Optimization Design And Temperature Control Of Hot Zone Of Die Surface For Tailor B-Pilliar Hot Stamping Process

Automobile B-Pillar plays an important role for car safety.With the increased high requirement in automobile crash safety,the tailored B-Pillar are gradually adopted,because the head of the parts has better ductility with higher energy absorption,and the tail has ultra-high strength mechanical properties to improve side collision performance.The hot stamping process of die zone heating can adjust the cooling rate of the plate to achieve the forming and manufacturing of tailored parts by controlling the heating or cooling conditions in different die zones.The hot stamping process based on die zone heating requires the temperature of the die surface in the hot zone to be evenly distributed at a high temperature.Furthermore,the thermal expansion effect will cause the die deformation,which leads to the difficulty of die design.In terms of die heat transfer numerical simulation,die surface design,temperature control and so on in the B-pillar hot stamping process,the following researches have been carried out in this paper:1)Thermal parameters experiment of die materialThe thermal experiment was conducted to obtain the thermal expansion,conductivity and specific heat parameters of die material.The die heating experiment was set up according to the temperature control system of the actual die.In addition,the die temperature data under different power conditions was obtained.The heat transfer FE model of the experimental die was established by using ABAQUS software.Taking the temperature data obtained in the test as the optimization objective,the heat transfer coefficient and radiation coefficient between the die and air were calculated by using Hooke-Jeeves optimization algorithm.Finally,the accuracy of the finite element simulation of heat transfer and thermal expansion process of the experimental die was verified.2)Optimization design of hot zone die surfaceHeat transfer simulation model of hot zone of the die was established.To optimaze surface temperature,heating rod power was calculated by using modified method of feasible directions algorithm.According to the balance power of the heating rod,the die thermal expansion simulation model was established,and the die surface size after expansion was obtained.Moreover,based on coordinates of the surface nodes,the die surface after compensation was used to reconstruct the 3D model of the die,the die surface was obtained at room temperature.Finally,the positioning method between two dies was determined,according to deformation and stress distribution analyses of the thermal expansion simulation results.3)Die surface temperature control in heating processThe transient heat transfer finite element simulation was established based on simplified die model.Taking die surface temperature as the optimization target and uniform distribution as the constraint condition,the die temperature control simulations of heating process under fuzzy control and fuzzy PID control strategy were complete based on the ABAQUS Python secondary development.The die temperature during the heating process was obtained.and the die heating experiment under fuzzy PID control was conducted to vertify the simulation reliability.Finally,the influence of different factors on the heat transfer simulation of die heating process were discussed respectively.4)Die surface temperature control in stamping and quenching processAccording to the cooling pipe of the existing die model,the flow rate of cooling water in each pipe under the maximum inlet pressure was simulated with FUENT software.And the convection heat transfer coefficient between different pipes and the die was obtained according to the empirical formula.The stable temperature field of the die obtained in the third chapter was taken as the initial temperature field of the die.The hot stamping simulation was carried out with ABAQUS software to analyze the blank forming state and obtain the temperature field of the blank and the die.Finally,the fuzzy model reference learning control strategy was applied to control the die cooling system,and the heat transfer finite element simulation was carried out.The temperature changes in the whole stamping process of blank and die as well as in the quenching process process were discussed.