Research On Technology And Joint Mechanical Properties Of AA5052-DP590 Electromagnetic Single-side Riveting

Under the development trend of automobile lightweight policy,the application of lightweight materials on the body continues to increase.However,structural components related to automobile safety are still mainly made of steel.For the connection requirements of aluminum/steel dissimilar material structures,traditional spot welding,fusion welding and other technologies have poor stability,low automation level and high rejection rate.In addition,conventional self-piercing riveting(SPR),clinching riveting,bolting and other mechanical connection technologies can solve the problem of reliable aluminum/steel connection,but they all require double-sided operation.Electromagnetic single-side riveting(E-SSR)is a new type of joint technology which combines high-speed nailing process(HSN)and electromagnetic riveting(EMR).It is especially suitable for the connection of dissimilar materials such as high strength steel because it does not need pre-hole,only needs one-side access,short connection period and reliable connection quality.It has a wide range of application prospects and value.In this paper,aluminum alloy and high strength steel materials were used.The research in this paper was carried out from the aspects of E-SSR process test,finite element simulation,microscopic morphology analysis of cross-section,shear and push-out mechanical performance test,fatigue performance test,microscopic observation of failure fracture,failure mechanism analysis and fatigue life prediction,etc.In addition,the structural parameters of rivet were designed and optimized.Firstly,the connection mechanism and joint performance of the aluminum alloy5052(Al)/high-strength steel DP590(HSS)structure were studied using simulation and experiment methods.A two-dimensional axisymmetric model based on mechanical-thermal finite element analysis(FEA)was proposed to explore the formation process of the joints.Microscopic observations and effective plastic strain field analysis showed that excessive deformation of the Al sheet caused serious damage to the HSS sheet,thereby making the joint more susceptible to failure.Through mechanical properties tests,it was found that the mechanical properties of the joints with different discharge energies varies.Specifically,the joints at the discharge energy of 5.3 k J had the highest maximum shear load.While the joints at the discharge energy of 5.1 k J showed higher push-out strength because of the better wrapping and higher interlocking degree.Secondly,the fatigue performance of E-SSR joints was systematically studied.The Basquin equation was used to fit the fatigue test data and compared with the test data.The results showed that the predicted values were all within the 2 times error band,which indicated that Basquin equation could effectively predict the fatigue life of E-SSR joints.In addition,the different failure modes of the joints were explored.It was found that the cyclic stress of 253 MPa was the critical point of the two fatigue failure modes.At the same time,the fatigue fracture after the test was studied,and the fatigue failure mechanism of the joint was revealed.According to the damage evolution model and the solution method of damage parameters,the fatigue life prediction values of E-SSR joints were successfully obtained.The prediction results were basically distributed within 2 times error band.Finally,the rivet structure parameters were designed and optimized for the E-SSR process.The design concept of the structural parameters for rivets was to reduce the stress concentration factor of the rivet shank as much as possible on the premise of ensuring the quality of joints.The results showed that the stress concentration factor of the arc-shaped ring grooves of the nail shank was reduced by26% compared with that of the original sharp-angle.By combining Simufact.Forming finite element software with the calculator on Isight,a stress concentration factor calculation model was established.The optimal Latin hypercube sampling technique,response surface model and Hooke-Jeeves algorithm were used to optimize the rivet structure parameters.The results showed that the stress concentration factor of the nail shank was reduced by 44% after optimization.Compared with the original sharp-angled rivet,the stress concentration factor was reduced by 81%.The uniform distribution of stress on the rivet shank after optimization was the main reason for improving the riveted joint and reducing the stress concentration of the rivet shank.