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Hot isostatic pressing (hipping) is a manufacturing process capable of producing mechanical parts in only one operation by the hot forming of metal powders. The aim of this process is the production of net shape parts notably for aeronautics or nuclear applications. In the past, the trial and error method was used in order to find the right container and insert geometries giving the net shape parts. Several prototypes must therefore be manufactured before a successful conclusion is reached. This forming procedure results in expensive developing costs due to the quasi unitary production, pressure and temperature environment and the high temperature tooling involved.Numerical simulation raises hopes on the optimisation of this manufacturing process through the use of viscoplastic constitutive equations implemented in the finite elements software PRECAD/M.The rheological functions of this viscoplastic model are usually determined by assuming that the mean pressure in the sample is homogeneous and equal to the external applied pressure. The numerical simulations of hipping experiments show that this assumption is often false: pressure is partially transmitted to the powder because of the container rigidity. New rheological functions have been determined with the stress values obtained by numerical simulation of these tests. The new numerical simulations are then in better agreement with the experimental values and the prediction of an industrial complex part final shape is also improved. PM/1083 Dr Sanchez is with Federal Mogul Operation France/ Centre Technique, Voie des Collines, 38800 Le Pont De Claix, France. Dr Ouedraogo (Evariste.Ouedraogo@ hmg.inpg.fr) is with Laboratoire 3S (Sols, Solides, Structures), Domaine Universitaire, BP 53, 38041 Grenoble, France. Dr Dellis is with CEA/DEN/

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