Finite element modelling of hot isostatic pressing should be based on constitutive equations describing the deformation of the powder under miscellaneous states of stress in a wide range of temperature. The few experiments, which can be performed with industrial materials in order to identify these equations, are delicate and often inaccurate, due to the required conditions of pressure and temperature. Hence, simulation materials with low melting points can be used to deeply investigate the constitutive behaviour of metal powders. An experimental study has been achieved with lead powder as a simulation material. Classical tests, as uniaxial compression and die pressing - with radial stress measurement -, have been performed at 150°C. The obtained results cannot correctly be described with classical viscous models. A new formulation of the constitutive equations based on the "unified" theory, which accounts for plastic effects, is then proposed.
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