Kinetic locus design for longitudinal stretch forming of aircraft skin components

Longitudinal stretch forming is a vital fabricating process for the aircraft skin components with large dimensions. Loading trajectory of clamping jaws in stretch forming is significant for the qualified skin components fabrication. However, the traditional design methods based on estimation, experience, and trial-and-error are unable to manufacture skin components precisely and efficiently. A precision design method of loading trajectory for longitudinal stretch forming was developed and discussed in this paper. The sectional profile of the stretched sheet was considered to determine an optimal deformation state in the final stretching process. In view of the optimized sectional profile, the extending method of sectional curve was proposed to define the spatial locations of the clamping jaws. Furthermore, the numerical control parameters of the stretch forming press were transformed from the kinetic locus of the clamping jaws through the mechanism-solving algorithm and the computer-aided software was developed to integrate the methodology. For a fuselage skin component, the finite element (FE) simulation and experiment were conducted to verify the validity of the methodology of loading trajectory design and the algorithm of mechanism solving. The experimental and simulative results revealed that the developed methodology and algorithm are accurate and valid for the fabrication of aircraft skin components. By the examination of the formed skin part, the developed methodology thus provided relevant knowledge for loading locus design in longitudinal stretch forming.