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Application d'une formulation explicite en vitesse à la modélisation numérique du forgeage

Abstract : The present work is a contribution to the numerical modelling of high velocity hot forging processes. In this framework, a dynamic partly-explicit acceleration/pressure formulation is investigated. First of all, some velocity/pressure implicit formulations (quasi-static and dynamic) are presented and analysed in order to obtain a reference formulation for the partly-explicit formulation we propose. Second, the dynamic partly-explicit formulation is presented in a viscoplastic context. As the current velocity is supposed to be known, we do not have to deal with the non-linear feature of the material. Consequently, the system coresponding to our problem is linear. The mixed finite element discretisation is based on a simple triangular mini-element P1+/P1. Analysis concerning the bubble properties and its influences on the equation system were realized and some approximations were done in order to simplify the formulation. This new dynamic formulation has been successfully implemented in a version of the code FORGE2. Comparisons with implicit approaches, considered as references, have been performed for some numerical examples. This proves the relevance of our approach. An improvement concerning the volume loss is noted for the new procedure. Furthermore, a CPU time reduction of at least 20% is obtained, when the same time step is considered for the implicit simulations as well as for the partly-explicit simulations. The procedure is then extended to the elastic viscoplastic case. In order to simplify the problem resolution, a new strategy is exposed and analysed. It consists in solving a linear system with the pressure as a single unknown and then obtaining explicitly the acceleration as a pressure function. The estimations realised show that this technique would reduce significantely the computational time in 2D as well as in 3D. The partly-explicit dynamic formulation proposed could consequently be considered as an attractive alternative for the hot forging simulation.
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  • HAL Id : tel-00274705, version 1

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Mihaela Teodorescu. Application d'une formulation explicite en vitesse à la modélisation numérique du forgeage. Mécanique [physics.med-ph]. École Nationale Supérieure des Mines de Paris, 2002. Français. ⟨NNT : 2002ENMP1086⟩. ⟨tel-00274705⟩

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