Research On Electromagnetic Assisted Bulging And Numerical Simulation Of AA6061 Aluminum Alloy

Increasingly stringent standards for energy saving and emission reduction have made lightweighting an inevitable direction for the development of the automotive industry,and lightweighting of materials is an important means.Due to its good performance,aluminum alloy is gradually replacing traditional steel as one of the key materials in the field of automobile manufacturing.However,in the traditional forming process at room temperature,the forming limit of aluminum alloy sheet is lower,which is not conducive to the processing of complex shaped parts.Electromagnetic assisted forming technology can combine the advantages of traditional forming and high-rate electromagnetic forming technology,and has better forming effect for shaped parts with lower forming limit and more complicated shapes.At present,the process is still in the process realization stage,and further exploration work is still needed in material constitutive model,numerical simulation and process realization.Therefore,this paper takes AA6061 aluminum alloy sheet as the research object.The following studies were conducted:Firstly,tensile tests with different strain rates under different pre-strains were carried out by the method of composite tensile test.Non-contact optical measurement technology(DIC)was used to obtain an accurate stress-strain relationship.Based on the tensile test under different pre-strain conditions,the corresponding room temperature Johnson-Cook(J-C)constitutive model of AA6061 aluminum alloy was established.By analyzing the parameter relationships in the J-C model under different pre-strain conditions,an improved J-C constitutive model with pre-strain was established.Secondly,based on LS-DYNA finite element analysis software,numerical simulation including three stages of quasi-static preforming,springback and electromagnetic bulging was carried out.The DYNAIN file was used to transfer the initial stress,strain,node position and other information between each stage of numerical simulation,and the whole process simulation of electromagnetic assisted bulging was realized.In the electromagnetic bulging process,two models(the original constitutive model and the variable constitutive model)were used for simulation.The variable constitutive model was constructed by re-defining the elements of different pre-strained regions of the specimen as subparts through the MATLAB user program.Finally,the electromagnetic assisted bulging process test was realized through the design of quasi-static preforming mold,electromagnetic bulging mold and forming coil.In the experiment,the process of electromagnetic bulging was recorded using the DIC three-dimensional shooting system.Based on the test results and simulation results,a comparative analysis of displacement,strain and other aspects was carried out.The comparison results shown that the simulation and test were more consistent,verifying the accuracy of the constitutive model and simulation model established in this paper.