Dissertations / Theses on the topic 'Élastomères – Effets de la température – Oxydation'
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Hottin, Andréas. "Fatigue thermomécanique des élastomères : critère de durée de vie basé sur l'endommagement avec prise en compte du vieillissement physico-chimique." Electronic Thesis or Diss., Université de Lille (2022-....), 2023. http://www.theses.fr/2023ULILN001.
Thanks to their particular mechanical properties, in particular their ability to undergo large deformations on the one hand, and to dissipate energy on the other hand, filled elastomers are used in many industrial fields and more particularly in that of transport. In service, most components are subjected to cyclic stresses and the loads are often multiaxial and non-relaxing. The optimization of such components in terms of service life requires the implementation of predictive tools to quantify their mechanical strength for these complex loads. On the other hand, their dissipative behavior associated with their low thermal conductivity leads to an accumulation of heat in the material leading to a rise in temperature during repeated loadings. We are talking about self-heating. Since this phenomenon tends to reduce the fatigue strength, it has been widely studied in recent years but rarely for multiaxial loadings. Finally, elastomers subjected to high temperatures for a certain time see their mechanical properties deteriorate. Studies that focus on this phenomenon called thermo-oxidative aging often focus on its impact on the fracture properties of the material and unfortunately neglect its impact on fatigue behavior.This thesis work consists in building a lifetime prediction tool based on the accumulation of damage taking into account both the multiaxiality of cyclic loadings, the phenomenon of self-heating as well as thermo-oxidative ageing
Bouhanek, Karima. "Oxydation à haute température de superalliages monocristallins." Toulouse, INPT, 1997. http://www.theses.fr/1997INPT016G.
Desserrey, Franck. "Comportement mécano-chimique du nickel vis à vis de l'oxygène à haute température : aspects expérimentaux et prévisionnels." Dijon, 2002. http://www.theses.fr/2002DIJOS057.
Celette, Nathalie. "Vieillissement sous irradiation d'EPDM : modification des propriétés d'usage." Lyon 1, 2001. http://www.theses.fr/2001LYO10202.
Peraldi, Raphaëlle. "Relations entre cinétiques de croissance des couches d'oxyde et leurs microstructures lors de l'oxydation à haute température du nickel de haute pureté." Phd thesis, Toulouse, INPT, 2000. http://oatao.univ-toulouse.fr/7247/1/peraldi1.pdf.
Rabillaud, Fabienne. "Réactivité à haute température des fibres de carbone en atmosphère oxydante : effets de gaz inertes et du chlore sur la cinétique d'oxydation." Mulhouse, 1991. http://www.theses.fr/1991MULH0188.
Vandenbroucke, Aude. "Étude du comportement mécanique pour différentes températures d'un élastomère : caractérisations expérimentale et numérique." Lorient, 2010. https://tel.archives-ouvertes.fr/tel-00836556.
The objective of this study is to develop a model to reproduce the elastomer mechanical behaviour function of the temperature. For this study, preliminary experimental work is performed to highlight the different mechanical phenomena to present the material with changing temperature. The studied material is a fluoro-carbon synthetic elastomer (FKM), Viton. This elastomer has excellent performance at high temperatures and chemical attacks. Its properties are used for various applications such as sealing, damping, isolation, etc. The mechanical characterization of materials is performed using conventional tension, compression and relaxation tests on a range of temperatures from -40°C to 100°C. The cyclic loading tests reveal a significant presence of hyperelasticity for elastomers. The relaxation tests enable us to describe the viscosity of the material. In addition, loading tests interrupted by relaxations have also been carried out for different strain rates with relaxation times of 900s. They show equilibrium hysteresis demonstrating the presence of hysteresis for our material. In this study, we have chosen to consider only the temperature range from -8°C to 100°C to reproduce correctly the material behaviour. The model is a phenomenological constitutive model based on an additive decomposition of powers. The model consists of three stress contributions: hyperelasticity, viscosity and hysteresis. This model will be named Hyperelasto-visco-hysteresis (HVH) where the contribution is taken into account hyperelastic using phenomenological potential of Hart-Smith. The viscosity is described using the generalized Maxwell model and the hysteretic contribution is taken into account using an original model. In this study we consider only the first loading cycle of our material. A method of identification has been established to better take into account the different contributions of the model. The identification of material parameters for isotherms are performed in the range of temperature studied. Validation of the model will be initially tested at room temperature on a loading case of industrial gasket relaxation. To validate the model as a function of temperature we simulate different cases of loading isotherm. Then, the simulation of a relaxation test in compression undergoing temperature cycles is performed to compare the model to calculate temperature dependent
Geuffrard, Marion. "Amorçage et micro-propagation de fissure en fatigue à haute température à partir de défauts dans un superalliage monocristallin." Phd thesis, École Nationale Supérieure des Mines de Paris, 2010. http://pastel.archives-ouvertes.fr/pastel-00609109.
Lavedrine, Alain. "Etude de la décomposition thermique de polyvinylsilazanes : comportement à l'oxydation du carbonitrure de silicium obtenu." Limoges, 1991. http://www.theses.fr/1991LIMOA001.
Bouchaud, Baptiste. "Electrosynthèse de nouveaux revêtements à base d'élément de terres rares destinés à accroître la durabilité à haute température des matériaux des turbines." La Rochelle, 2009. http://www.theses.fr/2009LAROS284.
Zarrou, Hanan. "Production d'hydrogène par oxydation partielle du méthane sur catalyseurs oxydes mixtes." Lille 1, 2006. https://pepite-depot.univ-lille.fr/RESTREINT/Th_Num/2006/50376_2006_403.pdf.
Brisebourg, Mathieu. "Corrosion active/passive de matériaux en présence de mélanges réactifs à très haute température." Thesis, Bordeaux 1, 2012. http://www.theses.fr/2012BOR14325/document.
Experimental and theoretical studies have been carried out in order to obtain further knowledge and understanding of the corrosion behavior of silicon carbide under complex gas mixtures at very high temperatures. To that purpose, two original experimental methods based on Joule-heating have been designed for the in-situ following of SiC oxidation kinetics, and a model accounting for both heterogeneous kinetics and gas-phase transport phenomena has been developed thanks to a finite volume method. At high temperatures and low oxidant partial pressure, oxidation of SiC is « active » and associated with the formation of gaseous products and high degradation rates of the original materials, the reaction being rate-determined by species transport through a gaseous boundary layer. At low temperatures and high oxidant partial pressures, oxidation is « passive » and associated with the growth of a condensed oxide scale acting as a protecting diffusion barrier. An analytical study has been conducted in order to try and isolate the effects of the various physical and chemical phenomena involved during this passive oxidation, such as different growth mechanisms, volatilization or bubble formation, and quantify how temperature and gas composition influence them.An experimental study of the active/passive transition in the oxidation of SiC has been conducted under gas mixtures including one or two different oxidant species. Numerical simulation tools as well as new insights on oxidation mechanisms were used to analyze different predictive models of the active/passive transition and evaluate and understand the differences between these theoretical results and the ones obtained experimentally
Berthier, Daphné. "Développement, caractérisation et modélisation d'un nanocomposite haute température de type élastomère chargé pour application aéronautique." Thesis, Tours, 2018. http://www.theses.fr/2018TOUR4026.
In aeronautics application, elastomers are generally subject to severe cyclic, mechanical and thermal stress. This thesis is part of a global research project to improve the performance of elastomers. The aim is to achieve the longest possible life in terms of thermomechanical behavior. This need is justified by the development of ever more powerful engines and therefore with a prospective to generate higher temperatures. New materials are essential to limit the replacement of parts in these conditions of use. Fluoroelastomers are matrices widely used in the context of high temperature applications. In these works, nanoparticles selected for their known impact on thermal properties are integrated into a crosslinked FKM matrix. The aim is to improve the thermal and mechanical behavior of the resulting nanocomposites. Two types of nanocomposites have been developed: crosslinked FKM/POSS and FKM/CNT. Nanocomposites are realized in thin film format. Dispersion parameters influence is a crucial point directly responsible for the quality of surface conditions as well as the thermomechanical properties obtained. Despite improved mechanical properties, the incorporation of CNT did not have the expected effect on the thermal properties of crosslinked FKM/CNT. The first two reasons are probably the use of a high load rate and an unsuitable means of implementation. POSS are more hopeful for reinforcement of fluoroelastomers properties. In particular POSS-A, due to a grafting on the FKM backbone impact the thermal and mechanical properties. As an indication, the thermal resistance obtained presents in an improvement of 5°C of the degradation temperature when 5phr are added in the FKM matrix. In addition, the storage module E' is greatly improved, up to 4.0MPa at 200°C to 20phr (+210% compared to the unfilled FKM matrix). The apparent activation energy at the beginning of degradation by TGA is stronger in the case of this nanocomposite. This data correlates with the Tg measurements estimated by DMA and shows that the addition of the nanoparticles hinders the molecular motions proper to the matrix. These nanoparticles have an inhibiting power on the degradation of the nanocomposite. Thermal aging tests have also highlighted that crosslinked FKM/POSS-A have mechanical characteristics superior to the industrial reference. The variations of these properties are explained by different interactions (chemical grafting of POSS on the polymer and physical interactions by the creation of a charge network) between the POSS and the matrix. The incorporation of POSS-A into a crosslinked FKM matrix for 5phr seems to be the most suitable nanocomposite for high temperature applications
Perez, Thomas. "Oxydation à haute température d’alliages modèles Ni-25Cr, Influence des éléments mineurs Mn et Si sur les mécanismes de croissance des oxydes protecteurs." Electronic Thesis or Diss., Université de Lorraine, 2019. http://www.theses.fr/2019LORR0234.
Nickel-based refractory alloys are mainly used in oxidizing atmosphere at high temperature. These alloys are generally capable to form chromia oxide scales at temperature between 700 and 1100°C. A few relationships between composition, microstructure and kinetic are known, but the systematic study of the oxidation behaviour of new industrial alloys is required because the impact of minor elements and their possible synergy are not fully understood. Thus, this PhD thesis aims to refine the understanding of the relationship between the chemical composition and the chemical reactivity of metallic materials in an oxidizing atmosphere in order to contribute to the design of alloys with optimized oxidation properties. To reach this purpose, the oxidation behaviour of model alloys, simplified compared to those proposed today by industry, was studied. The techniques available nowadays (EBSD, SEM-FIB, MET-HR) were used in order to determine the oxidation mechanism and the effect of manganese and silicon additions on these mechanisms. The characterization of the first oxidation step was performed in-situ in an environmental SEM (Collaboration with the ICSN in Marcoule) and allowed the observation of the former oxide, the Mn1+xCr2-xO4 spinel regardless the alloy Mn content. Manganese addition led to an increase of the oxidation rate in comparison to the one of a Ni25Cr (% wt.) and to a decrease of the chromia oxidation rate thanks to the presence of the spinel Mn1+xCr2-xO4 at the oxide/gaz interface. In opposite, the silicon addition decreased the parabolic constant by a factor 5. This dramatic effect was attributed to the presence of silica at chromia grain boundaries which decreased the chromium diffusion rate across the oxide scale. The addition of both manganese and silicon led to the same oxidation rate than the reference alloy in isothermal condition whereas, the lifetime in cyclic oxidation was considerably increased. The knowledge of the growth direction coupled to that of the semiconductivity type, determined by photoelectrochemical measurements at SiMaP laboratory in Grenoble, allowed the identification of the major point defects in formed oxide scales. Based on the collected results, the involved solid state diffusion mechanisms responsible of the oxide layer growth were proposed
Cabrera, Salcedo Andrea. "Modélisation du comportement mécanique "post-trempe", après oxydation à haute température, des gaines de combustible des réacteurs à eau pressurisée." Phd thesis, Ecole Nationale Supérieure des Mines de Paris, 2012. http://pastel.archives-ouvertes.fr/pastel-00705085.
Le, Saux Vincent. "Fatigue et vieillissement des élastomères en environnements marin et thermique : de la caractérisation accélérée au calcul de structure." Phd thesis, Université de Bretagne occidentale - Brest, 2010. http://tel.archives-ouvertes.fr/tel-00542506.
Brix, Florian. "Contribution à la recherche de matériaux de type «siliciures» résistant à l’environnement à haute température en vue d’applications dans le domaine de la thermoélectricité." Electronic Thesis or Diss., Université de Lorraine, 2018. http://www.theses.fr/2018LORR0174.
The constant deployment of new sensors networks in confined areas of turbomachines or difficult to access, requires the input of energy to power these sensors. Many researches are thus focused on a permanent power supply of sensors to monitor new components. One possible way of permanent power supply is the use of thermoelectric modules to convert the thermal energy from combustion into the turbines. Among the thermoelectric materials, silicides seem to be the most promising family for high temperature applications (above 700 °C). The subject of this thesis is the study of silicides known for their high temperature oxidation resistance in order to produce thermoelectric modules that can operate at optimal temperatures around 700 °C. To this end, different representatives of the silicide family have been studied by ab initio calculation using the density functional theory. This tool allowed to calculate their potential thermoelectric properties and showed that the two best candidates for cheap applications were the disilicides of manganese and iron. The calculation also showed the metallic character of many ternary silicides. The promising silicides were developed by sintering method and their aging as well as their coefficients of thermal expansion were studied. This knowledge has made it possible to develop thermoelectric modules based on silicides resistant to 900 °C in air. Although possessing modest thermoelectric properties, their resistance to high temperature oxidation makes it possible to envisage the manufacture of thermoelectric modules
Courty, Colette. "Détermination par diffraction X des contraintes résiduelles dans les oxydes formés sur les métaux à haute température : cas des sytèmes Ni/NiO et Co/Co3O4." Compiègne, 1988. http://www.theses.fr/1988COMPD115.
Dorgans, Céline. "Study of interactions between glass and tungsten during glass hot forming processes." Grenoble INPG, 2010. http://www.theses.fr/2010INPG0022.
During syringe hot forming, tungsten-glass interactions lead to oxidation and wear of the tungsten tool and contamination of the syringe by tungsten. Direct consequences are unwanted reactions with sensitive medicines I contained in the syringes. Oxidation and wear of the tungsten tool was studied in air and in glass at high temperature, during dedicated experiments and during the syringe forming process. Thanks to the understanding of these phenomena, solutions to avoid contamination of the syringe by tungsten were proposed
Brix, Florian. "Contribution à la recherche de matériaux de type «siliciures» résistant à l’environnement à haute température en vue d’applications dans le domaine de la thermoélectricité." Thesis, Université de Lorraine, 2018. http://www.theses.fr/2018LORR0174/document.
The constant deployment of new sensors networks in confined areas of turbomachines or difficult to access, requires the input of energy to power these sensors. Many researches are thus focused on a permanent power supply of sensors to monitor new components. One possible way of permanent power supply is the use of thermoelectric modules to convert the thermal energy from combustion into the turbines. Among the thermoelectric materials, silicides seem to be the most promising family for high temperature applications (above 700 °C). The subject of this thesis is the study of silicides known for their high temperature oxidation resistance in order to produce thermoelectric modules that can operate at optimal temperatures around 700 °C. To this end, different representatives of the silicide family have been studied by ab initio calculation using the density functional theory. This tool allowed to calculate their potential thermoelectric properties and showed that the two best candidates for cheap applications were the disilicides of manganese and iron. The calculation also showed the metallic character of many ternary silicides. The promising silicides were developed by sintering method and their aging as well as their coefficients of thermal expansion were studied. This knowledge has made it possible to develop thermoelectric modules based on silicides resistant to 900 °C in air. Although possessing modest thermoelectric properties, their resistance to high temperature oxidation makes it possible to envisage the manufacture of thermoelectric modules
Choquet, Patrick. "Étude de l'oxydation à haute température de dépôts d'alliages Ni (Co) Cr Al réalisés par pulvérisation cathodique : influence des éléments d'addition Y, Hf ou Zr." Paris 11, 1987. http://www.theses.fr/1987PA112453.
Metallic coatings (composition: Ni-23Cr-7A1 and Ni-22Co-23Cr-7Al, weight %, thickness = micrometers) containing Y, Hf or Zr (content: 0 to 2 %) have been deposited by two-target triod sputtering on substrates having similar compositions but without these elements. Oxidation tests at 1100°C (duration: 100 h for isothermal and up to 1000 one-hour cycles for cyclic tests) have shown that: - the addition of Y, Hf or Zr increases the oxidation kinetics of these alloys;- yttrium is more efficient for improving the adhesion of the alumina scales in thermal cyclic conditions, than hafnium or zirconium. According to the observations and analyses (by SEM, XRD, EDS, EPMA) Y, Hf and Zr are present as YAl03, Y3Al5 O12, HfO2 or ZrO2 in the Al2 O3 scale. The microstructure (pores, grain sizes, precipitates) of NiCoCrAl alloys, containing or not Y, has been determined by TEM. Residual stresses in the alumina scale and the alloy have been measured by XRD. The results obtained suggest that the addition of Y, Hf or Zr changes the growth mechanisms in the alumina scale: these elements contained in the alumina increase the oxygen diffusion rate towards the alloy, and new oxides form the scale/alloy interface with less important growth stresses
Rolland, Raphaël. "Etude de l'Influence de la vapeur d'eau sur l'oxydation à haute température d'un alliage chromino-formeur à base de nickel." Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2012. http://tel.archives-ouvertes.fr/tel-00721006.
Portebois, Léo. "Développement de matériaux réfractaires pour applications turbines aéronautiques : étude des effets microstructuraux sur le comportement en oxydation des alliages composites Nbss-Nb5Si3 et optimisation des solutions de protection associées." Thesis, Université de Lorraine, 2014. http://www.theses.fr/2014LORR0153/document.
Progress in the field of gas-Turbine engines for aircrafts is controlled by the availability of new structural materials able to withstand higher temperatures than nickel based superalloys. The present PhD work was conducted in this context, within the framework of the European FP7-HYSOP project, in which Nbss-Nb5Si3 alloys are studied. From a mechanical point of view, the physicochemical properties (room temperature fracture toughness and creep rate) are compatible with the targeted temperature (1300°C). However, starting from the intermediate temperatures (800°C), the oxidation resistance of those alloys is the major obstacle to their use. In this work, two ways are investigated to improve this behavior: The first one aims at studying the effect of a refinement of microstructure synthesizing the Nbss-Nb5Si3 alloy both by fusion method and powder metallurgy route. It was shown that refining the microstructure led to decrease the oxidation kinetics at 1100°C and suppressed the catastrophic breakaway oxidation (pesting) typical of the Nb-Si alloys with coarse microstructure at 815°C. Furthermore, diffusion models were proposed to describe oxidation kinetics both at 815°C and 1100°C. The second part of this study is devoted to the development of silica forming protective coatings. Diffusion silicide coatings were manufactured by the halide activated pack-Cementation method. The various conditions of oxidation/corrosion tests (isothermal or cyclic, in air, air containing water vapor, CMAS silicate melt) allowed assessing and ranking the performance of coated systems
Meghiref, Nyhal. "Vieillissement thermique de mélanges HNBR réticulés au peroxyde - Modélisation cinétique - Influence d'un hydrocarbure." Thesis, Paris, HESAM, 2020. http://www.theses.fr/2020HESAE026.
Hydrogenated acrylonitrile-butadiene copolymer (HNBR) is a synthetic elastomer commonly used in advanced sectors such as aeronautic, automotive and off-shore industry for seals and hoses. This elastomer is often exposed to severe environments in a large temperature range, typically in immersion in oils between -30 °C to 150 °C. Despite its wide use, its durability has been the subject of only a few studies. This is why the aim of this PhD work was to elucidate its thermal aging between 90 °C and 150 °C, and its aging in immersion in a model hydrocarbon oil (IRM 903), in both absence (under nitrogen) and presence of oxygen (under air). Six HNBR formulations were aged: a model HNBR without any additive, three HNBR with different contents of acrylonitrile (17, 36 and 44 wt%) only containing ZnO, the stabilized model HNBR with ZnO, and the stabilized model HNBR with ZnO and carbon black. A both multiscale and multi-techniques approach has been developed to determine the chemical functions consumed and the main degradation products of HNBR (FTIR spectroscopy), but also the consequences of this degradation on the macromolecular structure of HNBR (swelling measurements and DSC analysis) and its mechanical properties (micro-indentation and uniaxial tensile experiments). This approach leads to the elaboration of a general mechanistic scheme for HNBR oxidation, from which has been derived a kinetic model, as well as the establishment of several structure-property relationships. Finally, the reciprocal effects of oil absorption and HNBR thermal ageing have been analyzed
Knittel, Stéphane. "Elaboration et caractérisation du comportement en oxydation d'alliages composites à base de niobium et de siliciures de type M7Si6 et M8Si7 envisagés comme revêtements protecteurs." Thesis, Nancy 1, 2011. http://www.theses.fr/2011NAN10127/document.
The improvement of the efficiency of turbine engine can be achieved by increasing the working temperature. The development of new alloys based on Nb-Si system allows a jump of 200°C of the operating temperature in comparison to that offered by current nickel based alloys. The first part of this manuscript focuses on the evolutions which have led to the development of niobium silicide in situ composites (Nbss-Nb5Si3). The microstructure of these alloys consists in a ductile niobium matrix where number of alloying elements can solubilise and of strengthening niobium silicides which are intended to provide creep and oxidation resistance at high temperature. Unfortunately, these alloys exhibit a poor oxidation resistance characterised by a high metal recession rate and the formation of non-protective oxide scale. Thus, oxygen can easily react with the substrate, dissolve in Nbss and diffuse quickly through this phase. The effect of Al, Si and Ti additions on both microstructure and oxidation resistance were investigated. Although, these composition optimisations lead to a significant enhance of oxidation resistance, some compositions still suffers from catastrophic oxidation behaviour around 800°C. In these alloys tin additions involve high microstructural changes, especially by initiating the formation of A15- Nb3Sn phase. At 800°C, Sn additions suppress oxygen dissolution in Nbss responsible of the catastrophic oxidation behaviour of these alloys. Nevertheless, the oxidation resistance of these alloys remains too low for the foreseen applications and protective coatings are required. Thermodynamic stability and oxidation resistance of two silicide families (Nb3X3CrSi6 and Nb4X4Si7 (X = Fe, Co or Ni)) were investigated. These silicides have exhibited a high oxidation resistance up to 1300°C by the formation of a protective silica layer. Finally, these silicides were deposited on Nbss-Nb5Si3 substrate by using the pack cementation process. Some coated alloys have then exhibited lifetime going up to 3000 one hour cycle at 1100°C
Bouvier, Pierre. "Étude Raman des distributions de phase et de contrainte dans des couches d'oxydation d'alliages de zirconium : étude spectroscopique des effets de pression et de température sur différentes zircones nanométriques." Grenoble INPG, 2000. http://www.theses.fr/2000INPG0136.
Ledoux, Xavier. "Contribution à la mise au point de matériaux métalliques pour les unités de production d'hydrogène par vaporéformage du gaz naturel : 1/ Étude de l'oxydation de matériaux de structure à l'air entre 650 et 1050°C. 2/ Élaboration de revêtements et étude de leur résistance à l'oxydation." Thesis, Université de Lorraine, 2012. http://www.theses.fr/2012LORR0017/document.
The LokiR project aims to develop new steam reforming reactor to optimize the production of hydrogen. In this context, the protection of metallic alloys composing the reactor must be improved. In this thesis, the behavior of two chromia-forming alloys (Haynes© 120 and 230) was studied at high temperature under oxidizing conditions and protective coatings, able to improve their resistance against oxidation, have been developed. The study reveals that the alloys protect themselves by the growth of a chromia layer during their oxidation in air in the range 650-1050°C. This leads to a parabolic-like oxidation kinetics with low constant values for these types of alloys. The magnitude of the alloys life time at 1000°C was estimated at about 8 years in air. Chromia growth is controlled by the diffusion of the oxygen vacancy defect as well as high and low oxygen pressure. The tests indicate that the chromization of Haynes© 120 alloy leads an alpha-(Cr, Fe, Ni) phase that can be enriched with silicon. However, the behavior of these coatings oxidation at 1050°C, is, overall, unsatisfactory. The aluminization of the alloy Haynes © 120 leads to the formation of a beta-Al (Ni, Fe, Cr) coating. The oxidation study of the alloy thus coated leads to the initial growth of a transition alumina and, then, to the growth of the steady alpha-Al2O3. This last reduces the rate of oxidation and improves the thermal shock resistance. The aluminized alloy maintains the alumina-forming nature at least 10000 hours at 1000°C
Chosson, Raphaël. "Étude expérimentale et modélisation du comportement en fluage sous pression interne d'une gaine en alliage de zirconium oxydée en atmosphère vapeur." Thesis, Paris, ENMP, 2014. http://www.theses.fr/2014ENMP0092.
During hypothetical Loss-Of-Coolant-Accident (LOCA) scenarii, zirconium alloy fuel cladding tubes creep under internal pressure and are oxidized at high temperature (HT). Claddings become stratified materials: zirconia and oxygen-stabilized alpha phase, called alpha(O), are formed on the outer surface of the cladding in beta phase.The strengthening effect of the oxidation on the cladding creep behavior under internal pressure was highlighted at HT. In order to model this effect, the creep behavior of each layer must be known.This study focused on the characterization of the creep behavior of the alpha(O) phase at HT, through axial creep tests performed under vacuum on model materials containing from 2 to 7 wt.% of oxygen, representative of the alpha(O) phase. The strengthening effect and the embrittlement due to oxygen on the alpha(O) phase creep behavior at HT was quantified and creep laws were identified.Relevance of the creep laws for each layer, identified in this study or from the literature, is discussed. Then, a finite elements model, describing the oxidized cladding as a stratified material, is built. Based on this model, a fraction of the experimental strengthening during creep is predicted
Brossard, Maxime. "Influence de l'eau (vapeur, liquide) et du régime d'oxydation sur la dégradation de revêtements alumino-formeurs sur superalliage à base nickel." Thesis, La Rochelle, 2014. http://www.theses.fr/2014LAROS018/document.
Upon service, aero-turbine blades (nickel-based superalloys) are submitted to high temperature degradation that may alter their structural properties. The oxidizing atmospheres are particularly complex (O2, H2O, CO2, SO2, NOx…) with variable water vapour contents as function of the engine regime and the atmospheric conditions (clouds, rain, relative humidity of air). These substrate materials are protected by alumina-forming coatings to improve their oxidation resistance, while additional thermal barrier coatings insulate the hottest parts. This PhD project aims at studying the effect of water (vapour, liquid) on the degradation of conventional and new coatings (Al slurry, electrodeposited CeO2) developed at the LaSIE laboratory under different oxidation regimes (isothermal and cyclic). An approximation to service conditions was proposed through an original methodology in which several oxidation and post-ageing conditions for different oxidation ranges (hot, upon cooling, at room temperature) were performed. The experiments showed little effect of water vapour mixed with air at 1100°C in isothermal conditions, in particular when the alumina scale grew over the surface. In contrast, water-containing environments at room temperature (relative humidity, water drops) increased the spallation of the oxide scales above a critical threshold time. Cyclic oxidation with water cooling provoked in turn, a catastrophic failure of the aluminide coatings by a mechanism involving thermal fatigue and pitting corrosion
Conrath, Élodie. "Élaboration et caractérisation de superalliages base chrome pour utilisation lors du fibrage centrifuge du verre à très haute température." Thesis, Université de Lorraine, 2016. http://www.theses.fr/2016LORR0018.
The TEL process is used to produce glass wool at very high temperature. The main piece of this process is the “spinner”, which is exposed, in service, to numerous operating constraints (oxidation, corrosion, erosion and creep). This spinner is currently made of cobalt- or nickel-based superalloys and is fabricated by casting. To fiberize new glasses or to increase the current maximal fiberizing temperature, a new type of superalloy is required. Chromium is an ideal candidate to be the principal element of a new superalloy because of its very high melting point and its ability to develop a chromia protective scale against oxidation and corrosion at high temperature, reason for which it is usually added to many classical superalloys. During this Ph.D work, the synthesis and the study of more than a hundred of chromium-based alloys with different chemical compositions was done by casting. These alloys are brittle at room temperature during their cutting. Laboratory tests of hardness at room temperature, oxidation and 3 points flexural creep at high temperature were performed. Metallographic characterisations were carried out (XRD, SEM, EPMA) on all alloys in their as-cast state, after isothermal annealing or isothermal oxidation. The detailed study of simple alloys permitted to discover some compositions removing the brittleness problem of these alloys. Then, the enrichment of the composition of the alloys by addition of new elements, allowed to correct some inherent problems of chromium-based alloys
Chaaban, Hind. "Étude cinétique et modélisation des effets des traitements thermiques et de l’environnement physico-chimique sur la dégradation et l’activité antioxydante des flavonoïdes." Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0065/document.
The objectives of this thesis are to study the effects of a heat treatment and the physicochemical environment on the stability of 6 flavonoids of different structure and on the evolution of their antioxidant activity. The heat treatment conditions were as follows: (i) heating under isothermal conditions for 2 h at temperatures ranging from 30 to 130 ° C and (ii) heating under non-isothermal conditions by microcalorimetry (30 to 130 ° C, 4 ° C / hour). The flavonoids were solubilized in water. We found that the glycosylated flavonoids are more resistant than the aglyconic flavonoids. The calculated degradation activation energies also depend on the structure of the flavonoid. To degrade, glycosylated flavonoids require high energy relative to the aglycone form. Exposure to light was carried out for 15 days with and without oxygen, the experimental control being a dark storage with and without oxygen. The degradation of flavonoids is influenced by the presence of light and by the amount of oxygen. The molecules have a different sensitivity according to their structure, the following classification is obtained according to: naringine, ériodictyol then rutin, luteolin, luteolin 7-O-glucoside and finally the mesquitol. Indeed, the presence of a hydroxyl group at position 3 and a C2-C3 double bond reduces the stability of the flavonoids. Furthermore, it has been observed that, despite the total degradation of certain flavonoids by the heat treatment and the physical-chemical environment, the treated solutions retain an antioxidant activity
Oulfarsi, Mostafa. "Contribution à l’amélioration de la fiabilité de modules thermoélectriques : développement de solutions matériaux alternatives." Electronic Thesis or Diss., Université de Lorraine, 2020. http://www.theses.fr/2020LORR0228.
Energy conversion from waste heat through thermoelectric effects (Seebeck effect) is a potential new renewable energy source. The thermoelectric (TE) technology is nevertheless limited to niche terrestrial applications due to its low efficiency (5-6%), but also due to the technological challenges to be overcome to avoid a degradation of the TE generators (TEG). Our thesis is devoted to this problem within the framework of a research program supported by the ANR (RELIATEG project) including HotBlockOnBoard (HBOB), CEA LITEN, CIRIMAT and IJL as partners. The objective is to make reliable the TEG, manufactured by HBOB, based on silicides, Mg₂Si₁₋ₓSnₓ (n-type) and MnSi₁₊ᵧ (p-type), for long-term use in the vicinity of 400-500°C. Our main role is to understand the mechanisms leading to their embrittlement, particularly to the oxidation problems linked to the Mg₂Si₀,₆Sn₀,₄ material. As they are unavoidable, we turned to the solutions of finding a protective coating and/or testing the thermal stability under air of a Mg₂Si₁₋ₓSnₓ material, less sensitive to oxidation. After a bibliographical synthesis of the basic concepts of TE and of the state of the art of TE materials, the choice of materials used by HBOB have been justified. The various stages of TEG manufacturing and the experimental techniques used to characterize the microstructure of TE materials and their thermal stability are presented. The performance tests performed on TEGs show that the power obtained, measured up to 450°C, is reproducible for the 25 devices tested. However, it is about 25% lower than what one could achieve with a perfect TEG, as shown by the simulations we carried out using the Comsol MultiPhysics software. The stability tests showed that the devices are stable under air at 250°C, for 500 hours or under 1000 cycles, and that they begin to degrade under air at 350°C through a pesting phenomenon linked to the oxidation of Mg₂Si₀,₆Sn₀,₄. Under vacuum, this process is slowed down but the presence of residual oxygen does not completely stabilize the material. At 500°C under air, the pesting is observed from 3 hours of testing. The oxidation tests carried out on the two materials with different Sn content showed the significant role of tin on the oxidation phenomena. A model explaining the pesting phenomenon was developed by the combined analyses of results obtained by thermogravimetric measurements, scanning electron microscopy and X-ray diffraction. On the basis of bibliography and phase diagrams of the differents systems, protective coatings based on ceramics, metallic silicides, metals and glasses have been studied. Several deposition methods were explored: sintering by Spark Plasma Sintering, electrochemical nickel plating, pack cementation, slurry, PVD and spray deposits. The most promising coatings were obtained with a glass whose CTE is close to that of the n-type material
Rakotovao, Felaniaina Nirisoa. "Relaxation des contraintes dans les couches de chromine développées sur alliages modèles (NiCr et Fe47Cr) : apport de la diffraction in situ à haute température sur rayonnement Synchrotron à l’étude du comportement viscoplastique : effets d’éléments réactifs." Thesis, La Rochelle, 2016. http://www.theses.fr/2016LAROS015/document.
Integrity of protective oxide scales developing at the metallic alloys surface at high temperature depends on the stress generation and their relaxation mechanisms. In this work, the behaviour of chromia scales formed on NiCr and Fe47Cr model alloys has been investigated. Raman spectroscopy was used to determine the residual stress level in chromia thin films after oxidation at different temperatures (700°C-1000°C) for 3 h and 18 h. A monotonous evolution of residual stresses with oxidation conditions was noted for the Ni30Cr/Cr2O3 system but not for the Fe47Cr/Cr2O3 one. The strain variations at microscopic scale was also determined by using atomic force microscopy. For the first studied system, non destructive relaxation by creep of the oxide and buckling can be more or less activated, in agreement with the residual stresses evolution. And a third additional stress release mode by intra film cracking could take place for the second system. In situ high temperature oxidation coupled with Synchrotron X-rays diffraction was also used to characterize the viscoplastic properties of chromia scales grown on Ni30Cr and Ni28Cr, with dissociating the effects related to thermal activation and grain size. The creep mechanism responsible of stress release in chromia scales has been evidenced by comparing experimental results with a diffusional creep model. Confrontation of the obtained activation energy (130 kJ.mol-1) with literature results has shown that this non destructive relaxation mode was likely governed by grain boundary transport of oxygen species. When a reactive element (Y or Zr) was added to the metallic substrate Ni28Cr, an important decrease of the oxidation rate was noted when increasing the amount of introduced element. No significant effect of this quantity on the residual stress level was however observed. At microscopic scale, a reduction of grain size has been also noted and two distinguished grains distribution appeared for the higher quantities. Results of in situ Synchrotron diffraction measurements and those of atomic force microscopy (grain boundary sliding) showed that the ability of chromia films to release stress thanks to their viscoplastic properties could be delayed and/or decreased with the presence of an active element. However, this mechanism could operate for smaller chromia films thicknesses
Francès, Maurice. "Oxydation et corrosion à chaud par NA:(2)SO::(4) de l'alliage nicocral(Y)+Ta coulé et projeté." Nancy 1, 1986. http://www.theses.fr/1986NAN10054.
Nozahic, Franck. "Elaboration par Spark Plasma Sintering et caractérisation de composites et multi-couches zircone yttrié/MoSi2(B) pour application barrière thermique auto-cicatrisante." Phd thesis, Toulouse, INPT, 2016. http://oatao.univ-toulouse.fr/17475/1/NOZAHIC_Franck.pdf.
Garnier, Pierre. "Etude des propriétés viscoélastiques d'un nitrile chargé sous sollicitations cycliques : application à la prédiction de la durée de vie des pompes à rotor excentré." Thesis, Clermont-Ferrand 2, 2012. http://www.theses.fr/2012CLF22274.
The study of the sustainability of the rubber, which is the main constitutive material of the Moineau pump stator, was carried out using finite element analyses, thermomechanical experiments and physic-chemical analysis. The numerical simulations were performed to identify the range and location of the maximal stress and strain within the pump stator. The experimental tests allowed to characterize the mechanical behaviour of rubber under cyclic solicitation at several temperatures. The first part of the study focused on the Payne effect during fatigue loading while the second dealt with the effect of a thermomechanical loading on the rubber microstructure evolution
Cervellon, Alice. "Propriétés en fatigue à grand et très grand nombre de cycles et à haute température des superalliages base nickel monogranulaires." Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2018. http://www.theses.fr/2018ESMA0009/document.
High and very high cycle fatigue properties of Ni-based single crystal superalloys have been studied at 1000°C using three frequencies (0.5, 70, 20000 Hz), four stress ratios (-1, 0.05, 0.3, 0.8) and CMSX-4 alloy as reference.Firstly, the very high cycle fatigue regime (VHCF) has been studied at 20 kHz. At R = -1, fatal crack always initiates between 106 and 109 cycles from an internal casting pore et then propagates in a crystallographic mode, despite the presence of other metallurgical defects such as eutectics and carbides. The elaboration process controls VHCF life under these conditions as it directly affects casting pore size, whereas microstructure has no relevant influence. At R = 0.8, creep controls VHCF life and makes this regime sensitive to microstructure and alloy’s chemical composition. Long term tests (> 109 cycles) have also been characterized and have enabled to propose a crack initiation mechanism operating in the VHCF regime.Secondly, the influence of frequency on time-dependent damages such as oxidation and creep, and their interaction, has been studied. At R ≤ 0, reducing frequency inhibits the harmfulness of internal critical defects by promoting oxidation surface damage. At R ≥ 0.8, creep damage leads to specimens rupture for all frequency test and loading conditions. Intermediate stress ratios present an important interaction between oxidation, fatigue and creep damage according to the frequency and loading conditions. Based on these observations, a damage model that predicts CMSX-4 fatigue life has been proposed and presents satisfying results in comparison to experimental data
Guibaud, Augustin. "Flame spread in microgravity environment : influence of ambient flow conditions." Electronic Thesis or Diss., Sorbonne université, 2019. http://www.theses.fr/2019SORUS129.
Flame spread and smoke emission are two primary threats in spacecraft environment, and soot radiations play a major role in both. In this context, the first objective of this PhD is to develop an optical diagnostic to probe soot particles in the axisymmetric laminar spreading flame. None of the existing techniques is able to probe the densely sooted flames expected in microgravity, while accommodating space station material constraints. A new methodology extending a laser-based diagnostic to broadband optics is thus developed to provide soot volume fraction and temperature mappings, which are required to detail soot-related radiative losses in the flame. Radiative losses in turn give access to radiative feedback to the fuel surface. This methodology is successfully assessed at normal gravity, before being implemented in parabolic flight. Numerical investigations are conjointly carried out to highlight the robustness of the measurements, and to investigate potential errors linked to the radiative model adopted. Results from parabolic flight campaigns show that flame spread rate mainly is a function of oxygen content, while smoke emission is affected by oxygen content and pressure. Focusing on the evolution of soot radiative properties with pressure, flame radiative losses are found to increase with pressure, reducing temperature at the trailing edge until soot oxidation reactions are frozen. Measured smoke point temperature and radiative properties are consistent with observations at Earth gravity. At any pressure, a stable portion of the soot-related radiative losses is fed back to the wire surface, and compensates part of the fuel surface radiative losses
Babicz, Sylvain. "Etude diélectrique des isolants plats anodisés pour la conception de machines électriques." Thesis, Artois, 2016. http://www.theses.fr/2016ARTO0204/document.
The use of state of the art organic enamels, capable to withstand 280 °C, makes the temperature class increase of electrical machine reaching its maximum. A technological breakthrough can be found by the substitution of organic enamel by a ceramic based insulation. Those materials are good dielectrics and their temperature resistance is very high compared to a classical technology. In this work, the studied conductor is an aluminum tape which insulation is obtained by an anodisation, an electrochemical process. This surface treatment makes the aluminum oxidizing: a thin layer of a few micrometres is obtained, thus representing the insulation layer of the conductor. The objectives of those PhD works is to identify and characterize this particular type of conductor so as to demonstrate the ability of using an anodized aluminum tape to makeelectrical machine running up to 400 °C. Measurements of PDIV, PDEV, and breakdown voltage are carried under various environmental conditions (temperatures varying from -70 °C up to 650 °C, variable humidity level). The use of an inverter to supply this high temperature machine induces steep fronts and over voltages. As a consequence, a theoretical model of a coil, made with this kind of conductor, is then proposed and based upon the impedance spectrum of the coil. The aim of this model is to help the designer to predict the first over voltage amplitude and to make the insulation of the first coil according to that. At least, a coil insulation improvement is depicted, using boron oxide: an impregnation is held to reinforce the alumina layer on the edge of the tape
Colin, Alexis. "Vieillissement thermique de peintures anticorrosion : corrélations entre les évolutions de la chimie, de l'architecture macromoléculaire et des propriétés fonctionnelles." Thesis, Clermont-Ferrand 2, 2015. http://www.theses.fr/2015CLF22640.
Anti-corrosive multilayer coatings, or anti-corrosive paints, are used in several industrial applications such as metallic package protection used for transportation or storage of radioactive materials. In working conditions, functional properties of these paints could be degraded under the influence heat or environmental conditions (light, oxygen, moisture …). Such evolutions had been attributed to the aging of the different paint layers that constituted the anticorrosive coating (acrylic-siloxane topcoat, epoxy resin with amine hardener undercoats). In order to properly carry out this study, a « bottom-up multiscale approach » has been developed. This methodology, initially focused on the physico-chemical modifications of neat polymers that constituted each layer of the coating (from chemical structure and macromolecular architecture evolutions to functional properties), is then complexified by adding filers to the paint formulations (pigments, barrier or anti-corrosive particles …). The complete multilayer coating analyses are the last steps of that methodology. The aim of this thesis is to identify and correlate the evolution of anti-corrosive multilayer coating functional properties to the chemical and architectural modifications in each different layer
Chrétien, Gaëlle. "Etude de la propagation de fissures physiquement courtes dans les alliages de titane pour turbomachines d'hélicoptères à différentes températures." Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2017. http://www.theses.fr/2017ESMA0022.
Damage tolerance analyses of rotating parts, containing 2D-short crack, in turbomachines of helicopters is the main focus of this thesis.Fatigue crack propagation tests were performed at R=0.1 on two bimodal Titanium alloys at different temperatures (20°C and 400°C for TA6V and 20°C, 200°C and 500°C for Ti6242). Near-threshold effective behaviors (after crack closure correction) were approximately the same for the two alloys attested temperatures. Crack closure was principally due to oxide layer at high temperatures and to fracture surface roughness at ambient temperature.Then the variations of the crack propagation threshold with crack length was studied at R=0.1 and different temperatures. A numerical tool was developed to automatically detect crack closure level more precisely for, as short as, 80μm cracks. Crack closure levels measured at different crack lengths obtained from progressive machining of the plastic wake were quite similar to the ones obtained during propagation of 2D-short cracks near the threshold, except at high temperatures where oxide-induced crack closure developed rapidly. Differences in behavior of long cracks and short cracks were explained by a reduction of crack closure level when crack wake was not fully developed.A non-propagation criterion based on formalism initially proposed by Kitagawa and a modified-Paris propagation law allow to give a better description of physically 2D-short crack propagation resistance
Rannou, Benoît. "Slurry coatings from aluminium microparticles on Ni-based superalloys for high temperature oxidation protection." Phd thesis, Université de La Rochelle, 2012. http://tel.archives-ouvertes.fr/tel-00839790.