New developments in theory and processes of internal high pressure forming

Important progresses and achievements in fundamental theory, key processes and industrial applications of tube hydroforming realized in engineering research center of hydroforming/harbin institute of technology (ERCH/HIT) were introduced. Typical stress states in tube hydroforming process and the corresponding thickness changing tendency were given on the plane stress yield loci. Thickness changes along the axial direction of tubular part with changeable diameters and the hoop direction of tubular part with rectangular cross-section were given. The concept of limited corner radius in calibration process was proposed and analyzed. Ring hoop tension test was proposed to evaluate the mechanical properties of tube along hoop direction. Multi-step method for the forming of thin Y-shaped branch tube, and double-layered hydro-bending method for the forming of thin-walled bent tubular part were proposed. Ultra-thin Y-shaped branch tube, integral stainless steel tube, and bent tubular part for aerospace application were manufactured. Hydroforming machine of 55 MN maximal closing force was developed. Typical parts for automotive industry, such as engine cradle, front beam holder and torsion beam, were manufactured.