Forming Limit of Holed Dome in Two-Stage Stretch Forming
This paper deals with the accurate prediction of forming limit of a dome with a circular hole in two-stage stretch forming. Since this two-stage forming is a process of non-proportional deformation, a fracture criterion, which is capable to predict fracture limit of sheet metal under non-proportional strain path, is introduced. The limit dome height of steel blank is predicted by utilizing numerical optimization technique, in which the fracture criterion is used as a constraint function to avoid sheet breakage. The calculated result and the corresponding experimental result show that the fracture criterion can successfully predict the limit dome height in the two-stage forming while the classical forming limit diagram (FLD) overestimates it.
Sihai Jiao, Zhengyi Jiang and Jinglong Bu
A. Hirahara et al., "Forming Limit of Holed Dome in Two-Stage Stretch Forming", Advanced Materials Research, Vols. 146-147, pp. 844-847, 2011