Mechanical degradation and failure behavior of Al/steel electromagnetic assisted clinched joint in chloride salt environment

Abstract

In this paper, mechanical degradation and failure behavior after salt spray test of Al/steel electromagnetic assisted clinched (EAC) joint were investigated. The Al/steel structure was firstly joined by EAC. These joints were exposed to the neutral salt spray environment, and then gravimetric method, cross-section observation and mechanical properties tests were carried out. The mechanical degradation laws and failure mode evolution were obtained. Results showed that the peak shear and pull-out load of joints decreased after the salt spray test. At the ageing time of 24 days, the peak shear and pull-out load of joints decreased by 22.6% and 41.5%, respectively. In addition, all shear failure modes were neck fractures. Pull-out failure modes ranged from neck fracture to mixed failure, and finally separation. This indicated that the pull-out performance of joints was greatly affected by salt spray ageing, compared with the shear performance of joints. Furthermore, the degradation of shear performance was mainly due to the gradual corrosion and dissolution of Al sheets under salt spray environment, while the degradation of the pull-out performance was mainly due to the damage of the interlocking structure. Therefore, it was necessary to develop appropriate corrosion protection measures for Al/steel joints.