Research On The Automobile Panels Forming By Hydrodynamic Deep Drawing Based On Numerical Simulation

The structure of automobile panels has huge dimension and complicated shape, so the conventional process of product will lead to many product quality problems, such as crack, wrinkle and so on. The hydrodynamic deep drawing (HDD) process of automobile panels belongs to advanced soft mould forming technology, that the basic principle of HDD used high pressure liquid to instead of the female die. The HDD process has wide application prospect, which was suitable for the current automobile industry of multi-product and small batch production, because of the super flexibility, better qualification and lower cost.The design of addendum surface and binder surface is crucial to the automobile panel drawing dies, which determines the forming feasibility of drawing parts and the ultimate product quality. Aimed at the structural profile characteristics of front fender bending has relatively high boundary and huge camber, the design of bending addendum is gradually flatten groove structure, which plays draw-bead and supports uniform feeding. The parameter optimizing design of drawing die face is obtained by applied die face engineering (DFE) in DYNAFORM, and the die face quality is judged by numerical simulation results, so that the optimization design of die face can be realized rapidly and efficiently.In order to overcome the appearance of crack, deforming deficiency and multiplicity of processing operations in the common drawing process of the automobile panels, the common drawing and HDD process of front fender and outdoor plate were comparatively analyzed, which were carried out by the numerical simulation that was based on the large non-linear dynamic explicit analytical software ETA/Dynaform5.6. The influence of the two processes on automobile panels'forming quality and procedure was investigated and analyzed by taking the thickness distribution and Forming Limit Diagrams (FLD) as standard. The results shows that hydro-mechanical deep drawing has excellent performances for the outdoor plate with stamping undercut and the front fender with relatively deep groove, under the reasonable chamber pressure loading path. By the HDD process, the forming procedure can be effectively reduced, high quality of automobile panel with complicated shapes can be formed by one procedure. On the quality of forming parts, hydro-mechanical deep drawing can more effectively control crack and deforming deficiency, improve the flow uniformity of sheet and the die fittingness. The formed automobile panel obtained higher quality with uniform thickness distribution.The liquid chamber pressure variations to the HDD formability effects of front fender and outdoor plate were analyzed. The optimal loading curve of chamber pressure was obtained. The results shows, according to the large surface and shallow drawing of automobile panels, the too high and early liquid chamber pressure should be avoided due to the too great reverse expanding at the initial hydrodynamic deep drawing. The too great reverse expanding would lead to drawing breakage of sheet metal, or feeding too large material margin which would generate accumulation wrinkle.