Theoretical Calculation for Forming Limit Stress Diagram of Composite Nickel Coating Sheet

Based on experimental stress and strain datas, the stress-strain constitutive relation of composite nickel coating sheet was calculated by using Hollomon equation and the polynomial fitting, and then by using quintic polynomial fitting constitutive relation, Hill48 yield criterion and Swift diffuse instability criterion, a thoretical calculation model for the composite nickel coating sheet′s forming limit stress diagram (FLSD) was derived. Sheet metal stamping experiment was done to verify the validity of the model of composite nickel coating sheet. The results show that the model could predict the FLSD of the composite nickel coating sheet accurately. After applying the model in production process of composite nickel coating sheet forming, some forming defects would prevented effectively, and the model could help finding the causes of these defects.