Forming Mechanism And Defect Control Of Hollow Components With Rectangular Section Manufactured By 3D Free Bending

Due to their structural advantages,hollow components with rectangular sections have essential and extensive applications in many fields such as aerospace,nuclear,construction,and other civil applications.Nevertheless,during the free bending process,defects such as inner wall thickness thickening and wrinkling,outer wall thickness thinning and cracking,cross-section distortion,etc.are easy to appear,which seriously influence the formability of hollow components.Thus,the forming mechanism and the defect control of hollow components with a rectangular cross-section area manufactured by 3D free bending were conducted using ABAQUS finite element code and three-axis free bending forming equipment,and the specific research contents and the obtained results can be drawn as follows:(1)The stress-strain distribution characteristics of 3D free bending forming of the hollow components with rectangular cross-sections were analyzed.The results showed that the inner and outer walls of hollow components with rectangular sections were in the state of three-dimensional stress and plane strain,while the lateral walls were in the state of three-dimensional strain and plane stress.Thereafter,based on the basics theory of plasticity,the stress-strain analysis was carried out,and the analytical formulas for stress-strain and strain-neutral layer during the free bending process were obtained(2)Taking AA6061-T6 aluminum alloy hollow component with a rectangular section(15 mm*10 mm*0.8 mm)as the research object,the precise mechanical properties parameters were detected through the tensile tests,and the material constitutive model was acquired by the fitting.Besides,the influences of material parameters,dimensional parameters,and process parameters on the formability and forming accuracy of the hollow component with a rectangular section were systematically studied by using the finite element modelling.The results showed that,except for the axial feeding speed,the wall thickness change rate of hollow components gradually decreased with the increase of various parameters;The width distortion ratio has little change,while height distortion ratios decreased with the increase of various parameters;The axial feeding speed had little impact on the relative error of the bending radius,and except for Young’s modulus and fillet radius,the relative error of the bending radius increased with the increase of other parameters(3)The maximum thinning rate of the outer wall thickness φo,the maximum height distortion ratios ΔHm,and the relative error of the bending radius Re were defined as objective functions,and wall thickness,clearance,chamfer radius,and axial feeding speed were set as design variables,then the defect prediction and control models were obtained by using the Latin hypercube sampling method and response surface model method.Besides,the accuracy of predicted models was verified by the free bending experiment.