Experimental and numerical study of springback effect of advanced high strength steel in a V-shape bending

Advanced high strength (AHS) steel sheets are increasingly used for the production
of various automotive structural parts. The components of new lightweight vehicles have very
complex shapes, for which more precise forming procedures are required in order to achieve a
desired geometry. Hereby, springback occurrences of such AHS parts are often the most
critical concern. In this work, it aimed to investigate springback effects of the AHS steel grade
980 in a V-shape bending process. Experimental bending test and its corresponding FE
simulations were conducted. The Hill’48 and Barlat89 yield criteria, and the Yoshida-Uemori
(Y-U) kinematic hardening model were applied. The yield function parameters were obtained
from the tensile tests of samples in various orientations. The Y-U model parameters were
determined from a cyclic tension-compression test and were afterwards calibrated with the 1-
element simulation. The resulted bend angles measured from the experiment and predicted by
FE simulations using the different models were compared and evaluated. For the bending in
this work, the Hill’48 and Barlat89 models showed the predictive errors of springback angle
1% and 2% higher than the Y-U model, respectively. The accuracy of springback prediction
could be improved by the Y-U model using C1 and C2 parameters around 1%. In addition,
effects of sheet thickness and punch radius on the springback were afterwards studied and
discussed by using the Y-U model.