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Neag A.,Technical University of Cluj Napoca | Favier V.,Arts et Metiers ParisTech | Bigot R.,CNRS Laboratory of Design, Manufacturing and Control | Atkinson H.V.,University of Leicester
Journal of Materials Processing Technology | Year: 2016

Semi-solid processing is a promising forming process for shaping metallic alloys in one shot. Numerical simulations are of great interest for optimizing the process. Generally, numerical simulation results are compared with interrupted flow experiments but these do not fully reflect the progress of material into the die because of the inertia of the flowing material which continues to move after the interruption to the shot. Results are available for in situ visualization of flow using transparent sided dies. Here die filling with a 90°change of flow path was simulated using the FORGE© finite element code and a constitutive equation based on a micro-macro modelling approach. The predicted flow behaviour was compared to the in situ visualization images obtained with a transparent glass sided die and reported in the literature. The impact of the presence of an obstacle, ram speed and friction coefficients on the material flow front is discussed. The initial solid skeleton is broken as soon as the material is deformed. The effect of the ram speed on the flow front is successfully represented by keeping the same parameters for the constitutive laws but requires a change in the friction coefficients. Friction modelling using the Coulomb law limited by Tresca cannot represent the ram speed effect on experimental friction conditions for the in situ visualisation tests used for the comparison here. However, the effect of an obstacle within the die on the material flow front is predicted well. © 2015 Elsevier B.V. Source


Etienne A.,CNRS Laboratory of Design, Manufacturing and Control | Guyot E.,University of Technology of Troyes | Van Wijk D.,University of Technology of Troyes | Roucoules L.,CNRS Systems and Information Sciences Lab LSIS
International Journal of Product Lifecycle Management | Year: 2011

This paper describes the specifications of an interoperability platform based on the Product Process Organization (PPO) model developed by the French community IPPOP in the context of collaborative and innovative design. By using PPO model as a reference, this work aims to connect together heterogonous tools used by experts easing data and information exchanges. After emphasising the growing needs of collaborative design process, this paper focuses on interoperability concept by describing current solutions and their limits. Then a solution based on the flexibility of the PPO model adapted to the philosophy of interoperability is proposed. To illustrate these concepts, several examples are presented (robustness analysis, CAD and product lifecycle management systems connections). Copyright © 2011 Inderscience Enterprises Ltd. Source


Khan A.,CNRS Laboratory of Design, Manufacturing and Control | Giraud-Audine C.,French National Center for Scientific Research | Bigot R.,CNRS Laboratory of Design, Manufacturing and Control | Abba G.,CNRS Laboratory of Design, Manufacturing and Control | Abideen M.Z.,Pakistan Institute of Engineering and Applied Sciences
Journal of Materials Processing Technology | Year: 2016

This article addresses the effects of vibrations on a viscoplastic workpiece applied during the forging process. To achieve this goal, a phenomenological model based on the slice method combined with a Norton-Hoff viscoplastic law is developed. It allows to study the impact of vibration on the reduction of the mean forging load which has been experimentally observed before, and demonstrates that the sensitivity to strain rate is a key parameter. Moreover, based on the model, a new waveform of the vibrations is proposed that enhance the mean forging load reduction. Finite element simulations and experiments have been performed to evaluate the validity of the model in the case of sinusoidal and triangular waveforms, and are in good agreement with the analytical model's predictions. © 2015 Elsevier B.V. All rights reserved. Source


Gu G.C.,CNRS Laboratory of Design, Manufacturing and Control | Pesci R.,Arts et Metiers ParisTech | Langlois L.,CNRS Laboratory of Design, Manufacturing and Control | Becker E.,CNRS Laboratory of Design, Manufacturing and Control | And 2 more authors.
Acta Materialia | Year: 2014

Microstructure is of crucial importance to the flow behavior of semi-solid slurries during the thixoforging process. Therefore, a thorough understanding of the microstructure evolution is required. In order to achieve this, high temperature confocal laser scanning microscopy (CLSM) and high energy X-ray microtomography were used to investigate the microstructure evolution of several steel grades (M2, 100Cr6 and C38LTT) during the heating process from as-received conditions to the semi-solid state. It was found that the microstructure development of M2 can be directly studied at high temperature via these two techniques. Two types of small carbides (MC and M6C) were present in the as-received state, while totally new interconnected carbides of specific size and composition were formed from liquid zones after cooling. It was also noted using CLSM that the diffusion rate of the alloying elements during the cooling of M2 was very low. This confirms that the volume fraction of the liquid phase of M2 at high temperature can be evaluated by three-dimensional X-ray microtomography in situ at high temperature and on quenched specimens. Contrary to M2, the microstructure of the steel grades 100Cr6 and C38LTT in the semi-solid state can only be revealed by CLSM at high temperature. All these observations are discussed in terms of microstructural development and liquid fraction during heating. © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. Source


Gu G.,CNRS Laboratory of Design, Manufacturing and Control | Pesci R.,Arts et Metiers ParisTech | Langlois L.,CNRS Laboratory of Design, Manufacturing and Control | Becker E.,CNRS Laboratory of Design, Manufacturing and Control | Bigot R.,CNRS Laboratory of Design, Manufacturing and Control
Journal of Materials Processing Technology | Year: 2014

The microstructure investigation and flow behavior during thixoforging of M2 steel parts were investigated. Partial remelting was performed at processing temperatures ranging from 1290 °C to 1340 °C corresponding to a liquid fraction range between 10% and 30% (according to differential scanning calorimetry measurements and quantitative image analyses). A conventional microstructure for thixoforming process was obtained: spherical solid grains surrounded by liquid phase. The microstructure across the heated billets was relatively homogeneous with bigger grain size near the surface. Successful thixoextrusion for producing parts was finally achieved at processing temperatures. By investigating the microstructure and load-displacement curves, different mechanisms in various forming stages were proposed. © 2014 Elsevier B.V. All rights reserved. Source

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