Determination of the Optimum Blank Shape of Nonaxisymmetric Drawn Cup by Finite-Element Method. (4th Report, Conventional Determination of Optimum Blank Shape and Limiting Drawing Ratio by Inverse Finite-Element Procedure).

Abstract

The conventional determination of the optimum blank shape and the limiting drawing ratio is presented, with particular reference to the improvement of the blank design of deep drawing of sheet metal for nonaxisymmetric cups by a flat-headed punch, using an inverse finite-element method. The authors' inverse approach has been applied to a cylindrical cup with a square flange, and square cup, and the prediction was made in terms of the relationships between the optimum blank shape and the drawing height and between the optimum blank shape and the drawing force, as well as the limiting drawing ratio of the optimum blank. The forming limit diagrams of those drawing cups were conceived theoretically, taking account of the die radius, blank shape, coefficient of Coulom's friction and the blank holder force. The theoretical predictions were compared with experimental results in the previous paper, for deep-drawing square cups from optimum blank shapes, and the two results agreed reasonably well.