Abstract: The instability behavior of two kinds of metal sheets is experimentally studied on the left of FLD, [-R/(1-R)≤ρ＝dε2/dε1<0]. The experimental results show that the in homogeneity of the strain distribution of the sheets increases with deformation, after the load instability (dp=0), the strain state of the centre region of the specimens, where the tensile strain is the biggest, gradually drifts to the plane strain state, and the localized instability occurs at dε2＝0. Based upon the experimental results, a now model of tensile instability is presented, and the computed results according to this model are coincident with the experimental curves.

Key words: Deformation, Instability, Limit strain, Metal sheet, Motion stage, Dynamics modeling, Electronic Packaging Equipment, High-speed responding controller, Precision inspection device