Reverse Reconstruction Of The Automobile Panel And The Numerical Simulation Of Drawing Process

The design and manufacture of automobile panels are the key processes in the development of automobiles, which determine the developing period and cost. By combining the reverse engineering technology and numerical simulation of drawing process, the reverse modeling and numerical simulation of the front fender were accomplished in the thesis.Technical principles of contact and noncontact measuring were analyzed and the advantages and disadvantages were compared. The ATOS optical scanner was introduced and taking the front fender in the company as an example, the procedure and the key techniques of data collection were discussed. Through the point clouds pretreatment of the front fender, the general operation procedure of data pretreatment was summarized, which can improve the efficiency of data treatment. The mathematical models of commonly used curve and surface were stated and the construction methods of NURBS curve and surface were summarized. Based on NURBS surface, the automobile fender was remodeled; meanwhile the modeling procedure and main techniques were discussed, which included surface reconstruction, surface editing and surface modification. Taking one of the fundamental surfaces of the fender as an example, the surface modifying technique was discussed and the reverse reconstruction of the front fender was accomplished. By comparing the traditional die-face design and parametric design based on CAE, the advantages of parametric design were stated and based on the FEM software DYNAFORM, the parametric die-face design of the reconstructed fender was implemented. Applying the theory of drawing process of automobile panels, the finite element modeling procedure of the fender and the setting foundation for process parameters were studied. According to the characteristics of stamping process and the selected material, the Balart 3-parameter yielding model and Belytschko-Tsay shell element were adopted in the numerical simulation. The drawing process of the fender was simulated using FEM software DYNAFORM, the simulation results of which predicted the defects of drawn parts. The measures for process improvement were put forward. It can provide references for the selection of material parameters, yielding model, blank size calculation and element types in further study.Applying uniform design method, the die-face parameters of the fender and the drawbead depth were optimized. The uniform design method can make experimental points distribute uniformly and reduce the blindness of parametric modification, which can obtain the satisfying parameters setting in fewer simulating experiments. In the last part, the effect of variable blank holder force on the fender formability was studied.