局所くびれ解析におけるStören-RiceとHillの手法の等価性

抄録

Application range of Stören-Rice Method is discussed which is used for estimating the formability in stretch forming of sheet metals. One of the famous methods for analyzing localized necking had been proposed by Hill. But, the application of his analysis must be confined in the bi-axial forming where there is at least the direction with no stretching, ie, ε_tt=0 in the forming sheet. Hence, this condition becomes an obstacle for its application in biaxial stretch forming. Stören-Rice proposed Δε_tt=0, in place of ε_tt=0, where Δ denotes difference between the regions separated by necking plane. This proposal is suggesting that the condition ε_tt=0 might be removed, but it has not been proved whether the removal of the condition is realized or not. Then, on the equilibrium condition proposed in their analysis, the range of applicable forming is examined where the existence of multiple solution can be made sure. Consequently, it is found that it is possible to have multiple solution in the only forming condition satisfying ε_tt=0. Therefore, the forming limit obtained in biaxial stretching are in the outside of the application range, and they are an imaginary solution.