Global-cumulative incremental hole-flanging by tools with complementary-shape cross section

A novel method using special featured tools is proposed for double-sided incremental hole-flanging (DSIHF), which can perform successful hole-flanging in one-step due to the globally cumulated deformation mode. Tools with complementary-shape section curves are used to constrain the material flow for better part geometry. The proposed method has been verified by two cases: an axisymmetric circular flanging and an asymmetric clover flanging. Experimental results demonstrate that the new method is feasible for flanging of complex shapes with simplified tools, reduces processing time and improves geometric accuracy. Moreover, numerical simulations were conducted to show that the proposed method has a different deformation mode compared with the conventional incremental forming. Specifically, the circumferential strain becomes the dominant strain, and its value depends on the in-plane curvature and the distance from the part edge.