A combined material model for numerical simulation of hot isostatic pressing

In modelling of hot isostatic pressing (HIP) of powder materials the consti tutive model should be able to describe different deformation mechanisms du ring the consolidation process. In the early stage, the consolidation is do minated by granular behaviour. As temperature and pressure increase in the powder the deformation can be described by a viscoplastic model. Experiment al observations show substantial time-independent deformation in the early stage. At this stage of the densification process, pores in the powder are still interconnected. This cannot be described properly by a viscoplastic m odel. The inconsistency between the deformation mechanisms can be treated b y a combined elasto-plastic and elasto-viscoplastic model. Here a granular plasticity model is combined with a viscoplastic model. In previous works t he viscoplastic model, power-law breakdown, has been used to describe the e ntire deformation process. The combined model is implemented into an in-hou se finite deformation code for the solution of coupled thermomechanical pro blems. The simulation of a hot isostatic pressing test with dilatometer is performed in order to compare calculated results with the experimental meas urement. The results from previously performed analysis carried out with a viscoplastic model only are also compared. Analysis with the combined mater ial model shows good agreement with the experiment for the whole densificat ion process. (C) 2000 Elsevier Science S.A. All rights reserved.