Optimization of initial blank shape to minimize earing in deep drawing using finite element method

Abstract

Deep drawing of highly anisotropic sheets causes earing in the formed cup (formation of wavy edge at the top). In the present work, an attempt has been made to study this earing problem in deep drawing of cylindrical cups using a flat bottom punch from extra-deep drawing steel sheets using a finite element method based software LSDYNA. The mechanical properties and the formability parameters of the sheets were determined from the simple tensile tests. These properties along with experimental design parameters were used as input for simulation of deep drawing. Significant earing was observed and it compared with experimentally determined earing (by measuring cup height at several points) with reasonably good accuracy. To optimize the initial blank shape to minimize earing, the flow of material was observed at various steps during the process and accordingly blank shape was modified. Simulation of blanks with modified initial shape showed significant reduction in earing. Experiments were carried out on a 40 t hydraulic press using the modified blank shapes and it has been found that results agreed well with the analysis results.