Comprehensive fatigue assessment for different types of aluminum fillet welded joints by local approaches

This paper investigates different types of MIG-welded fillet joints (lap welded joints, T welded joints, non-load-carrying cruciform welded joints, load-carrying cruciform welded joints) of 7N01 aluminum alloys under fully reversed pulsating axial loading. Fatigue assessments of the as-welded test results based on nominal, and local approaches are performed considering geometrical factors in different types of welded joints. The fatigue strength for these joints was compared with the international standard codes and those of other materials. Subsequently, the geometric parameters on the fatigue characteristic indicators in different types of welded joints were studied systematically by combining finite element calculated results and analytical methods, such as weld length, notch angles, incomplete penetration length, et al. The results show that the 7N01 lap welded joint owns the lowest fatigue strength (29 MPa) at 2*106 cycles. The corresponding geometrical analytical solutions of local fatigue indicator Strain Energy Density (SED) were established for these welded joints, which could quantitatively describe the fatigue characteristic relationships among different types of welded joints. The theoretical predictions based on SED notch geometric semi-analytical models are relatively higher than the recommended design curves of other local approaches.