A DUCTILE GROWTH-MODEL FOR ELASTOPLASTIC MATERIAL

In bulk forming processes, the soundness of a manufactured part can be related to the final mechanical properties of its material, which can be locally deteriorated by an induced porosity increase. In order to predict such damage evolution, a void growth model, based upon the Ric e and Tracey analysis and suited for thermo-elasto-plastic finite-elem ent modelling is discussed and compared to existing models. The workpi ece material is considered as a metallic matrix, following the classic al plasticity theory, with microscopic spherical voids. Its slightly c ompressible macroscopic behaviour is predicted by the Rice and Tracey analysis, the results of a numerical study of a unit cell with or with out an incompressible inclusion filling the void showing that the plas tic volume changes come mainly from geometric effects. Comparisons bet ween existing growth models and this new model are carried out with th e same finite-element software for axisymmetric thermo-mechanical clos ed-die modelling of a forward extrusion and the collar test. (C) 1998 Elsevier Science S.A. All rights reserved.