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Special Section Guest Editorial: Quality Control by Artificial Vision VII: Preface
No full textIssue du 16th international conference on quality control by artificial vision 2023 - AlbiInternational audienceGuest Editors Igor Jovančević and Jean-José Orteu introduce the Special Section on Quality Control by Artificial Vision VI
Multi-scale effects of the tool shape and length on the interfacial microstructure and the mechanical behaviour of Al2024/Ti-6Al-4V lap friction stir welds
No full textInternational audienceIn this study, Al2024-T3 aluminium alloy and Ti-6Al-4V titanium alloy were lap jointed by friction stir welding (FSW). New insights are given into the multiscale effects of the pin tip shape and length on both the interface microstructure and the tensile-shear properties of dissimilar joints. The correlation between the stress distribution at the joint interface, governed by the pin shape, and the phase formation sequence was notably studied. The microstructure of the joints was examined from macro-to-nanoscale by optical microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM), while their mechanical properties were investigated with tensile-shear tests, coupled with digital image correlation (DIC). It was found that with a semi-spherical pin tip, the joint interface was sharp and semi-coherent. Al and Ti solid solutions were identified by HRTEM analysis over a distance of 10 nm on both sides of this interface. Conversely, a longer flat pin tip generated a 15 μm thick multi-layered interface containing Ti3Al, TiAl and TiAl3 intermetallic compounds. The effect of the welding conditions on the reaction kinetics during friction stir welding of Al/Ti alloys has been investigated. It was found that the intermetallic compounds were formed by atomic diffusion favoured by both temperature and plastic deformation. The interfacial joint microstructures were explained by the different stress and strain fields generated by the distinct pin tip shapes and by their different penetration depths in the Ti-6Al-4V bottom plate. Although these microstructural features at the joints interface very likely governed the tensile-shear properties of safe joints, they were, in this case, less critical than the hooks and the deformed Alclad layer which led to the joint fracture. Stronger and more ductile joints were obtained with the semi-spherical tip shorter pin. A maximum joint coefficient of 50 % compared to Al2024 base material was found. Some ways of optimization were finally proposed
Increase in elastic and hardness anisotropy of titanium with oxygen uptake due to high temperature oxidation: A multimodal framework using high speed nanoindentation mapping
No full textInternational audienceTitanium and its alloys combine an important mechanical anisotropy and a high capacity to dissolve oxygen. The detailed evolution of the elastic compliance of titanium as a function of its oxygen content is only partially known, despite its importance in structural applications. Here, high speed nanoindentation mapping (HSNM) was conducted on a grade 2 commercially pure titanium (CP-Ti) to probe elastic and hardness anisotropy as well as property evolution as a function of the oxygen content within Ti using pre-oxidized specimens. The oxygen concentration investigated ranged from 600 ppm to 20% atomic. Pre-oxidation of the CP-Ti was performed at 700 °C for 100 h under air to create a gradient of oxygen content within the metal, denoted oxygen-rich layer (ORL). Local oxygen content was quantified using microprobe analyses (EPMA) and crystal orientation using electron backscattered diffraction (EBSD). Reduced modulus and hardness maps were obtained on the pre-oxidized sample within the ORL and far from the ORL using large but highly resolved nanoindentation technique in continuous stiffness measurement (CSM) mode. Data merging techniques were used on this multi-modal dataset to statistically link local mechanical properties to chemical and crystal orientation information. Oxygen insertion in the Ti lattice was found to significantly increase the hardness and elastic moduli of titanium and was correlated to orientation of the c-axis of the α-Ti as a function of the nanoindentation loading direction. Using the Vlassak and Nix theory, it was possible to identify the evolution of the Cij terms of the stiffness matrix as a function of the oxygen content up to 20% at. in O
Biocarbon graphenization processes and energy assessment: Review
No full textInternational audienceReducing energy consumption and environmental impact in the graphenic material production is of foremost importance. While using lignocellulosic biomass is gaining momentum, processing such a non-graphitizable resource is energy consuming as it requires a thermal treatment above 2000 °C. Three alternative carbonization routes are analyzed: catalytic, hydrothermal pre-treatment and solar. We discuss the sustainability of the biocarbon production as compared to conventional high temperature biomass carbonization. The mechanisms of carbonization and graphenization is unveiled using a variety of characterization methods from macroscopic to nanoscopic scale. In catalytic graphenization, it is showed that metal carbides play a crucial role as intermediate phases in the graphenization mechanism. Solar-driven pyrolysis focused intense radiative flux resulting in an improve of the growth and flattening of graphene layers in biocarbon. For each process considered, the operating conditions can finely be tuned to control the graphenization degree, and successfully convert non-graphitizable lignocellulosic biomass into graphenic biocarbon. This review provides new insights on mechanisms in relation to the energy and environmental assessment. For calcium-doped biomass we estimate an energy saving of 22 % when working at 1600 °C compared to carbonization of raw biomass at 2000 °C attributed to the formation of calcium carbide around 1300 °C. Hydrothermal pre-treatment provides a carbon pre-structuration which could save up to 85 % of pyrolysis energy input by lowering the graphenization temperature to 1200 °C, while solar pyrolysis consumes half the energy as compared to the conventional one. This drastically reduces the environmental impact of the biocarbon production
Granulométrie d'un liquide dispersé par explosif
No full textAs part of its studies on detonation, the CEA at Gramat is interested in the dispersion of liquids in air, with high speed/energy constraints and multi-scale aspects. Measuring the particle size of the dispersed liquid is attracting a great deal of interest, but is proving complex because no commercial solution can be used under these particular conditions. However, under these conditions and given the impossibility of using laser sources in a pyrotechnic environment, no commercial solution is available. For this thesis, a new granulometry identification method was developed, based on a measurement known as "extinction", which is particularly easy to deploy and robust in harsh environments. This is a multispectral approach (measurement with cameras or a spectrometer) using a regularised inversion method in the sense of Tikhonov, based on the measure of spectral transmissions and which makes it possible to reconstruct the granulometry of the latter a posteriori using the Beer-Lambert law combined with the Mie model. Given the complexity of the phenomena involved in using explosives for dispersion, the method developed was tested on liquid dispersions reproduced on a small scale on sprays. The general method was developed by exploiting spectral information from controlled water sprays confined in an enclosure placed in a Fourier transform infrared spectrometer (high resolution). However, as this equipment is poorly suited to field conditions, the measurement method was downgraded by using cameras that allow "low resolution" but faster measurements. The use of an infrared camera operating in the 2-5 µm spectral band with spectral filters and a flat black body was therefore tested to monitor changes in spray particle size as a function of time. This method was subsequently applied to water dispersions using explosives, with promising results. The complete measurement and analysis process was therefore validated at each stage of the study.Dans le cadre de ses études sur la détonique, le CEA de Gramat s'intéresse à la dispersion de liquides dans l'air, avec des contraintes de haute vitesse/énergie, et des aspects multi-échelles. La mesure de la granulométrie du liquide dispersé suscite un vif intérêt et s'avère complexe car aucune solution commerciale n'est utilisable dans ces conditions particulières. Toutefois, dans ces conditions et avec l'impossibilité d'utiliser des sources laser en environnement pyrotechnique, aucune solution commerciale n'est disponible. Pour ce travail de thèse, une nouvelle méthode d'identification de la granulométrie a donc été développée, et se base sur une mesure dite "par extinction", particulièrement simple de déploiement et robuste en environnement sévère. Il s'agit d'une approche multispectrale (mesure avec des caméras ou un spectromètre) faisant appel à une méthode d'inversion régularisée au sens de Tikhonov, s'appuyant sur la mesure de transmissions spectrales, et qui permet de reconstruire la granulométrie de ce dernier a posteriori à l'aide de la loi de Beer-Lambert combinée au modèle de Mie. De par la complexité des phénomènes liée à l'usage d'explosif pour la dispersion, la méthode développée a été testée sur des dispersions de liquide reproduites à petite échelle sur des sprays. La méthode générale a été développée en exploitant les informations spectrales provenant de sprays d'eau contrôlés et confinés dans une enceinte placée dans un spectromètre infrarouge à transformée de Fourier (haute résolution). Cependant, cet appareillage étant peu adapté aux conditions terrain, la méthode de mesure a été dégradée en utilisant des caméras permettant des mesures à "faible résolution" mais plus rapides. Ainsi, l'utilisation d'une caméra infrarouge opérant en bande spectrale 2-5 µm avec des filtres spectraux et d'un corps noir plan a été testée pour suivre l'évolution de granulométrie du spray en fonction du temps. Par la suite, cette méthode a pu être appliquée à des dispersions d'eau par explosif et a fourni des résultats prometteurs. La démarche complète de mesure et d'analyse a donc pu être validée à chaque étape de l'étude
Advanced characterization techniques to inform digital twins of deformed Inconel 718 and predict plastic localization using FFT-based simulations
No full textInternational audienceThis work’s long-term objective is to assess the continuity of material deformation at the grain- and mesoscopic scale from processing to subsequent mechanical loading using crystal plasticity strain gradient models. To that end, advanced digital image correlation (HR-DIC) is performed on a pre-deformed microstructure of an Inconel 718, in order to provide plastic localization and discrete slip events necessary to instantiate simulation volumes. A numerical non-local crystal plasticity model has been developed, and implemented using FFT spectral method, to take into account initial deformation gradients and to describe their evolution under different loading conditions. Advanced experiment/simulation dialogue is expected to predict both localization of plastic strain at the sub-grain level and the macroscopic stress-strain behavior in recrystallized and pre-deformed microstructures. The process history of this latter microstructure will be purposely generated using stress-path change strategies on bi-axial specimens
Future AI in crisis management: Proposing a bio-inspired, neuro-symbolic architecture
No full textInternational audienceThis paper addresses the evolving relationship between Artificial Intelligence (AI) and crisis management, spanning over a decade. Initially sparked by social sciences’ interest and facilitated by abundant data, particularly from social media, the collaboration between these fields has streamlined decision-making processes. However, the distinctive, uncertain nature of crises presents challenges in adapting AI to varying contexts. In exploring existing frameworks like Common Operational Picture (COP), Situational Awareness (SA), and Sensemaking, the paper finds a potential misalignment between recent AI architectures, predominantly symbolic or neural, and these established frameworks. To bridge this gap, the paper proposes a bio-inspired neuro-symbolic AI architecture, emphasizing its application at the Sensemaking level during crisis data exploitation. Leveraging insights from neurosciences advancements, the paper aims to enhance the adaptability and effectiveness of AI systems in crisis situation
Latent Thermal Energy Storage System for Heat Recovery between 120 and 150 °C: Material Stability and Corrosion
No full textThis paper is an extended version of our conference proceeding published in Annales du Congrès Annuel dela Société Française de Thermique 2020, Tome 1, Strasbourg, France, 9–12 June 2020, pp. 145–152.DOI : 10.25855/SFT2020-117International audienceThermal energy represents more than half of the energy needs of European industry, but is still misspent in processes as waste heat, mostly between 100 and 200 °C. Waste heat recovery and reuse provide carbon-free heat and reduce production costs. The industrial sector is seeking affordable and rugged solutions that should adapt the heat recovery to heat demand. This study aims to identify suitable latent heat materials to reach that objective: the selected candidates should show good thermal performance that remains stable after aging and, in addition, be at a reasonable price. This paper details the selection process and aging results for two promising phase change materials (PCMs): adipic and sebacic acid. They showed, respectively, melting temperatures around 150 °C and 130 °C, degradation temperatures (mass lost higher than 1%) above 180 °C, and volumetric enthalpy of 95 and 75 kWh·m−3. They are both compatible with the stainless steel 316L while their operating temperature does not exceed 15 °C above the melting temperature, but they do not comply with the industrial recommendation for long-term use in contact with the steel P265GH (corrosion speed > 0.2 mm·year−1)
How partners’ knowledge base and complexity are related to innovative project success: The roles of trust and trust capability of partners
No full textInternational audienceCompetitive pressures and the need for innovation are shaping strategic partnerships. Participants involved in these partnerships share knowledge, collaborate in project activities, and make joint decisions to achieve complex project objectives. However, achieving effective collaboration in partnerships is challenging due to miscommunication, missing skills, missing resources, and lack of trust. This study develops a conceptual model based on existing literature, to investigate the effect of partners’ knowledge bases, project complexity, and trust between partners on innovation and project success. We analyze the model using a survey of managers of European research projects and Partial Least Squares Structural Equation Modeling (PLS-SEM). Our results show the significant impact of changes in a project itself on its success, and the considerable impact of project complexity and trust on the ability of partners to alter the project itself. We also observe the significant impacts of similarity and complementarity of knowledge on trust between partners, and introduce the issue of whether partners jointly command the knowledge needed to complete the project, showing its importance in determining project success
Renewable and high-purity hydrogen from lignocellulosic biomass in a biorefinery approach
No full textInternational audienceUnprecedented efforts are being deployed to develop hydrogen production from bioresources in a circular economy approach, yet their implementation remains scarce. Today’s Challenges are associated with the shortage in the value chain, lack of large-scale production infrastructure, high costs, and low efficiency of current solutions. Herein, we report a hydrogen production route from cellulose pulp, integrating biomass fractionation and gasification in a biorefinery approach. Softwood sawdust undergoes formic acid organosolv treatment to extract cellulose, followed by steam gasification. High-purity hydrogen-rich syngas at a concentration of 56.3 vol% and a yield of 40 g H2 /kg cellulose was produced. Char gasification offers the advantage of producing free-tar syngas reducing cleaning costs and mitigating downstream issues. A comprehensive assessment of mass and energy balance along the hydrogen value chain revealed an efficiency of 26.5% for hydrogen production, with an energy requirement of 111.1 kWh/kg H2 . Optimizing solvent recovery and valorization of other constituents as added-value products in a biorefinery approach would further improve the process and entice its industrial takeoff