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Spallation caused by the diffusion and agglomeration of vacancies in ductile metals
Affiliation:1. Department of Structural, Geotechnical and Building Engineering, Politecnico di Torino, C.so Duca degli Abruzzi 24, 10129 Torino, Italy;2. IMT Institute for Advanced Studies Lucca, Piazza San Francesco 19, 55100 Lucca, Italy;1. Department of Civil Engineering, K. N. Toosi University of Technology, P.O. Box: 15875-4416, Tehran, Iran;2. Institute for Nanoscience and Nanotechnology, Sharif University of Technology, P.O. Box: 11155-9161, Tehran, Iran;3. Department of Civil Engineering, Sharif University of Technology, P.O. Box: 11155-9313, Tehran, Iran;1. Institute of Information Science, Beijing Jiaotong University, Beijing 100044, China;2. College of Information Engineering, Hebei United University, Tangshan 063009, China;3. Beijing Key Laboratory of Advanced Information Science and Network Technology, Beijing 100044, China;1. National Centre for Advanced Tribology (nCATS), Faculty of Engineering and the Environment, University of Southampton, UK;2. Department of Mechanical Engineering and Mathematical Sciences, Oxford Brookes University, UK;3. Faculty of Engineering and the Environment, University of Southampton Malaysia Campus (USMC), Nusajaya, Johor, Malaysia
Abstract:In this paper, the spallation process for the ductile metals under plane shock loading is discussed in theory. By employing the phase transition theory and non-equilibrium theory, the spallation process may be understood as a result of the diffusion and agglomeration of the generated vacancies. Through the detailed theoretical analysis, the following important points are concluded: (1) the spalling temperature, a new concept, is proposed first and the appearance of spallation critical behavior is proved; (2) the quantitative grain size, tensile strain rate and temperature dependence of both the damage evolution rate and the void growth velocity is obtained; (3) the existence of a characteristic size for the voids and a characteristic stress at the void boundary is discovered first, and their magnitude depend on the vacancy excitation energy and the average volume of one vacancy; (4) the temperature of metal near the growing void is found to be high, possibly causing the metal to melt, and it decreases quickly with the distance away from the void; (5) the area of the plastic zone, surrounding one formed spherical void, is clarified; (6) the viewpoint is put forward that the void growth may arise from the agglomeration of vacancies rather than the emission of dislocations when the shocking temperature approaches spalling temperature. Most of the above theoretical results are novel and obtained first.
Keywords:Spallation  Ductile metals  Damage  Void
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