Improvement in Prediction Accuracy by Finite Element Methods of Stretch-formed Aluminum Alloy Sheets with a Large Aspect Ratio

Abstract

Many parts of an aircraft, such as aircraft fuselage skins, Aluminum alloy sheets are applied for producing these parts. In order to develop dies for stretch forming in a short time, it is necessary to develop forming simulation technologies for prediction In addition, the skin is deformed by its own weight at all times because of the large but thin shapes of the skin panels. To predict accurately the parts shapes after forming by finite element method (FEM) analysis, not only springback but also own-weight deformation must be considered. The purpose of this study is to improve the accuracy of stretch forming analysis by FEM for sheets with a large aspect ratio, such as those used for airplane skin. For investigating the optimal simulation parameters for predicting springback and own-weight deformation accurately, own-weight deformation test and stretch forming tests with large curvature (1500mm in radius) were conducted. The aluminum alloys A2024-T3 and A7075-T6 are applied for the forming tests. In order to investigate the accuracy of the own-weight deformation and the forming simulation, mesh size was investigated. For own-weight deformation analysis, the simulation results with the mesh size of smaller than 25mm were in good agreement with the experimental results.Regarding springback deformation after stretch forming, the simulation results correspond with experimental results qualitatively for all mesh size.