Simulation And Experimental Study On The Hot Forming Of Lightweight High Strength Steel Body Integrated Door Rings

The concept of integrated door rings has been proposed based on the application of high-strength steel materials and tailor-welded panels technology.The integrated door ring is made of high-strength steel material,which is stamped and formed as a whole after laser welding.One part replaces multiple parts of the traditional door ring structure,which can effectively reduce the weight of the body door ring while ensuring the performance of the car door ring.High strength steel parts are generally processed by hot forming.Due to the differences in material properties of heterogeneous welded blanks and the influence of welding seams,defects such as rebound,wrinkling,fracture,and weld deviation may occur during hot forming.Therefore,in order to achieve precise forming of the integrated door ring,this article conducts research on the hot forming process of the integrated door ring using two materials,Usibor1500 P and Ductibor500,and conducts hot forming experiments on the integrated door ring,as follows.(1)By analyzing the structural strength and lightweight requirements of the integrated door ring,the welding seam and material distribution of the integrated door ring were designed,and two materials,Usibor1500 P and Ductibor500,were ultimately determined to be used.The door ring was arranged with six welding seams at different positions.(2)Isothermal uniaxial hot tensile tests were conducted to analyze the stress-strain curves of two types of substrates and tailor-welded blanks under different strain rates and temperatures.The metallographic structure and fracture morphology of the substrate and weld were observed,and the thermal deformation behavior of the material was analyzed from a microscopic perspective.(3)We have established Norton Hoff and Arrhenius constitutive models for two materials,Usibor1500 P and Ductibor500.From the perspectives of calculation process and accuracy,it was found that the Norton Hoff model is more suitable for calculation.A method for calculating the stress-strain relationship of welds at high temperatures was proposed,and a Norton Hoff constitutive model of welds was established based on the calculated stress-strain.After verification,it was found that the stress-strain data obtained by this calculation method was reliable,and the weld constitutive model had good predictive performance.(4)An integrated door ring hot stamping simulation model was established using ABAQUS software.Through analysis of simulation results under different process parameters,it was found that the hot stamping forming of the integrated door ring was suitable when the blank holding force was 10 KN,the forming temperature was 800 ℃,and the stamping speed was 100mm/s.The integrated door ring hot stamping test was conducted using the simulated process parameter combination,and good forming results were achieved.