Prediction and Experimental Verification of the Critical Fracture Blank Holder Force for Deep Drawing of Box-Shaped Parts

抄録

In this paper, the deformation law of box-shaped parts drawing was analyzed, and the mathematical expression for calculating the critical fracture blank holder force (BHF) was deduced. In order to determine the fracture parameters of 08Al sheet, notched specimen tensile tests were conducted, the full-field strain of the specimens from deformation to fracture was obtained by the digital image correlation (DIC) technology. The evolution law of the stress triaxiality and Lode parameter with plastic deformation was obtained, and the fracture parameters of the modified Mohr-Coulomb (MMC) fracture criterion were fitted by the least squares method. The finite element (FE) simulation model coupled with MMC ductile fracture criterion was established to simulate the fracture behavior of sheet. The reliability of theoretical calculation was evaluated by FE simulation and experiments under various process conditions. The results demonstrated that the prediction of the critical fracture BHF by theoretical calculation and FE simulation were both partial safety predictions and all fracture earlier than the tests. In the theoretical calculation, when the flange shrinkage rate was 0.19, the critical BHF was the smallest, and the error was 17.5% compared with the tests, the theoretical calculation was closer to the test results. The theoretical calculation and FE simulation coupled with ductile fracture criterion provide a reference value for predicting the critical fracture BHF and intelligent control in actual production.