Abstract:An optimization method was presented for cold stretch forming of titanium-alloy aircraft skin to determine process parameters and to reduce springback. In the optimization model, a mathematical formulation of stress difference was developed as an indicator of the degree of springback instead of implicit springback analysis. Explicit finite element method (FEM) was used to analyze the forming process and to provide the stress distribution for calculating the amount of the stress indicator. In addition, multi-island genetic algorithm (MGA) was employed to seek the optimal loading condition. A case study was performed to demonstrate the potential of the suggested method. The results show that the optimization design of process parameters effectively reduces the amount of springback and improves the part shape accuracy. It provides a guideline for controlling springback in stretch forming of aircraft skin.

Key words: titanium alloy; aircraft skin; stretch forming; springback; optimization