Research On Hydroforming Deep Drawing Of 6061 Aluminum Alloy Based On Outer Layer Sheet

For large-size thin-walled hemispherical parts,there are serious wrinkling problems in the hanging area of the parts during traditional drawing forming.The wrinkle of the part can be avoided by increasing the pressure of the liquid chamber when the part is formed by filling deep drawing.However,this method is often accompanied by serious thinning of the wall thickness of the part and instability and rupture of the suspension area.In order to solve the appeal problem,this paper adopts the combination of finite element numerical simulation analysis and experimental verification,and takes 6061-T6 aluminum alloy thin-walled hemispherical parts as the research object to carry out the formability analysis of double-layer plate hydro-mechanical deep drawing.For improve the accuracy of numerical simulation,improve the accuracy of numerical simulation,uniaxial tensile tests were carried out on tensile specimens of AA6061-T6,and the constitutive model that can truly reflect the plastic deformation characteristics of materials was established based on BP neural network prediction model.By comparing the data of tensile test and predicted by BP neural network model,the fitting coefficient reached 0.9989,and the average error was 0.92%.The constitutive model is imported into the finite element analysis software to provide more accurate material properties for subsequent numerical simulation.In this paper,taking the wall thickness and die bonding as the evaluation index,the forming simulation analysis of double-layer sheet hydroforming is carried out.Firstly,the formability of the parts was analyzed for different liquid chamber loading paths,and the maximum liquid chamber pressure of the forming of the double-layer plate was determined to be 20 MPa.Combined with the pre-bulging process,the feeding is carried out in the early stage of drawing to avoid excessive thinning of sheet metal in the forming process.Through the forming simulation of different prebulging pressures,the optimal pre-bulging pressure is 4 MPa.Compared with the parts formed by single-layer plate and double-layer plate in liquid-filled drawing,the superiority of double-layer plate in liquid-filled drawing was verified,and the forming law of sheet metal under different outer coating conditions was explored.The optimal friction coefficient between plates for forming parts was 0.1,and the thickness of outer plate was 1.5 mm.In addition,the influence of temperature on the forming quality of the parts was explored.Temperature softens the sheet metal and further improves the forming quality of the suspended area of the parts.Finally,the forming experiment results were basically consistent with the simulation results,with the simulation accuracy reaching 99.33%.