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How to Better Identify and Mitigate Risks in Call for Tenders: Towards a Dedicated Risk Ontology
No full textInternational audienceWhen preparing a commercial offer concerning technical systems, suppliers working in engineer to order can either make a detailed design job or just decide key solution choices. With a detailed design, if the customer accepts the offer, the supplier has a good confidence in its ability to provide a solution matching offer contents because requirements have been studied in details. With key technical choices, it is not the case, and the supplier takes the risk of not being able to provide an adequate solution because requirements have been just superficially studied. The goal of the communication is to propose and discuss the key knowledge elements in order to manage this kind of supplier risk when preparing the offer. By management we mean, according to ISO 31000, identifying, assessing and processing risk. The proposed key knowledge elements are a risk taxonomy and a risk mitigation action taxonomy. Actually, risk management relies fully on human expertise, these modeling elements will allow companies to design a knowledge-based system that can assist the human in charge and improve commercial offers quality
Physics of Decision for Polling Place Management: A Case Study from the 2020 USA Presidential Election
No full textInternational audienceIn the context of the global pandemic, the practical management of the 2020 presidential election in the USA was a strong concern. To anticipate and prepare for this election accurately, one of the main challenges was to confront: (i) forecasts of voter turnout, (ii) capacities of the facilities and, (iii) potential configuration options of resources. The approach chosen to conduct this anticipative study consists of collecting data about forecasts and using simulation models to work simultaneously on resource allocation and facility configuration of polling places in Fulton County, Georgia's largest county. This article presents the results of the simulations of such places facing pre-identified potential risks. These results are oriented towards the efficiency of these places according to different criteria (health, trust, comfort). Then a dynamic framework is introduced to describe risks as physical forces perturbing the efficiency of the observed system. Finally, the main benefits and contributions resulting from this simulation campaign are presented
Développement d’une méthode de corrélation d’images numériques en deux dimensions (2D-DIC) pour la mesure de champs de déformation à chaud applicable à la mise en forme d’alliage de titane
No full textTo predict final shape of aerospace parts manufactured by hot forming processes, numerical models by finite elements are usually suggested. To validate these numerical models, it is necessary to develop a reliable full-field measurement method applied for the cooling phase of the part, from 750°C to 25°C. Among kinematic measurement methods, the Digital Image Correlation (DIC) can satisfy this requirement. Nevertheless, the DIC method at high temperatures needs to be improved because of three main problems: i) the speckle resistance, ii) the loss of image contrast and iii) the mirage effect. The study aims to improve the Two-Dimension Digital Image Correlation (2D-DIC) method by dealing with these three problems. First, a speckle fabrication method that can resist high temperatures and high strain is developed. The speckle pattern is repeatable, and its size, distance and density are controlled thanks to a computer-generated speckle pattern. Therefore, the spatial strain resolution is improved. Secondly, the 2D-DIC system is improved for a mechanical test in a limited space (in a closing furnace). Thirdly, correction methods to reduce the influence of mirage effects on strain measurements using the 2D-DIC method is suggested. Results obtained from three studies are then used to measure "small" strain of experimental tests at high temperatures. The Young’s modulus and the Thermal Expansion Coefficient (TEC) of the material are identified from improved 2D-DIC method for temperatures up to 700°C. After corrections, the Young’s modulus and the TEC of the TA6V material are close to reference values found in literature. The coefficient R2 from the linear regression method to determine the Young’s modulus from tensile test at 600 °C increases from 0.783 to 0.989. In conclusion, results show a great potential of using the improved-2D-DIC method for full-field kinematic measurements of mechanical tests at high temperatures. The perspective of this study is to measure thermo-mechanical strain fields on an industrial piece during the cooling phase using the improved-2D-DIC method.Afin de prédire la forme finale des pièces pour les structures aéronautiques après mise en forme à chaud et refroidissement, des modèles de simulations numériques par éléments finis sont utilisés. Pour une validation des champs de déformation obtenus par des modèles de calcul au cours du refroidissement des pièces, il est nécessaire de comparer les résultats calculés à ceux mesurés. Ceci nécessite l'utilisation d'une méthode de mesure fidèle et précise de la cinématique au cours du refroidissement, i.e., lors du passage d’une température de 750°C à 25°C. Parmi les méthodes de mesure de champs, la méthode de corrélation d’images numériques (DIC) peut répondre à cette demande. Cependant, cette méthode nécessite d’être améliorée à hautes températures car elle est moins fiable à cause de trois problématiques : (i) la tenue du mouchetis, (ii) la perte de contraste et (iii) l’effet mirage. L’objectif principal de cette thèse est donc d’améliorer la mesure de champs cinématiques à hautes températures, entre 400°C et 700°C, en utilisant la méthode de corrélation d’images en deux dimensions (2D-DIC), par la levée des trois verrous scientifiques précédemment cités. Premièrement, une méthode de fabrication de mouchetis résistant à hautes températures et à des grandes déformations est développée. Grâce à la génération numérique de mouchetis, ceux-ci sont répétables et leur taille, distance et densité sont contrôlées. La résolution spatiale est donc améliorée. Deuxièmement, la mise en place de système 2D-DIC est optimisée pour les tests mécaniques dans un espace réduit, comme un four fermé. Cette optimisation permet une amélioration notable du contraste de l'image. Troisièmement, des méthodes de correction pour réduire l’erreur de mesure de déformation causée par l’effet mirage sont suggérées. Une application de cette approche est réalisée dans le cadre de la mesure du module de Young et du coefficient de dilatation thermique d'un alliage TA6V jusqu'à 700°C. Après l’application des éléments correctifs proposés aux mesures, les valeurs de module de Young et de coefficient de dilation sont réalisés et les valeurs obtenues sont proches de celles de références présentes dans la littérature. Le coefficient de corrélation linéaire R² de la courbe liant la déformation à la contrainte obtenue lors de l’essai de traction passe, à 600 °C par exemple, de 0,783 à 0,989. Pour conclure, les résultats obtenus dans cette thèse montrent que la méthode 2D-DIC avec les corrections proposées peut être envisagée pour mesurer de manière fiable des champs de déformation lors de tests mécaniques à chaud. Le passage à des mesures sur pièces mise en forme reste à réaliser
Measuring Complexity for Collaborative Business Processes Management
No full textPart 7: Safety and Collaboration ManagementInternational audienceOrganizations are increasingly working on business processes improvement to meet stakeholders’ requirement. Process engineering and improvement projects are challenged by identifying proper metrics to guide improvement effortsand mitigate process complexity. This latter is intuitively related to factors such as usability, modularity, reliability and maintainability. A process that is too complex is more likely to fail and produce costly quality problems. In a context of collaborative decision-making, complexity management must consider the expectations of several stakeholders, and the definition/use of suitable metricsis the starting point. The current paper identifiesandusesa set ofmetrics to enable the evaluation of process models. The proposed metric system is used within a case study highlighting the key role of modularity inmitigating processcomplexity.More generally, the results show how using the metric system can support complexity mitigation and therefore performance improvementin (re)engineered processes
Physical Internet inspired Atomic Modeling for Supply Chain Risk Management
No full textInternational audienceAt a time when instability is the norm, as the global health situation confirms, managers have to deal with increasingly complex situations. Managers expect to have decision support tools that allow them to manage this instability in order to suffer as little as possible. Simulation is one of the main tools to meet this demand. This paper presents the work in progress for the development of a modular supply chain simulation model inspired by the Physical Internet (PI). Its modules are developed from the processes defined in the Supply Chain Operations Reference (SCOR) tool. This simulation model will generate the inputs to apply Physics Of Decision (POD) approach, an innovative approach to risk management approach that draws on analogies with physical forces. This approach is dedicated to steering the performance trajectory of systems evolving in an unstable environment
Thermocline thermal energy storage optimisation combining exergy and life cycle assessment
No full textInternational audienceThermocline thermal energy storage is one of the most promising solutions for recovering waste heat in industrial plants. This paper aims to optimise the shape of a thermal energy storage to minimise its environmental impacts and maximise its exergy efficiency. The reference storage is an existing industrial high-temperature air/ceramic packed-bed heat storage called EcoStock®. The physical model used to determine the performances of the tank is a one dimensional model with two equations: one for the heat transfer fluid and one for the filler material. The environmental impacts are analysed using a life cycle assessment through four selected indicators: cumulative energy demand, global warming potential, abiotic depletion potential and particulate matter. To solve this multi-criteria problem, a particle swarm optimisation algorithm was applied with several exergy and environmental weighting factors. A Pareto set is obtained, bounded by the single exergy or environmental optimisations. Favouring exergy efficiency reduces the volume of the tank. However, environmental footprint of the tank is increased: the indicators of cumulative energy demand and abiotic depletion potential are considerably higher. The shape of the tank evolves with the exergy weight, from a square shape (environmental optimisation) to a tapered shape (exergy optimisation)
Aging
No full textInternational audienceAging applies to the changes in microstructure and properties - mechanical and physical - with time when a material is exposed to high temperatures, high stresses, aggressive chemical environments, and high levels of radiation. The chapter is dedicated to present the microstructure evolution in the bulk, but also at the surface, due to oxidation, of bare and coated (e.g., nickel aluminide, MCrAlY overlay, and γ-γ' coatings) SX superalloys. The isotropic and directional coarsening phenomena are reported at high temperature and their dependence on the loading condition (i.e., uniaxial/multiaxial, tension/compression, creep/fatigue, and isothermal/nonisothermal), the plastic prestraining, and the length scale (micro- vs. meso-scale, viz. dendritic scale) is examined. Furthermore, the phase transformation of coatings due to selective oxidation and interdiffusion with the substrate is presented depending on the thermal conditions (isothermal versus thermal cycling), their chemistry, and that of the substrate. The effects of microstructure evolutions in the bulk and because of the coatings on the mechanical performance - mechanical behavior and lifetime - are discussed. © 2021 Elsevier Inc. All rights reserved
Effect of oxidation on spectral and integrated emissivity of Ti-6Al-4V alloy at high temperatures
No full textInternational audienceThermomechanical simulation is challenging for the optimization and virtual monitoring of high temperature shape processes, such as SuperPlastic Forming (SPF) of Titanium alloys alike Ti-6Al-4V (TA6V). Part of this challenge is the accurate and process-representative knowledge of emissivity, which controls radiative heat transfer during the process. In this paper, the characterization of TA6V emissivity, with regards to its oxidation stage, is performed within the [600–1000 °C] thermal range. The main contribution of this work is the use of an in-house characterization bench, enabling the fast radiative heating of samples, and the control of oxide layers thicknesses ranging from 250 nm to 120 µm. An oxidation law is established thanks to post-mortem mass gain and oxide thicknesses measurement, and the various oxide phases are identified. Oxide thicknesses versus heating time were then calculated and implemented in the emissivity analysis. Two patterns are observed for oxide thickness versus temperature: below 900 °C, emissivity values are quasi-continuously increasing with oxide thickness, exhibiting an oxide layer mainly composed by TiO2, above 900 °C, emissivity values are also continuously increasing but with a different trend, due to the formation of alumina, confirmed by X-Ray Diffraction (XRD) measurements. Finally, the dependence of emissivity to temperature and oxide thickness emphasized in this paper constitutes a non-trivial mandatory input to increase the radiative heat transfer simulations codes accuracy
Navigation autonome d'un robot agricole
No full textNational audienceThis thesis explores the field of agricultural robotics. It aims at developing navigation strategies allowing a mobile robot to navigate safely and autonomously inside a farm. This kind of agricultural environment is highly evolutive and includes many static obstacles (buildings, storage areas, etc.) and dynamic obstacles (cars, agricultural machines, human operators, animals, etc.). The proposed navigation strategy must therefore be both reactive and adaptive. Consequently, this thesis focuses on the design of sensor-based navigation methods (LiDAR, vision, ...) and obstacle avoidance techniques in static but also highly dynamic environments. Due to the diversity of environments and possible cases, we have developed methods that are as generic as possible, able to handle both static and dynamic cases. Thus, we will first introduce the spirals, which allow to obtain relevant and flexible avoidance trajectories. Then, we will present our method of navigation and obstacle avoidance, based on a dynamic parametrization of the spirals according to the evolution of the environment. We will show that due to the generic aspect of spirals, this method can be easily adapted to avoid both static and dynamic obstacles. Finally, these solutions will be first validated in simulation, then implemented on a mobile robot for experiments in real conditions.Le travail sur lequel porte cette thèse s'inscrit dans le domaine de la robotique agricole. Il s'agit de développer des stratégies de navigation permettant à un robot mobile d'évoluer et d'intervenir de manière autonome et en toute sécurité dans une exploitation. Ce type d'environnement agricole est fortement évolutif et comporte de nombreux obstacles statiques (bâtiments, zones de stockage, etc.) et dynamiques (voitures, machines agricoles, opérateurs humains, animaux, etc.). La stratégie de navigation proposée doit donc être à la fois réactive et adaptative. Par conséquent, cette thèse se concentre sur la conception de méthodes de navigation référencées capteurs (LiDAR, vision, ...) et d'évitement d'obstacles en environnements statiques mais aussi fortement dynamiques. De par la diversité des environnements et des cas possibles, nous avons souhaité développer des méthodes qui soient les plus génériques possible, pouvant gérer les cas à la fois statiques et dynamiques. Ainsi, nous introduirons d'abord les spirales, qui permettent d'obtenir des trajectoires d'évitement pertinentes et flexibles. Ensuite, nous présenterons notre méthode de navigation et d'évitement d'obstacles, basée sur une paramétrisation dynamique des spirales en fonction de l'évolution de l'environnement. Nous verrons que de par l'aspect générique des spirales, cette méthode peut être aisément adaptée pour fonctionner dans un cadre statique mais aussi dans un cadre dynamique. Pour finir, ces solutions seront validées en simulation, puis portées sur un robot mobile pour des expérimentations en conditions réelles
Oxidation of Thin Nickel-Based Superalloy Specimens: Kinetics Study and Mechanical Integrity
No full textInternational audienceThe oxidation behavior of a nickel-based superalloy was investigated from 650 to 1,000 °C for up to 1,000 h in air. Samples with thicknesses ranging from 20 to 500 µm were used to document the evolutions of microstructure and oxide scale. Oxidation products and subsurface evolution of the metal microstructure were characterized by XRD and EDS analyses. Local breakaway was observed after 600 h at 800 °C and after 100 h at 900 °C due to the full consumption of Cr from the alloy. Room temperature tensile tests were performed on aged and pre-oxidized specimens with thicknesses ranging from 20 µm to 500 µm, at 800 °C. The results were compared to tensile tests performed on the as-received metallurgical state. Both size effects due to sample thickness reduction and to sample thickness/pre-oxidation width ratio were examined onto the mechanical behavior. Interestingly, the formation of TCP phases, the oxide layer and the subsequent Cr-depleted subsurface region from either aging or oxidation treatments impairs the mechanical integrity. Bulk and subsurface regions are impacted, especially for tens-of-micrometer thin samples