Research Of Finite Element Modeling & Experiment Of Die Structure For High-strength Steel Stamping

Recent years have seen many new developments in steel technology and manufacturing processes to build vehicles of reduced mass and increased safety with steel. The ULSAB (UltraLight Steel Auto Body) and ULSAB-AVC (Advanced Vehicle Concepts) programs, sponsored by the global steel industry, focused attention on advances in lightweight design concepts and on more extensive use of Advanced High-Strength Steel (AHSS). Along with the advantages of these newer steels came the serious problems to the design and manufacturing of automotive panel stamping die because of its high yield strength and tensile strength, such as die breakage and wear during the tryout and stamping operations, elastic and plastic deformation of die and press and the excessive weight of die. To solve the problems mentioned above, a new method of FEA for die structural analysis was developed to provide a math-tool to validate the design and guarantee the safety of die structure. In addition, a experiment of measuring the stress on the die during drawing process was used to validate the FEA results In this paper, FEA for die structural analysis was based on the FEA of sheet metal forming using DP600. Firstly, FEA for sheet metal forming was performed with LS-DYNA and the loads of every simulation step between the tool and blank were extracted from forming process for die structural analysis. Secondly, FE model of solid body of die in HyperMesh with Hex8 elements was created and then the loads extracted of each step were applied to the nodes of solid die surface using a loads mapping method. Finally, the FE model with the loads and other boundary condition was imported into MSC.MARC and the die structural analysis was performed. This integration of stamping forming and die structural analysis not only made the continuity of simulation available, but also resolved the issue of the calculation efficiency.Also, a strain-stress measurement system was developed in order to validate the results of die structural analysis by cutting several shallow grooves on the die surface on which strain gauges were stuck to measure the strain and stress.In FEA results, the distribution of strain, stress and elastic deformation on tools was clearly performed in every simulation step. Also the experimental results showed that they were in good correlation with FEA ones.