Finite element modeling of the deformation behavior of semi-solid materials

In the current study, the deformation behavior of semi-solid materials was modeled using the von Mises yield criterion in which the semisolid material was treated as a single phase material with the incompressibility condition in a global sense. The flow stress of the material was modeled as a function of strain in consideration of the solid fraction and the breakage ratio of dendritic structure. An algorithm based on mixture theory and D'Arcy's law was developed to update the solid fraction, the distribution of which varies within the material due to relative velocity between the solid and liquid phases during deformation. The parameters involved with the proposed model were determined through a parametric study in which numerous finite element analysis results were compared with the data from existing isothermal upsetting experiments for semi-solid Sn-15%Pb alloy. Comparison with experimental results showed that the current approach is improved compared to previous compressible approaches. The generality of the current approach was examined through rigid-thermoviscoplastic finite element analyses of the semi-solid forging of a ball-joint case under various preheating temperatures in consideration of the release of latent heat. The simulation results agreed well with the trend of the experimental findings but showed some quantitative errors. (C) 2001 Elsevier Science B.V. All rights reserved.