成形性および加工荷重に及ぼすパンチ形状の影響

―管材の内面しごき加工による差厚管の成形―

抄録

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.