| In sheet metal forming, the determination of shape and dimension of blank is the precondition of analysis of part's deformation, process of design and drawing up of process rules. Appropriate blank shape can eliminate unevenness of blank deformation, improve forming limit, reduce high of earing and volume of cutting. Besides, for those forming parts, if we can get accurate shape and dimension of blank, it will reduce try times. Accordingly manufacture cycle will be shorten and productivity will be improved.A scale coefficient method based on the FEM has been proposed to predict the optimum blank in sheet metal forming in this thesis. In order to improve the precision of results and reduce iterate time, at adjusting the original curve, this method isn't giving the same adjustment, but giving the corresponding adjustment based on calculation of scale coefficient and shape error of each node to the curve. The one-step method is used to calculate the original curve. This method can get original blank curve directly from part shape and compute very fast. Combining these two methods to predict the shape and dimension of blank, we can get accurate result at little time.In the last chapter of this thesis, we introduce two kinds of sheet metal parts. One is forming part which require very accurate prediction of blank shape, the other is drawing part which need just approximate prediction of blank shape. We apply the scale coefficient method to predict the blank shape of these two kinds of sheet metal parts. This method is proved to be reasonable by practice. Besides, it can also be applied to predict trimming line of sheet metal parts.
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