## 3 Results and Discussion  
### Self-Piercing Riveted Joint of Vibration-Damping Aluminum and Al5052-H32  
In this section, the quality of the self-piercing riveted joint formed between vibration-damping Al and Al5052-H32 is investigated. The cross-sectional views of the joints are shown in Figure 6. Three different die type profiles (A, B, and C), as shown in Figure 3, and two different configurations of panels (the vibration-damping Al panel on top and the AL5052-H32 panel on the bottom, and vice  
Figure 4: Geometrical indexes and the seals of a self-piercing riveted joint. Figure 5: The dimensions of the test sample used for the tensile-shear test (KS B ISO 14273). versa) were used to form the joints. The top images show that when the vibration-damping Al panel is on top, good top sheet penetration of the rivet is observed with minimal gaps between the two sheets comprising the vibration-damping Al. The figure shows that die type C produces the maximum seal qualities for the joint while die type B causes gaps within the top and bottom seals. The joint formed using die type A shows that the rivet tip is surrounded by the debris from the vibration-damping Al, but complete penetration of the top panel is evident, so that an interlock has been formed between the two panels. When the vibration-damping Al panel is on the bottom, as shown in the bottom images, the rivet does not completely penetrate the top panel, so that the interlock width is not clearly defined. In addition, local gaps between the two aluminum sheets are evident, although there is no complete separation between the two sheets due to the adhesive. Nevertheless, all joints show successful joining between the top and the bottom panels with marginal defects. The geometrical indexes, namely, interlock width, \(w_{t}\), and bottom thickness, \(t_{B}\), were measured along with the tensile shear loads, and the results are shown in Figure 7. The results in Figure 7a show that the geometrical indexes do not show significant differences between the die types, within the margin of error, when the vibration-damping Al panel is on top. The value for the configuration when the vibration-damping panel is on the bottom could not be measured since the rivet tip did not completely penetrate the bottom panel. The tensile shear test results, shown in Figure 7b, indicate that for the configuration where the vibration-damping Al panel is on top, the maximum tensile shear load of 3.28 kN results for the joint formed using die type C, consistent with the highest seal quality found in Figure 6. Tensile shear loads of 2.79 KN and 2.54 kN were measured for the joints formed using die type A and die type B, respectively. Although there were defects present for the configuration when the vibration-damping Al panel was positioned on the bottom, the panels remained joined; therefore, tensile shear tests were carried out. The results show that a maximum tensile shear load of 2.8 kN results for the joint formed using die type B but is significantly lower compared with that of the joint with the highest cross-sectional quality (the joint formed using die type C under vibration-damping Al in the top configuration). Figure 6: Cross-sectional images of the self-piercing riveted joint between vibration-damping Al and Al5052-H32 with respect to die types and configuration of the panels: (**a,d**) die type **A**, (**b,e**) die type **B**, and (**c,f**) die type **C**. The failure modes of the joints after the tensile shear tests were examined, and the results are shown in Figure 8. The figure shows that for the configuration where the vibration-damping panel was on top, no failure of the vibration-damping Al panel was observed for all of the joints. The joint failure eventually occurred by \"rivet pull-out\" failure accompanied by \"bottom sheet crack\" for (a) and (b), while only by \"rivet pull-out\" failure for (c).