Study On Warm Forming Constitutive Equation And Damage Of 5A06 Aluminum Alloy Sheet

With the introduction of the concept of lightweight,lightweight metal materials such as aluminum alloys have become more and more important in related fields such as automobile manufacturing,aerospace and transportation.Because of the advantages like good plastic deformation ability,uneasy to be corroded,and free of low temperature brittleness,5A06aluminum alloy is often used in the manufacture of aviation fuel tanks,ducts,ship plates,ship shells and etc.But it is difficult to be processed into complex deep cavity parts because of limited forming ability and poor surface quality at room temperature,so warm forming is often used.High temperature can effectively improve the plasticity of the material and reduce the deformation resistance,but it also significantly affects the damage evolution process in the deformation,making it more difficult to predict the fracture failure of the material.The GTN meso-damage model considers the damage rupture process of material as the initiation,growth and convergence process of internal micro-holes and links the macroscopic deformation with the meso-damage evolution process.It is widely used to study the fracture failure of ductile material.In this paper,uniaxial tensile tests of 5A06 aluminum alloy sheets were carried out at room temperature,150?C,200°C,250°C,300°C,and three strain rates of 0.001s^-1,0.01s^-1,0.1s^-1.Then the stress-strain curves under different conditions were obtained,and the modified Misiolek unified constitutive equation was established.Besides,the finite element model of uniaxial tension was established with ABAQUS simulation software.The influence of different damage parameters on tensile fracture was obtained while analyzing the simulation results.Accurately predicting the fracture moment and damage evolution of the material needs to find the optimal damage parameters for each experimental condition.In order to determine the nonlinear relationship between the four mesoscopic damage parameters:,1),1)_?8?,1and the fracture displacement and fracture load,the BP neural network model was established,and the genetic algorithm was used to get a set of Pareto solution for the corresponding damage parameters at 250°C?0.001s^-1,whose accuracy was verified by the tensile simulation results.The cupping finite element model coupled with GTN damage model was established with ABAQUS.While analyzing change rules of the stress and strain fields and the volume fraction of the holes,the predicted IE value and rupture position were obtained.The high temperature cupping experiment was designed to obtain the IE value of the 5A06 aluminum alloy sheet,and parts'thinning rate changes of the experiment and simulation were compared.Results show that the numerical simulation coupled with GTN mesoscopic damage model can effectively predict the formability of sheets and provide theoretical guidance for the actual process design and forming.