Numerical Simulation And Experiment On Hydroforming Of Cups With Controllable Radial Pressure

To meet the demand for aluminum alloy deep cups formed in one step, sheet hydro forming with controllable radial pressure was proposed. Based on traditional sheet hydroforming, by applying controllable radial pressure to the periphery of blank, inward pushing force and double-sided lubrication can be generate. Thereby, the forming limitation of aluminum alloy sheet is improved, and the drawing of deep cups can be achieved.Aiming at aluminum alloy cups with a hemispherical bottom and a flat bottom, sheet hydroforming with controllable radial pressure was investigated by numerical simulation and experiment.Using numerical simulation software ETA/Dynaform5.5 which is based on LS-DYNA3D, sheet hydroforming with controllable radial pressure was studied for cups with a hemispherical bottom and a flat bottom. Effects of radial pressure and chamber pressure were analyzed on the thickness distribution, the failure types and the stress state of typical point. A reasonable match was obtained between chamber pressure and radial pressure. The numerical results indicated that the reasonable match between chamber pressure and radial pressure could decrease the radial tensile stress, reduce the thinning of part thickness effectively, and improve the drawing forming limitation of aluminum alloy deep cup.By the experimental research on the cups with a hemispherical bottom and a flat bottom, failure types appeared in sheet hydroforming with controllable radial pressure were analyzed, and the effective ways to avoid defects were found. The experimental results indicated that qualified parts with no defects can be obtained under the optimal chamber pressure 20MPa and within the reasonable loading range of radial pressure. For the material used in the experiment, limiting drawing ratio 2.8 of cup with a hemispherical bottom and a flat bottom were obtained under the radial pressure 35 MPa.