A hybrid membrane/shell method for calculating springback of anisotropic sheet metals undergoing axisymmetric loading

To reduce the computation cost of finite element analyses aiding die design for sheet metal stamping, a hybrid membrane/shell method was developed to determine the springback of anisotropic sheet metal undergoing axisymmetric loading. The hybrid membrane/shell method uses a membrane model to analyze the stamping operation. The bending/unbending strains and stresses varying through thickness are calculated analytically from the incremental shape determined by the membrane analysis. These bending strains and stresses and the final membrane shape are used with a shell finite element model to unload the sheet and calculate springback. The accuracy of the springback prediction with the hybrid method was verified against the springback of 2036-T4 aluminum and a DQAK steel sheet drawn into a cup. It was found that, in comparison with a full shell model, a minimum of 50% CPU time saving and a comparable accuracy was achieved when the hybrid method was used to predict springback.