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Influence of Surface Integrity and Coating on the High Cycle Fatigue Properties of 300M Steel from Self-Heating Tests under Cyclic Loads
No full textInternational audience300M, an ultra-high strength steel used in aeronautics for landing gears, is generally shot-peened and coated with High Velocity Oxygen Fuel sprayed WC-10Co-4Cr to improve tribological behavior. In literature, few treatment parameters have been tested to analyze the surface integrity influence on fatigue properties. The self-heating method under cyclic loading is used to quickly determine fatigue properties by coupling them with intrinsic dissipation. Investigations on dissipation mechanisms of coating and substrate enable to develop self-heating models. That is the first step to build a lifespan forecast model based on temperature measurement to study shot-peening and coating influence on fatigue properties
Proposition de mesure de la qualité technologique des brevets : utilisation de l’analyse des réseaux sociaux
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Fisher Information Neural Estimation
No full textInternational audienceFisher information is a fundamental quantity in information theory and signal processing. A direct analytical computation of the Fisher information is often infeasible or intractable due to the lack or sophistication of statistical models. In this paper, we propose a Fisher Information Neural Estimator (FINE) which is computationally efficient, highly accurate, and applicable for both cases of deterministic and random parameters. The proposed method solely depends on measured data and does not require knowledge or an estimate of the probability density function and is therefore universally applicable. We validate our approach using some experiments and compare with existing works. Numerical results show the high efficacy and low-computational complexity of the proposed estimation approach
Helmholtz resonator analogue for water waves
No full textInternational audienceWe present a theoretical and experimental study of a resonator of the Helmholtz type for the wave control. An experimental demonstration of the shielding effect by a belt made of evenly distributed resonators is given. We then provide in-depth analysis of the Fano resonance resulting from the interference between the dock scattering (the background) and the resonant cavity scattering. This is done thanks to space–time resolved experiments which provides the complex valued scattering coefficients and amplitude within the resonator. We provide a one-dimensional model derived in the shallow water regime owing to asymptotic analysis. The model contains the two ingredients of the Fano resonance and allows us to exhibit the damping due to leakage. When adding heuristically the damping due to losses, it reproduces the main features of the resonance observed experimentally
Analyse microtomographique et vibroacoustique d'anches synthétiques pour saxophone
No full textInternational audienceProfitant des innovations en ingénierie des matériaux depuis plusieurs décennies, des anches synthétiques pour saxophone et clarinette sont apparues sur le marché dans le but de répondre aux attentes des fabricants et des musiciens à la fois en termes de prédictibilité, de reproductibilité et de durabilité. Nous proposons ici une étude comparative de différentes anches disponibles actuellement dans le commerce. Dans cette étude exploratoire, nous nous concentrons sur une étude de paramètres objectifs, sans inclure l'instrumentiste. Le premier volet porte sur l'analyse d’images des anches obtenues par micro-tomographique à rayons X. Elle permet un relevé tridimensionnel des géométries et l'examen de la structure interne des matériaux. La variété des profils d'épaisseurs est mise en rapport avec l'architecture des matériaux (naturelle pour les fibres de roseau, tissée et/ou renforcée pour les composites, et fragmentée pour les anches à base de poudre). Dans un second temps, les anches sont montées sur un bec de saxophone - sans lèvre artificielle - et soumises à des essais vibro-acoustiques par sollicitation acoustique via le bec et mesure des champs de déplacement transverse par vibrométrie laser à effet Doppler. On s'intéresse tout d'abord aux fréquences de résonance et aux facteurs de qualité associés. La variabilité liée aux incertitudes de montage d'une même anche sur le bec est comparée à la variabilité entre différentes anches d'une même série, puis entre les différentes conceptions d'anches synthétiques, confirmant le caractère discriminant des essais vibro-acoustiques
TIO2-BASED PHOTOCATALYST, METHODS FOR PREPARING THE PHOTOCATALYST AND USE THEREOF IN DEGRADING A BIOMASS
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Nouvelles approches numériques pour la modélisation des massifs rocheux dégradés. Application au creusement des ouvrages souterrains soutenus.
No full textDegraded rock masses are increasingly encountered in development projects because the constraints (environmental, land price, etc.) lead to projects being carried out in these geologically unfavorable grounds. The very unsatisfactory state of rock engineering for this type of grounds leads to significant discrepancies between the calculations and the actual behavior. In the field of tunnels, the classic method (convergence-confinement) gives uncertain results for this type of grounds and has not been updated for about fifteen years, and the different formulations used to improve the results are reaching their limits, not having been established for rocks.The objective of this thesis is to develop tools to model the behavior of rock masses in a more realistic way. This behavior is represented by the Hoek and Brown criterion regularized in the deviatoric plane, which takes into account the effect of the intermediate principal stress and the Lode angle. The theoretical developments were built in the stress space represented by the hydrostatic axe and the deviatoric plane, which allows the calculation of the plastic deformations according to the orthogonal projection, or by integrating a chosen dilatancy angle. These developments are then used to model a supported tunnel in rocks, using a steady-state algorithm. The results of the modeling made it possible to establish the validity of the convergence-confinement method and new formulas for the rocks and rock masses.Les massifs rocheux dégradés sont de plus en plus rencontrés dans les projets d'aménagement car les contraintes (environnementales, foncières…) amènent à conduire des projets dans ces terrains géologiquement défavorables. L’état de l’art très insatisfaisant de l’ingénierie rocheuse pour ce type de terrains induit des écarts importants entre les calculs et le comportement réel. Dans le domaine des tunnels, la méthode classique (convergence-confinement) donne des résultats incertains pour ce type de terrain et n’a plus été actualisée depuis une quinzaine d’années, et les différentes formulations utilisées pour améliorer les résultats atteignent leurs limites, n'ayant pas été établies pour les roches.L'objectif de cette thèse est de développer les outils permettant de modéliser de manière plus réaliste le comportement des massifs rocheux. Ce comportement est représenté par le critère de Hoek et Brown régularisé dans le plan déviatorique, qui prend en compte l'effet de la contrainte principale intermédiaire et de l'angle de Lode. Les développements théoriques ont été construits dans l'espace des contraintes représenté par la trisectrice et le plan déviatorique, qui permet le calcul des déformations plastiques selon la projection orthogonale, ou en intégrant un angle de dilatance fixé. Ces développements sont ensuite utilisés pour la modélisation d'un tunnel soutenu en milieux rocheux, en utilisant un algorithme stationnaire. Les résultats des modélisations ont permis d'établir la validité de la méthode convergence-confinement et de nouvelles formules pour les massifs dégradés
Advanced methods of identification of sea-breeze and low-level jet events from near ground measurements with specific implication for energy production by offshore wind farms
No full textInternational audienceSince an uniform high-speed wind is required for maximum power production, it is important to survey the meteorological phenomena which can boost up or down the power production by offshore wind turbines. The study is focused on developing and validation of advanced methods of detection of such mete-orological phenomena. In situ measurements were performed at an experimental site located in Dunkirk, northern France. The wind variability was measured by Sonic anemometer during a period starting from 11th January 2018 to 18th December 2019. Automatic detection algorithms have been developed to detect sea-breeze (SB) and nocturnal low-level jet (NLLJ) events from Sonic anemometer measurements near ground. The SB detection is based on a recurrent neural network algorithm (RNN). The accuracy of event identifica-tion by this network is 95%. We found 67 and 78 SB days in 2018 and 2019 respectively. NLLJ detection al-gorithms developed, using wavelet transformation methods, show a better performance than other existing methods. A total of 192 and 168 NLLJ days were found in 2018 and 2019 respectively. The wind speed was found higher during the nighttime for NLLJ than for non-NLLJ days, which can increase the peak power pro-duction up to 40 times, compared to normal days. To evaluate the skill of detection algorithms based on ane-mometer measurements, simultaneous Sonic and lidar wind measurements have been done at site for 86-day long period. The wind speed and turbulence kinetic energy were computed from Sonic anemometer and com-pared to the lidar measurements. The comparison suggests that the point measurements by Sonic anemometer can be very useful for the algorithms of automatic detection of meteorological events
