Effects of local stiffness on the spot joints mechanical properties: Comparative study between resistance spot welding and resistance spot clinching joints

Abstract

Different types of aluminum alloy 5052 (AA5052) resistance spot clinching joints with different local stiffness values were designed in this study. The values of the polar moment of inertia in the cross-section of the fusion zones were calculated. Digital image correlation (DIC) technique was used to study the local rotation and in-plane strain distribution during the lap-shear test of half-cut samples. The results show that the joint with higher local stiffness (polar moment of inertia) value experiences the lowest joining zone rotation during the lap-shear test. This leads to higher proportion of normal component of strain/stress at the periphery of the joining zone. According to Tresca or von Mises failure criterion, for a spot joint, high proportion of normal stress at the load-bearing site enables the global joint to sustain high peak load during tensile test. This mechanism indicates that, compared with conventional resistance spot welding process, the resistance spot clinching technique can improve the mechanical properties of AA5052 joints by increasing the local stiffness.