Abstract: Isotropic yield surfaces of bcc and fec metals have been simulated with TBH theory.Using the five-dimensional stress space proposed recently by Lequeu et al.,the yield subsurfaces on any two of the three shear stresses can be considered as the inscribed circles of their corresponding subsurfaces on n plane.Based on this concept,Hershey,Hosford and Hill (HHH) yield func- tion has been transformed into the formula where the parameters are uniquely determined by two crystallographic factors:the mean Taylor factor in plane strain (M_p) and the critical shear stress (τ_) on slip systems.

Key words: Polycrystalline plasticity, yieldfunction, cubic metals