Springback Determination By Springback Index Approach

A new mechanical parameter, Springback Index (SBI), is proposed to reflect the magnitude of sheet-metal springback at a given flow stress level. Through conducting Tension-Unloading-Reloading (TUR) tests and measuring the Effective Unloading Modulus (EUM) Parameter, which is defined as the ratio of the non-linear recovery vs. total recovery, SBI can be determined for the sheet metal after complex forming processes.

To verify this SBI approach, U-free bending tests are conducted with galvanized and galvannealed DP600 sheet steels. The results indicate that the determination of SBI is remarkably simplified and the accuracy of springback prediction is significantly improved.