Creep Aging Forming And Its Finite Elementanalysis Of Double-curvatured 7075aluminum Alloy Components

With the development of modern aircraft towards integrity,long life and lightweight,integral panels have gradually replaced riveted panels and become the key components of modern aircraft structure design.Age-dependent forming technology provides an effective way for the formation of such components.In this paper,the typical aeronautical high-strength 7075-T651 aluminum alloy is taken as the research object.The ageing forming law of the double curvature components is studied by experiments and finite element simulation.The aging forming experiments were carried out on self-designed and manufactured guide-post tooling,and the rule of aging forming of double curvature components was studied.Orthogonal experiments were conducted to investigate the primary and secondary effects of different technological parameters on springback and the optimum technological parameters within the scope of the study.The results of range analysis and variance analysis show that aging temperature is the most important factor,aging time and specimen thickness are the secondary factors,and sample width has the least influence.The optimum technological parameters in this research range are: aging temperature 180 C,aging time 12 h,sample thickness 3 mm,sample width 70 mm.On the basis of the conclusion of orthogonal experiment,the main factors are selected to carry out the aging forming test of the double curvature components,and the influence of the factors on springback is studied.The rule of aging forming of single curvature and double curvature components under different aging time is studied.It is found that the effect of aging forming of double curvature component is better than that of single curvature component,and the coupling effect of bending stress in two directions can restrain springback.The appropriate creep constitutive model is selected and the parameters of the constitutive model are fitted by creep tensile test.The fitting curves of the test curves and the derived constitutive equations are in good agreement with each other,which is in line with the practical engineering application.On the basis of the derived constitutive model,the finite element model of ageing forming of double curvature components was established based on ABAQUS.The experimental and simulated values of springback rate are in good agreement.The established model can betterdescribe the ageing forming process of 7075 aluminum alloy double curvature components.Based on the finite element analysis of the aging forming process of 7075 aluminum alloy bi-curvature components,the evolution and distribution of Mises equivalent stress,stress on the creation path,creep strain and springback in the aging forming process were obtained.It is found that the stress relaxation rate and creep rate are the fastest four hours before aging,reaching more than half of the whole aging process,and the creep rate at the reverse center is the largest during the whole aging stage.Through springback simulation,the springback law of double curvature components under different process parameters(aging time,sheet thickness,sheet width,die radius,loading pressure)was obtained,and the springback law of single curvature and double curvature components under different sheet thickness was compared and studied.