Characterisation of fatigue fracture surfaces of friction stir channelling specimens tested at different temperatures |
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| Affiliation: | 1. Instituto Superior Técnico, University of Lisbon, Av. Rovisco Pais, 1049-001 Lisbon, Portugal;2. LAETA, IDMEC, Instituto Superior Técnico, University of Lisbon, Avenida Rovisco Pais, 1049-001 Lisboa, Portugal;3. Department of Engineering Design and Production of the School of Engineering, Aalto University, Finland;1. Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352, United States;2. Environmental Molecular Sciences Laboratory (EMSL), 3335 Innovation Blvd., Richland, WA 99354, United States;3. University of California, Riverside, 3401 Watkins Dr., Riverside, CA 92521, United States;4. University of Pittsburgh, 4200 5th Avenue, Pittsburgh, PA 15260, United States;1. Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais 1, 1049-001, Lisboa, Portugal;2. DTU Physics, Technical University of Denmark, Fysikvej, 2800 Kgs, Lyngby, Denmark;3. DTU Nutech, Technical University of Denmark, DTU Risø Campus, Frederiksborgvej 399, DK-4000, Roskilde, Denmark;1. REPSOL POLÍMEROS, Sines, Portugal;2. Setúbal School of Technology, Instituto Politécnico de Setúbal, 2910-761 Setúbal, Portugal;3. Department of Mechanical Engineering, Setúbal School of Technology, Instituto Politécnico de Setúbal, 2910-761 Setúbal, Portugal;4. Department of Mechanical Engineering, Instituto Superior Técnico, University of Lisbon, Av. Rovisco Pais, 1049-001 Lisboa, Portugal;5. CeFEMA, Instituto Superior Técnico, University of Lisbon, Av. Rovisco Pais, 1049-001 Lisboa, Portugal;6. LAETA, IDMEC, Instituto Superior Técnico, University of Lisbon, Av. Rovisco Pais, 1049-001 Lisboa, Portugal;1. National Centre for Advanced Tribology at Southampton, Faculty of Engineering and the Environment, University of Southampton, UK;2. Perpetuum Ltd, Southampton, UK;1. Department of Mechanical Engineering, School of Technology, Pandit Deendayal Petroleum University, Raisan, Gandhinagar, India;2. Advanced Manufacturing and Materials Group, Department of Mechanical Engineering, School of Engineering, Aalto University, Finland;3. Department of Mechanical Engineering, Shankersinh Vaghela Bapu Institute of Technology, Gandhinagar, India;4. Department of Mechanical Engineering, Wichita State University, Wichita, United States;1. Department of Mechanical Engineering Science, University of Johannesburg, Auckland Park Kingsway Campus, Johannesburg, 2006, South Africa;2. Department of Mechanical Engineering, Dr. N.G.P. Institute of Technology, Coimbatore, 641048, Tamil Nadu, India;3. Department of Mechanical Engineering, University of Aveiro, Campus Santiago, 3810-193 Aveiro, Portugal |
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| Abstract: | The fatigue fracture surfaces of friction stir channelling specimens tested at room temperature, 120 °C and 200 °C were observed in a scanning electron microscope (SEM) in order to analyse their morphology and the crack propagation mechanisms. Three different friction stir channelling conditions were tested and analysed. For all specimens tested the developing fatigue-crack has always initiated at the advancing side, namely on the boundary between the nugget and the thermo mechanically affected zone (TMAZ) into the interior of the specimen. The crack has propagated through the channel nugget with a path tangential to the advancing side. After the crack has reached the processed surface, a second crack initiated at the channel bottom. The fracture surfaces have shown a semi-elliptical shape crack front. This second crack has propagated uniformly through the base material. Fatigue crack propagation on the TMAZ was mainly characterised by fatigue striations. It was found, on most of the surfaces observed, a clear coexistence of the intergranular fracture mode and the transgranular fracture mode. A relationship between the fatigue testing temperature and the roughness of the fracture surfaces was found. The fracture surfaces roughness was considerably lower at a testing temperature of 200 °C for the three friction stir channelling conditions analysed. |
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| Keywords: | Friction stir channelling AA5083-H111 Fatigue at elevated temperature Fracture surfaces |
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