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Durin A.,CNRS Nantes Thermocinetique Lab | Chenot J.-L.,Transvalor SA | Haudin J.-M.,MINES ParisTech | Boyard N.,CNRS Nantes Thermocinetique Lab | Bailleul J.-L.,CNRS Nantes Thermocinetique Lab
European Polymer Journal | Year: 2015

In this paper, a general numerical method to simulate polymer crystallization under various conditions is proposed. This method is first validated comparing its predictions with well-validated analytical models in infinite volumes. Then, it is compared to Billon et al. validated model for thin films, without or in presence of transcrystallinity on the films surfaces. It is also compared with Chenot et al. model for thin films, proposed in a conference in 2005 and never yet compared with other methods. Finally, it is also compared with an extension of this model for the transcrystalline case. These models are valid for general nucleation cases (not only sporadic or instantaneous), and can be used for any thermal conditions. All the numerical and analytical results are consistent, except in a case which is shown to be out of the validity domain of the transcrystalline case extension of Chenot et al. model. © 2015 Elsevier Ltd. All rights reserved.


Cao T.-S.,MINES ParisTech | Maire E.,CNRS Laboratory for Materials: Engineering and Science | Verdu C.,CNRS Laboratory for Materials: Engineering and Science | Bobadilla C.,ArcelorMittal | And 3 more authors.
Computational Materials Science | Year: 2014

The present paper deals with the identification of the parameters of a generalized GTN model and the characterization of ductile damage for a high carbon steel by both X-ray micro-tomography and "macroscopic" mechanical tests. First, in situ X-ray micro-tomography tensile tests are performed and the results are used for the modeling of ductile damage mechanisms (voids nucleation, growth and coalescence) using analytical formulations. Interrupted in situ SEM tensile test is also carried out to examine the microstructure evolution. The damage process during in situ X-ray micro-tomography tensile tests is the result of continuous nucleation of small voids and significant growth of large voids; whereas the coalescence takes place locally. In addition, tomography results combined with the results of macroscopic mechanical tests at different loading configurations are used to identify the Gurson-Tvergaard-Needleman model extended for shear loading by Xue (2008). It proved necessary to propose an improvement to account for the influence of the stress triaxiality level on the nucleation formulation of the GTN model. This new formulation is then identified via experimental tests. The results show that, with the parameters obtained from both microstructure measurements and macroscopic considerations, the modified GTN model can reproduce quite accurately the experimental results for different loading configurations. © 2013 Elsevier B.V. All rights reserved.


The "secret" of an efficient Ring rolling production process is the ability of the ring rolling machine to maintain centered the ring, and drive the growt in height and diameter, avoiding non-round shapes and defects. In the real process, this work is done directly from the numerical control acting on the mandrel, cones and on the centering rolls (position and force), starting from a definition of the lamination curves, defined in the software by the operator. The machine try to respect this program, monitoring the shape of the ring, by some laser measuring system and load sensors, correcting the kinematic of the tools. In the last years several approaches have been used to simulate this process, always with the limit that the lamination curves must be inserted manually from the user and cannot change during the simulation. This paper is a summary of the work made by Muraro Spa, together with Transvalor S.A., the developer of FEM software Forge® and Enginsoft Spa, competence center on production process simulation. The aim of this work was to develop an interface able to read, in real-time during the calculation, the position of some virtual sensors (virtual laser measuring), pass informations like position, but also loads and others, to an external routine, able to calculate corrections of the kinematic of all the tools and write back these corrections in Forge. During the simulation, this approach allows to correct step-by-step the lamination curve. The logic in the simulation external black-box and in the program driving the piloting of the press is the same, so this guarantees that the results obtained with this new approach in the simulation are close to the real one. Next step of the work will be to extend the application of this interface to other models of special machines, but also to different kind of presses normally used to deform metallic (an non-metallic) materials.


De Micheli P.,Transvalor SA | Perchat E.,Transvalor SA | Ducloux R.,Transvalor SA | Digonnet H.,MINES ParisTech | Fourment L.,MINES ParisTech
Key Engineering Materials | Year: 2013

Improvements in parallel computing and adaptive remeshing have permitted to simulate a wide range of metal forming processes within few hours or days on modern multi-core workstations. However, they do not tackle the issues encountered in incremental forming processes, making them very challenging. Multi-mesh methods opens very interesting doors in this domain, making possible to take advantage of adaptive remeshing techniques (optimizing the ratio precision/cost) without its usual drawbacks (loss of information and diffusion issues). We present in this article a fully parallel Dual-Mesh implementation in the commercial FEA software FORGE®, compatible with a wide range of other FEM facilities. Speed-up larger than 4 are common for incremental forming simulations, and speed-up larger than 10 can be reached in favorable cases. Parallel efficiency is the same than for our standard computations (>80% for more than 2000 nodes per core). Copyright © 2013 Trans Tech Publications Ltd.


Francois G.,Transvalor SA | Ville L.,Transvalor SA | Silva L.,MINES ParisTech | Vincent M.,MINES ParisTech
Key Engineering Materials | Year: 2013

In this paper, we present an innovative adaptive meshing method developed in the injection simulation software Rem3D®. This method generates a full optimized mesh with a high accuracy for strong flow/heat/rheology coupling as well for complex interface evolutions, and with a reduced number of nodes. Results show good agreement with analytical solutions, as well as for full industrial process experiments. Copyright © 2013 Trans Tech Publications Ltd.

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