Experimental Evaluation of Work-hardening Behavior Using Simple Shear Test and Formulation of Strain Dependence of Work-hardening Exponent for Steel Sheets

Simple shear tests and hydraulic bulge tests of IF steel sheet, 590 and 980 MPa grade dual phase high strength steel sheets were carried out to investigate the work-hardening behavior, i.e. equivalent stress-equivalent plastic strain curves and Instantaneous n-values, in large strain region over uniform elongation. Parameter κ that correlates simple shear (or bulge) stress to uniaxial tensile stress used to obtain the equivalent stress-equivalent plastic strain curve. The work-hardening behaviors obtained by simple shear tests and bulge test were good agreement with those of uniaxial tensile test. On the other hands, work-hardening equations proposed by previous studies were less likely to reproduce behaviors of the Instantaneous n-value, i.e. a strain dependency of the n-value, in a variety of steel sheets. Thus a new work-hardening equation that can reproduce the strain dependency of the n-value proposed. This equation can reproduce the work-hardening behavior of a variety of steel sheets.