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    Multi-scale Analysis of Dislocation Emission for Nano-crystalline Structures

    , M.Sc. Thesis Sharif University of Technology Fattahi Faradonbeh, Mehran (Author) ; Khoei, Amir Reza (Supervisor) ; Jahanshahi, Mohsen (Supervisor)
    Abstract
    In this study, a new multi-scale hierarchical technique has been employed to investigate the role of edge dislocation on nano-plates with hex atomic structure in large deformation. Two multiscale hierarchical atomistic/molecular dynamics (MD)–finite element (FE) coupling methods are proposed to illustrate the influence of temperature on mechanical properties of Magnesium in large deformation. The atomic nonlinear elastic parameters are obtained via computing second-order derivative of Representative atom’s energy and RVE’s strain energy density with respect to deformation criterions (deformation gradient and Green strain tensor) to bridge between atomistic and continuum level, the... 

    A Coupling Atomistic-continuum Approach for Modeling Dislocation in Plastic Behavior of Nano-structures

    , M.Sc. Thesis Sharif University of Technology Omrani Pournava, Amir Mohsen (Author) ; Khoei, Amir Reza (Supervisor) ; Jahanshahi, Mohsan (Co-Advisor)
    Abstract
    In this study, a novel multi-scale hierarchical method has been employed to explore the role of edge dislocation on Nano-plates with hexagonal atomic structure in large deformation. multiscale hierarchical atomistic/molecular dynamics (MD) finite element (FE) coupling methods are proposed to demonstrate the impact of dislocation on mechanical properties of Magnesium in large deformation. The atomic nonlinear elastic parameters are attained via computing first-order derivation of stress with respect to strain of Representative Volume Element (RVE). To associate between atomistic and continuum level, the mechanical characteristics are captured in the atomistic scale and transferred to the... 

    Computational modeling of the interaction of two edge cracks, and two edge cracks interacting with a nanovoid, via an atomistic finite element method

    , Article Computational Materials Science ; Volume 42, Issue 2 , 2008 , Pages 186-193 ; 09270256 (ISSN) Adelzadeh, M ; Shodja, H. M ; Rafii Tabar, H ; Sharif University of Technology
    2008
    Abstract
    The competition and interaction of two edge cracks within the triangular lattice of an fcc material are addressed. We have also examined the effect of presence of a nanovoid in the vicinity of one of the crack-tips, on the competition of the cracks. An atomic scale finite element method (AFEM) [B. Liu, Y. Huang, H. Jiang, S. Qu, K.C. Hwang, The atomic-scale finite element method, Comput. Methods Appl. Mech. Eng. 193 (2004) 1849-1864], based on the Morse interatomic potential, is employed to explore the events in the (1 1 1) plane. Particular attention is given to the phenomenon of brittle-to-ductile transition (BDT) that occurs during crack propagation. © 2007 Elsevier B.V. All rights...