Influence of Parameter Identification of Anisotropic Yield Function on Spring-Back Prediction in Finite Element Simulation of Sheet Metal Forming Process

The anisotropic plastic behavior of metallic sheet has a significant influence on spring-back, and is usually modeled by anisotropic yield function in numerical simulation. Material parameters of anisotropic yield function are generally identified either by yield stresses or by r-values, or both of them. For Hill1948 and Yld89 anisotropic yield functions, r-values are still widely used to calibrate their material parameters in spring-back prediction. Here, yield stresses and r-values were respectively used to calibrate them, and the differences of the spring-back simulated by these two identification methods were discussed. To evaluate their accuracy, the simulation results were compared with the spring-back calculated by Yld2000-2d anisotropic yield function. The result shows that when yield stresses were used to identify the material parameters of Hill 1948 and Yld89 yield functions, the simulated spring-back was closer to that of Yld2000-2d yield function.