Size effects on stress concentration induced by a prolate ellipsoidal particle and void nucleation mechanism |
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| Institution: | 1. Department of Mechanics, Huazhong University of Science and Technology, Wuhan 430074, PR China;2. Chair of Applied Mechanics, University of Kaiserslautern, P.O. Box 3049, D67653 Kaiserslautern, Germany;1. Department of Engineering Mechanics, School of Aerospace Engineering, Huazhong University of Science and Technology, Wuhan 430074, China;2. Hubei Key Laboratory of Engineering Structural Analysis and Safety Assessment, Luoyu Road 1037, Wuhan 430074, China;1. State Key Laboratory of High-Performance Complex Manufacturing, Central South University, Changsha 410083, China;2. School of Mechanical and Electrical Engineering, Central South University, Changsha 410083, China;1. School of Energy, Power and Mechanical Engineering, North China Electric Power University, Baoding 071003, PR China;2. School of Materials Science and Engineering, Tianjin University, Tianjin 300350, PR China;1. Department of Mechanics, School of Aerospace Engineering, Huazhong University of Science and Technology, Wuhan 430074, PR China;2. Hubei Key Laboratory of Engineering Structural Analysis and Safety Assessment, Wuhan 430074, PR China;3. State Key Laboratory of Materials Processing and Die & Mould Technology, Wuhan 430074, PR China;1. Department of Mechanical Engineering, Faculty of Technology, University of Brasília, Brasília, DF, Brazil;2. IDMEC – Institute of Mechanical Engineering, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, Porto 4200-465, Portugal;1. Department of Mechanical Engineering, K. Ramakrishnan College of Engineering, Trichy, Tamil Nadu 621112, India;2. Department of Mechanical Engineering, K. Ramakrishnan College of Technology, Trichy, Tamil Nadu 621112, India;3. Department of Mechanical Engineering, M.Kumarasamy College of Engineering, Karur, Tamil Nadu 639113, India |
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| Abstract: | There generally exist two void nucleation mechanisms in materials, i.e. the breakage of hard second-phase particle and the separation of particle–matrix interface. The role of particle shape in governing the void nucleation mechanism has already been investigated carefully in the literatures. In this study, the coupled effects of particle size and shape on the void nucleation mechanisms, which have not yet been carefully addressed, have been paid to special attention. To this end, a wide range of particle aspect ratios (but limited to the prolate spheroidal particle) is considered to reflect the shape effect; and the size effect is captured by the Fleck–Hutchinson phenomenological strain plasticity constitutive theory (Advance in Applied Mechanics, vol. 33, Academic Press, New York, 1997, p. 295). Detailed theoretical analyses and computations on an infinite block containing an isolated elastic prolate spheroidal particle are carried out to light the features of stress concentrations and their distributions at the matrix–particle interface and within the particle. Some results different from the scale-independent case are obtained as: (1) the maximum stress concentration factor (SCF) at the particle–matrix interface is dramatically increased by the size effect especially for the slender particle. This is likely to trigger the void nucleation at the matrix–particle interface by cleavage or atomic separation. (2) At a given overall effective strain, the particle size effect significantly elevates the stress level at the matrix–particle interface. This means that the size effect is likely to advance the interface separation at a smaller overall strain. (3) For scale-independent cases, the elongated particle fracture usually takes place before the interface debonding occurs. For scale-dependent cases, although the SCF within the particle is also accentuated by the particle size effect, the SCF at the interface rises at a much faster rate. It indicates that the probability of void nucleation by the interface separation would increase. |
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