Spring-back simulation of sheet metal forming for the HT-7U vacuum vessel

The HT-7U vacuum vessel is an all-metal welded double wall toroidal structure, which has characteristics of ultra-high vacuum and thin shell. Some of the forming tools will be fabricated according to its outline dimensions. In order to design a optimal shape for the forming tools and avoid an undesirable local deformation at the head of sheet, the software package ANSYS/LS-DYNA and DYNAFORM were utilized to simulate the process of the deep drawing in sheet metal forming and develop a parameter optimization system for the design of the die and punch. During the numerical simulation the updated LaGrange formulation and elastic-plastic constitutive equation were adopted to solve the problem of large strain and large deformation in sheet forming process. According to the simulation analysis results the optimum shape of the die and punch surface was finally determined