Application of Constitutive Model Considering Nonlinear Unloading Behavior for Gen. 3 AHSS

Nonlinear unloading behavior has been reported as an important factor for accurate springback prediction. In this study, a newly proposed special component of strain: "Quasi-Plastic- Elastic" ("QPE") strain was utilized to study the springback behavior of Advanced High Strength Steels ( AHSS). Several types of steels, including IF steel, DP780, TRIP780, DP980, TWIP980 and QP980 were considered in this research. The results showed that all the tested steels have following behavior: 1) QPE strain is recoverable, like elastic deformation. 2) It dissipates work, like plastic deformation. A 3-D constitutive model considering QPE behavior was implemented in Abaqus/Standard with shell element and applied to draw-bend springback test for Gen. 3 AHSS, QP980. Predictions for springback using the QPE model were more accurate compared with standard elastic-plastic models.