| Friction between the sheet and tooling is a very important act during sheet metal forming, whose existence influences the sheet metal forming performance, distribution of stress and strain and the change of thickness. The finite element model and friction boundary conditions must be built exactly during the process of finite element simulation on sheet metal forming. If the friction information can not be provided exactly , the exactness of simulation will be lost.. This paper studies the friction problem during the sheet metal forming simulation. The main content is as follows:1) The finite element theory of the sheet metal forming, contact searching arithmetic and the friction model are widely discussed in the paper.2) The modeling methods of numerical simulation of sheet metal forming are analyzed . By redevelopment in the ABAQUS/Explicit user subroutine VFRIC, the modified coulomb friction model is successfully applied to ABAQUS forming simulation. At last ,the feasibility is proved through a example.3) The changes of stress, strain and thickness influenced by friction during the sheet metal forming are analyzed by the finite element simulation of concave-convex combination flanging.4) A non-linear mapping relation for thickness of sheet metal forming and friction coefficient is established by combining the Artificial Neural Network technology and the numerical simulation technology. According to the experiment and simulation, implementing to predict friction coefficient of sheet metal forming by artifical neural network ,which affords a practical method to determine the friction coefficient in numerical simulation of sheet metal forming.
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