2枚板･3枚板ハイドロフォームの成形技術

―材料流入をともなう鋼板のハイドロフォーム技術の開発 第2報―

抄録

Sheet hydroforming using high- and ultra high-strength steel has the potential to realize the manufacture of lightweight and complex car parts. In this study, forming characteristics and limits in sheet hydroforming with the material inflow of welded double blanks (double sheet hydroforming) without a blank holder are investigated by finite element (FE) analysis. On the basis of the obtained results, technology of welded triple blanks (triple sheet hydroforming) is demonstrated in experiments. The main results are as follows. (1) In double sheet hydroforming, wrinkles occur owing to the difference between the upper and lower material inflows. (2) The limits of wrinkle occurrence depend on the differences between the upper and lower die circumferences, the upper and lower sheet tensile strengths, and the upper and lower sheet thicknesses. (3) The formable range of double sheet hydroforming using dies with concave and convex beads differs, even in the same upper and lower die circumferences. (4) Two methods of triple sheet hydroforming are proposed. Experimental products have no defects. It is confirmed that the new methods are effective in reinforcing automotive parts.