Abstract: Springback is unavoidable in aircraft skin forming, which reduces the part shape accuracy. The shape error caused by springback can decrease if the tool surface is compensated. The surface improvement procedure based on springback compensation for aircraft skin stretching tool, in which the key is the obtainment of the gaps between blank and tool and the amount of surface adjustment, is presented. The gap in virtual stretching is defined and two algorithms, directly projecting algorithm and nearest element projecting algorithm, are proposed to compute the gaps. The latter is considered better after comparison. The equations for surface modifying based on springback compensation and two methods to establish the mapping of the gaps from blank to tool in the equations are proposed and demonstrated on three typical skin parts. The results indicate that the two mapping methods are all effective and obtain nearly the same maximum gap but different stability after multiple tooling modification.

Key words: Aircraft skin gap, Finite element, Skin stretching, Springback compensation, Surface modification