ESTABLISHING THE FORMING LIMIT DIAGRAM BASED ON FEM SIMULATION

摘要

The forming limit of sheet metal is defined to be the state at which a localized thinning of the sheet initiates during forming, ultimately leading to a split in the sheet. The forming limit is conventionally described as a curve in a plot of major strain vs. minor strain. This curve was originally proposed to characterize the general forming limit of sheet metal. The traditional method for establishing forming limit diagram (FLD) of sheet metal is experimentation, yet it is time consuming and needs high cost. In finite element simulation, when the contact force between male die and blank reaches its peak value, the strain of the element adjacent to the maximum thickness reduction element on the blank is the necking ultimate strain, which can be obtained through altering the shape and dimension of the specimens under different strain state. The curves by connecting all these ultimate strain points in 2D strain space is the sheet metal forming limit diagram (FLD) obtained by FEM. This paper establishes the FLD of 08Al steel sheet of lmm thick on the basis of finite element simulation with PAMSTAMP commercial FEA package, using rigid-plastic flow method, compares the FLD obtained through the above method and the FLD measured from the drawing specimens of experiments using the half ball male die according to GB/T 15825.8-1995 "Sheet Metal Forming Property and Experimental Method: the Forming Limit Diagram (FLD) Experiments", and the results conform well.