Research On Forming Numerical Simulation Of Aluminum Alloy Automotive Panel

Automobile lightening technique has become a major development direction forautomobiles as environmental pollution, energy crisis become increasingly serious.Aluminum alloys as a lightweight material has attracted numerous attention owing toits advantages such as low-weight and improved crash safety performance. However,due to the distinct crystal structure of aluminum to that of steel, the formability ofaluminum panels is inferior to the steel panels. In addition, the structural complexityand large-scale of automotive panel can also lead to problems such as wrinkle, crack,insufficient deformation and springback, which in turn increase the difficulty ofquality control and mold design and restrict the application of aluminum alloys inautomotive panel. Thus, exploration of the mechanism of stamp forming andspringback is critical for the application of aluminum alloys in automotive industry.This thesis conducted numerical simulation on the stamping process ofaluminum alloy automotive outdoor using the stamping simulation software ofPam-Stamp, and provided some control measures against defect and springbackduring the production of components. The major research works are as follows:（1）By taking the double-curved panel as a typical example, the effects ofmaterial parameters, process parameters and mold parameters on the forming andspringback of aluminum alloy sheet were analyzed by using the numerical simulationsoftware of Pam-Stamp. As the results showed that, when forming the same shape ofstamping parts, the forming force of aluminum alloy sheet is less than steel sheet, butthe forming performance of aluminum alloy sheet is poorer than steel sheet. Besides,the springback problem of the aluminum alloy sheet is more serious than ordinarysteel, even larger than that of high strength steel. Meanwhile, increasing the friction coefficient is beneficial to decrease springback displacement of aluminum alloy panel,but it will destroy the quality of part’s surface. In the case of assuring no fracturedefects on part, increasing the blank-holder force not only can effectively control thematerial flow and prevent stamping part wrinkling, but also decrease the springbackdisplacement. Reducing the mold clearance is beneficial to decrease the springbackdisplacement of aluminum alloy panel, but it is harmful for the formability ofaluminum alloy sheet if the clearance is too small, which can lead to some defects,such as serious thickness reduction. Reducing the mold fillet is helpful to decrease thespringback displacement, and which is more effective to control springback byreducing the die fillet. But the mold fillet which is too small will make the mold wearseriously and lead to the quality of parts unstable.（2）Stamp forming analysis and numerical simulation based on the aluminumalloy automobile outdoor were studied by using Pam-Stamp. According the feature ofpart and the material properties of aluminum alloy, the author established a finiteelement model of automobile outdoor. The simulation results of initial draw showedthat due to the forming process was not used drawbeads, resulting in the most regionsof automobile outdoor deformation insufficient，the part of flanged edges wrinkledseriously. According to the above defects, laying some drawbeads on the mold toincrease the resistance of material flow. As a result, the area lack of deformationdecreased greatly, but the flange corners still had the wrinkle and some new defectsoccurred on part such as crack. Therefore, increasing the blank-holder force toimprove the insufficient deformation again, cutting the blank corners to preventwrinkle, adjusting the fillet of addendum surface to eliminate crack defects. Thesimulation results demonstrated the feasibility of the program, and the forming defectsof outdoor were basically eliminated.（3）Simulation was carried on about unloading springback and trimingspringback of outdoor after drawing forming process, the results have shown thatcontour precision of part is good, but serious springback occurred on some peripheralareas. Considering characteristic of part’s shape and actual manufacturing process,springback was effectively controlled with optimizing process parameters and modifying addendum surface.The experimental results confirmed the successful production of automotiveoutdoor by optimizing the forming program. We can effectively predict and controlthe potential defects and springback of aluminum alloy panel through numericalsimulation technology, thus improve the effectiveness of production design andforming quality. The above research is believed to provide a more rational designinformation and technical support for industrial stamping technology and moulddesign.