Applying Nagata Patches in the Description of Smooth Tool Surfaces Used in Sheet Metal Forming Simulations

This study deals with the new strategy currently implemented in DD3IMP in-house code to describe the forming tools using Nagata patches. The strategy is based on the use of the Nagata patch interpolation to generate smooth contact surfaces over coarse faceted finite element meshes. The description of the adopted algorithm is briefly presented, highlighting the contact search algorithm employed. The reverse deep drawing of cylindrical cups, proposed as benchmark at the Numisheet’99 conference, is selected to examine the accuracy and robustness of the proposed approach. The effect of the gap between the blank-holder and the die is studied, adopting two distinct strategies: fixed gap and variable gap. The numerical results are compared with the experimental ones, previously presented and discussed in [1]. It is shown that the agreement is very good both in terms of punch force evolution and thickness distribution.