel-based surface discretization coupled with finite element-based modal shapes, enabling a consistent machined surface generation representation. Finally, the equations of motion are formulated for modal degrees of freedom and solved by a time marching algorithm. Based on these analyses, the limitations of resulting process damping force terms representations are considered regarding vibrations and interaction force magnitudes