2021 Volume 62 Issue 726 Pages 87-94
With the focus on the forming of a tube with differential wall thickness by the ironing of the inner surface, the interaction of the effects of punch geometry (length of parallel part L P, semiangle α P and clearance C P ) on the formability and forming load is investigated by experimentally consistent finite element analysis. Results of the analysis show that L P and α P significantly affect the forming load, while C P has little effect on the load. The punch with larger L P, or the punch with smaller α P or smaller C P, realizes a higher formability because the slipping of steel tube, which is a result of shape defects, does not occur even if Δμ is small. Furthermore, it is theoretically clarified, through discussions on the forces that suppress/induce the slipping of the tube, that slipping does not occur if a large surface pressure is generated on the parallel part of the punch. Since the surface pressure generated on the parallel part of the punch during tube forming varies depending on α P and the area of the parallel part of the punch varies depending on L P, L P and α P should both be taken into account in designing the punch. On the other hand, C P does not affect the other design factors and can be designed independently.
