摘要
A thermo-viscoplastic damage potential and Hill's normal anisotropy (isotropy in plane) yield criterion in the quadratic form of stress components were combined to describe the interaction process of damage and instability during superplastic deformation, based on the kinetic equation for damage during superplastic deformation and the deformation features of superplastic materials. The superplastic deformation process was divided into four stages, namely, stable; quasi-stable; strain path drift to plane strain and plane strain stages, and a damage instability model during superplastic deformation of sheet metals was developed through numerical method. On the basis of the above results and taking the occurrence of localized instability or the cavity volume fraction reaching the critical value as a fracture criterion, the forming limit during superplastic deformation of sheet metals was predicted.
A thermo-viscoplastic damage potential and Hill's normal anisotropy (isotropy in plane) yield criterion in the quadratic form of stress components were combined to describe the interaction process of damage and instability during superplastic deformation, based on the kinetic equation for damage during superplastic deformation and the deformation features of superplastic materials. The superplastic deformation process was divided into four stages, namely, stable; quasi-stable; strain path drift to plane strain and plane strain stages, and a damage instability model during superplastic deformation of sheet metals was developed through numerical method. On the basis of the above results and taking the occurrence of localized instability or the cavity volume fraction reaching the critical value as a fracture criterion, the forming limit during superplastic deformation of sheet metals was predicted.
