A new process of hydroforming with controllable radial pressure was proposed to overcome difficulties in the forming of low plastic materials and large height-to-diameter ratio workpieces. A typical 5A06 aluminum alloy dome was numerically and experimentally investigated. The reasons for typical defects were analyzed under different radial pressures. Effects of radial pressure on the thickness distribution were discussed and optimal radial pressure was determined. It is shown by numerical simulations and experiment that a cup with a drawing ratio of 2.4 is formed by the new process of hydroforming with controllable radial pressure. It is significantly effective for the forming of low plastic materials and large height-to-diameter ratio workpieees. Two typical thinning points exit along the dome wall. With the radial pressure, thinning is decreased effectively at the two points, the dome forming is achieved and thickness distribution is more uniform.
In order to overcome the limitation of hydro-rim deep drawing, a new process of hydrodynamic deep drawing （HDD） with independent radial hydraulic pressure was proposed. By employing the dynamic explicit analytical software ETA/DynaformS.5 which is based on LS-DYNA3D, the effects of independent radia! hydraulic pressure on the stress, strain and the sheet-thickness of aluminum-magnesium cylindrical cup with a hemispherical bottom were analyzed by numerical simulation. The feature of stress distribution is that there exists a stress-dividing circle in the flange, and the radius of dividing circle was determined by theoretical analysis and stimulation. The experimental results indicate that the reasonable match of independent radial hydraulic pressure and liquid chamber pressure can effectively reduce the thinning at the bottom of hemisphere, decrease the radial stress-strain, and improve the drawing limit of aiuminum-magnesium alloy cylindrical cup.
