Amélioration de la modélisation de contact pour les procédés à faible zone de contact

Abstract : Finite element simulation of forming processes is now widely recognized as an efficient tool for designing actual forming processes in industry. However, for metal forming processes where the contact area is quite small with respect to the component size, like wire drawing, extrusion and rolling, there is still an extensive need for increasing the accuracy and robustness of the results while decreasing the computational time. In the finite element code FORGE®, the contact model is inappropriate to properly simulate these processes. The specific goal of this work is to develop new techniques for improving contact model. In the first part, an implicit scheme of contact is developed on the basis of the first formulation. This work is divided on two steps. First, a general implicit scheme based on an updating of unilateral contact condition at each Newton-Raphson iteration is implemented. Secondly, a fully implicit formulation of the problem of contact and the smoothing of tool surfaces by using their analytical description specific for ring rolling process is developed. The second part, a smoothing contact procedure is implemented. The smoothing of contact surfaces, which are defined by linear triangles, is based on a higher order quadratic interpolation of the curved surface. This interpolation is derived from the node positions and their normal vectors, as proposed by Nagata. The normal vectors are calculated at each node from the existing discretized surface by considering a patch of surrounding elements using Normal Vector Voting method. The efficiency and reliability of different resulting contact model are assessed on several examples, such as the indentation of a parallelepiped and the drawing of a wire.
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Maha Hachani. Amélioration de la modélisation de contact pour les procédés à faible zone de contact. Matériaux. École Nationale Supérieure des Mines de Paris, 2011. Français. ⟨NNT : 2011ENMP0078⟩. ⟨pastel-00682124⟩

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