平面ひずみの引抜き,押出し加工における中心割れ発生について

抄録

Central bursting is dealt with, with respect to the collapse of a unique solution. In general, there are two cases bringing about multiplicity : one is statical and the other is kinematical one. The latter corresponds to localized necking. These two multiplicities occur simultaneously in plane strain processes. There are two modes which can be realized at localized necking, but only one mode is possible in a plane strain process. The criterion for central bursting is given as(ε₁/n)(P/k)=-1, where P=average pressure, k=shear strength, ε₁ is the tensile strain in forming direction, and n is work hardening exponent. The influences of die geometry and manufacturing conditions on the central bursting are examined.