Study On The Influence Of Rivet Die Dimension On The Deformation Of Rivet And Joint Performance Of Electromagnetic Riveting

To solve the difficulty of the connection for aluminum automobile body,electromagnetic riveting has drawn more attention,which was used in the field of aerospace.In this paper,the establishent of a finite element model and process test for electromagnetic riveting were performed.Firstly,a multi-physics finite element model was established based on ANSYS Multiphysics and LS-DYNA.The calculating result of the electromagnetic model showed that the trend of the magnetic pressure loaded on the driver plate was as same as the loaded current curve.The equivalent concentrated force in the center of the driver plate was about 220 kN.The rivet die can effectively increase the relative interference of riveted joint.Several optimal dimensions of rivet die were selected for the further research.Then the plastic strain field,temperature field were analysed.The formation of adiabatic shear band in formed head was the result of the interactio n of relative slide and thermal softening effect of materials.Then the electromagnetic rivet process test was conducted with 2A10 rivet and 6082-T6 aluminum alloy sheet.The accuracy of the finite element model was verified by making comparison of the dimension of different formed head between the numerical result and experimental result.Metallographical observation showed that there were two obvious adiabatic shear band in flat formed head and 40o formed head,while only one adiabatic shear band were found in 60o and 80o formed head.The grains in adiabatic shear band were crushed severely.By measureing the Vickers hardness and make comparision with numerical result.It was found that the distribution of effective plastic strain was consistent with the m icrohardness.Moreover,the strengthening effect in formed head was weakest.Finally,the quasi static pull-out test and pull out fatigue test were performed.Results showed that the maximum pull-out load increased with the decrease of the rivet die angle.40o specimen has the highest pull-out load,which improved 8.4% with flat formed head specimen.The result of fatigue test showed that rivet die can improve the fatigue life.The fatigue life of specimens formed by rivet die were longer than flat formed head electromagnetic riveting specimen and pressing riveting specimen.Moreover,80o specimen had the longest fatigue life.The fracture observation of fatigue specimen showed that microcracks in rivet hole was found in 40o and 60o specimens,which was formed in the riveting process,due to excessive relative interference,and the microcracks accelerate the failure of specimens.