Forming of thin-walled AA6061-T4 tubular joint by elastomeric bulging: experiment and computation

Tubular joint forming by elastomeric bulging (EB) is a feasible way to connect aluminum alloy tubes to high-strength sleeve fittings. It is critical to fully and deeply understand the deformation-induced sealing performance of tubular joints for precise manufacturing of high performance tubular joints. In this paper, thin-walled AA6061-T4 tubular joints fabricated by EB was investigated experimentally and numerically. Firstly, the anisotropic AA6061-T4 tube, the polyurethane elastomer (PUE) tube with hyperelasticity and the 15-5PH stainless steel (SS) sleeve fitting were characterized and modeled. Compared with the explicit algorithm, the implicit axisymmetric finite element (FE) models of the whole joining process, including EB forming and springback, were established. The influence of the groove structure of the sleeve fitting on the shearing-related pull-out strength and sealing-related bonding strength was discussed, and then the reasonable sleeve fitting’s structure with two grooves was obtained. Thus, the accurate ranges of extrusion pressure and tube bulging heights were derived for precise control of forming quality. Finally, the experimental set-up and forming dies for EB joining tests were established, and the reliability of these parameters determined by the FE model was verified experimentally. It is concluded that the forming quality of this tubular joint can be controlled precisely based on FE modeling of whole joining process, and thin-walled AA6061-T4 tubular joint fabricated by EB has a reliable seal performance.