Effects of riveting misalignment on forming quality and mechanical properties for pre-punched self-piercing riveted joints
For the increasingly stringent collision safety regulations,the multi-layer high-strength steel sheets is required in the thin-walled structures of steel-aluminum hybrid bodies,however,the multi-layer high-strength steel sheets cannot be effectively joined by conventional self-piercing riveting(C-SPR)technology.Therefore,the three-layer sheet connection of high-strength steel DP780 with a thickness of 1.2 mm,high-strength steel DP590 with a thickness of 1.2 mm and die-casting aluminum alloy Al Si10Mn Mg-T7 with a thickness of 3.0 mm was achieved by pre-punched self-piercing riveting(PH-SPR)technology,and the influences of different riveting misalignment parameters on the forming quality,mechanical properties and failure mechanism of PH-SPR joints were analyzed systemat-ically.The results indicate that riveting misalignment leads to the ineffective mechanical interlock between rivets and sheets,resulting in a significant decrease in load-bearing capacity.The rivets on the off side are severely deformed in upsetting and unable to penetrate the middle steel sheet,with only some positions experiencing the mechanical interlock.Compared to the mechanical interlock failure of normally aligned riveted joints,no plastic deformation or material failure is observed in the failure of misaligned joints,and compared to mechanical properties of normally aligned riveted joints,the shear and cross-tension peak forces of misaligned joints are reduced by over 57%and 52.3%,respectively.
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