Abstract
Recently, tube—hydroformed automobile parts have been appreciated for their features in improving fuel economy and crash safety. Hydroforming using conical tubes could be effective to obtain further complex shaped parts of cars. Generally, in hydroforming using conical tubes, it is difficult to obtain a large expansion ratio and a large work hardness because of difficulties in axial feeding. In this paper, two newly developed hydroforming technologies are proposed in order to enable axial feeding in hydroforming. Both technologies are relatively easy methods using special dies. Fundamental tests of the new hydroforming methods using conical tubes, which are made of high tension steel, are carried out. The expansion ratio and plastic strain after hydroforming are investigated. The effects of axial feeding on deformation are discussed.
