非共軸モデルによるひずみの局所化解析におけるスピンの影響

抄録

The effects of various spin tensors on strain localization phenomena predicted by a noncoaxial viscoplasticity model are investigated by finite-element analysis. The noncoaxiality between the plastic strain rate and the stress arises from a directional dependence of the plastic strain rate on the stress rate. The spins considered here are continuum spin, plastic spin, Green-Naghdi spin and Euler spin. Using these spins, the simple shear problem and tension and compression problem involving shear band formations are analyzed. The spins that can produce monotonic stress responses in simple shear noticeably restrain the shear band formations. Actually, in large torsion tests of metals which were newly carried out, we observe monotonic torque responses. Consequently, it is found that it is difficult for the noncoaxial model to predict realistic strain localization phenomena if we choose a spin on the bases of the results of torsion tests. This inconsistency should be recognized as an important problem that must be subjected to further investigations.