Fatigue lives of friction stir spot welds in aluminum 6061-T6 sheets |
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| Authors: | D.-A. Wang C.-H. Chen |
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| Affiliation: | 1. Helmholtz-Zentrum Geesthacht, Institute of Materials Research, Materials Mechanics, Solid-State Joining Processes, Max-Planck-Str. 1, Geesthacht, Germany;2. Federal University of São Carlos, Materials Engineering Department, R. Washington Luís Km 235 – SP 310, Sao Carlos, Brazil;1. Shanghai Key Laboratory of Materials Laser Processing and Modification, Shanghai Jiao Tong University, Shanghai 200240, China;2. The State key Lab of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240, China;3. Shanghai Spaceflight Manufacture (Group) Co., Ltd, Shanghai 200240, China;1. Helmholtz-Zentrum Geesthacht, Institute of Materials Research, Materials Mechanics, Solid State Joining Processes Department, Max-Planck-Str. 1, 21502 Geesthacht, Germany;2. Innovation Management and Product Development, Lufthansa Technik AG, Weg beim Jäger 193, 22335 Hamburg, Germany;1. Department of Materials Science and Engineering, The Ohio State University, United States;2. Center for Design and Manufacturing Excellence (CDME), The Ohio State University, United States;3. Honda R&D Americas, Inc., United States;1. Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal;2. LAETA, IDMEC, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal;3. Helmholtz-Zentrum Geesthacht, Instituto of Materials Research, Materials Mechanics, Solid-State Joining Processes, Max-Planck-Str. 1, 21502 Geesthacht, Germany |
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| Abstract: | The fatigue lives of friction stir spot welds in aluminum 6061-T6 lap-shear specimens under cyclic loading conditions are investigated in this paper. The paths of fatigue cracks near friction stir spot welds in lap-shear specimens are first examined. The experimental observations suggest that under cyclic loading conditions, the fatigue crack is initiated near the possible original notch tip in the stir zone and propagates along the circumference of the nugget, then through the sheet thickness and finally grows in the width direction to cause final fracture. A fatigue crack growth model based on the Paris law for crack propagation and the local stress intensity factors for kinked cracks is then adopted to predict the fatigue lives of friction stir spot welds. The global and local stress intensity factors are used to estimate the local stress intensity factors of kinked cracks with experimentally determined kink angles. The results indicate that the fatigue life predictions based on the Paris law and the local stress intensity factors as functions of the kink length agree well with the experimental results. |
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