BLANK SHAPE OPTIMIZATION IN SHEET METAL HYDROMECHANICAL DEEP DRAWING (HDD)

In order to perform a successful sheet metal forming operation and to avoid shape deviations and tearing and wrinkling defects, process and material variables, such as tools geometry, blankholder force, friction, blank shape, sheet thickness and material properties, should be optimized. One of the main parameters which must be defined at the beginning of any sheet metal forming process design is the initial blank shape and its main dimensions [1]. In this paper, the authors' attention is focused on a non-conventional sheet HDD process for which optimal blank shape and dimensions are not fully explored yet [2]. It will be demonstrated that, when the traditional One Step finite element method calculation, realised through the implicit code, is applied to HDD, the process shows various limits. In fact, while the One Step analysis is able to predict the optimal initial blank for the traditional Deep Drawing (DD) process, the same blank could not be the optimal one in a HDD process. The goal of this paper is to develop a methodology by which, with the aid of optimization algorithms, it will be possible for the user to define the best shape and dimensions for the initial blank in HDD processes, even when starting from the blank obtained by a One Step analysis.