Guo, ShihuiShah, LuqmanRanjan, RakeshWalbridge, ScottGerlich, Adrian P.2018-10-222018-10-222019-01-01https://dx.doi.org/10.1016/j.ijfatigue.2018.09.004http://hdl.handle.net/10012/14046The final publication is available at Elsevier via https://dx.doi.org/10.1016/j.ijfatigue.2018.09.004 © 2019. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/This paper describes fatigue tests performed on 6061-T651 and 5083-H321 aluminum friction stir welded joints with dimensions and loading conditions typical for structural applications. Butt and lap joint details with various defects intentionally introduced were tested under tension-only constant and variable amplitude loading conditions. In this paper, the fatigue test results are presented along with supporting metallurgical and nonlinear fracture mechanics analyses. Based on this work, it is concluded that kissing bond defects on the order of 0.3–1.0 mm can result in a significant fatigue life reduction and a shift in the failure mode to the weld root. The investigated toe-flash defect had less of an effect on fatigue performance. The lap joint did not perform as well as the butt joint detail.enAttribution-NonCommercial-NoDerivatives 4.0 Internationalhttp://creativecommons.org/licenses/by-nc-nd/4.0/AluminumDefectsFracture mechanicsFriction stir weldsVariable amplitude loadingArticle