Search results for "Propriétés mécaniques"
showing 10 items of 12 documents
Multi-experimental study of micro-structural and mechanical consequences of thermal cycles applied to a martensitic stainless steel « APX4 »
2010
The Direction des Applications Militaires at the Commissariat à l’Énergie Atomique, a French government-funded technological research organisation, selected a low carbon chromium rich martensitic stainless steel (APX4) to manufacture components with high yield strength and ultimate tensile strength. As such, this thesis is developed around three main axes. Firstly, the thesis summarizes the existing bibliography on this steel as well as its neighboring nuances. Secondly, it engages in a precise characterization of the material that is currently used for industrial manufacturing. Finally, this highly experimental work undertakes to observe and interpret the micro-structural and mechanical co…
Contribution to the development of 100% bio-based composites : synthesis of bio-based polyepoxides, supercritical CO2 treatment of hemp fibers and im…
2018
This thesis contributes to the development of 100% bio-based hemp/epoxy composites. Current environmental issues favor the emergence of materials derived from renewable resources such as plant fibres and a wide range of bio-based building-blocks, source of epoxy prepolymers in particular. An intensive investigation of the two constituents (hemp fibres and polyepoxidic matrix) is carried out before the composites manufacturing. Supercritical CO2 treatment is applied to hemp fibres used as reinforcement in composite materials. This treatment, not optimized, leads to better individualization as well as a decrease in the hygroscopic power of the fibres. These aspects, which are essential in ord…
Study of interface formation during diffusion bonding : compact heat exchangers application
2014
Compact diffusion bonded heat exchangers are an attractive option in many fields (nuclear, (petro-)chemistry, solar…) due to their performance. This type of concept is especially intended for manufacturing the energy conversion system of the ASTRID reactor. During diffusion bonding by HIP, the problem is twofold: the channel deformation and microstructure evolution must be controlled, while at the same time, highly resistant interfaces are desired. This thesis is focused on the understanding and the control of the bonded components microstructure prepared by HIP in order to define « process » criteria to achieve welds in agreement with specifications of components containing fluidic channel…
Mechanical properties, internal structure and transport mechanism of oxygen in cork
2015
During the post bottling aging, premature oxidation reactions could occur and the oxygen barrier properties of the stopper are often pointed out. Nowadays, the internal structure of this material or the effect of hydration on its mechanical properties are still undetermined. Moreover, regarding the barrier properties, the limiting step of the oxygen transfer was not yet fully understood as well as the effect of compression or the role of the glass/cork interface in a bottleneck. The study of the internal structure of cork stopper allowed us to visualize the macroporosity of the material and conclude that there is no interconnectivity between lenticels, for the two qualities studied. The eff…
Additive manufacturing Processing and characterization of Fe-Si soft magnetic alloys
2021
Iron silicon (Fe-Si) alloys, also named silicon steels, are the most widely used owing to their excellent soft magnetic properties and economic costs. As electronic devices become diversified and automated, it is urgent to develop high-performance soft magnetic alloys with good reliability. For functional soft magnetic alloys, the SLM technique shown the potential to manufacture soft magnetic components directly from raw materials, such as the rotor and stator of the motor. In order to explore and develop new routes for manufacturing Fe-Si alloys, the investigation into the microstructures and properties of SLMed Fe-Si alloys from pre-alloyed powders was presented in this work. The most imp…
Polygalacturonate hydrogels using Fe2+ as cross-linkers : impact of the local association mode on gelation mechanisms, control of the multiscale stru…
2018
This pHD thesis describes the design of polygalacturonate hydrogels (polyGal) cross-linked by the Fe2+ cations, and their experimental characterization from the molecular scales up to the macroscopic scales, by combining EXAFS spectroscopy, Small Angle Neutron Scattering (SANS) and rheological measurements. We designed a robust gelling protocol that allowed to obtain reproducible cylindrical gels with controlled concentration gradients from the lower side to the upper side of the gel. The ratio [Fe]/[Gal] has a constant value all along the gel, which demonstrate that the Fe2+ cations are associated with 4 galacturonate units. The comparison of EXAFS measurements and molecular dynamics simul…
Influence de l'orientation des fibres sur un essai Arcan = Influence of fiber orientation on Arcan test data
2009
National audience; Ce papier présente les résultats d'une étude expérimentale portant sur le comportement d'éprouvettes ‘papillon' en verre/époxy, soumises à des chargements de cisaillement pur et de traction-cisaillement combinés, au moyen d'un dispositif Arcan. Des éprouvettes dont les fibres sont orientées parallèlement à la direction des entailles et d'autres pour lesquelles les fibres sont perpendiculaires à cette direction, respectivement désignées Mat31 et Mat32, ont été testées pour différents angles de sollicitation, dans une plage comprise entre 0° et 90°. Le mode de rupture observé pour les éprouvettes Mat31 est répétitif, alors qu'il dépend de la direction de la sollicitation po…
Development and characterization of a bio-based epoxy matrix for high-grade bio-based composites
2019
This study aims to develop 100% bio-based hemp/epoxy composites for semi-structural and structural applications. The thermal and mechanical performances of a 100% bio-based matrix derived from biomassare evaluated and reveal properties in the same order of magnitude as those obtained for polyepoxides based on DGEBA, that means a glass transition temperature of approximately 150°C and mechanical properties in the order of 120MPa for the maximum stress and 3.2 GPa for the tangent apparent modulus. This natural origin matrix is then used for the manufacture of composites reinforced with hemp rovings. The bending properties of these 100% bio-based materials are equivalent to those determined fo…
Development and characterization of a bio-based epoxy matrix for high-grade bio-based composites
2019
This study aims to develop 100% bio-based hemp/epoxy composites for semi-structural and structural applications. The thermal and mechanical performances of a 100% bio-based matrix derived from biomassare evaluated and reveal properties in the same order of magnitude as those obtained for polyepoxides based on DGEBA, that means a glass transition temperature of approximately 150°C and mechanical properties in the order of 120MPa for the maximum stress and 3.2 GPa for the tangent apparent modulus. This natural origin matrix is then used for the manufacture of composites reinforced with hemp rovings. The bending properties of these 100% bio-based materials are equivalent to those determined fo…
Physical, chemical and mechanical evolution of the fuel-cladding interface in irradiated PWR fuel rods
2022
During the fuel irradiation in nuclear reactor, the fuel-cladding assembly is exposed to several irradiation-induced modifications. The fuel swelling coupled with cladding creep leads to a contact between the fuel and the cladding. The oxygen transport from the UO2 fuel to the zirconium layer induces progressively the Zr-cladding oxidation. This oxidation is initially local with the formation of islets. Then, with the increasing burnup of the fuel, it conducts to a continuous layer of about 8-µm thickness, localized at the fuel-cladding interface. At high burnup, zirconia growths anchor themselves in the periphery of the fuel (which is restructured) leading to pellet/cladding interlocking. …