Research on hydro-pressing process of closed section tubular parts

摘要

A hydro-pressing method was proposed to solve the problems in tube hydroforming process, such as too high pressure, nonuniform thickness distribution, and difficult forming of section corners. The process of hydro-pressing a tube seems like pressing of a solid bar. Theoretical analysis was performed, and the calculation formulas of hydro-pressing process parameters were given. Experimental research was conducted on hydro-pressing process of rectangular cross section with curved sides and bowtie cross-sectional components. The effects of supporting pressure, displacement of the pressing on section shape, and thickness distribution were investigated. The difference was compared between the hydro-pressing forming and the conventional mechanical pressing. It is demonstrated that the supporting pressure and pressing displacement are the essential parameters that influence cross-sectional shape and thickness. The dent defect disappears gradually as the supporting pressure increases and the thickness varies unobvious during hydro-pressing process of a rectangular cross section with curved sides. When the supporting pressure is 15 MPa, the maximum thinning of the rectangular cross section with curved sides is only 1.92 %. For a bowtie cross section, the required pressure is far less than that of conventional hydroforming for the same corner radius. Thickness distribution of section corner zone is more uniform than that formed by conventional hydroforming. Compared with conventional hydroforming, the hydro-pressing is a valid method to form the closed section tubular parts with the same perimeter and different cross-sectional shapes, which remarkably improves thickness distribution and reduces the forming pressure.