A unified model of fatigue kinetics based on crack driving force and material resistance |
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| Affiliation: | 1. US Naval Research Laboratory, Materials Science and Technology Division, Washington, DC, USA;2. Air Force Institute of Technology, Wright-Patterson AFB, OH, USA;3. Materials Research Centre, University of Wales Swansea, UK;1. Department of Mechanical Engineering, Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka-shi, Fukuoka 819-0395, Japan;2. Department of Mechanical and Automotive Engineering, Seoul National University of Science and Technology, 172 Gongreung 2-dong, Nowon-gu, Seoul 139-743, Republic of Korea;1. Department of Mechanical Engineering, Korea University, Anam-Dong, Seongbuk-Gu, Seoul 136-701, Republic of Korea;2. School of Energy Systems Engineering, Chung-Ang University, Dongjak-Gu, Seoul 156-756, Republic of Korea;3. The University of Manchester, Manchester M13 9PL, UK;4. Assessment Technology Group, EDF Energy, Barnwood, Gloucester GL4 3RS, UK;5. AREVA-NP, Tour AREVA, Paris La Défense Cédex, France;1. BiSS (P) Ltd, 497E 14th Cross, 4th Phase, Peenya Industrial Area, Bangalore 560058, India;2. Tomsk Polytechnical University and Institute of Physics of Strength of Materials, Russian Academy of Sciences, Tomsk, Russian Federation |
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| Abstract: | ![]()
Fatigue in Al-alloys is largely a process of crack growth from pre-existing defects occurring by several different mechanisms, each of which dominates a particular rate-driven segment of fatigue kinetics. These include fatigue void formation through interfacial cracking of secondary particulates, crack extension by brittle micro-fracture (BMF) in near-threshold fatigue, slip driven crack growth in the Paris regime and quasi-static crack extension by the well-known micro-void coalescence (MVC) and the less known fatigue void coalescence (FVC). BMF is mean stress and sequence-sensitive.Mechanism selection for fatigue crack extension in each load cycle occurs on the principle of least resistance to crack driving force represented by ΔK and Kmax. Crack extension will switch to a different failure mechanism given reduced resistance to that mechanism by comparison to the current one. Increasing driving force will thus force a switch from BMF to shear and then onto MVC or FVC in that order, over each rising load half-cycle. Higher growth rates will therefore always be associated with a mix of all these mechanisms. |
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