Prediction of springback after bending under tension

Abstract

The effect of kinematic hardening on springback predictions in sheet metals was rigorously clarified using a modular bending-under-tension test. DP600 sheet samples were tested over a wide range of tool radii and tension forces. Specifically modified isotropic hardening and combined isotropickinematic hardening models were compared, which provide strictly identical predictions under monotonic loading. Loading configurations (combinations of tool radius and sheet tension) were identified which require the use of one or the other type of hardening model, in order to ensure the predictive accuracy. The two models predicted similar springback for high backforces or for high R/t ratios. In turn, both models failed to predict the springback accurately for small R/t ratios, in particular when combined with small backforces. This combination of loading conditions appeared as the most discriminant one, in which the combined hardening model clearly appears qualitatively superior although not entirely sufficient, designating the potential application areas for more advanced material models.