多価性に準拠した成形性の予測

概要

論文の詳細を見る
The necessary condition for the multiplicity in deformation rate was given by Hill. The condition is Δε_uΔs_u=0,where s_u denotes the nominal stress rate, and Δ shows the difference between any two multiple solutions. However, many proposed criteria of plastic instability in published literature did not take into consideration this necessary condition. They were based on phenomenological aspects. The sufficient condition for the multiplicity is deduced from the requirement which makes the equivalent strain rate ε_s indefinite. This is given by ε_uε_u=0,which is called Z-plane in s_u space. Plastic instability or unloading from a stable state always occurs on Z-plane. With respect to the formability in metal forming, especially, the possibility of plastic instability, processes are examined in plane stress, plane strain and three dimensional conditions. In sheet forming alternative cniterion, s_1=0 is also proposed for positive γ which is defined by the ratio ε_2/ε_1. In bulk forming, the dependency of ductility upon mean normal stress is discussed, and the decrease of ductility is shown with increasing the mean stress. Furthermore, the occurrence of shear banding and its mode are studied. Since the shape of loading path is normally monotonic in s_u space, a loading path intersects Z-plane only once and then plastic instability also can occur only once. Therefore, localized necking, in general, is merely the plastic deformation confined into a very thin layer with a rigid region on its both sides.
一般社団法人日本機械学会の論文
1998-06-25

多価性に準拠した成形性の予測

スポンサーリンク

概要

著者

関連論文

スポンサーリンク