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Iorio L.,Polytechnic of Milan | Fourment L.,MINES ParisTech | Marie S.,TRANSVALOR | Strano M.,Polytechnic of Milan
Key Engineering Materials | Year: 2015

The Game Theory is a good method for finding a compromise between two players in a bargaining problem. The Kalai and Smorodinsky (K-S) method is a solution the bargaining problem where players make decisions in order to maximize their own utility, with a cooperative approach. Interesting applications of the K-S method can be found in engineering multi-objective optimization problems, where two or more functions must be minimized. The aim of this paper is to develop an optimization algorithm aimed at rapidly finding the Kalai and Smorodinsky solution, where the objective functions are considered as players in a bargaining problem, avoiding the search for the Pareto front. The approach uses geometrical consideration in the space of the objective functions, starting from the knowledge of the so-called Utopia and Nadir points. An analytical solution is proposed and initially tested with a simple minimization problem based on a known mathematical function. Then, the algorithm is tested (thanks to a user friendly routine built-in the finite element code Forge®) for FEM optimization problem of a wire drawing operation, with the objective of minimizing the pulling force and the material damage. The results of the simulations are compared to previous works done with others methodologies. © (2015) Trans Tech Publications, Switzerland.

Chen N.,French National Center for Scientific Research | Chen N.,Beihang University | Ducloux R.,Transvalor | Pecquet C.,Transvalor | And 4 more authors.
International Journal of Material Forming | Year: 2011

As one of important mechanical joining methods, rivet joints are widely used in buildings, bridges, aircrafts and automotives and in many other fields. Many variables have influences on the response of the rivet joints, such as the geometry of the joints, the material parameters of the parts, the clearance of the assembly, etc. In this paper, a finite element numerical model is developed for the analysis and optimization of the riveting process. Our approach is three-dimensional in order to be able to model non axisymmetric situations of riveting and testing of the joint strength. Four different sizes of solid rivets are considered for simulation and experimental study of the process. The comparison of the results between the numerical simulations and the experiments allows us to validate our approach. © 2010 Springer-Verlag France.

Ducloux R.,Transvalor | Fourment L.,MINES ParisTech | Marie S.,Transvalor | Monnereau D.,Bollhoff Ottalu
International Journal of Material Forming | Year: 2010

The use of material processing numerical simulation has spread widely in recent years in the engineering industry. It allows a strategy of trial and error to improve virtual processes without incurring material costs or interrupting production and therefore save a lot of money. On the other hand, it requires user time to analyze the results, adjust the operating conditions and restart the simulation. Automatic optimization seems the perfect complement to simulation. Evolutionary Algorithm coupled with metamodelling makes it possible to obtain industrially relevant results on a very large range of applications within a few tens of simulations and without any specific automatic optimization technique knowledge. In the frame of the LOGIC ANR French project, ten industrial partners have been selected to cover the different area of the mechanical forging industry and provide different examples of the forming simulation tools. An optimization module, fully embedded within the Forge2009 IHM, makes possible to cover all the defined examples, and the use of new multicore hardware to compute several simulations at the same time reduces the needed time dramatically. The presented examples demonstrate the method versatility. They include billet shape optimization of a common rail and the cogging of a bar. © 2010 Springer-Verlag France.

Kpodzo K.,MINES ParisTech | Fourment L.,MINES ParisTech | Lasne P.,Transvalor | Montmitonnet P.,MINES ParisTech
International Journal of Material Forming | Year: 2016

Within the frame of implicit velocity based formulations with solid elements, usual time integration schemes often turn out unsatisfactory when the movement has large rotations, especially in metal forming applications such as ring rolling or cross-wedge rolling. These rotations generally require using a much higher order integration scheme with inherent difficulties in implementing such schemes. For pure rotation motions, it is possible to use a low order integration scheme by rewriting the motion equations in the cylindrical frame that is supported by the rotation axis. Accordingly, a first order scheme is sufficient to accurately integrate the movement but it is restricted to specific problems. In the more general case, it is possible to derive parts of the domain where rotations are predominant along with the governing rotation axis from the velocity field gradient. The motion equations are then rewritten in the resulting local cylindrical frame. Performances of this first order scheme are first evaluated and highlighted over simple analytical problems, before being applied to the finite element simulation of the torsion test, and then to more complex metal forming problems involving large rotations. The accuracy and efficiency of this scheme is so numerically demonstrated. © 2014, Springer-Verlag France.

Chenot J.-L.,Transvalor | Chenot J.-L.,MINES ParisTech | Beraudo C.,Transvalor | Bernacki M.,MINES ParisTech | Fourment L.,MINES ParisTech
Procedia Engineering | Year: 2014

The basic formulation for finite element modeling of metal forming processes is briefly recalled with the aim of treating the case of multi body interactions. This situation occurs when the tools are considered as deformable, when the work-piece includes several materials or when the physical structure is analyzed at the micro scale. The classical approach utilizes separate meshes for each body and the contact is enforced using different numerical methods: The complete coupling, the master and slave approach and a quasi-symmetrical formulation. The single mesh method with different constitutive equations corresponding to each material is more computationally effective, but its use is restricted to the cases when the contact between the different bodies does not evolve. Finally the Euler formulation can be used with a level set method for the description of the interfaces between different materials and its application to recrystallization for example. © 2014 The Authors. Published by Elsevier Ltd.

Material processing simulation originally started with the prediction of defects created by the forming stages as the main focus. More recently and driven by the quest for vehicle mass reduction we are seeing an emerging interest for enlarging the scope of simulation to "components in-use properties" predictions. This new scope requires a shift from a stage limited simulation focus to one that encapsulate the whole manufacturing process inclusive, of course, of heat treatment. In the first part of this paper we will demonstrate how Simulation can now predict and validate the whole manufacturing process using as an example a bevel gear forging from the initial phases through carburization, quenching and tempering. This idea that the whole process should be used to increase results quality may also be applied in other cases. Typically, when people are interested in tooling life (die,...), a standard approach is to do a stress analysis of the forming stage and eventually compute some abrasive wear but a closer look will show that the accumulation of the blows may have to be taken into account. In case of hot or warm forging, the tooling properties will heavily depend on local die temperature which cannot be obtained only from one simple forming stage simulation. © 2014 The Authors. Published by Elsevier Ltd.

Ducloux R.,Transvalor | Barbelet M.,Transvalor | Fourment L.,Transvalor
AIP Conference Proceedings | Year: 2013

Most forming processes are multi-stages processes. Typically, a standard forging sequence consists of three operations: Pre-forming, Blocker, Finisher, which are followed by heat-treatments. We call this the complete manufacturing chain. Simulation-wise, all these stages have to be computed one after the other; we call this the 'simulation chain'. From the optimization point of view, it is quite challenging because the process parameters which could be modified usually belong to the early stages of forming (blocker) while the quality or non-quality of the formed part only appears during the last stage (finisher or heat treatment). For any modification on the early stage, all the following stages have to be re-computed to evaluate the benefit of the modification. This is time consuming and then often people renounce to do it. In this paper, we show how the concept of 'simulation chain' used in the Forge software can be coupled with automatic optimization techniques to address this point. In order to get a smooth integration in the user workflow, all the geometries to be optimized (both initial shape of the part and dies) are generated and modified through CAD system driven by the Forge automatic optimization engine. © 2013 AIP Publishing LLC.

Marie S.,Transvalor | Ducloux R.,Transvalor | Lasne P.,Transvalor | Barlier J.,Transvalor | Fourment L.,MINES ParisTech
Key Engineering Materials | Year: 2014

In the field of materials forming processes, the use of simulation coupled with optimization is a powerful numerical tool to support design in industry and research. The finite element software Forge®, a reference in the field of the two-dimensional and three-dimensional simulation of forging processes, has been coupled to an automatic optimization engine. The optimization method is based on meta-model assisted evolutionary algorithm. It allows solving complex optimization problems quickly. This paper is dedicated to a specific application of optimization, inverse analysis. In a first stage, a range of reverse analysis applications are considered such as material rheological and tribological characterization, identification of heat transfer coefficients and, finally, the estimation of Time Temperature Transformation curves based on existing Continuous Cooling Transformation diagrams for steel quenching simulation. In a second part, a novel inverse analysis application is presented in the field of cold sheet forming, the identification of the material anisotropic constitutive parameters that allow matching with the final shape of the component after stamping. The advanced numerical methods used in this kind of complex simulations are described along with the obtained optimization results. This article shows that automatic optimization coupled with Forge® can solve many inverse analysis problems and is a valuable tool for supporting development and design of metals forming processes. © 2014 Trans Tech Publications, Switzerland.

Fourment C.,Transvalor | Barlier J.,Transvalor | Barbelet M.,Transvalor | Lasne P.,Transvalor | Cardinaux D.,Transvalor
SAE Technical Papers | Year: 2014

Virtual forming tools based on Finite Element simulation are routinely used in order to improve process design and to reduce time to market. However, with the growing requirements with regards to in-use properties of forged components, not only the forming processes must be simulated but the entire process chain, including the heat treatment processes that are carried out to improve the mechanical properties of the final part. In order to meet these needs, new heat treatment features have been introduced into the commercial code FORGE®. This paper presents an application of induction hardening to an industrial component. This application demonstrates the strategic capabilities of FORGE® commercial software to achieve production challenges. Copyright © 2014 SAE International.

Thomas C.,Transvalor | Corpetti T.,RSIU Group | Memin E.,French Institute for Research in Computer Science and Automation
IEEE Transactions on Geoscience and Remote Sensing | Year: 2010

This paper focuses on the tracking and analysis of convective cloud systems from Meteosat Second Generation images. The highly deformable nature of convective clouds, the complexity of the physical processes involved, and also the partially hidden measurements available from image data make difficult the direct use of conventional image-analysis techniques for tasks of detection, tracking, and characterization. In this paper, we face these issues using variational-data-assimilation tools. Such techniques enable us to perform the estimation of an unknown state function according to a given dynamical model and to noisy and incomplete measurements. The system state we are setting in this study for the cloud representation is composed of two nested curves corresponding to the exterior frontiers of the clouds and to the interior coldest parts (core) of the convective clouds. Since no reliable simple dynamical model exists for such phenomena at the image grid scale, the dynamics on which we are relying has been directly defined from image-based motion measurements and takes into account an uncertainty modeling of the curve dynamics along time. In addition to this assimilation technique, we show in the Appendix how each cell of the recovered cloud system can be labeled and associated to characteristic parameters (birth or death time, mean temperature, velocity, growth, etc.) of great interest for meteorologists. © 2006 IEEE.

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