Experimental and numerical studies on the formability of AA5754 and AA6082 thin sheets in nonisothermal warm redrawing process

Abstract

The present work demonstrates a comparative investigation of the nonisothermal warm forward redrawing behavior of AA5754-H22 and AA6082-O sheets. The design and development of a new warm forward redrawing process was demonstrated. The complete redrawing was obtained by keeping the redrawing die and binder at 200 °C and cooling punch near to room temperature using water circulation. This process improved the thickness and surface strain distribution in redrawn cups without the onset of strain localization at the bottom corner. A thermomechanical finite element (FE) model of the nonisothermal warm redrawing process was developed applying the temperature-dependent Barlat-89 yield criterion and the Cowper–Symonds strain rate sensitive hardening model. The FE model reasonably predicted the part depth, earing development, thickness distribution, and surface strain evolution of the redrawn cups. The evolution of temperature distribution within the redrawing cup during the process was captured from FE simulations, and its role in the improvement in redrawing depth was demonstrated. Furthermore, the post-forming characterization of redrawn cup wall was also evaluated by microhardness and ring hoop tensile tests. It was found that the hardness, hoop tensile strength, and energy absorption capacity of AA5754-H22 cups were better than AA6082-O cups.