Fatigue life assessment of load-carrying 60° oblique cruciform full penetration welded joints

To study the local stress distributions and fatigue performance of load-carrying 60° oblique cruciform full-penetration welded joints (OCFWJs), three test specimens were designed for fatigue tests under three nominal stress amplitude levels, and the numbers of loading cycles until fatigue failure of the specimens were obtained. Using ABAQUS finite element software, the finite element models of 60°OCFWJs were established, and the hot spot normal stress, hot spot shear stress, and equivalent hot spot stress at the weld toe were calculated. Based on the nominal stress S-N curves and the hot spot stress S-N curves defined in the specifications, the fatigue life of 60° OCWJs under the combined action of tensile and shear stress were evaluated by using the nominal principal stress method, the equivalent hot spot stress method, and the interaction equation method, respectively. The results showed that whether the nominal stress range, the nominal tensile stress range, or the nominal shear stress range are used, the fatigue life of 60° OCWJs cannot be reliably evaluated. According to the International Institute of Welding specification, whether the hot spot tensile stress ranges or the hot spot shear stress ranges cannot be used to evaluate the fatigue life of 60° OCFWJs reliably. The fatigue lives predicted by the interaction equation method in Eurocode 3:Design of Steel Structures are much lower than the experimental values , and the fatigue lives predicted by the equivalent hot spot stress method are in good agreement with the experimental values .