Comparative Analysis of SPR and SPR-Bonded Joints of Hot Press Forming Steel and AA5052 under Corrosive Conditions

Abstract

The increasing demand for effective joining techniques in dissimilar materials has led to the widespread use of self-piercing rivet (SPR) mechanical joints, particularly in aluminum combinations. Studies in this field aim to enhance joint strength by optimizing process conditions, including the use of SPR-bonded processes with structural adhesives. Structural adhesives in SPR-bonded processes introduce different corrosion behavior owing to galvanic corrosion caused by potential differences between sheets over time. In this study, we utilize SORPAS® simulation to optimize SPR conditions and analyze stress and deformation. A tensile shear test was performed on a hot pressforming steel/AA5052-H32 combination for SPR and SPR-bonded processes. The experimental results indicated die sticking during SPR optimization, increased tensile strength through AA5052-H32 surface cleaning in the SPR-bonded process, varying corrosion conditions, and consistent SPR-bonded strength after salt spray exposure. The difference in failure modes between the processes concerning corrosion time can be attributed to the corrosion- mitigating effect of structural adhesive within the galvanic coupling region formed by potential differences. Additionally, adhesive and rivet failure modes were observed. Moreover, adhesive failure occurred in the SPR-bonded process after shear tensile tests, characterized by a fracture between the lower AA5052-H32 interface and adhesive. Furthermore, we found a linear relationship between the remaining adhesive area and shear tensile strength.