Fatigue crack growth of a double fillet weld

The welded structures have a broad applicability, steel constructions, car industry, aeronautical, marine, pipelines, etc. These structures are generally subjected to cyclic requests. A simple existing defect after welding can generate a catastrophic fracture. This work studies the fatigue crack growth of a double fillet weld with the existence of a semi-elliptical crack. Two types of aluminum alloys are studied with knowing the alloy 2024 T351 and the 7075 T6. Crack growth analysis uses linear elastic fracture mechanics and related crack growth material properties to determine how fast a crack or crack-like defect will grow. Fracture mechanics is based on the concept of stress intensity (K) that describes the magnitude of both the stress and strain fields around a crack. It is computed from the stress range (Δσ), and crack size (a) and crack shape (β). The effect on the fatigue life of the geometrical parameters of the crack (a/c ratio), the angle of inclination of the weld bead and the level of loading are studied. In order to predict the fatigue behavior of the welded structure, a constant amplitude loading is applied where the influence of the load ratio over the fatigue life is presented. A comparative study of fatigue crack growth of the cited aluminum alloys are detailed in order to show the effect of several parameters.