Study Of Finite Element Modeling Technique For Clinching Joints Based On Crashworthiness

Joining of autobody sheet is critical to autobody structure strength, stiffness and vehiclecrashworthiness. A lot of kinds of connections, such as spot-weld, bonding, rivet etc., arewidely used on autobody structure. At the same time, many finite element models for theseconnections are developed in LS-DYNA, especially for whole vehicle crash simulation.The objective of this study is to develop an efficient modeling technique for mechanicalclinching joint. The modeling technique could be used on vehicle crash simulation withpredicting deformation and failure behavior accurately. In order to fulfill the objective, themain work in this study contains two parts. The first part is that elastic and plastic behaviorof mechanical clinching joint under different loading conditions and loading speeds wasacquired. And the second part is that, all parameters of failure criterion for different modelsin LS-DYNA were identified.In the paper Gurson-JC model was chosen to simulate base materials, low-carbon steelQ235and aluminum6061T6. Quasi-static and dynamic uniaxial tensile tests,2mm and4mmnotch tensile tests and simple shear test were carried out. Based on these material tests,parameters for Gurson model and Johnson-Cook model were determined. Simulations for allkinds of material tests were finished by using Gurson model and Johnson-Cook modelseparately. According to the simulation results, stress triaxiality range for Gurson model andJohnson-cook model could be defined separately, which was used for Gurson-JC modelfailure criteria. And then, simulation of shear tests by using Gurson-JC model got a bettercorrelation.Cross-tension, lap-shear and couch-peel tests at1mm/min and6m/s loading speeds anddifferent loading angles quasi-static tests of single mechanical clinching joint specimenswere carried out. Based on these test results, we could investigate clinching joint mechanicalbehavior and failure mechanism. Beam element with MAT₁00, solid element withMAT₁00and constrained elements were chosen to simulate mechanical clinching joint assimplified model for three kinds of single mechanical clinching joint specimen tests. Thelap-shear, cross-tension and couch-peel test with1mm/min and6m/s loading speeds werechosen as loading conditions to verify the best simplified mode. According to the simulationresults, best simplified model was determined. The optimal simplified model for mechanical clinching joint was used to establish tubefinite element model connected by mechanical clinching joints. Many tube axial crashsimulations were carried out to investigate the optimal joint distance for the max energy.