Investigation On Hydro-forming Of 5A06 Aluminum Alloy Double-layer Sheets

For a rocket tank bottom, it has an ellipsoidal shape. Usually, some segmented parts like a melon petal are formed, and then welded into a whole tank bottom. The forming of melon petal has some shortcomings, such as the low precision and the large springback and high residual stress by welding. It has a poor bearing capacity and a low reliability. Therefore, sheet hydro-forming technology is an effective way to form the whole tank bottom and improve the reliability.For the ultra-thin walled aluminum alloy ellipsoidal tank bottom, the thickness to diameter ratio is small, and it’s anti instability capability poor. Due to the over-large tangential compressive stress, it is easy to wrinkle at the unsupporting area. It results in a rupture at the unsupporting area if chamber pressure is increased. In order to solve the above problem for the tank bottom with a complex curved surface, large size and thin wall, a new method of double-layer sheets hydro-forming is proposed.Through the combination of numerical simulation and experimental method, the mechanism of deformation and defect of hydro-forming using 5A06 aluminum alloy double-layer sheets are studied. By applying the static implicit software MSC.Marc2011, the forming performances of 5A06 aluminum alloy sheets of various thicknesses under single-layer and double-layer sheets forming as well as different hydraulic loading paths are evaluated. Besides, the wrinkling, the walled thickness distribution, the frictional stress during forming along with strain distribution are also analyzed.Experiments of double-layer sheets hydroforming were conducted to verify it’s feasibility for the thin-walled parts with complex curved surface. The wrinkle law, thickness distribution, longitudinal springback law and local typical strain were analzed under different conditions. Finally, the influence of different forming methods and hydraulic loading paths were obtained on the sheet forming. The forming conditions were summarized for 5A06 aluminum alloy sheets with different thicknesses.