where R = 0.1, k ¼ 0:6
ffiffi
t
p
, Mx=2.5Fy; with d, Fy, Mx and t being the diameter of the weld nugget, maximum tensile force, bending
moment and sheet thickness of Aural2, respectively.
Eq. (1) indicates that the diameter of the spot welds competes with sheet thickness in determining the structural stress. A
larger nugget diameter is beneficial for lowering the structural stress level that usually leads to longer fatigue life. The nugget
size of the spot welds used in the present study were measured and shown in Table 4.