抄録
By applying Campbell's analytical method for the divergence condition of (∂ε/∂x) (ε; the true strain, x; Lagragian coordinate along pulling axis) to those of (∂e/∂x) and (∂A/∂x) (e; the nominal strain, A; the cross-sectional area), instability criteria in various tests were formulated for a rate sensitive material, and the correlation between the divergence condition of these imperfections and the load maximum condition was obtained in uniaxial tensile tests.
The growth of the imperfection in the cross sectional area after necking was formulated in a rate sensitive as well as work hardening (softening) material (σ∝εm[1+α*ε], σ; the true stress, m and α*; constants). The analytical results give that not only m-value but α*-value have a significant effect on the stable growth of the area imperfection. The present analysis seems to be very useful to discuss such large elongation after necking as in superplastic material.
