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International audience; Microstructural predictions on multi-pass processes are very challenging because the grains topology evolves in a very wide range, due to the coupled action of hardening, recovery, grain growth (GG), discontinuous dynamic and post dynamic recrys-tallization (DRX and PDRX). Classical models reach their limits. More physical approaches taking into account the complexity of the topology becomes necessary. In this article, DIGIMUQ®, the first commercial full field (FF) simulation software dedicated to grain growth and recrystallization modeling will be presented. Its ability to model industrial processes will be illustrated on an industrial-like 2D plate rolling process.

In this paper, numerical simulations of flows in a co-rotating intermeshing twin-screw extruder are performed using a previously presented 3D finite elements model. Some numerical improvements recently introduced are presented. The computations are performed for several processing conditions and screw arrangements. Values of specific energy, pressure and filled length are compared to the results issuing from the 1D Ludovic software in order to compare both approaches. The 3D simulation method is found to be more accurate to describe the effect of varying staggering angle and thickness of kneading discs. On the other hand, 1D model provides very satisfactory results for flows in screw elements.

We introduce an innovative formulation for simple linear tetrahedral elements non-sensitive to volumetric locking. Tetrahedral meshes enable to deal with high deformation by using efficient and robust adaptive meshers—while standard explicit formulations based on linear hexahedral elements with reduced integration and hourglassing stabilization cannot be coupled with efficient remeshing procedures. The principle of this anti-locking modification is to impose the volumetric constraints at each node instead of at each integration point, as been done in the averaged nodal pressure formulation proposed by Bonet in 1998. However, the modification made here is material independent: the strain tensor is directly modified before any stress or pressure calculus. The formulation is extended to incompressible elasticity and von Mises incompressible isotropic inelasticity (elastic–visco-plasticity). An infinitesimal strain formulation has been chosen in order to obtain a very simple and thus computational time saving algorithm. This choice can be easily justified taking into account the value of the critical time step in explicit simulations, especially for metal-forming processes. Standard elastic and inelastic benchmarks issued from the literature validate qualitatively and quantitatively this promising formulation for quasi-incompressible deformations cases. Copyright © 2009 John Wiley & Sons, Ltd.

International audience; We will adapt a recent explicit FE formulation with modified linear tetrahedral elements for high speed metal forming simulation. This formulation both enables the use of efficient adaptive non structured meshers, and tackles the locking effect in quasi-incompressible cases. We implement this formulation for the infinitesimal elastic plastic case. The anti-locking modification effect will be underlined on two 3D bench marks: an elastic compression test and an elastic-plastic bar impact test.

Special Issue on Modelling of Machining Processes; International audience; This paper presents the several advantages of a new explicit formulation using modified linear tetrahedral elements non-sensitive to volumetric locking in the scope of high speed machining simulations. First, the explicit time integration allows obtaining very interesting computational time in very dynamic cases with complex behaviour laws. Then, the use of a tetrahedral mesh permits to use robust non-structured adaptive remeshers too. No chip separation criteria or damage model is used. Our 2D orthogonal cutting model detects automatically the apparition of an adiabatic shear band, and simulates very precisely its evolution and the chip formation. Phenomena relative to adiabatic shearing bands already described in the literature can be observed in detail in the simulation. This model is a powerful tool to improve the understanding of chip formation and adiabatic shear band propagation, and to simplify the optimisation of high speed machining processes in industries.