Research On Hydroforming Of Double Layered Sheet Of Inner Tailor-welded Blank Of 2219 Aluminum Alloy

In general,the propellant tank dome of launch vehicle is with ellipsoidal surface. A few of sheet components are respectively formed by conventional method with a shape of melon petal, and then are welded into a whole bottom. The welding residual stress is easy to generate.When hydro-mechanical deep drawing(HDD) is adopted, the wrinkling could be avoided. However,HDD requires higher liquid pressure and larger drawing force. The existing equipment cannot provide such a pressure or force. The width of aluminum alloy sheet is generally about 2600 mm,which still can’t meet the demand for the blank size, therefore a tailor welded blank(TWB) is used. Due to the non-uniform properties of TWB, the method of double-layered sheet hydro-forming was proposed in this article.The hydroforming process of 2219 aluminum sheet and 2219 aluminum TWB was investigated by simulation and experiment. The effects of the thickness and strength of outer sheet and the lubrication condition between two sheets on distribution of stress and strain, together with the thickness of the inner sheet was explored in this paper. Meanwhile, the deformation uniformity of the inner sheet and outer sheet was verified then. Results show that the distribution of the strain and stress as well as the thickness of inner sheet are homogenerous.The thinning trend of thickness of inner sheet is declined. The slide between two sheets is relatively small near the top of the blank while the slide becomes bigger with the increase of radius.Experiments for hydroforming limit were conducted to analyze the influence of different parameters on the limited hydroforming properties of 2219 aluminum sheet and 2219 aluminum TWB. The limited height and limited strain of aluminum sheet and the TWB under the different experimental conditions were verified in this article.Results show that the limited height of the inner sheet increases when outer sheet is applied. The limited height of 2219 aluminum blank with stainless steel outer sheet is 47.32 mm which is 22.85% higher than that of the single blank. The limited height of TWB reaches up to 36.82 mm as well. But the limited height decreases to 31.8mm after annealing at 380℃ for 2 hours. Meanwhile, the limited height of TWB decreases when the welds deviate from the center of the blanks. This research lay a foundaton for the aluminum TWB hydroforming of large, complex-shaped sheet components.