Seepage and Stress Coupling Algorithm of Fractured Rock Mass by Composite Element Method

Le travail de thèse porte sur l'analyse du couplage écoulement – contrainte dans les roches fracturées et son application aux barrages. Le rapport de thèse est composé de 5 chapitres. Le premier chapitre présente une synthèse des travaux réalisés sur les roches fracturées et plus particulièrement sur le couplage écoulement – contrainte. L’accent est mis sur la modélisation numérique. Le second chapitre concerne la formulation de l’Élément Composite pour les roches fracturées. Il présente cet élément pour le problème mécanique ensuite pour le problème d’écoulement. Le 3ème chapitre présente l’extension de l’élément composite aux roches fracturées en prenant en compte le couplage contrainte – écoulement. Après une présentation de la formulation mathématique, on décrit l’introduction de cet élément dans un code de calcul. Le chapitre décrit aussi le fonctionnement de cet élément pour une fracture soumise à une contrainte normale puis à un cisaillement. Le 4ème chapitre traite de l’application de l’élément composite aux masses de roches fracturées contenant des drains. La performance de l’élément composite pour ce type d’applications est montrée à travers sa confrontation à la méthode des éléments finis classique. Le dernier chapitre présente l'application de l'élément composite à l'analyse du barrage de Xiaowan ayant un système de fondation complexe. La fondation contient trois ensembles de fractures et des drains. Cet exemple montre les performances de l'élément composite pour l'analyse des projets à géométrie complexe contenant des fractures.The thesis concerns analysis of the stress-seepage coupling in fractured rock mass and its application on dams. The thesis is composed of 5 chapters. The first chapter presents a literature review on researches conducted on fractured rock mass and on seepagestress coupling in fractured rock with a particular focus on numerical modeling. The second chapter concerns the formulation of the composite element method for fractured rock mass. It presents the composite element method for stress and seepage problems. The third chapter concerns the formulation of the composite element for fractured rock mass considering seepage- stress coupling. After the mathematical formulation, it presents the numerical implementation of the composite element and its performances under both normal and shearing stress states. The 4th chapter presents analysis of the seepage-stress coupling for fractured rock mass with drainage holes. The numerical model is validated by its comparison to the convention al finite element method. The last chapter presents the use ofthe composite element for the analysis of the Xiaowan arch dam with complex fractured rock mass. The later contains three sets of fractures and drainage holes. This example shows the advantage and performances of the composite element for the analysis of complex projects

Seepage and Stress Coupling Algorithm of Fractured Rock Mass by Composite Element Method

Le travail de thèse porte sur l'analyse du couplage écoulement contrainte dans les roches fracturées et son application aux barrages. Le rapport de thèse est composé de 5 chapitres. Le premier chapitre présente une synthèse des travaux réalisés sur les roches fracturées et plus particulièrement sur le couplage écoulement contrainte. L accent est mis sur la modélisation numérique. Le second chapitre concerne la formulation de l Élément Composite pour les roches fracturées. Il présente cet élément pour le problème mécanique ensuite pour le problème d écoulement. Le 3ème chapitre présente l extension de l élément composite aux roches fracturées en prenant en compte le couplage contrainte écoulement. Après une présentation de la formulation mathématique, on décrit l introduction de cet élément dans un code de calcul. Le chapitre décrit aussi le fonctionnement de cet élément pour une fracture soumise à une contrainte normale puis à un cisaillement. Le 4ème chapitre traite de l application de l élément composite aux masses de roches fracturées contenant des drains. La performance de l élément composite pour ce type d applications est montrée à travers sa confrontation à la méthode des éléments finis classique. Le dernier chapitre présente l'application de l'élément composite à l'analyse du barrage de Xiaowan ayant un système de fondation complexe. La fondation contient trois ensembles de fractures et des drains. Cet exemple montre les performances de l'élément composite pour l'analyse des projets à géométrie complexe contenant des fractures.The thesis concerns analysis of the stress-seepage coupling in fractured rock mass and its application on dams. The thesis is composed of 5 chapters. The first chapter presents a literature review on researches conducted on fractured rock mass and on seepagestress coupling in fractured rock with a particular focus on numerical modeling. The second chapter concerns the formulation of the composite element method for fractured rock mass. It presents the composite element method for stress and seepage problems. The third chapter concerns the formulation of the composite element for fractured rock mass considering seepage- stress coupling. After the mathematical formulation, it presents the numerical implementation of the composite element and its performances under both normal and shearing stress states. The 4th chapter presents analysis of the seepage-stress coupling for fractured rock mass with drainage holes. The numerical model is validated by its comparison to the convention al finite element method. The last chapter presents the use ofthe composite element for the analysis of the Xiaowan arch dam with complex fractured rock mass. The later contains three sets of fractures and drainage holes. This example shows the advantage and performances of the composite element for the analysis of complex projects.LILLE1-Bib. Electronique (590099901) / SudocSudocFranceF

Microstructural Evaluation and Tensile Properties of Al-Mg-Sc-Zr Alloys Prepared by LPBF

Laser powder bed fusion (LPBF) is a typical additive manufacturing technology that offers significant advantages in the production of complex components. With the rapid heating and cooling characteristics of LPBF, a large amount of solid solution of alloying elements in the matrix can be achieved to form supersaturated solid solutions, thus enhancing the properties of LPBF alloys. For the unique microstructure, the heat treatment process needs to be adjusted accordingly. In this work, a Zr/Sc-modified Al-Mg alloy processed by laser powder bed fusion (LPBF) with relatively low cost and good mechanical properties was investigated. The fine microstructure was obtained under rapid solidification conditions. The nanoscale Al3(Sc,Zr) particles precipitated at the molten pool boundary during solidification. These particles, as effective heterogeneous nucleators, further refined the α-Al grains and improved the mechanical properties of the alloy. As a result, the alloy exhibited a heterogeneous microstructure consisting of columnar grains in the center of the molten pool and equiaxed grains at the boundaries. The rapid solidification resulted in the supersaturation of solute atoms in the α-Al matrix, which significantly enhanced the solid solution strengthening effect. With the LPBF processing parameters of a combination of a laser power of 250 W, a laser scanning speed of 833 mm/s, and stripe scanning mode, the tensile strength of the alloy reached 401.4 ± 5.7 MPa, which was significantly higher than that of the cast alloys with aging treatment (281.1 ± 1.3 MPa). The heat treatment promoted the formation of secondary Al3(Sc,Zr), Mn/Mg-rich phases. The ultimate tensile strength and elongation at fracture after aging at 325 °C for 2 h were 536.0 ± 1.7 MPa and 14.8 ± 0.8%, respectively. The results provide insight into the preparation of aluminum alloys with relatively low cost and excellent mechanical properties

Droplet-based mechanical transducers modulated by the symmetry of wettability patterns

Abstract Asymmetric mechanical transducers have important applications in energy harvesting, signal transmission, and micro-mechanics. To achieve asymmetric transformation of mechanical motion or energy, active robotic metamaterials, as well as materials with asymmetric microstructures or internal orientation, are usually employed. However, these strategies usually require continuous energy supplement and laborious fabrication, and limited transformation modes are achieved. Herein, utilizing wettability patterned surfaces for precise control of the droplet contact line and inner flow, we demonstrate a droplet-based mechanical transducer system, and achieve multimodal responses to specific vibrations. By virtue of the synergistic effect of surface tension and solid-liquid adhesion on the liquid dynamics, the droplet on the patterned substrate can exhibit symmetric/asymmetric vibration transformation when the substrate vibrates horizontally. Based on this, we construct arrayed patterns with distinct arrangements on the substrate, and employ the swarm effect of the arrayed droplets to achieve three-dimensional and multimodal actuation of the target plate under a fixed input vibration. Further, we demonstrate the utilization of the mechanical transducers for vibration management, object transport, and laser modulation. These findings provide a simple yet efficient strategy to realize a multimodal mechanical transducer, which shows significant potential for aseismic design, optical molding, as well as micro-electromechanical systems (MEMS)