Finite Element Analysis of Springback Process in Sheet Metal Forming

Springback prediction is essential to ensure the economics of sheet metal forming operations. To achieve accurate results, current nonlinear recovery applications in finite element (FE) analysis have become more complicated and therefore require complex computational programming work to develop a constitutive model. At the end of a plastic deformation and after the load is released from the sheet metal, the change of stress in the elastic area becomes nonlinear. The change of elastic modulus is influenced by the amount of plastic strain, yield locus size, and stress normalization point. The effects of nonlinear recovery on the residual stress distribution and the sheet metal final shape after springback were investigated. The analysis results show that the formed hysteresis loops due to the unloading and reloading process were able to be simulated successfully by the proposed method. It was found that the distribution of non-zero residual stresses at the end of springback process was highly related to the nonlinear recovery curve