Effect of Dwell Time on Fracture Load of Friction Stir Spot Welded Dissimilar Metal Joints

Table 5

Influence of dwell time on failure pattern.

Dwell time (sec)	Top view of top sheet	Bottom view of top sheet	Top view of bottom sheet	SEM fractography	Observation
4					FL = 8.49 kN
					FM : nugget debonding
					FP : ridges
5					FL = 8.81 kN
					FP: shear ridges
					FM : partially curved
6					FL = 9.56 kN
					FP : elongated and fine dimples
					FM : nugget pull-out
7					FL = 9.28 kN
					FM : nugget debonding
					FP : cleavage
8					FL = 9.06 kN
					FM : nugget debonding
					FP : cleavage