Formability Predictions in Stamping and Process Parameter Optimization Based on the Inverse Approach Code Fast_Stamp

A simplified (one step) method called “inverse approach” (IA) for the numerical analysis of the stamping process has been continuously developed by the authors since the end of the eighties. In the present paper we recall the main finite element formulation aspects, for an efficient estimation of the large elastoplastic strains encountered in deep drawing operations. The capabilities of the code Fast_Stamp include: fixed (imposed) initial blank, bending effects due to tool curvatures, blankholder restraining forces (including drawbeads). Considerations of bending and unbending during forming stages can improve the IA regarding stresses distribution. In this case satisfactory estimation of springback can result. Since 1996 we also developed “math based” optimization algorithms and strategies. The cost functions and constraints are mainly expressed to reduce or control the thickness changes, the localized necking, the wrinkling tendency, the springback after forming. The design variables are describing the shape of the blank, the additional (addendum) surfaces, the restraining forces due to drawbeads and the material properties such as anisotropy coefficient and hardening exponent. Optimization algorithms are mainly based on surface response techniques with moving least square approximation and SQP to find the optimum solution at each iteration. Selected results will be presented related to the design of additional surfaces.