Research On Dissimilar Materials In Self-piecing Riveting By Simulation And Experiment

Under the multiple pressures of energy security,low carbon economy and ecological environment,the future of automobile producing and manufacturing is developing towards light weight.To meet the requirements of lightweight design,the use of light materials such as aluminum alloy has been greatly increased,but the traditional connection mode can’t satisfy the requirement of the new material connection.As a kind of cold forming sheet metal connection technology,self-piecing riveting(SPR)can effectively solve the connection problem of new materials,and the application prospect is very wide.In order to systematically study the process of SPR,numerical simulation and experimental research are combined in this paper,by means of macro and micro analysis,the deformation mechanism of rivet and sheet metal is studied,the influence laws of each technological parameter on forming process and tensile shear performance of the SPR joint is discussed.The FEA models of SPR process of aluminum/steel dissimilar sheet metal and tensile shear test are established by using Simufact.forming software.The forming process,stress and strain distribution,deformation and stress in tensile shear test of SPR joint are analyzed to research the influence of each parameter on the forming of SPR joint.The numerical simulation results show that sheet metal placed order,type of die,thickness of connected sheet metal,length and tail fillet radius of the rivet have a greater effect on SPR joint.Bigger interlock value and bottom residual thickness can be obtained as the bottom sheet is thicker.It can effectively reduce the strain concentration of the bottom sheet by using of the die with moderate height convex platform.Increasing thickness of connected sheet metal can improve the bottom residual thickness of the SPR joint,but the interlock value is decreased.The interlock value increases with the increase of the rivet length.Increasing the fillet radius of rivet tail can reduce the clearance between connected sheet metal,making the structure of SPR joint tighter.Increasing the interlock value and bottom residual thickness can improve the tensile and shear property of the joint.On the basis of numerical simulation,the process test of SPR is carried out to study the influence of each parameter(the place order of sheet metal,the type of die,the thickness of the connected sheet metal)on the forming of SPR joint.The experimental results show that when different thickness sheet metal are riveted,the thick one should be placed in the lower layer to obtain greater interlock value and bottom residual thickness.When the same thickness of sheet metal are riveted,the plasticity one should be placed in the lower layer to obtain better surface quality.It is beneficial to improve the material flow performance of the bottom sheet metal,make the deformation more uniform and effectively avoid producing cracks by using of the die with moderate height convex platform.With the increase of the thickness of the connected sheet metal,the deformation of rivet increases,the interlock value decreases,and the bottom residual thickness increases.The tensile shear property of the SPR joint under various technological parameters are tested.The tensile shear test result show that the tensile shear property of SPR joint can be improved by making the thicker sheet as bottom sheet.For the combination of 1.2mmSPFC340 and 2mmAA6061-T6,the tensile shear property of SPR joint under convex platform die B1 is best.For the combination of 2mmAA6061-T6 and 2mmSPFC340,the tensile shear property of SPR joint under flat die A is best.With the increase of sheet metal thickness,the maximum shear force of SPR joint is improved when the energy absorption decreasing.It is found that the tensile shear property of SPR joint is positively correlated with the interlock value and the bottom residual thickness.But the maximum shear force and energy absorption are not simple linear correlation with the interlock value and the bottom residual thickness,it is necessary to consider other factors such as integral structure of SPR joint,surface crack,gap between components.