Issue 37

L. Susmel et alii, Frattura ed Integrità Strutturale, 37 (2016) 207-214; DOI: 10.3221/IGF-ESIS.37.27 207 Focussed on Multiaxial Fatigue and Fracture Designing aluminium friction stir welded joints against multiaxial fatigue L. Susmel The University of Sheffield, Sheffield S1 3JD, United Kingdom l.susmel@sheffield.ac.uk D. G. Hattingh Nelson Mandela Metropolitan University, Private Bag X6011, Port Elizabeth 6000, South Africa danie.hattingh@nmmu.ac.za M. N. James University of Plymouth, Drake Circus, Devon PL4 8AA, England, United Kingdom m.james@plymouth.ac.uk E. Maggiolini, R. Tovo University of Ferrara, via Saragat 1, 44100 Ferrara, Italy mggnrc@unife.it, roberto.tovo@unife.it A BSTRACT . The present paper investigates the accuracy of the Modified Wöhler Curve Method (MWCM) in estimating multiaxial fatigue strength of aluminium friction stir (FS) welded joints. Having developed a bespoke joining technology, circumferentially FS welded tubular specimens of Al 6082-T6 were tested under proportional and non-proportional tension and torsion, the effect of non-zero mean stresses being also investigated. The validation exercise carried out using the experimental results have demonstrated that the MWCM applied in terms of nominal stresses, notch stresses, and also the Point Method is accurate in predicting the fatigue lifetime of the tested FS welded joints, with its use resulting in life estimates that fall within the uniaxial and torsional calibration scatter bands. K EYWORDS . Friction stir welding; Multiaxial fatigue; Critical plane. I NTRODUCTION riction stir (FS) welding is a joining process that allows joints with high mechanical performance to be manufactured at a relatively low cost. Thanks to its specific features, in recent years this joining technology has been employed successfully in different industrial sectors [1] which include, amongst others, ship building [2], transportation [3], and aircraft [4]. In terms of design against fatigue, whilst a tremendous effort has been made since the F