Comparative Study of Joint Performance According to Joining Methods Between Al7075-T6 and SPFC590DP for Lightweight Car Body

Abstract

The necessity of dissimilar joining between aluminum alloy and steel is increasing in order to meet the demand for weight reduction in automobiles. However, dissimilar joining between 7000 series aluminum alloy and steel is challenging with mechanical joining methods such as self-piercing rivet(SPR) and flow drill screw(FDS) without hole processing. In this study, mechanical performances of dissimilar joints between 3 mm thick Al7075-T6 and 1 mm thick SPFC590DP were evaluated for use in lightweight B-pillar assembly. Self-Piercing Rivet(SPR) and Flow Drill Screw(FDS) with one-hole processing, bolt/nut and blind rivet with two-hole processing and adhesive bonding were compared with respect to joint performance. In SPR joining, rivet did not penetrate and rivet buckling occurred in the rivet due to the thickness and high strength of the Al7075-T6. By processing pre-hole on Al7075-T6 and applying an additional Al5052-H32 sheet to induce mechanical interlock in SPR joint, it became possible to join Al7075-T6 to SPFC590DP with an SPR. The tensile shear load of the SPR joint was 9.8 kN. In FDS joining, it is also necessary to process pre-hole on Al7075-T6 since the fastener could not penetrate the Al7075-T6. The tensile shear load of the FDS joining was 8.1 kN. In bolt/nut and blind rivet joining, the tensile shear load were measured respectively 11.1 kN and 5.2 kN. In adhesive bonding with 1K glue, the tensile shear load was measured 18.5 kN when the interfacial surface was roughened with a sand paper.