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Udimet 720Li as a potential alternative for optimised aeroengine turbines : Thermophysical and thermomechanical characterisation under wide-ranging testing conditions.
No full textInternational audienceThe need to reduce fuel consumption and emissions is driving advances in aeroengine performance. Efficiency gains are limited by the capacity of the turbine material to withstand the high thermomechanical loads of the combustion process. Nickel-based alloy Udimet 720Li has emerged as a promising alternative to the most widely used Inconel 718 for critical aeroengine components. Nonetheless, its material properties under industry-relevant conditions remain understudied, hindering industrial implementation. Furthermore, discrepancies in the methodology for applying adiabatic heating correction in thermomechanical tests on nickel-based alloys prevent comparability of studies and alloys. This paper presents the thermophysical and thermomechanical properties of forged and heat-treated Udimet 720Li to enable advanced aeroengine design and manufacture. A novel adiabatic heating correction procedure is also proposed for thermomechanical tests. Thermophysical properties (specific heat, density, diffusivity, thermal expansion, and conductivity) were characterised for temperatures 20–1200 °C. Thermomechanical properties were obtained for temperatures 20–1100 °C and strain rates 0.01–100 s-1 with cylinder compression tests. The results show that Udimet 720Li exhibits higher thermomechanical properties than Inconel 718 at elevated temperatures and can withstand greater in-service temperatures (8–23 %) due to the higher γ’ strengthening phase content which remains stable up to 760 °C
A novel fuzzy-logic-improved direct power control strategy for DFIG-based wind turbine through real-time OPAL-RT validation
No full textInternational audienceDirect Power Control for doubly-fed induction generator-based wind turbines are a widely used strategy, but it inherently suffers from significant power ripples and high total harmonic distortion, which compromise grid power quality and can induce mechanical stress on the turbine's drivetrain. To address these critical issues, this paper introduces and validates a novel fuzzy-logic-improved direct power control strategy. The proposed method replaces the conventional hysteresis comparators and switching table with a single, parameter-free fuzzy logic controller that provides a more intelligent and smoother selection of rotor voltage vectors. The performance of this strategy was rigorously evaluated using comprehensive software simulations in MATLAB/Simulink under realistic, variable wind speed with local reactive powers compensation profiles, followed by real-time hardwarein-the-loop validation using an OPAL-RT simulator. The main results demonstrate substantial performance gains over the conventional approach, with the proposed controller achieving a 72.13 % reduction in generated active power ripples and accelerating the control system's response time by up to 31.71 %. Crucially, power quality was significantly enhanced, with the stator current's total harmonic distortion being reduced from 7.06 % to just 2.04 % during super-synchronous operation. The conclusion drawn from these results is that the fuzzy-logic-based approach is a simple and robust solution whose high effectiveness and practical feasibility have been successfully demonstrated in a real-time environment, making it a promising candidate for improving the grid integration of modern wind energy systems.</div
Life Cycle Assessment of PLM System Scenarios: Sensitivity Insights from an Academic Use Case
No full textInternational audienceThe 2020s represent both the digital decade and the pivotal period in the fulfillment of long-standing commitments made by public, private, and institutional actors in favor of sustainable development. In the manufacturing context, Product Lifecycle Management (PLM) systems are used during the design phase to reduce product environmental footprint. However, only a few studies have thoroughly identified the environmental impacts associated with these technological solutions. This study proposes a sensitivity analysis of five environmental impact categories associated with two PLM system architectures and three mitigation scenarios. To this end, we use an engineering school as a representative PLM system case study, relying on the Life Cycle Assessment (LCA) methodology and leveraging specialized tools that enable the execution and comparative analysis of multiple LCA scenarios. Our results consistently identify the manufacturing and usage phases of PLM system users’ equipment as the main contributors of the PLM system to climate change, acidification, and the depletion of abiotic mineral and metal resources. End-of-life contributes significantly to particulate matter impact, and usage phase, in a nuclear mix country, to ionizing radiation. The policy of purchasing and reselling reconditioned users’ equipment is clearly identified as a key lever for reducing the magnitude of these five environmental impacts
Assessing VOIP intelligibility in a low-connectivity environment
No full textInternational audiencePrevious work has shown that telecollaboration is a suitable solution for remote assistance of industrial maintenance operations, provided that an audio chat solution is available. There are several reasons why audio chat may not be available: the quality of the available Internet network, both in terms of bandwidth and stability (jittering), but also the presence of too much noise at the site of the operation, which interferes with voice capture. This paper presents a methodology to evaluate the quality provided by an audio chat solution. This methodology is then tested on a specific audio chat solution built on a lossy compression algorithm based on the grouping of successive similar values to overcome the jittering problem and significantly reduce bandwidth requirements. We suggest evaluating the audio quality by assessing the intelligibility of different audio recordings using standard speech therapy methods. Our results suggest that an audio chat can be provided even in a low bandwidth scenario and in a noisy environment, which provides promising insights for the further development of telecollaboration. Moreover, the assessment of audio quality using restitution exercices to evaluate intelligibility, tested on a real use case gives interesting results on the usability of an audio chat solution as well as detailed feedbacks on which part of the altered signal is to be improved
Contribution to the analytical determination of uncut chip thickness for cutting force modelling in milling with refinements for high-feed milling
No full textInternational audienceIn modern manufacturing, accurately predicting cutting forces is essential for the design and control of machining operations. Common mechanistic models of cutting forces rely on a precise description of the local uncut chip area. However, in milling, the specific trajectories of cutting edges create challenges in modelling this quantity. Existing analytical models are typically limited to 2D contexts or assume circular tooth trajectories, which are mostly valid for cylindrical end mills. These assumptions limit their applicability to high-feed milling, especially due to low lead angles and complex insert cutter geometries producing non-circular paths.This article presents a new three-dimensional analytical model for evaluating the local uncut chip thickness in high-feed milling. It relies on closed-form expressions derived from geometric analysis and Taylor expansions to approximate the uncut chip area and cutter-workpiece engagement, even in regions where conventional models fail. The model applies to linear-path milling and accounts for tool run-out and differential pitch. Compared to a Newton-Raphson numerical method, it achieves a relative error below 5% while being 3 to 9 times faster, enabling efficient integration in force models.Beyond its computational efficiency, the explicit formulation enables analysis of geometric influence, such as sensitivity to feed per tooth or tooth count-capabilities not easily accessible with purely numerical approaches. This work contributes a rigorous and interpretable alternative for improving cutting force prediction in high-feed milling
Towards Efficient Monitoring for WAAM Processes on a Robotized and Reconfigurable Manufacturing Cell
No full textInternational audienceWire Arc Additive Manufacturing (WAAM) is an efficient technology for producing metal parts. Itoffers high deposition rates, low material waste and reduced machining costs. However, the process'scomplex multi-physics nature presents several challenges, particularly with regard to residualstresses, deposition accuracy, and internal defects. Internal defects that occur during the WAAMprocess are difficult to detect in real time or immediately after fabrication without the use of non-destructive testing methods.This study focuses on enhancing an experimental protocol that employs a monitoring methodanalysing the geometry of each deposited layer using a laser sensor. This approach, combined withsegmentation techniques, aims to identify and locate internal defects. Specifically, the proposedmethod relies on segmenting individual layers and comparing normalised values to detect and localisedefects. This paper presents the developed methodology and an initial validation of its effectiveness.</p
Dissipation in unsteady grid-generated turbulence
No full textInternational audienceUnsteady turbulent flows are relevant in several natural and industrial situations, as they play a significantrole in atmospheric processes, engines, etc. Classical Kolmogorov arguments predict that for sufficientlyhigh Reynolds numbers in nominally stationary flows, an equilibrium range of scales emerges for averagedquantities, relegating unsteady and viscous terms to subdominant roles. However, multiple theoretical andnumerical studies have shown that moderate departures from stationarity can significantly alter energy dis-sipation. In particular, the unsteady dissipation constant Cε (t) is expected to evolve as the inverse of theturbulent Reynolds number Reλ (t) 1 . To probe these effects experimentally, we have performed and ana-lyzed hot-wire-anemometry (HWA) and particle image velocimetry (PIV) measurements of grid turbulenceunder forced oscillatory inflow conditions in two facilities (see Figure 1a).In the first series of experiments, performed at the wind tunnel located at University of Colorado Boulder,three distinct grids were used with the HWA probe measuring at a location ≈ 3 m downstream: (i) a fractalsquare grid (FS), (ii) a large classical rectangular grid (LG, mesh size M = 102 mm), and (iii) a smallerclassical rectangular grid (SM, M = 52 mm). An oscillatory component of a 1 Hz modulation of amplitude3 m/s was superimposed on the mean inflow velocity of 14.7 m/s. The resulting global Reynolds numberswere approximately ReG ≈ 156,000 (FS), 83,000 (LG), and 42,000 (SM). The unsteady flow is then ana-lyzed by segmenting the data into 20-degree segments, following a triple decomposition performed onto thee and turbulent u′ components. Resultsmeasured velocity time signal into mean U, coherent oscillatory U,show the oscillation of Reλ , as seen in Figure 1a. Notably, a hysteresis emerges in the relationship betweenReλ and Cε , as shown in Figure 1b, where the flow retraces a different path in (Reλ , Cε )-space dependingon whether it accelerates or decelerates. This hysteresis underscores the non-stationary character and ques-tions the universality of a constant Cε .Figure 1: Example of the results obtained with the FS grid: a) phase and ensemble-averaged Reλ (φ ) (lefte velocity is also plotted (right y-axis),y-axis) against phase φ . One period of the mean U plus the coherent Ub) phase and ensemble-averaged Cε (φ ) as a function of Reλ (φ ).Complementary experiments conducted at the LMFL wind tunnel with a classical rectangular grid (M =91 mm) used a similarly forced inflow but with a larger wind-tunnel test section and multiple mean velocitiesof 4, 5, and 7 m/s, each modulated by 1 m/s at periods of 20, 40, 80, and 160 s, resulting in ReG ≈ 24,000,30,000, and 43,000. Once more, HWA and PIV measurements were taken at 45 M downstream. The resultsrevealed consistent deviations from classical equilibrium, reinforcing the significance of large-scale forcingin reshaping the inter-scale equilibrium in forced turbulent flows
S'adapter et créer du lien : quand le projet sort des murs
No full textInternational audiencePoster de conférence (Colloque S.Mart 2025
Les approches participatives en conception pour la transformation soutenable des aires urbaines
No full textInternational audienceD’après la banque européenne d’investissement [1],plus de trois quarts de la population européenne vit dansdes aires urbaines et ce taux est en augmentation. En plusde ces flux humains, ces villes et agglomérations attirentune quantité importante de flux matériels et immatérielsafin de répondre aux différents besoins de leurs habitants.Ces flux s’accompagnent inexorablement d’émissionsd’un certain nombre de polluants, de déchets et de gaz àeffet de serre engendrant, en plus des conséquences bienconnues et documentées à l’échelle de la planète, desconséquences locales sur la qualité de l’air, de l’eau, sur lasanté et le confort des habitants [30]. La densité de cesflux augmentant, la pression sur l’environnement, sur lesressources et les infrastructures vitales de la ville devientcritique. Afin de supporter cette augmentation, en plusdes problématiques sociales auxquelles elle fait déjà face,la ville doit muter vers un modèle ayant à cœur unelogique de soutenabilité [29].Afin d’assurer cette transformation, l’implication d’unemultitude d’acteurs (économiques, société civile,citoyens) par des méthodes de co-création est essentiellecomme l’illustre le plan d’action pour une nouvelleéconomie circulaire de la commission européenne [2].Les Urban Living Lab (ULL), nouvelle approche dessciences participatives mettant l’accent surl’expérimentation en contexte réel, se positionnentcomme une solution prometteuse pour répondre à cesenjeux. En effet, de par son milieu d’étude (la ville), sesobjectifs souvent associés à des enjeux de transitionécologique, et son système de gouvernance, cetteapproche semble réunir les différents points cléspermettant l’adoption de nouvelles solutions soutenablespour les aires urbaines
Modélisation des lois d'aimantation des aciers électriques à grains orientés avec prise en compte de la contrainte mécanique
No full textThe magnetic core of high-power energy conversion devices, such as turbo-generators and distribution transformers, is usually made of grain oriented electrical steels (GOES). These make it possible to reduce the size of the devices and improve their energy efficiency. However, the constraints of shaping and operation on magnetic circuits impact their properties. On the one hand, iron losses under certain operating conditions (over saturation and/or 3D magnetic flux) can lead to overheating that degrades the performances, or even to the deterioration of the device. In addition, the mechanical stresses induced on the magnetic core by the manufacturing processes (cutting, assembly, etc.) modify the magnetic properties. This problem, made more complex by the high magnetic anisotropy of GOES, is of prime importance for designers, who need reliable and accurate GOES models to be able to incorporate them into the design tools.In this P.h.D. thesis, an ODF based-modelling approach is proposed for describing the magnetic behavior laws of GOES while considering the uniaxial tensile and compressive mechanical stress. Optimal selection of angular input data for the ODF-Based Model was implemented to achieve the best compromise between accuracy and the quantity of data required for the model identification.In the last chapter, a coupling with Fiorillo's model is introduced to allow for FEM implementation accounting for the demagnetising field.Le noyau magnétique des dispositifs de conversion d‘énergie de fortes puissances, tels les turbo-alternateurs et les transformateurs de distribution, est usuellement fabriqué à partir de tôles magnétiques à grains orientés (GO). Celles-ci permettent de réduire les dimensions des dispositifs mais aussi d'améliorer leur efficacité énergétique. Néanmoins, les contraintes de mise en forme et d'exploitation des circuits magnétiques impactent les propriétés d'usage de ces tôles qui sont au cœur de la conversion d'énergie. D'une part, les pertes fer dans certaines conditions d'opération (sursaturation et/ou circulation tridimensionnelle du flux magnétique) peuvent conduire à des échauffements qui dégradent les performances, voire à la détérioration du dispositif. D'autre part, les contraintes mécaniques induites sur le noyau magnétique par les procédés de fabrication (découpe, assemblage…) modifient les propriétés magnétiques. Cette problématique, rendue complexe par la forte anisotropie magnétique des tôles GO, est un sujet de préoccupation pour les concepteurs qui doivent disposer de modèles de tôles GO fiables et précis pour les intégrer dans les outils de dimensionnement. Une modélisation des lois d'aimantation des tôles GO est proposée dans cette thèse avec prise en compte des contraintes mécaniques uniaxiales de traction et de compression. Pour cela, une approche basée sur la fonction de distribution d'orientation (ODF en anglais) a été utilisée. Un algorithme de sélection optimale des données d'entrée a été mis en œuvre pour le meilleur compromis précision/quantité de données nécessaire à l'identification du modèle.Une approche couplée au modèle de Fiorillo est proposée dans le dernier chapitre en vue d'une implémentation dans un code de calcul par éléments finis pour rendre compte du champ démagnétisant