ED 139, Connaissance, langage, modélisation

Southampton Conference – Margaret Cavendish on Literature Conference Program, 10–12 June, University of Southampton
My talk: Milena Louise Liers (University of Paris Nanterre), “The Concept of Contemplation: Philosophy and Literature in Margaret Cavendish’s Writings”

The role of Contemplation in Margaret Cavendish's Philosophy of Nature and whether it is an active or passive capacity of the human intellect. Workshop: Cavendish: Mind, Consciousness and Perception, at the Center for the History of Women Philosophers and Scientists (HWPS), University of Paderborn

-Nous proposons un modèle de comportement élastoplastique adapté au calcul thermomécanique à haute température, rencontré par exemple en simulation numérique du soudage. Ce modèle permet de prendre en compte la restauration d'écrouissage à l'état solide. Ce modèle a été implanté via le générateur de code MFront, développé par le CEA, et permettant en particulier l'intégration de lois de comportement dans un code de simulation numérique. Le modèle est validé sur un essai de dilatométrie bloquée (essai Satoh), en comparant les résultats numériques à des résultats expérimentaux. Mots clés-plasticité, thermomécanique, simulation numérique du soudage, seuil surfacique, restauration d'écrouissage, dilatométrie.

This paper presents a numerical simulation of a shear-wall mock-up subjected to monotonic loading with a new steel-concrete bond model. First, global responses (forcedisplacement curves) are compared to the experimental results and show a good agreement between simulation and experiment. In order to compare the local responses such as crack orientation, crack spacing and crack opening, a new post-processing method is presented. It is based on the definition of the crack path from the displacement field or the change in the sign of the bond slip. The crack opening is then obtained using the displacement in the normal direction of the crack. The method is applied on the shear wall and the results are compared to the experimental data obtained with digital image correlation. A good agreement is once again obtained.

Purpose – The purpose of this paper is to present a new bond slip model for reinforced concrete structures. It consists in an interface element (3D) which represents the interface between concrete (modeled in 3D) and steel, modeled using 1D truss elements. Design/methodology/approach – The formulation of the interface element is presented and verified through a comparison with an analytical solution on an academic case. Finally, the model is compared with experimental results on a reinforced concrete tie. Findings – Contrary to the classical perfect or “no-slip” relation which supposes the same displacement between steel and concrete, the proposed model is able to reproduce both global (force-displacement curve) and local (crack openings) results. Originality/value – The proposed approach, applicable to large-scale computations, represents a valuable alternative to the no-slip relation hypothesis to correctly capture the crack properties of reinforced concrete structures.

This paper presents the application of a new steel-concrete bond model on a reinforced concrete shear wall, experimentally tested during the French National Project CEOS.FR. The proposed results include both global (evolution of the force as a function of the displacement for example) and local results (crack opening and spacing). A new post-processing method to compute these local properties even in a case of a complex crack pattern (oriented cracks for example) is proposed. It is based on the change in the sign of the bond slip between steel and concrete. The simulated results are in a good agreement with the experiment and validate the developments. Finally, the interest of including a specific steel-concrete bond model in the finite element simulation is highlighted, compared to classical "no-slip" relation.

In the framework of the level-set method we propose a topology optimization algorithm for linear elastic structures which can exhibit fractures. In the spirit of Grith theory, brittle fracture is modeled by the Francfort-Marigo energy model, with its Ambrosio-Tortorelli regularization, which can also be viewed as a gradient damage model. This quasi-static and irreversible gradient damage model is approximated using penalization to make it amenable to shape-dierentiation. The shape derivative is determined using the adjoint method. The shape optimization is implemented numerically using a level-set method with body-tted remeshing, which captures shapes exactly while allowing for topology changes. The eciency of the proposed method is demonstrated numerically on 2D and 3D test cases. The method is shown to be ecient in conceiving crack-free structures.

-Cette contribution concerne l'industrialisation de l'optimisation de forme topologique par la méthode des lignes de niveaux. La stratégie d'évolution de domaine est basée sur un double paramétrage de la forme : d'une part, la pièce est décrite de manière implicite par une fonction de ligne de niveaux, d'autre part, elle est discrétisée de manière explicite par un maillage ajusté. Ces deux représentations sont complémentaires : la première autorise des évolutions arbitraires de la forme, incluant des changements topologiques, tandis que la deuxième permet de calculer l'état du système sans nécessiter d'artifice numérique et facilite l'évaluation des contraintes de fabrication exprimées sous forme géométrique. Mots clés-optimisation topologique ; méthode des lignes de niveaux ; adaptation de maillage ; contrainte de fabrication.

Topology Optimization (TO) is a powerful tool customarily used in industrial applications to enhance the design of mechanical structures. However TO tends to generate complex topologies, often comprising a network of structural members of arbitrary thicknesses, which are hard to build with traditional manufacturing techniques such as casting. Hence, a significant effort has been devoted to the incorporation of manufacturing constraints directly into the TO design process. This presentation focuses on the development of a minimally-intrusive modular software architecture based on the level-set method, a work performed in the context of the TOP project at IRT SystemX (https://www.irt-systemx.fr/en/project/top/). The classical notions of shape derivative and advection of the implicit domain via the solution of a Hamilton-Jacobi equation [1] are coupled with mesh adaptation techniques [2], enabling the generation of a computational mesh conformal to the shape interface at each iteration...

The additive manufacturing process (i.e. Selective Laser Melting) allow us to produce lattice structures which have less weight, higher impact absorption capacity and better thermal exchange property compared to the classical structures. Unfortunately, geometrical imperfections in the lattice structures are by-product results of the manufacturing process. These imperfections decrease the lifetime and the strength of the lattice structures and alterate their mechanical responses. The objective of the paper is to present a simulation strategy which allows us to take into account the effect of the geometrical imperfections on the mechanical response of the lattice structure. In the first part, an identification method of geometrical parameters of the lattice structure based on tomography measurements is presented. In the second part, a finite element model for the lattice structure with the simplified geometrical imperfections is obtained. In what follows, based on experimental tests, distributions of geometrical imperfections are proposed. Based on these distributions, a mathematical approach is presented to propagate the effect of uncertainties of the geometrical imperfections on the strength variability of the lattice structure.

Topology optimization is devoted to the optimal design of structures: It aims at finding the best material distribution inside a working domain while fulfilling mechanical, geometrical and manufacturing specifications. Conceptually different from parametric or size optimization, topology optimization relies on a freeform approach enabling to search for the optimal design in a larger space of configurations and promoting disruptive design. The need for lighter and efficient structural solutions has made topology optimization a vigorous research field in both academic and industrial structural engineering communities. This contribution presents a Research and Development software platform for shape and topology optimization where the computational process is carried out in a level set framework combined with a body-fitted approach.

Le comportement des structures en béton armé peut s’avérer extrêmement complexe en cas de dépassement de la limite de fissuration du béton. Le caractère composite du béton armé doit être représenté finement. Pour la simulation des structures industrielles, les modèles numériques employés supposent une relation parfaite entre le béton et les armatures qui non seulement ne prennent pas en compte la complexité de la relation entre les deux matériaux mais aussi ne permet pas de présenter finement les caractéristiques de la fissuration étant directement liée à celle des aciers. Dans la littérature, plusieurs méthodes numériques sont proposées pour étudier finement les caractéristiques de la liaison acier-béton, mais toutes ces méthodes posent des difficultés pour les calculs de structures complexes en 3D. En partant des résultats obtenus dans le cadre de la thèse de Torre-Casanova (2012), une nouvelle formation d’un modèle de liaison acier-béton a été développée pour améliorer les perfor...