Abstract: Lightweight ways of automotive and application trends of tube hydroforming are introduced. Latest progresses and achievements in fundamental theories, key processes and tools and industrial applications of tube hydroforming are illustrated. In fundamental theories aspect, circumferential stress, axial stress, circumferential strain, axial strain and normal strain states of curved tubular components in hydroforming process are disclosed. The existence of limited corner radius in calibration process is clarified and the effect of internal pressure and friction on limited corner radius is analyzed. In key processes and tools aspect, the methods that the calibration pressure is reduced by the petal-like preform shapes and that the large diameter and ultra thin thickness tube is hydroformed integrally are proposed. Key technologies on hydro-piercing processes and tools with multiple holes synchronously are solved. In industrial applications aspect, key technologies on facilities are solved for extra high pressure establishment, high water media transmission, real-time and closed loop control system of extra high pressure and multiple spindle displacements. Several hydroforming machines are developed for automotive factories and automobile accessories factories in mass production of typical parts, such as engine cradle, torsion beam and front beam holder.

Key words: Hollow structure, Hydroforming, Internal high pressure forming, Lightweight, Five-axis CNC machine tools, Geometric characteristics, Processing characteristics, Test specimen