Research On Statics And Fatigue Characteristics Of Aluminum Alloy Self-Piercing Riveting Joint In Salt Environment

Due to its unique advantages,self-piercing riveting(SPR)technology has developed rapidly in recent years.Now it has been applied in the field of automobile manufacturing,and also involves aerospace,shipbuilding,construction and other fields.However,in practical engineering application,the SPR joints in extreme environment will inevitably suffer corrosion and affect the reliability of load-bearing.This paper mainly studies the static mechanical properties and fatigue characteristics of self-piercing riveting joints under different corrosion conditions,and analyzes the corrosion evolution process of the joints in combination with simulation.The main work is summarized as follows:1.The research on the corrosion test of SPR joints.Combining the corrosion kinetics and the corrosion morphology of the lap area to analyze the changes of the joints,it is found that the corrosion rate of the five groups of joints selected decreases with the increase of the corrosion time.The overall corrosion rate of heterogeneous joints is much higher than that of homogeneous joints,and the corrosion rate of heterogeneous joints of adhesive riveting is still relatively high.The overlapping area of the joint is more susceptible to corrosion,and the addition of adhesive changes the corrosion morphology of the overlapping area.2.The research on the static performances of SPR joints.The static test was carried out on five groups of joints after corrosion,and the change of joints performance was explored from failure mode,static failure load,energy absorption value and static failure fracture.The results show that the salt environment does not change the failure mode of the joints,and the average failure load of the joint without adhesive increases first and then decreases.The energy absorption capacity of the homogeneous joints is not as good as that of the heterogeneous joints,but the stability is strong.However,the overall change trend of joints with adhesives is gentle,and the shock absorption capacity of heterogeneous joints is significantly improved.The typical failure parts of the two groups of joints added with adhesives show uneven corrosion.Only a small amount of Cl appears in the lap area of the Aluminum-Aluminum homogenate joints.The corrosion products in Steel-Aluminum heterogeneity group joints are mainly oxides of Al and Fe elements,and Cl~-is more easily adsorbed on the surface of the lap joint area of the upper plate during the corrosion process.3.The research on the corrosion fatigue characteristics of SPR joints.The fatigue test was carried out on the joints of different corrosion stages of Aluminum-Aluminum homogenate group.The F-N fatigue life curve was fitted based on the power function fitting method.The fatigue failure form and micro failure mechanism of the joints were analyzed.The fatigue life of the joints after corrosion was predicted by Paris formula and related inference.The results show that the fatigue life of corrosion joints is lower than that of the non corrosive joint,and the stability of the joint fatigue failure is affected.The fatigue fracture of corroded joints is caused by multiple crack sources.In the fatigue life prediction of corroded joints,the prediction effect is better in the medium and short life region,but not ideal in the long life region.4.The research on the corrosion simulation of SPR joints.The polarization curves of dissimilar bonded riveted composite joints of steel and aluminum were measured and analyzed in salt environment,and the corrosion simulation of the joints was solved by taking the self corrosion potential as the boundary condition.The results show that AA5052 Aluminum Alloy undergoes three processes of"corrosion dissolution-passivation-corrosion aggravation"in the measurement test,while DP590 dual-phase steel is always in a corroded and dissolved state.Compared with DP590 dual-phase steel,AA5052 Aluminum Alloy and galvanized boron steel rivets are more prone to corrosion.In the simulation results,there are obvious potential changes in 4 areas that are prone to corrosion damage.Compared with the actual corrosion test results,it is found that although the simulation has many shortcomings,it can still accurately simulate the corrosion-prone areas of the joint,which has certain reference significance.