Finite-element simulation of springback in sheet metal forming using local interpolation for tool surfaces

Graduate School of Energy Science, Kyoto University, Yoshida-Honmachi, Sakyo-ku, Kyoto 606-8501, Japan; Volume-CAD System Research Program, The Institute of Physical and Chemical Research, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan; LPMTM-CNRS, University Paris 13, 93430 Villetaneuse, France
International Journal of Mechanical Sciences (Impact Factor: 1.61). 01/2008; DOI: 10.1016/j.ijmecsci.2007.07.005

ABSTRACT This paper describes new techniques for the sheet metal forming simulation using a local interpolation for tool surfaces proposed by Nagata [Simple local interpolation of surfaces using normal vectors. Computer Aided Geometric Design 2005;22:327–47] and the effect of tool modeling accuracy on springback simulation of a high strength steel sheet. The Nagata patch enables the creation of tool models that are much more accurate, in terms of not only shape but also normal vectors, than those of conventional polyhedral representations. Besides allowing an improved description of the contact between the sheet nodes and the tool surfaces, the proposed techniques have the advantage of relatively straightforward numerical implementation. Springback simulations of a two-dimensional draw bending process of a high strength steel sheet are then carried out using the polyhedral and Nagata patch models. It is found that the simulation results are largely influenced by the tool mesh when using polyhedral representations, while they are rather independent when using the Nagata patch representations. This demonstrates the efficiency and reliability of the numerical solution using the Nagata patch model.

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    ABSTRACT: 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.
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Jun 4, 2014