Design And Simulation Research Of Pre-hem Mechanism Of Automobile Covering Panels Hemming Die

As the last step of the automotive panels stamping, hemming has significant impact on the forming quality of the appearance and the dimensions on the edge of the automotive panels. The structure design determines the production quality of the hemming die, and the pre-hem mechanism is the most important part of it. The kinematic of pre-hem mechanism was analysed, the design of pre-hem structure and the FEM simulation of hemming was studied, including the following research work:(1) Classify the pre-hem structure of the hemming die according to the mechanism characteristic, and the kinetic equations of pre-hem motion were deduced, analysis the impact of the pre-hem parameters on the quality of hemming, and the impact of springs on the combined pre-hem motion. And point out the constraint condition of the combined motion pre-hem to have a steady pre-hem quality.(2) The kinetic equations of pre-hem motion were applied in the hemming FEM modeling, and the various hemming FEM model were built. The impact of pre-hem motion on hemming quality is analyzed based on the FEM results. Design the simulation experiments based on Latin hypercube sampling, analysis the results using the multiple liner regression analysis and summarize the impact of the parameters on the hemming roll in and roll out.(3) The modeling method of pre-hem structure was studied, and the factors in each step of the modeling was analysed, the flow chart of the pre-hem structure building was summarized. A car door hemming mechanism was designed according to the characteristic. The FEM model of this hemming mechanism was built using explicit FEM method. Eliminate the defects of the die by modifying the die based on the analysis of the FEM results. The inspections on the product demonstrated the validity of the modification.The kinematic analysis of pre-hem in this thesis can provide references for the design of pre-hem mechanism. The pre-hem kinematic equations can be used to all the FEM simulation of similar hemming to obtain a more accurate simulation results. Using multiple liner regression analysis the relation of the hemming defects and the hemming parameters can provide references for the hemming parameters selection.