A fundamental study of can forming by the stretch-drawing process

The double stretch-drawing process is studied experimentally within the scope of the best or better combination of first and second drawing ratios in which the second punch diameter is fixed, for a the sheet thickness of 1.0 mm. It is concluded that the largest total limiting drawing ratio (=initial blank diameter BD divided by the second punch diameter) is achieved when the smallest first drawing ratio and the largest second drawing ratio are adopted, both for the double stretch-drawing and the usual double deep-drawing processes, in which case the deepest cup can be formed for both processes, respectively. It is emphasized that the deepest cup can be formed by the double stretch-drawing from a smaller limiting BD, applying an appropriately small die profile radius. Stretch- and deep-drawing processes accompanied by ironing are also studied with respect to a thick sheet (=3.0 mm) experimentally. Numerical simulation of the stretch-drawing process is also performed by the use of the explicit dynamic FEM code, DYNA3D code, to confirm that a satisfactory prediction, especially of the depth of the drawn cup, can be done at least in a practical sense, although this kind of numerical analysis is very difficult because of the severity or localization of deformation around the die profile.