Deforming Characteristics of Mild Steel Sheets in Various Strain Paths

Abstract

In the previous paper, it has been clarified that the r-value of mild steel sheets changes during a deep-drawing process, and the change influences markedly the deep-drawability. This paper deals with the strain path dependence of the work hardening characteristics of the mild steel sheets. The stress σ-strain ε relations are described under three linear strain paths, that is, uni-axial tension, plane strain tension, and equi-biaxial tension. The results are as follows : (1) under the uni-axial and plane strain tension, the rates of the work hardening d log σ/d log ε hardly change, or increase somewhat by increasing the strains ; that is, ten n power low σ=Fεⁿ or the initial strain type σ=F(ε+ε₀)ⁿ holds. (2) Under the equi-biaxial tension, the same relations as in (1) hold in the small strain range (ε⥶0.2), but by increasing the strain (ε≥0.2∼0.3), the rate of work hardening increases linearly ; that is, σ=Fe^aεε^b holds there. The limit strains calculated by using the above relations show good agreement with experimental values.