Study On The Defects Of Clinch Forming Joint Of Steel Aluminum Heterogeneous Sheet

Under the development concept of low-carbon,environmental protection and energy security,the development of machinery industry products gradually tends to lightweight,especially in the automotive industry,the requirement of lightweight is higher and higher.To meet the requirements of lightweight design,some heavy metal materials are replaced by aluminum alloy,titanium alloy,and other light metal materials.But for heterogeneous metal sheet connection,the mechanical properties of the joint are more demanding,and the traditional connection method can not meet the requirements of industrial use.As a new type of sheet connection technology,rivetless connection technology can effectively solve the problem of heterogeneous metal sheet connection and is widely used.In this paper,numerical simulation and experimental research are combined to study the non-riveting joint defects of steel aluminum heterogeneous metal sheet,discuss the spring-back deformation of the connected sheet in the non-riveting process,and analyze the influence of thickness parameters and lap mode on the stress concentration and gap value caused by spring-back of formed joint.Based on the tensile test,the stress-strain curves of 6061-T6 aluminum alloy and HC340/590 DP dual-phase steel are obtained,and the important parameters for numerical simulation are obtained.The forming defects of riveted joints in the process of non-riveting connection are analyzed.By using ABAQUS software,the finite element analysis model of rivetless connection of steel aluminum heterogeneous sheet metal is established.The validity of the numerical model is verified through comparative analysis of numerical simulation and experiment,which shows that the model can be used to analyze the forming defects of steel aluminum heterogeneous sheet metal.At the same time,based on numerical simulation,this paper analyzes the stress distribution and spring-back deformation of sheet metal before and after riveting forming,puts forward that the gap value caused by stress concentration and spring-back is taken as the index to evaluate the forming defects,and studies the influence of thickness parameters and lapping mode on the gap value caused by stress concentration and spring-back.The numerical simulation results show that the thickness of sheet metal and the lapping sequence of sheet metal have a great influence on the forming defects of the joint,and the larger the thickness of sheet metal can obtain a smaller gap value as the lower connecting plate;With the same thickness parameter,the gap value of the upper steel and lower aluminum lap joint is smaller and the joint morphology is better than that of the upper aluminum and lower steel.The spring-back defect of the riveted joint can be effectively reduced by changing the lapping mode and thickness parameters of sheet metal.