ステンレス/アルミニウム積層板の成形限界

抄録

The forming limit of sheet metal laminates under a biaxial stress condition is investigated by performing punch-forming experiments on two-ply laminate of aluminum/SUS 430, three-ply laminate of SUS 304/aluminum/SUS 430 and their component sheet metals. The data of necking-limit strains of the laminates lie between those of their component sheet metals. A criterion of localized necking for the laminates, in the negative strain-ratio condition (β=ε₂/ε₁<0), is derived based on Hill's theory of localized necking. For the case of the positive strain-ratio condition (β=ε₂/ε₁>0), the modified Marciniak-Kuczynski-type analysis, which assumes that an initial inhomogeneity in a sheet develops into localized necking, is conducted with the consideration of void growth in the groove of the sheet. The calculated forming limit diagrams show the same tendency as seen in the experimental results. The effect of prestrain generated in the roll-bonding process on the formability is discussed.