Evaluation Method of Formability through Development onto Tangential Planes

―Geometrical Evaluation for Forming of Closed Section Parts from Sheet―

Abstract

New formability evaluation methods are investigated for closed section parts manufactured from sheet blanks. New methods are based on an analytical approach and geometrical information. The authors proposed the developmental evaluation method in which in-plane strain is calculated by the development of product shapes. By the double-stage development using principal curvatures and series of tangential planes, the developmental evaluation method becomes applicable to shapes with large curvature. In this paper, the results of calculation by the proposed method are compared with the results of FEM simulation regarding on sheet forming into horn tubes. The horn tube, which consists of circular, conical and transient portions, is one of the typical shapes of automotive parts. The conclusion is that the two sets of calculation results are in good qualitative agreement. For product shapes with widely spread relatively small strain which is introduced in forming processes, the geometrical condition is dominant for the strain distribution and the prediction accuracy of the developmental evaluation method is improved.