This paper on "Using FEM to Optimise Sheet Metal Forming Tools with Regard to Residual Stresses" was presented at the NAFEMS World Congress on Design, Simulation & Optimisation: Reliability & Applicability of Computational Methods - 9-11 April 1997, Stuttgart, Germany.

Summary

With FEM is has become possible to predict both the magnitude and the distribution of the residual stresses in the workpiece due to the forming and it has thus become possible to optimise the forming process with regard to the residual stresses. The deep drawing of cylindrical cups has been simulated and it is shown that the residual stresses in the cup wall are mainly due to the unbending which the material is subjected to when leaving the draw die profile. FEM-simulations show that by changing the conventional circular draw die profile to a profile having a tractrix or an elliptic shape a substantial reduction of the residual stresses can be achieved. Changing the shape of the draw die profile can also lead to a substantial increase in the straightness of the outside of the cup wall.