Fatigue behaviour in friction stir welded 2198-T8 Al-Li alloy joint for integral metal fuselage application

Applications of friction stir weld in fuselageare studied. Samples with two different friction stir weld orientations in the fuselage panel were tested, one is along fuselage longitudinal direction, and another one is along fuselage circumferential direction. Then fatigue cracks that are set in three different types, parallel and perpendicular to friction stir welds and between double welds are investigated. A range of sample geometries are machined from identical welds in order to remove the effect of weld process on fatigue behaviour. Tests are conducted on M(T) specimens with either longitudinal or transverse welds. Cracks growing into or growing away from the weld centre, as well as in the nugget zone are investigated. It is shown that fatigue crack growth (FCG) for that crack grows away from the centre seems similar to parent material ; for crack grows in the nugget ; crack grows slower than in the parent material ; for cracks start between double welds, crack grows slower than both another two types. The virtual crack closure technique (VCCT) method is used to calculate K_res and R_effective in aim to explain the experimental findings.