Research On The Reinforcement Characteristics Of Aerospace Aluminium Sheet Metal Parts With Positive And Negative Loading And Rubber Forming Process

Aluminum alloy sheets are widely used in aerospace and other fields because of their comprehensive properties such as high specific strength-specific stiffness,high corrosion resistance,good impact resistance and easy recycling.In some aerospace parts with high customization requirements and small batches,the rubber forming process is widely used,and the deformation behavior of aluminum alloy sheets becomes difficult to predict as the complex forming process is often accompanied by complex strain paths.Therefore,based on the Hill48 yield criterion and the Chaboche combined hardening model,this paper uses a combination of theory,finite element simulation and rubber forming process tests to investigate the forming process characteristics of the plates under complex loading paths and the key factors affecting the forming quality in the rubber forming process.The unidirectional tensile tests of the plates were carried out,and the DIC full-field strain measurement system was applied to obtain the elastic-plastic mechanical property parameters and the thick-directed anisotropy coefficients of the plates,and the Hill48 yield criterion plate anisotropy parameters were calibrated.The results showed that the AA-2A11-O sheet exhibited obvious Bauschinger effect and the yield strength of reverse loading after unloading under different pre-strain conditions increased with the increase of forward prestrain.Combining the characteristics of the rubber forming process,the problem of calibrating the parameters of the Chaboche combined hardening model for plates is proposed to be solved by using the plastic deformation segment data of the tensile-compressive stress-strain curve of plates and combining it with a multi-objective improved non-dominated ranking genetic algorithm.The results show that the obtained hardening model parameters can accurately describe the positive and negative loading characteristics of the sheet.The modeling and simulation of the rubber capsule forming process was carried out to analyze the forming process of large-diameter parabolic-shaped parts,and the difficult part of the forming process was mainly to find the forming window between wrinkling and rupture in the overhanging area.The forming process path of the part is obtained,and by comparing the effects of different friction coefficients between all contact surfaces and different pressure loading paths on forming,the trend of the effect of friction on forming and the suitable pressure loading curve are obtained.A process test was conducted on the rubber bladder forming process,based on the load path obtained from the simulation,to compare the effects of different lubrication media between the flange and the plate and the size of the undercut on the forming quality,and to study the effects of different undercut sizes on the forming.