Comparison of the work-hardening of metallic sheets using tensile and shear strain paths

This work deals with the characterization of the kinematic work-hardening of a bake-hardening steel. A shear test device has been designed and its use for the characterization of the work-hardening of sheet metals is described. Two main results are presented. Firstly, a local strain measurement, based on the following of three dots drawn on the gauge area, gives the evolution of the strain tensor eigenvalues during the test. It is shown, by comparing the theoretical kinematics of simple shear with a slightly perturbated one, that the strain state is close to the ideal one in the center of the gauge area. Secondly, reversal of the shear direction is performed after several prestrain and the evolution of the kinematic work-hardening with the equivalent plastic strain has been identified using an anisotropic elasto-viscoplastic model of Hill 1948 type. Isotropic and kinematic contributions of the work-hardening are also calculated from loading–unloading tensile tests and are compared to those obtained from the simple shear tests. The results show a discrepancy between both identification for the isotropic and the kinematic hardening. However, they are in agreement concerning the evolution of the global work-hardening.