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Détermination des propriétés élastiques et du retrait d'un cerne annuel de chêne dans le plan transverse : description de la morphologie, mesures des propriétés microscopiques et calculs d'homogénéisation

Abstract : Because of its biologie origin, wood is a very variable composite. The aim of this work is the understanding of the variability of mechanical and shrinkage properties of oak by a deterministic approach that takes into account the spatial distribution of the components and their intrinsic properties. Realized at the annual ring scale, this approach requires two kinds of data and needs the development of specific tools : * The morphology specifies the components (ray cells, fiber. .. ) and describes their spatial distribution inside the representative volume (the annuai ring) of the material. A numerical imaging device, using Xray attenuation principle, has been developed in order to perform images of the structure. * The microscopie properties of the main components. Within the context of this work, we are interested by mechanical and shrinkage properties. So, two types of microscopie samples areprepared within each component: - On the one hand, micro tensile tests under microscope are performed. The comparison of images at different stress levels permits to obtain elastic properties (Young modulus and Poisson's ratio) for each kind of tissue. - On the other hand, other samples are placed in a specifie climatic chamber which is installed inside the previous X-cay imaging device. Images are performed at different humidity rates. A specifie process permits to compare them and calculates the swelling coefficients of the sample simultaneously in two directions. Finally, the use of a numerical tool, MorphoPore, permits to connect ail these data in order to calculate the macroscopic properties of annual rings. A numerical mesh is built from the image provided by the X-ray device and the measured microscopie properties are injected in the calculation. The possibilities of this tool are presented with few examples Especially, this approach permits to separate the influences of genetic parameters, as the specific structural characteristics, and of growth parameters as silviculture or station. For example, we propose to quantify the influence of growth speed of a tree on mechanical and shrinkage properties of its wood.
Keywords : CHENE
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Submitted on : Sunday, June 7, 2020 - 1:55:44 PM
Last modification on : Tuesday, June 15, 2021 - 2:57:29 PM

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  • HAL Id : tel-02840165, version 1
  • PRODINRA : 17063

Citation

Eric Badel. Détermination des propriétés élastiques et du retrait d'un cerne annuel de chêne dans le plan transverse : description de la morphologie, mesures des propriétés microscopiques et calculs d'homogénéisation. Ingénierie des aliments. Ecole Nationale du Génie Rural des Eaux et Forêts, 1999. Français. ⟨tel-02840165⟩

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