Search

International audience; Enterprises now face a global, dynamic, and unpredictable economic environment. In response to quick changes of the demand, the production needs to have the ability to adapt rapidly to meet the production requirements. The Reconfigurable Manufacturing System (RMS) paradigm enables such capabilities. However, defining design and reconfiguration rules is highly challenging, as it requires a broad knowledge encompassing the inclusion of technological, production, and economic metrics, as well as an understanding of a reconfiguration strategy, determining the necessary reconfiguration frequency of the system. For now, no global methodology taking all those aspects into account has been proposed. This article presents an original framework for the design, evaluation, and reconfiguration of the Reconfigurable Production System (RPS). New metrics to measure reconfigurability are defined. The design approach consists in three main steps which are individually developed. The selection of the appropriated production system is based on the comparison of reconfigurability and productivity indicators. Finally, the reconfiguration strategy is presented. The methodology is applied on a case study from the automotive industry.

International audience; Le succès d’un service d’autopartage en free-floating dépend d’une bonne répartition des véhicules dans la ville,c’est-à-dire où et quand les utilisateurs en ont besoin. Celanécessite de prédire la demande des utilisateurs, ce qui représente un défi en raison du peu de données disponibleset de la variabilité de ces demandes. L’objectif de ces prédictions est d’aider à calculer la meilleure relocalisationpossible de voitures pour le jour suivant. Ainsi il est nécessaire de modéliser à la fois une tâche de prédiction dela demande et une tâche d’optimisation du placement desvéhicules. Comme l’optimisation du placement des voituresimplique un raisonnement sur le nombre de voitures à affecter dans des zones précises de la ville, nous proposons deconvertir le problème de prédiction de la demande en prédiction de l’utilisation attendue d’une voiture lorsqu’elleest placée dans une zone de la ville. Nous abordons les défis liés à la modélisation de cette prédiction et du problèmede la relocalisation des véhicules de la flotte du serviced’autopartage. Ainsi, une méthode d’optimisation linéaireen nombres entiers est proposée pour résoudre ce problèmede relocalisation tout en tenant compte de la prédiction del’utilisation des véhicules selon leur placement et des distances de relocalisation. Les expériences se basent sur deuxensembles de données provenant de deux services d’autopartage en free-floating urbains et nous montrons commentnotre méthode peut améliorer les stratégies de relocalisation et donc la rentabilité des services; The success of a free-floating car-sharing service dependson a good allocation of the vehicles across the city, i.e.,where and when they are needed by citizens. This requirespredicting the demand across the geographical regions andacross time, which is challenging due to the sparsity and variability of the data. Furthermore, the purpose of these predictions is to help compute the best possible car relocationfor the next day, hence the need to model both the predictiontask and the optimization task in a compatible way. As theallocation optimization involves reasoning about the number of cars to assign to geographical regions, we proposeto convert the prediction problem into predicting the expected utilization of a car when added to a region. We discussthe challenges in modeling both the machine learning andthe relocation problem, and we propose a mixed-integer linear programming method that solves the relocation problem while taking into account the model predictions andrelocation distances. We experiment with two datasets fromcitywide car sharing companies and show how our methodcan increase the allocation strategies and hence profitability of the services.KeywordsCarsharing, Integer Programming, Regression1 IntroductionL’autopartage en free-floating a émergé comme une nouvelle méthode de transport public dans les zones urbaines.Il contribue à réduire l’empreinte carbone des villes en permettant à des voitures d’être partagées par de multiples utilisateurs en ville. Contrairement aux services d’autopartageone-way, il n’y a pas de stations prédéfinies dans un serviceen free-floating : les voitures peuvent être prises et garéessur n’importe quelle place de parking, généralement en villeet dans ses environs.Quand les utilisateurs d’un service d’autopartage ont besoin d’une voiture, il est indispensable que des véhiculesassez proches soient disponibles. À cette fin, les opérateursemploient du personnel, appelé jockeys, pour repositionnerles véhicules dans la ville. Cette opération est généralementeffectuée de manière empirique, principalement la nuit età petite échelle, avec une connaissance approximative deszones à forte demande où les véhicules doivent être déplacés. Plusieurs articles ont constaté l’absence de stratégies de relocalisation précise, et ont conçus des méthodesqu’un opérateur doit appliquer [16] ou des incitations afinque les utilisateurs envisagent de terminer leurs trajets dansdes zones sélectionnées par l’opérateur [2].Dans cet article, nous cherchons à maximiser l’utilisationde la flotte de voitures d’un service afin de rendre le service durable et rentable pour l’opérateur. Nous considéronsl’utilisation de jockeys pour relocaliser les voitures durantla nuit, comme seule action quotidienne concrète prise parle service d’autopartage pour augmenter l’utilisation de laflotte de véhicules. Par conséquent, l’objectif est de proposer un emplacement pour toutes les voitures de la flotte audébut de la journée, de manière à maximiser l’utilisationdurant la journée prédite des voitures.Il existe plusieurs stratégies pour résoudre ce problème. Laplus précise consisterait à prévoir les déplacements exactsdes clients pour un jour donné, c’est-à-dire le nombre de déplacements, et pour chaque déplacement, l’origine, la destination et l’heure de départ. En sachant cela, nous pourrionsenvisager les différentes manières de relocaliser les voituresau début de la journée afin de maximiser la satisfaction duclient. Ainsi, cela nous permettrait de modéliser la dynamique de la flotte afin de simuler différentes incitations austationnement et stratégies de relocalisation des voitures.Cependant cela est en pratique extrêmement difficile à réaliser. À la place, nous proposons une stratégie alternativemoins fine, mais efficace qui est décomposée en deux parties. Tout d’abord, nous prédisons l’utilisation prévue desvoitures lorsqu’elles sont placées dans des zones bien définies en ville au début de la journée, la prédiction est faiteen minutes d’utilisation. Ensuite en fonction de ces prédictions, une stratégie de relocalisation des voitures est conçueafin de maximiser l’utilisation totale attendue du service enune journée. Le problème de relocalisation est présenté sousla forme d’un problème d’optimisation linéaire en nombresentiers sur les prédictions, assujetti à des contraintes pratiques sur la relocation des véhicules.La Section 2 expose les travaux de l’état de l’art. Une modélisation générale de la ville, une stratégie de prédiction del’utilité d’une voiture et une méthodologie d’affectation desvoitures sont exposées dans la Section 3. La prédiction del’utilité des voitures et la relocalisation des véhicules sontévaluées dans la Section 4 avec deux ensembles de donnéespropriétaires provenant de services réels. Nous concluonsdans la Section 5.

International audience; This study investigates the catalytic activity for soot combustion of Ag nanoparticles dispersed on various supports showing different redox properties. Temperature programmed soot oxidation and isotopic exchange experiments were performed to assess the impact of the soot/catalyst contact, the oxygen partial pressure and the ageing toward activity. Three different contact modes have been used to clearly highlight the catalytic performances: loose, tight and supertight. Whatever the support, in both loose and tight contact modes, the catalytic performances are linked with the Ag surface concentration which was found to be high on zirconia-based catalysts and low on ceria-zirconia. The ignition of the soot combustion process occurs on Ag nanoparticles except for catalysts supported on Yttria-Stabilized Zirconia (YSZ), a pure oxygen ionic conductor, where Ag nanoparticles only promote the run-away of the reaction at higher temperatures. Catalysts based on SiO2, ZrO2 and YSZ exhibit a remarkable hydrothermal stability as performances in tight contact mode are fairly similar after the hydrothermal ageing.

International audience; This paper deals with the computation of the energy profile of a battery electric vehicle in order to find the optimal path in terms of travel time on a defined route in the presence of recharging terminals. The model used in this study to calculate the energy profile must respect constraints such as speed limits, desired initial and final battery energy states, and maximum terminal power. This problem can be written as an Optimal Control Problem and will be solved using the dynamic programming method in order to find the optimal speed and charging quantity at the terminal to save time. The results from a defined scenario show that recharging is done in favour of terminals with a higher maximum power and that our vehicle is constantly driving at the maximum speed allowed. The vehicle can also adapt its speed to reach the next charging station with the consideration of a waiting time at a station. The Dynamic Programming method allows us to respect the final energy constraints and shows that charging at high-powered terminals saves time.

International audience; This study focuses on the prediction of the stability behavior of an industrial automotive brake system under structural and environmental uncertainties. Uncertainties are modeled with a random distribution or an interval and are propagated with a hybrid surrogate model associating polynomial chaos and kriging. The objective is to create a surrogate model of each eigenvalue computed with the complex eigenvalue analysis (CEA). As the modes can be tracked only when unstable, the effective size of the training sets can become extremely small. Despite this limitation, it is shown the hybrid meta-model is still able to predict the stability of the brake system. Moreover, the hybrid meta-model gives a direct access to the mean and variance of the eigenvalues with respect to the design parameters without any additional Monte Carlo simulations (MCS). By considering different probability density function for the friction coefficient, it is shown it has a high influence on the stability and the latter should be accurately estimated.

International audience; The numerical prediction of the dynamic behaviour of mechanical systems subjected to friction-induced vibrations is still a tedious problem. Different methodologies exist nowadays to study it.The first one is the complex eigenvalue analysis, which is widely used by the scientists and the industrials to predict the appearance of instabilities despite its disadvantages. Other methodologies, namely temporal integration and frequential approaches, have been developed to determine the transient and/or the steady-state response toassess the history of the dynamic response, and so to identify the unstable modes involved in the nonlinear dynamic response as well as the vibration levels. However, because of their complex implementation, their high numerical cost and sometimes the strong assumptions made on the form of the solutions, these methods are not widely and currently used in industry. To cope with the limitations of the CEA, namely the over- or under-predictability and the lack of information about modal participations in the nonlinear dynamic response, developing complementary tools is necessary. Thus, this paper is devoted to the extension and generalization of a nonlinear approach, called the modal amplitude stability analysis, to the multi-instability case. The method, called the Generalized Modal Amplitude Stability Analysis (GMASA), allows to identify the evolutions and contributions of unstable modes involved in the nonlinear self-sustaining vibration response and to estimate the limit cycles. The method is applied on a phenomenological system for which it is easy to provide an understanding of the unstable mode(s) contribution to the nonlinear dynamic response of the system and for which the calculations can be performed with reasonable computational times. Thus, the efficiency and validity of the GMASA approach are investigated by comparing the GMASA results with those of the reference results based on temporal approach.

International audience; This work is devoted to the vibroacoustics of complex systems over a broad-frequency band of analysis. The considered system is composed of a complex structure coupled with an internal acoustic cavity. On one hand, the global displacements are associated with the main stiff part and on the other hand, the local displacements are associated with the preponderant vibrations of the flexible subparts. Such complex structures induce interweaving of these two types of displacements, which introduce an overlap of the usual three frequency bands (low-, medium- and high-frequency bands (LF, MF, and HF). A reduced-order computational vibroacoustic model is constructed by using a classical modal analysis with the elastic and acoustic modes. Nevertheless, the dimension of such reduced-order model (ROM) is still important when there is an overlap for each one of the three frequency bands. A multi-frequency reduced-order model is then constructed for the structure over the LF, MF, and HF bands. The strategy is based on a multilevel projection consisting in introducing three reduced-order bases that are obtained by using a spatial filtering methodology. To filter out the local displacements in the structure, a set of global shape functions is introduced. In addition, a classical ROM using acoustic modes is carried out for the acoustic cavity. Then, the coupling between the multilevel ROM and the acoustic ROM is presented. A nonparametric probabilistic modeling is then proposed to take into account the model uncertainties induced by modeling errors that increase with the frequency. The proposed approach is applied to a large-scale computational vibroacoustic model of a car.

Among Series-Parallel Hybrid Electric Vehicle (SPHEV) powertrains, the Power-Split architecture with a planetary gear has an exemplary energetic efficiency in mixed driving conditions. Nevertheless, a simple SPHEV architecture can be realized without a planetary gear. It consists of 2 Electric Machines (EM) mounted on the engine shaft and separated by a clutch. With no power-split operation, this architecture allows the vehicle to operate in pure electric, or series hybrid, or parallel hybrid mode. It was proven to be less efficient than a reference Power-Split SPHEV: the Toyota Hybrid System (THS). The aim of this paper is to investigate the potential of efficiency improvement of the simple SPHEV powertrain by topology modification: the addition of gears for the components or a gearbox with few number of ratios. Two new variants of SPHEVs are proposed. The versions of SPHEVs and the reference THS are optimized by a bi-level optimization technique using Genetic Algorithm and Dynamic Programming. Compared to the simple SPHEV, results show an efficiency worsening in one variant and an efficiency improvement in another variant with a fuel consumption comparable to the one of THS. A global sensitivity study is then performed on the worsened variant. The sensitivities of the added gears are determined and an elimination of some is suggested. A new variant with fewer gears is therefore proposed and optimized. The efficiency is improved but remains less than the one of THS.

International audience; Metamaterials designate structures with properties exceeding bulk materials. Since the end of the 1990s, they have attracted ever-growing attention in many research fields such as electromagnetics, acoustics, and elastodynamics. This paper presents a numerical and experimental study on a locally resonant auxetic metamaterial for vibration isolation. The designed materials combine different mechanisms—such as buckling, local resonances, and auxetism—to generate enhanced isolation properties. This type of structure could help to improve the isolation for machines, transportation, and buildings. First, the static properties of the reference and resonant structures are compared. Dispersion curves are then analysed to describe their periodic dynamic behaviour. An experimental validation carried out on a specially designed test bench is then presented and compared to corresponding finite structure simulation. As a result, huge bandgaps are found for the resonant case and strong isolation properties are also confirmed by the experimental data.

Remote sensing observations suffer significant limitations when used to study the bulk atmospheric composition of the giant planets of our solar system. This impacts our knowledge of the formation of these planets and the physics of their atmospheres. A remarkable example of the superiority of in situ probe measurements was illustrated by the exploration of Jupiter, where key measurements such as the determination of the noble gases' abundances and the precise measurement of the helium mixing ratio were only made available through in situ measurements by the Galileo probe. Here we describe the main scientific goals to be addressed by the future in situ exploration of Saturn, Uranus, and Neptune, placing the Galileo probe exploration of Jupiter in a broader context. An atmospheric entry probe targeting the 10-bar level would yield insight into two broad themes: i) the formation history of the giant planets and that of the Solar System, and ii) the processes at play in planetary atmospheres. The probe would descend under parachute to measure composition, structure, and dynamics, with data returned to Earth using a Carrier Relay Spacecraft as a relay station. An atmospheric probe could represent a significant ESA contribution to a future NASA New Frontiers or flagship mission to be launched toward Saturn, Uranus, and/or Neptune., 27 pages, 9 figures, White Paper submitted in response to ESA's Call for Voyage 2050 Science Themes. arXiv admin note: substantial text overlap with arXiv:1708.00235

Many numerical simulations have been dedicated to the brake squeal prediction by considering the predominant influence of the frictional interface between the pads lining and the disc. However, many others contact interfaces are present in an automotive brake system. Nowadays, the influence of the state of these contacts on the stability behavior of an automotive brake system and thus, on the squeal propensity is not yet well understood. This paper attempts to provide a huge investigation on the sensitivity of squeal propensity to the various contact interfaces between pads, piston, bracket and caliper. The main contribution of the present study aims not only to give a better understanding on the role of these numerous contacts in an automotive brake system but also to propose a strategy based on genetic algorithms in order to reduce the number of simulations to achieve by ranking the effects of all the independent contact states in a pre-design process.

Technological advances, promoted by the Industry 4.0 paradigm, attempt to support the reconfigurability of manufacturing systems and to contribute to adaptive operational conditions. These systems must be responsive to significant changes in demand volume and product mix. In this paper, a hybrid optimisation approach is suggested to solve sequencing and assignment problems of reconfigurable assembly lines, where mobile robots collaborate with human operators. The objectives are: i) to define a schedule of jobs, ii) to assign tasks to the mobile robots, and iii) to decide the allocation of robots to workstations, in order to minimise the number of robots required. Preliminary results show that the proposed methodology can make an efficient robot allocation under high demand variety. In addition to that, the hybrid optimisation approach can be adapted to other configurations of assembly systems, which demonstrates its applicability to solve problems in other contexts.

Brake squeal is a major issue for car manufacturers as it is the reason for the return of many vehicles to customer services, representing high costs for the companies. To meet customer’s expectations, squeal must be accurately predicted during the design process. In the context of the automotive industry, squeal usually refers to friction-induced vibrations that generate noise. The main methodology employed nowadays for friction-induced vibrations prediction of industrial systems is the well-known Complex Eigenvalue Analysis (CEA) despite its limitations. The latter suffers from an under- or over-predictive aspect and the vibration amplitudes cannot be estimated. A recent approach, called the Generalised Modal Amplitude Stability Analysis (GMASA), has been developed as a complementary approach of the CEA to identify the modes involved in the nonlinear dynamic response of systems subjected to friction-induced vibrations and to approximate the quasi-periodic oscillations. The objective of this paper is to predict the nonlinear dynamic response of a full industrial automotive brake system. The GMASA is employed to predict its nonlinear dynamic response. It is demonstrated that when the CEA predicts a single unstable mode, two are actually involved in the nonlinear dynamic response. The quasi-periodic oscillations are analysed, as well as the evolution of the contact conditions at the pad/disc interface and exhibits the presence of micro-impacts.

A new experimental approach is proposed to investigate the friction behaviour and highlight the relationship with the tribofilm formation. It is based on the accumulation of several free dynamic responses of a single-degree-of-freedom damped oscillating system on the same sliding surfaces. By analysing the decreasing amplitude of the damped free dynamic responses and their associated energy decays, it is not only possible to describe the evolution of the tribological behaviour, but also to accurately identify velocity-dependent and velocity-independent friction contributions as the gradually formation of tribofilm. To demonstrate the relevance of this original technique, two tribosystems were studied, each lubricated with either base oil or formulated one, and by comparing the results with those obtained by a conventional linear tribometer.

International audience

International audience; This paper presents the development of analytical solutions for the computation of Eco-Driving cycles for electric vehicles. The task of defining an Eco-Driving strategy is formulated as an Optimal Control Problem aiming to minimize the energy consumed during a trip subject to input and speed constraints. Here, the final time of the driving mission is set as a free parameter and only the relevant terms for the optimization are taken into account. The problem is solved using Pontryagin's Minimum Principle in a systematic way, allowing the derivation of closed-form expressions for the different (un)constrained solutions. The results obtained with the proposed approach are compared to the optimal solution given by Dynamic Programming, where a minor deviation from the optimal consumption is achieved while drastically reducing the computation time of the solution.

International audience; This paper is focused on variable amplitude loading spectra applied in the automotive industry, more specifically for the chassis system parts with respect to high cycle fatigue design. A first analytical model referred to as Heuler's model is considered. It is of the simplest use, with one parameter to be identified. A whole identification process, based on road measurement realized on carmaker's proving ground with instrumented vehicles, is developed and discussed. Once the model is identified, the cycles influence on damage production is also investigated. In the light of the obtained results with this model, a second one, noted modified Heuler's model, is introduced and investigated. This model, similar to the first, requires the identification of two parameters. Once again, the whole model identification process is applied, and the lifetime accuracy is assessed. A new tool is presented, enabling the visualisation on the loading spectrum representation of the most and less damaging cycles. Hence, a methodology is set to legitimize a gate implementation when studying a variable amplitude loading spectrum.

International audience; The reduction of vibration and acoustic levels of structures generally results in solutions with mass addition, which is a problem for products in the transport industry. Some solutions are sometimes studied for only one physical behaviour. This is the case of porous materials that are generally used for thermal insulation and/or sound absorption only. The purpose of this study is to better understand, or even control, the phenomena of dissipation on the vibration of structures when porous materials are inserted on them. To experimentally identify the damping added by the foam on a steel structure, a specific test bench is created. It consists of a foam-plate structure where the displacement field of the plate is measured thanks to a scanning laser vibrometer. For the post-treatment, an inverse method is used to determine locally the structural parameters. The Force Analysis Technique (FAT) and the Corrected Force Analysis Technique (CFAT) are here proposed to determine these structural parameters, such as the equivalent elastic modulus and the loss factor of the assembly. Mainly dissipation causes can contribute to the structure damping: dissipation in the foam skeleton, friction at the interface, viscothermic effects in the cell arrangements. Characterizations of materials properties and finite element models are then implemented to understand the influences of these different causes, depending of the foam and the type of contact at the interface.

International audience; The development of audio systems -as part of the global vehicle engineering process based on performance requirements- should also be driven by objective indicators. Up to now sound quality was mostly assessed from a subjective point of view. After a presentation of the perceived quality dimensions that are currently considered to handle the vehicle system design regarding audio issues, some technical (audio) performances may be easily defined. Nevertheless, sound quality itself remains mostly a subjective matter. New indicators are then proposed to handle some of the sound quality dimensions. In order to be integrated in the engineering process, these indicators may apply to the whole system (including acoustic propagation in the cabin) as well as single electroacoustic or software components. At the moment, they are limited to monophonic signals and tackle both spectral and dynamic (temporal) effects. After those indicators are defined, the results of their subjective assessment by an expert jury will be presented. At last applications for various transducers and associate filters will be presented.

International audience; This study assesses the perceived urgency of warning sounds according to different acoustic parameters. After a definition of a set of acoustic parameters (pulse duration, interpulse interval, frequency, number of bursts, bursts interval, timbre), two methods were investigated and compared in order to understand and optimize the perceived urgency of alert sounds. The first method uses a classical D-optimal Design of experiments, the second method is based on an Interactive Genetic Algorithm (IGA) for the optimization of the fitness of a population of sounds. With these two methods, two within-subjects perceptual tests were carried out during a first session with a panel of 30 participants. To compare the results, a second session was organized with the same participants in order to assess the performances of the optimal sounds generated by both methods. Individual sounds and also sounds at the group level were compared, and the possible interactions between the different acoustics parameters of the alert sounds were investigated. Results shows that the IGA method can be an interesting alternative to classical DOE to help the design of sounds

International audience; This paper introduces, analyzes and validates isogeometric mortar methods for the solution of thick shells problems which are set on a multipatch geometry. A particular attention will be devoted to the introduction of a proper formulation of the coupling conditions, with a particular interest on augmented lagrangian formulations, to the choice and validation of mortar spaces, and to the derivation of adequate integration rules. The relevance of the proposed approach is assessed numerically on various significative examples.

International audience; To face the variable demand of the market, modular and mobile equipment are integrated on production lines. Previous works proposed design and evaluation methodologies to build recon figurable production systems. However, taking the right decision concerning investments and the choice of equipment may be complex. In this paper, we present RAS design from a risk and decision analysis perspective to support decision making. Market demand scenarios are associated with occurrence probabilities. A decision tree represents consecutive scenarios, for which the decision maker is proposed to make a choice regardinginvestments for the assembly line. The utility function is computed based on the decision maker as attitude to risk. The objective function computing the final score of a scenario and a decision covers investments, recon figurability rate and performance of the system. Implications of early investments towards recon gurability can be identi ed. The approach is applied on a real use case from the automotive industry.

International audience; This article explains why current dependability techniques are not suitable for neural networks (NN). It also shows with an experiment that we need to justifiably trust neural networks modeling before formal verification can be used for critical applications.; Cet article montre les limites de l'application des techniques de sureté de fonctionnement actuelles aux réseaux de neurones. Il montre également à l'aide d'une expérience, le besoin d'apporter une confiance justifiée dans les modèles des réseaux de neurones pour permettre l'utilisation de la vérification formelle.

International audience; La maîtrise de la fiabilité dans l'automobile a des enjeux importants sur l'image de marque et la satisfaction client. Ce document présente la méthodologie d'évaluation de la fiabilité basée sur le guide « d'aide à l'estimation et à la validation de la fiabilité automobile » à travers un cas d'application.

International audience; Le but de cet article est de présenter les moyens mis en oeuvre pour protéger les logiciels des calculateurs automobiles de potentielles attaques. Face aux risques cyber sécurité, quelles peuvent être les réponses des concepteurs ?

National audience; To design a mechanical part, engineers need to identify critical areas. They resort to numerical calculations based on finite element models and use deterministic fatigue criteria. However, tests on prototypes do not always validate numerical results. The objective of this work is to improve the identification of critical areas using statistical methods.; Pour dimensionner une pièce en fatigue, les ingénieurs ont besoin d'identifier des zones critiques. Ils ont alors recours à des calculs numériques à l'aide de modèles par éléments finis et utilisent des critères de fatigue déterministes. Cependant, les essais sur des prototypes ne valident pas toujours les résultats numériques. L'objectif de ce travail est d'améliorer l'identification des zones critiques à l'aide de méthodes statistiques.

The study concerns the winding head thermal design of electrical machines in difficult thermal environments. The new approach is adapted for all basic shapes and solves the thermal behaviour of a random wire layout. The model uses the nodal method but does not use the common homogenization method for the winding slot. The layout impact can be precisely studied to find different hotspots. To achieve this a Delaunay triangulation provides the thermal links between adjoining wires in the slot. Vorono&iuml, tessellation gives a cutting to estimate thermal conductance between adjoining wires. This thermal behaviour is simulated in cell cutting and it is simplified with the thermal bridge notion to obtain a simple solving of these thermal conductances. The boundaries are imposed on the slot borders with Dirichlet condition. Then solving with many Dirichlet conditions is described. Some results show different possible applications with rectangular and round shapes, one ore many boundaries, different limit condition values and different layouts. The model can be integrated into a larger model that represents the stator to have best results.

International audience; This paper proposes an original method for characterising the Low Cycle Fatigue (LCF) lifetime using probability density functions. The protocol is based on statistics of microstructure heterogeneities taken as damage initiation sites, a qualitative mechanical analysis of the heterogeneities harmfulness and the definition of a micro-crack growth law. The technique is here established and the associated model identified for a nodular cast iron where the graphite nodules are assumed to be the damage initiation zones. The LCF lifetime is characterised from both a large set of experimental test between 300 and 600 • C and damage observations at the micro-scale. Experimental post-mortem observation combined with a simple numerical study first enable to assume the harmfulness of nodules according to their size and their probable role in the damage process A probability density function for the lifetime is then built from the following steps: (i) a quantitative analysis of the material micro-structure, which provides the probability density of nodules occurrence depending of their size (ii) an extreme value analysis using a Gumbel distribution and (iii) a micro-crack growth law associated with LCF conventional terms of energy densities. Its parameters are obtained using an optimisation process applied to laboratory fatigue experiment. The obtained probability function provides a good match for the lifetime and greatly improves results given by conventional criteria. It moreover provides a robust estimate of the lifetime scatter for different types of fatigue tests.

International audience

National audience; To design a mechanical part, engineers need to identify critical areas. They resort to numerical calculations based on finite element models and use deterministic fatigue criteria. However, tests on prototypes do not always validate numerical results. The objective of this work is to improve the identication of critical areas using statistical methods.; Pour dimensionner une pièce en fatigue, les ingénieurs ont besoin d’identifier des zones critiques. Ils ont alors recours à des calculs numériques à l’aide de modèles par éléments finis et utilisent des critères de fatigue déterministes. Cependant, les essais sur des prototypes ne valident pas toujours les résultats numériques. L’objectif de ce travail est alors d’améliorer l’identification des zones critiques à l’aide de méthodes statistiques.

An important control problem in the automotive powertrain domain is related to the relative use of the two engines of Hybrid Electric Vehicles (HEVs). Aiming to minimize energy and pollutants emissions, this online optimal control problem is highly constrained by the automotive context: very low computing resources, hardly predictable future vehicle dynamic, and need for strong algorithmic robustness. In this framework, the paper proposes two enhancements to the literature reference method. First, an analytical resolution of the optimal control problem is explained, allowing both algorithmic efficiency and simplicity. In the context of Plug-In HEVs, this method needs a battery State of Charge discharge reference, as these vehicles aim to empty their battery in a trip between two charging stations. The literature method aiming to plan this reference at the beginning of the trip fails to conserve optimality in certain heterogeneous trips cases developed in the paper. The second improvement proposed in the paper is then a new method using light cartographic information to deal with problematic cases. This method allows to attain online the optimality of an offline Dynamic Programming algorithm benefiting from a total a priori knowledge of the future powertrain operating points.

International audience; This talk was first given at the LIMOS on July the 9th 2020 and was mainly intended for an audience of non specialists of Gaussian processes (GPs). It was then updated for the GDR MascotNum ETICS2020 school in October and the Webinar Data analytics \& AI at Mines Telecom in November.The first slides (up to slide 12) about GPs and Bayesian Optimization should probably be skipped by readers already aware about these topics.The review of dimension reduction techniques is an attempt at providing a unified point of view on this ubiquitous topic.The two research contributions on variable selection for optimization 1) by kernel methods and, 2) by penalized likelihood in a mapped space, may be of interest to many experts.

International audience; Résumé – cet article présente une étude expérimentale d’une machine Stirling destinée à une application de véhicule hybride. Un prototype de puissance théorique 10 kW a été développé avec le groupe PSA avec comme gaz de travail de l’azote. Le banc d’essai utilisé pour valider le prototype est décrit. Les résultats présentés détaillent la marche du moteur à vide : pression au cours du cycle, températures, couple et vitesse instantanés, pertes dans les circuits de refroidissement.Experimental study of a Stirling engine for a hybrid vehicleAbstract – this article presents an experimental study of a Stirling machine for a hybrid vehicle application. A 10 kW theoretical power prototype has been developed with Groupe PSA using nitrogen as a working gas. The test bench used to validate the prototype is described. The results presents detailed operation of the machine in engine mode at no load : cycle pressure, temperatures, instantaneous torque and speed, losses in the cooling circuits.

National audience; Les faisceaux électriques dans les moyens de transport doivent répondre à de plus en plus d’exigences et de contraintes tel que l’augmentation du nombre de fils liée à la complexité croissante des systèmes embarqués, la diversité importante compte tenu des différentes configurations proposées aux clients, la variabilité de l’environnement thermique, la réduction de l’espace disponible pour le cheminement.En vue de dimensionner les faisceaux de manière optimale (en termes de qualité, de coût, de durabilité et de sûreté de fonctionnement), il est important de comprendre le comportement thermique interne au toron. Le processus de fabrication des faisceaux étant principalement manuel, il induit une variabilité importante dans la position des fils au sein des torons. De plus, la présence de fils dits de "communication" très peu alimentés peut servir de dissipateur thermique tandis que la présence de fils dits de "puissance" favorise l’échauffement thermique.Des essais expérimentaux sont présentés afin d’apprécier le comportement thermique d’un toron de 12 fils dont 6 sont alimentés. Les torons ont été peignés afin d’obtenir 3 dispositions maîtrisées qui ont été testées. Le but de cette étude est de montrer l’impact de la position des fils alimentés dans un toron. Dans un premier cas, les fils alimentés sont concentrés vers le centre du toron. Dans un deuxième cas, les fils alimentés sont positionnés l’extérieur du toron et dans un dernier cas, les fils de faibles sections (alimentés ou non) sont concentrés au centre.Cette étude montre un niveau d’échauffement différent notable dans les fils non alimentés. De plus, il est possible de projeter une tendance de disposition à privilégier pour mieux distribuer la chaleur générée par effet Joule.Cette étude expérimentale est complétée par une comparaison avec un modèle thermique 2D. Ce modèle thermique est basé sur une résolution d’un réseau nodal qui permettra par la suite de se substituer à ces essais.

International audience; The growing need for classical as well as quantum optical sensing places increasingly stringent requirements upon the desired characteristics of the engendered fields. Specifically, achieving superior field enhancement plays a critical role in applications ranging from chem-bio sensing, Raman and infrared spectroscopies to ion trapping and qubit control in emerging quantum-information science. Due to their low optical losses and ability to exhibit resonant field enhancements, all dielectric multilayers are emerging as an optical material system not only useful to classical photonics and sensing but also of potential to be integrated with quantum materials and quantum sensing. The recently introduced concept of zero-admittance layers [1] within dielectric multilayer materials, enables the creation and control of resonant fields orders of magnitude larger than the exciting field. Here, invoking the zero-admittance concept, we design, fabricate, and characterize an all-dielectric nonabsorbing stack and demonstrate the engendered huge field enhancement. Describing the fields in terms of Bloch surface waves, we connect the surface field to the semiperiodicity in the dielectric domains of the stack. As a specific application of the resonant field, we propose and demonstrate refractive-index sensing for the detection of trace amounts of an analyte. The results include a quantification of the sensitivity of the device with respect to the profile of the exciting field. The experimental results are shown to be in good agreement with theoretical calculations.

A detection device (DD) fitted to a vehicle (V) and comprising : - N photodiodes (Pn), with N ≥ 3, fixed in a zone of the vehicle (V) oriented towards the sky, and each delivering signals in the event of detection of photons having wavelengths belonging to at least one predefined interval, - N filters (Fn) placed respectively in front of the N photodiodes (Pn) and allowing passage towards the latter, a computer (CA) determining the heading of the vehicle (V) from the signals delivered by the N photodiodes (Pn) in the same time interval., Un dispositif de détection (DD) équipe un véhicule (V) et comprend : - N photodiodes (Pn), avec N ≥ 3, solidarisées dans une zone du véhicule (V) orientée vers le ciel, et délivrant chacune des signaux en cas de détection de photons ayant des longueurs d'onde appartenant à au moins un intervalle prédéfini, - N filtres (Fn) placés respectivement devant les N photodiodes (Pn) et laissant passer vers ces dernières, de façon privilégiée, des photons ayant respectivement N polarisations linéaires différentes, et - un calculateur (CA) déterminant le cap du véhicule (V) à partir des signaux délivrés par les N photodiodes (Pn) dans un même intervalle de temps.

International audience; Parametric shape optimization aims at minimizing an objective function f(x) where x are CAD parameters. This task is difficult when f is the output of an expensive-to-evaluate numerical simulator and the number of CAD parameters is large. Most often, the set of all considered CAD shapes resides in a manifold of lower effective dimension in which it is preferable to build the surrogate model and perform the optimization. In this work, we uncover the manifold through a high-dimensional shape mapping and build a new coordinate system made of eigenshapes. The surrogate model is learned in the space of eigenshapes: a regularized likelihood maximization provides the most relevant dimensions for the output. The final surrogate model is detailed (anisotropic) with respect to the most sensitive eigenshapes and rough (isotropic) in the remaining dimensions. Last, the optimization is carried out with a focus on the critical dimensions, the remaining ones being coarsely optimized through a random embedding and the manifold being accounted for through a replication strategy. At low budgets, the methodology leads to a more accurate model and a faster optimization than the classical approach of directly working with the CAD parameters.

In this note, we determine the bi-tangents of two rotated ellipses, and we compute the coordinates of their points of tangency. For these purposes, we develop two approaches. The first one is an analytical approach in which we compute analytically the equations of the bi-tangents. This approach is valid only for some cases. The second one is geometrical and is based on the determination of the normal vector to the tangent line. This approach turns out to be more robust than the first one and is valid for any configuration of ellipses.

International audience; The challenges of improving wiring harness designs in automotive, aerospace or transport fields are safety, ecology, weight, and cost. To this end, harnesses require superior thermal management, which involves considering several thermal sources with an uncontrolled layout. To date, the primary methods employed for thermal resolution are based on commercial softwares with meshing capabilities because evaluating temperature evolution influenced by several sources in an uncontrolled wire layout is difficult. This study presents a faster alternative method in which an equation based on the Infinite Line Source (ILS) model is used to create a nodal network. A more efficient matrix mathematical application is adapted to solve faster the ILS model. The ILS model relies on a fully connected node network. The wire bundle is a complex system with a variable environment and an uncontrolled wire layout. This work improves and adapts a fast mathematical model to complex geometries. Thus, the adaptation required by the model involves many assumptions. This new approach was tested on 2-wire and 10-wire layouts and then compared with results obtained by using a commercial software: Ansys Fluent. Some gaps exist between these methods. We propose a corrective model that uses equivalent conductivity to solve that issue.

International audience

This paper demonstrates the use of a new screen-printed corn starch-based sacrificial layer that decomposes entirely thermally at ∼550 °C. A comparison with a polyester-based sacrificial layer used in previous work is made. Both are used to make PZT microcantilevers and discs in a fully screen-printed fabrication process. Both designs are released during the sintering of the ceramics at 900 °C using the new sacrificial layer, with porosities of 6.7% and 2.2% for microcantilevers and discs, respectively.

International audience

The present experimental work investigates the response of woven glass fabric reinforced polyamide 6.6/6 subjected to drop weight impact loading. The main objective is the development and the introduction of a new experimental procedure/approach, based on different complementary detection techniques, that aims at investigating the damage induced by impact loading in thermoplastic woven fabric composites. The developed approach is intended to be generalized to other types of composite materials. The main idea is to assess all the experimental results obtained through the developed procedure with a direct investigation method. The latter consists in the Permanent Indentation (PI) measurement providing an indicator of the damage criticality in the composite sample. To this end, several non-destructive testing methods are carried-out and their experimental findings are analyzed and cross-linked. The identification of the different damage mechanisms, caused by the drop weight impact, is performed using X-Ray micro-computed tomography (mCT). C-scan ultrasonic investigation is conducted according to two types: transmission and reflection for the detection of the impact damage and the identification of the induced degradation area. B-scan imaging are then obtained through specific post-processing of the impacted surface to extract the permanent indentation (PI). The latter is validated through surface flatness measurement using the highly resolved 3D optical profilometry. The correlation between the X-Ray tomography results and the permanent indentation measurement is then established. It correlates the PI level with the damage mechanisms of a barely visible impact damage (BVID) in woven glass reinforced polyamide 6.6/6 composite. The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The present work is co-funded by Groupe PSA and ANRT. It is made in the framework of the OpenLab Materials and Processes involving Groupe PSA, Arts et Metiers (ENSAM) and Georgia Tech Lorraine.

Design of reinforced plastic parts against fatigue failure has become a serious issue these last few years for increasing engineering field applications. This is indeed a complex problem due to the strong anisotropy induced by the orientation of the fibers during the injection process and to the non-linear dissipative behavior of the matrix. This generates strong influences of numerous parameters (fiber orientation, environment, strain rate, load ratio, …), which complicates both the description of the constitutive response and the definition of a robust and efficient fatigue criterion. This paper presents a very wide fatigue database (480 tension-compression tests) obtained on Polyamide 66 reinforced with 50% of glass fibers (PA66 GF50), for an extended range of load ratios (from −0.5 to 0.7), three orientations from the injection direction (0 ° , 45 ° , 90 ° ) and two environmental conditions (50% humidity ratio and 80 ° C, 80% humidity ratio and 23 ° C). Beyond these experimental results, the goal of this paper is to compare the ability of numerous fatigue criteria to provide a robust description of the fatigue database, possibly with a unified set of parameters. Classical models as well as very recent ones are discussed and two variants of a new fatigue criterion are finally defined. This criterion is able to describe very accurately the full database with only four parameters. Finally, a focus is given to determine the minimal amount of experimental data needed to obtain a reliable description of the fatigue results, on the full ranges of load ratios, orientations and environmental conditions.

The objective of the present work was to experimentally investigate flow field instantaneous characteristics and their associated heat transfer for pulsating flows representative of engine exhaust flow operating conditions. The experimental apparatus consists of a stationary turbulent hot air flow, with a variable Reynolds number, excited through a pulsating mechanism and exchanging thermal energy with a water cooled steel pipe. Pulsation frequency ranges from 10 to 95 Hz. Simultaneous time-resolved measurements of velocity and temperature were achieved by mean of coupled hot-wire anemometry and micro-unsheathed thermocouples measurements to investigate the impact of the pulsation frequency on heat transfers. Flow pulsation was found to enhance heat transfers in the entire range of frequencies. Significant improvements were observed when the flow was excited with a frequency equal to a resonant mode of the system. With the increase in velocity-amplitude ratio, an increase in the convective heat transfer was observed, with a maximum enhancement corresponding to a factor three and higher, with respect to the relative Nusselt number. Combining experimental results with an analytical formulation, derived from the 1D energy balance equation for a turbulent pulsating flow, the velocity amplitude ratio was identified as the characteristic term representative of the predominant heat-transfer enhancement mechanism.

Published in Complex Systems Design & Management, Proceedings of the Tenth International Conference on Complex Systems Design & Management, CSD&M Paris 2019, Guy André Boy, Alan Guegan, Daniel Krob, Vincent Vion eds. p. 176-188, Springer 2020; International audience; The safety demonstration and validation of autonomous vehicles (AVs) remains a challenging activity. In this paper, we firstly review what those challenges are and how they affect the safety validation of the AV. Then, we particularly focus on the simulation-based validation process, which seems to be inevitable among the recommended safety validation approaches. We show what is actually done and required in terms of scenarios generation, their assessment taking into account uncertainty and the simulation architecture to test and validate them. Finally, we end our review by summarizing key research questions that need to be addressed to help with this safety validation issue.