The Application Situation And Simulation Analysis Of Stamping Of Automoble Sheet Metal

Generally speaking the category of steel plate of cars , including cold rolled steel plate , hot rolled steel plate , high strength steel plate and coated steel of cars . According to the characteristics of light weighted vehicle body structure , it puts emphasis on describing the application situation of high strength steel plate and Al alloy sheet , and generally introduces the major problems and research situation of light weight automobile both at home and abroad .High strength steel plate can be obtained from low carbon steel plate which is strengthened and Tensile strength is above 350 Mpa . The mechanical character of automobile's bodywork can be still satisfied , when high tensile steel plate is thinning . It is now used for Engine hood , decklid , front guard , front mudguard and rearbumper .Because of the good coating manufacturability , galvanized sheet is used for body outer panel . At present , in the production of automobile's bodywork , the using of galvanized sheet is growing , especially in intermediate and senior passenger vehicle , body in white is almost made of it . Automobile's bodywork can be also made of aluminum alloy , for example Audi A2 (Germany) , in the global construct ,Al alloy replace steel to bear weight and the effect of impact .Automobile covering parts stamping forming technique is very important for cycle-time reduction , cost reduction , design quality improvement and market competitiveness enhancing . This article has made some researches about FEM numerical simulation techniques in automobile covering parts stamping forming , and made some experiments about stamping forming simulations in some the external & under board of saloon cars'trunk .Describing the geometric nonlinear finite element equations ,dynamic explicit finite element method and its algorithm and implicit finite element method . Analyzing the basic concept of shell elements , describing the relationship between stress and strain , yield criterion , contact algorithm and forming defects judgments .Using DYNAFORM Programs to simulate the drawing process of the external & under board of saloon cars'trunk . This simulation analyzes the situation of drawn component wrinkles and thinning when there is a drawbead or is no drawbead . When there is no drawbead , the plate is easily transformed and metal flow rate is high . On the internal and edge of some forming places , under the state of drawing , board thickness increase and the maximum is 28% , and on the dents of board , it becomes thinning and the maximum is 6% . When there is a drawbead , thickness generally reduced and only increased on the board edge and on some corners , the maximum is 12% . It no wrinkles and the whole plate transformed equally , thinning rate is smaller than 10% , but the thinning rate of left up corner is larger than 20% and it breaks , this section is called undeformed section and it doesn't matter . The stress situation of drawn component : When there is drawbead , the average stress distribution of upper and lower surfaces can be shown on the ruler of forming , upper surface ? m (max)?183MPa , ? m (min) ??269MPa, lower surface ? m (max)?178MPa , ? m (min) ??281MPa . Do a forming simulation which take the influence of blank holder force is 150KN , 200KN , 250KN . The result shows that when it is 150KN and the max radial strain is 0.2 , tangential strain turns to -0.4 . The min strain is 0 , the whole blank has a undeformed section , the transformed is not enough . When it is 200KN and the max radial strain is 0.33 , tangential strain turns to -0.22 . Blank has few non-uniform deformation region and wrinkle region , there is no fracturing and forming limit is in the security zone . When it is 250KN and the max radial strain is 0.3 , tangential strain turns to -0.2 . Depend on the color of forming simulation , there is still wrinkle on this part and non-uniform deformation . The strain is in the security zone but with trend to fracturing . According to the analysis above , the final choice of blank holder force is 200KN .Expatiating on the mechanism of springback , analyzing the key influence factors of springback , finding out the ways to avoid springback , illustrating the formulation of bending springback , and simulating the average stress distribution and the maximum principal stress distribution after unloading .