Abstract:

In order to avoid the occurrence of wrinkle and fracture during the integral forming process of the huge curved parts with super thin wall, double-layer sheets forming method is developed. Double-layer sheets hydro-bulging with the inner side sheet of 5A06 aluminum alloy sheet of 2.0 mm thick and outer side sheet of 1Cr18Ni9Ti stainless steel sheet of 1.0 mm thick is investigated. The bulging radius of sheet is analytically calculated when material yields, and the effect of radial friction and normal pressure on the distribution of stress of blank is analytically studied. The distribution of stress and strain of the inner side sheet during the double-layer sheets hydro-bulging is obtained by Finite element analysis (FEA) method. In addition, experiment of double-layer sheets hydro-bulging is conducted to investigate the effect and of outer side sheet on the limited bulging height and limited strain of the inner side sheet, and the deformation compatibility of the inner and outer side sheets is verified. The results shows that, when 1Cr18Ni9Ti stainless steel outer sheet is imposed on the 5A06 aluminum alloy inner side sheet, the biaxial tensile stress of inner sheet decreases at the peak of the semi-sphere, and the stress and strain gradient of the whole deformation region of inner sheet decreases. As a result, the deformation of the semi-sphere is more uniform, and the limited bulging height increases by 32%, and the limited strain at the peak increases by 51.7%.

Key words: 5A06 aluminum alloy, hydro-bulging, limited bulging height, stress-strain, double-layer sheets