FLASH DESIGN OF DIE SHAPES FOR REDRAWING RECTANGULAR CUPS

This paper presents a die design technique for redrawing rectangular cups by the slip line field method. A slip line field is constructed around a redrawn cup of a product shape, and pre-drawn cups of arbitral shapes are also constructed in the field. The distributions of circumferential strain, streamline lengths and velocity in redrawing are calculated. Then die shoulder angles along the die fringe are determined so as to fill the condition that the material at a certain height on the wall of the pre-drawn cup must reach and pass through the inner fringe at the same time during the redrawing process. Because the calculation time for the analysis needs only a few seconds, it is possible to select the most proper process in which the strain distribution is relatively uniform among the pre-drawn shapes. The simulated result obtained using LS-DYNA shows the uniformity of the wall thickness of the redrawn product.