Springback Prediction with LS-DYNA and Die Face Compensation of Aluminum Hood Inner 2003-01-0571
The use of aluminum alloys as automotive body materials increases the need for springback control because of their higher yield strength-to-elastic modulus ratios. Math-based tools can be used to predict the amount of springback of sheet metal parts after stamping, and to further compensate the die face, based on the prediction, to reduce springback.
In this study, analysis was conducted with LS-DYNA  on an aluminum hood inner to verify the accuracy of springback prediction. This was used as a basis for the die face compensation through a morphing procedure [2, 3]. Reasonably accurate springback prediction was obtained in the rear region of the hood inner, while in the front center region, LS-DYNA over-predicted springback. Gravity loading, appropriate mesh size and adaptive level can all affect springback prediction. Material models have a significant effect on springback prediction of this part. Reasonably accurate predictions were obtained with the Barlat'89 model, while results with Hill'48 and transverse anisotropy showed large amounts of error.
Analysis was repeated with the compensated die, based on morphing. The new die enabled significant reduction of the deviation of the trimmed part. However, some errors still exist, which can be attributed to the accuracy of the morphing procedure, nonlinear stress changes due to the panel shape change, and the accuracy of numerical prediction. The impact of each of those factors is discussed.