Topology optimization of die weight reduction for high-strength sheet metal stamping

High-strength steels have been increasingly used for vehicle body structures to improve fuel efficiency and vehicle safety. In order to maintain the stiffness and forming conditions under higher forming loads, stamping dies have to be designed with larger dimensions and thicker structures which may result in heavier die weight. Targeting to save the die weight/cost and keep the required stiffness, a topology optimization method is proposed based on Solid Isotropic Microstructure with Penalty (SIMP) to reduce the weight of key die components. During optimization, multiple loading conditions at different forming positions are considered to assure the maximum deflection at the above mentioned positions within the limit values. Besides, the interaction behaviors between die components are also taken into account to reflect the real contact evolution. A step-bottomed cup is designed to testify the proposed method. Through topology optimization, the weight of blank holder is reduced by 28.1%. Based on the optimization result, the blank holder is redesigned and machined, stamping test results indicate that defect-free stamping parts are formed with same blank holder forces, and the thickness difference between the original and newly stamped parts along a cross section is less than 0.06 mm, i.e. 4.29% of the initial blank thickness. This verifies that the proposed approach can effectively reduce die weight and maintain the derived forming performance of stamped part.

► We consider the elastic deformation of tools in sheet metal forming simulation. ► We take the interaction behaviors of tools due to the elastic deformation or the tilting into consideration. ► Multiple load conditions are considered in topology optimization to obtain a global optimization result. ► We carry out the experimental verification to check the performances of the optimized die structure and the formability.