Research On High Strength Steel Sheet Hot Stamping Multi-physics Field Space-time Dynamic Coupling Numerical Simulation And Experiments

The application of ultra high strength steel in automobile manufacturing field is an effective method to realize the lightweight of automobile and improve vehicle passive safety. Hot stamping is a new technology specifically for manufacturing high strength automobile parts, and parts after hot stamping are basically no rebound. The process of hot stamping is in the following. First, the temperature of sheet is raised to a certain value above the recrystallization temperature. Then, the heated sheet is moved to the hot stamping die, simultaneously forming and quenching. Last, parts are obtained with high strength. At present, the shaping forming process is still in the fledgling stage at home, so that researches on hot stamping process have important guiding significance for its practical application.In this paper, thermal-mechanical-phase three fields coupling simulation method, a powerful means for quantitative analysis was proposed aiming at solving problems of hot stamping process lacking reasonable systematic researches and process parameter optimization methods. Ultra high strength steel BR1500 HS acted as the research object, the numerical model of hot stamping for U shaped part was established by adopting the most advanced finite element simulation technology. Furthermore, researches on forming mechanism, numerical analysis and optimization of process were conducted in order to provide a theoretical and technological basis for guiding the actual production processes. The work of the full text was summarized as follows:① Detailed analyses were done on heat transfer theory, rigid plastic finite element theory and phase transition theory in the numerical solution of the hot stamping process.② Based on the numerical simulation software, key techniques like multi field coupling, material modeling and phase transition model in the simulation were solved. Simplifying the analysis model, three fields coupling finite element analytical model covering heating, deformation and phase transformation was established. Moreover, quantitative analyses for the main process parameters were realized.③ Through finite element model, numerical simulation was carried out on the whole hot stamping process of ultra high strength steel BR1500 HS, based on which the temperature field, phase transformation field and hardness distribution characteristics were analyzed.④ The Forming temperature and martensite volume fraction were acted as the indexes to evaluate the quality and effect of hot stamping forming.⑤ A set of hot stamping die was designed and manufactured, and then, a series of hot stamping experiments were conducted. Through the analyses of microstructures and hardness of hot stamping parts, the reliability of finite element model was verified.