The Research On Al-Li Alloy Two Curvities Skin Stretching Process

The skin stretch is one of the most important forming processes in aviation manufacturing,which is a typical hard forming component on the two curvature skin part forming.With the development of Aluminum Lithium alloy material,The third generation of Al-Li alloy 2198 is applied to the aircraft fuselage skin.Because of the large size,complex structure and new material forming performance,the forming of 2198 Al-Li alloy to be a difficult problem.In this paper,the basic performance test of Al Li alloy was carried out in two 2198 heat treatment conditions,found that 2198-T3 is more suitable to form.Finished the large size hyperboloid skin stretch mould design by the CAE software.This paper also reasearched the numerical control skin stretch forming equipment parameters and movement mechanism,and the skin of the clamping,pre tension and supplement stretching digital design.The reasonable process scheme has been given from this paper.This paper also set process parameters such as the position of the mould,elongation and the wrap angle,the stretch forming process of wool and the deformation calculation,and then use the finite element software to simulate the stretch forming process,according to the results of the simulation,the paper analysed the possible problems during forming,such as the break,wrinkling and other defects,process parameters have been improved until to be reasonable.In the final production test,people could observe the skin stretch forming by setting the skin stretch forming process of subline and appropriate the jaw position adjustment as well.Finally,the qualified 2198-T3 Al-Li alloy skin part was formed in practice.