Fatigue assessment of friction stir channels

Friction Stir Channelling (FSC) is an innovative process within solid-state manufacturing technologies able to produce continuous internal or open channels in monolithic plates. The high level of adaptability of FSC makes it possible to apply to many different technical field domains and can bring significant advantages for already existent and new industrial applications. Because engineering components and structures are subject to accidental failures that occur due to unexpected or additional loadings, such as additional axial or torsion, this paper is focused on the effects of multiaxial loading paths on fatigue life of friction stir channelling monolithic plates of AA5083-H111 aluminium alloy. Uniaxial and biaxial fatigue tests were carried out with a stress ratio of R = −1. The FSC specimens used in this study were specially designed for the purpose. The fatigue behaviour was investigated by load controlled tests under uniaxial tension/compression loading and combined axial and torsional proportional loading. Metallographic analysis of the channel microstructure and fractograph analysis of the fracture surfaces were performed by optical microscope and SEM, respectively. For all tests carried out, the first crack always has initiated at the top of the advancing side namely in the boundary between the nugget and the thermo-mechanically affected zone.