Research And Optimization On The Mechanical Performance Of Mechanical Clinched Joint Of The Auto Body Structures

The world energy crisis and environmental crisis urge the automobiles lightening, so thelightweight materials such as aluminum and magnesium alloy sheets have been widelyapplied to the Auto-body panel. Because of aluminum and magnesium Material high thermalconductivity and Easy oxidation of surface it’s difficulty for the spot welding to join thealloy and different metal sheet. So TOX company raised the method of the Mechanicalclinched joint to join the lightweight materials.Mechanical clinching can join the lightweight materials such as aluminum andmagnesium alloy sheets, can also join the multilayer sheets and different sheets withoutDamage sheet coating and cause stress concentration. So the mechanical clinched joint hasbeen widely applied in the modern industry fields. The contents of this dissertation include:Firstly, Established the FEA model to simulate the clinch forming process used theABAQUS/Explicit software. Distribution of stress and strain during forming process isanalyzed. The results show that stress and strain are mainly concentrated on the sheet underthe punch and the neck of the joint. The joint neck region of the sheet is stretched seriously,which can fracture in the forming process. The deformation behavior of neck thickness,interlock and bottom thickness are discussed, and their affecting factors are studied. So Thedie depth and the die clearance show the most important influence on the neck thickness,interlock,and joint quality. Then Propose a way to confirm the initial dimension of themechanical clinching tools.Secondly, A FE model for the clinching joint mechanical performance is built, and themechanical performance to withstand axial load of joint is simulated numerically, the resultcan be verified through comparing with the product from TOX. Then studied the workinghardness characteristic of the sheets which undergoing the plastic deformation. The result ofnumerical simulations shows that working hardness characteristic has an obvious impact onimproving the mechanical performance and joining failure modes of mechanical clinchingjoint. Then propose a way to shape optimization of clinching tools. The arrange principle ofthe joint was also studied.At the last studied the influence of friction between the sheets to the joint dimension.Design Experiment to measure the friction coefficient in the contact between Al6063alloy sheets and the Al6063and steel alloy sheets. The result show that the friction coefficientbetween Al6063alloy sheets is0.41; Al6063and steel alloy sheets is0.35. FE-analysis andmechanical clinching test were performed to obtain the conclusion that with the frictioncoefficient increasing the interlock of the joint increase and the neck thickness decreases.