Strain-path change induced transients in flow stress, work hardening and r-values in aluminum

• Experimental investigation of orthogonal and reverse strain-path changes in aluminum.
• Model for transients after strain-path changes: Stress, work hardening and r-values.
• Comparison of strain localization by digital image correlation and FEM model.

Commercially pure aluminum with random texture was prestrained either by rolling or by uniaxial compression, and then tested in uniaxial tension to study the transients in flow stress, work hardening and r-value induced by the strain-path change. New experimental results are reported on the variation of the r-value and the permanently reduced work hardening subsequent to the strain-path change. A continuum plasticity model was developed that can reproduce the observed behavior. The model applies a second-order “delayed pointer” tensor to represent the microstructural anisotropy and was implemented into the finite element software LS-DYNA. The model was calibrated to the experimental data, and a simulation of early strain localization subsequent to an orthogonal strain-path change was compared to strain fields measured by a digital image correlation technique.