Assessment of Deep-Drawability of Mild Steel Sheets in Consideration of r-Value Change During Processing

Abstract

In the previous study, it was found that the plastic anisotropy of commercially pure aluminum sheets changed during the deep-drawing process, and that this change influenced markedly the deep-drawability. In the present study we discuss the deep-drawability of mild steel sheets with a crystal structure different from aluminum. The following have been confirmed: (1) The limiting drawing ratio correlates positively and nonlinearly with average r value (r̄ value). (2) Fracture strength correlates positively with r̄ value as in the theory, but the relation between them is nonlinear. Maximum drawing load remains almost constant irrespective of r̄ value against the theory. These relations can be connected with the result of (1). (3) The relations in (2) can be explained by the r̄ value measured from sheets prestrained in equibiaxial tension and pure shear, which resemble the strain paths of fracture site at punch profile and flange, respectively. (4) The results of (2) and (3) are quite different from those of commercially pure aluminum sheets.