Numerical And Experimental Study On Forming Limit Curve Of Advanced High Strength Steel

In hot stamping precess of advanced high strength steel, the forming temperatureof blank is high and ever-changing. The forming precess consists of the interaction oftemperature, deformation and organization. The complex interal changes of the blank inthe forming process of advanced high strength steel bring great difficulties to the studyon forming property, especially on the prediction of instability. Forming limit curve isable to accurately predict the forming limit of the blank in the forming precess, guidesthe design of the stamping dies and stamping process. It plays an important role in theoptimization and development of stamping process. In this paper, the high-temp forminglimit curves of advanced high strength steel BR1500HS are built by using numericalsimulation and experimental method.Using ANSYS to establish the numerical simulation models and modifying the Kfiles, the isothermal forming processes, variable thermal forming processes and theforming processes which consider the effects of phase transformations are simulated byLS_DYNA solver. The temperature, stress, strain and organization are analysed and thethree above types of forming limit curves are bulit and compared.Test dies and temperature control system are designed and the control interface isdeveloped. With modified spot welding machine for heating device structures, the hotstamping experiment platform is established and the defferent kinds of hot stampingexperiments can be conducted.New blank’s shapes are designed and the hot stamping experiments with differertinitial temperatures’ blanks are conducted. Then, analysing blanks and dies’ temperaturefields and the high-temp forming limit curves of advanced high strength steel are builtby experiment. Comparison and analysis of experimental and simulative results showthe following conclusions. Some of the blanks appear martensite structure afterstamping when the the initial temperature is700℃. The temperature has a greatinfluence on high-temp forming limit cuver. The forming limit cuver moves right andthe forming performance improves with the initial temperature of blanks rising. Theerrors between experimental and simulative results are all within5%. The accuracy ofthe high-temp forming limit curves is proved.