Research On Defects Control And Spring-back Compensationfor The Forming Process Of The Automobile Front Floor Part Using High Strength Steel

To manufacture the automobile covering parts of high quality has become one of the most importanttopicsin the field of sheet metal cold stamping.In order to improve the precision of the parts, different kinds of defects and flaws on the stamping parts should be eliminated. In this dissertation, thestampingdefects and flaws of the front-floor part of automobile were focused on.The formability of the stamping part of the automobile front-floor was modeled using "one-step"finite element method. The types of the defects and its location were predicted based on the result data from the simulation. The binder surface and the layout of the draw bead were designed according to the above analyzing. The FEM models of the stamping were built and the stamping defects were simulated. By adjusting the FEM model repeatedly,the qualified partwasobtained with these process parameters obtained from the simulation.By using sheet metal stamping theory and finite element method, the types and locations ofpotentialdefects were analyzed, different control strategies weredeveloped and carried out. The front-floor part was classified into four defect control areas according to the structure and feature of the part and based on the analyzing results of deep drawing model. Through the design of unequal clearance of blankholder, the imbalancedeformation problem at the outline edge area(area C) was solved. The springbackvalue was decreased to the acceptable range.A new type deep drawing die surface was established by designing the round bulge process supplement and the optimized design scheme was used to eliminate wrinkling instability of tail-parts (area B). Themagnitude of the regional spring-back was reduced by62%. The head area of the front floor (area A) was formed by thedie surface redesigned with the springback compensation. The reasonable magnitude of springback compensation in different positions of die surface was adjusted by iterative solution of the FEM model.Eventually,the magnitude of springback in the region was restrainedto the acceptable range.In order to solve the insufficient plastic tensile in the central position of U-shaped groove, two schemes of surface modeling were designed, which were die surface compensation and die surface by compressiontreatment.Through comparing with the two simulation results,the defect of insufficient of plastic tensile was effectively controlled by using die surface compensation scheme. But the part surface defects wouldre-emerge duringthe second step of the drawing.The surface defects in subsequent drawing can be avoided effectively by compressiontreatment. To sum up the defects of insufficient plastic deformation in the U-shaped groove can be solved by combining with the two schemes.