A manufacturing process and load bearing characteristics of aluminum alloy friction stir welding/hot forming hollow wall panels

Stiffened structures are one of the significant structural forms of aluminum alloy wall panel components, widely applied in the fields of aviation, aerospace, and rail transportation due to their lightweight and excellent load-bearing characteristics. In this study, a friction stir welding/hot forming composite process is proposed to realize the lightweight and high-load manufacturing of aluminum alloy hollow wall panel structures. Unlike traditional stiffened wall structures, an innovative hollow curved stiffener structure was designed for the wall panels, utilizing 5A06 and 2A97 aluminum alloy stiffener materials to achieve the same/different material combinations for the skin and stiffener structures. Finite Element Analysis (FEA) was used to simulate the wall thickness distribution of the hollow stiffeners after superplastic forming, and the experiments revealed that at a forming temperature of 430 °C and varying loading rates, a higher loading rate resulted in thinner wall thicknesses of the hollow stiffeners. The maximum thinning rate for 2 mm thick 2A97 aluminum alloy plates after superplastic forming was between 26.5% and 35%, while for 5A06, it was between 30% and 36%. To achieve the integration of the design and process of hollow wall panel structures, the wall thickness distribution was used as an input condition to simulate the load-bearing performance of different forming conditions, materials, and wall panel structures. The experiments found that the hollow stiffener wall panel structure displayed superior load-bearing performance, and the skin structure with 2A97 reinforced cap stiffeners also exhibited better load-bearing performance than those with 5A06, deforming only 0.53 mm under an external load of 1 MPa. Finally, the load-bearing performance of materials with different wall thicknesses obtained under various forming conditions was compared, and the wall panel structure that met the requirements.