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Continuum Analysis of Defects Based on Atomistic Simulat

Heidarzadeh, Narges | 2015

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  1. Type of Document: M.Sc. Thesis
  2. Language: English
  3. Document No: 48276 (53)
  4. University: Sharif University of Technology, International Campus, Kish Island
  5. Department: Science and Engineering
  6. Advisor(s): Khoei, Amir Reza; Jahanshahi, Mohsen
  7. Abstract:
  8. In this study, a new multi-scale hierarchical technique has been employed to investigate the role of temperature on nano-plates with hex atomic structure. Different number of primary edge dislocations is considered and the temperature varies from 0 up to 800 K. Primary edge dislocations are created by proper adjustment of atomic positions to resemble discrete dislocations (DD’s) and then the application of equations of motion to the relaxed configuration of this adjustment. The interatomic potential used for atomistic simulation is Finnis-Sinclair Embedded-Atom-Method (FS-EAM) as many-body interatomic potential and the Nose-Hoover thermostat has been implemented to adjust the modulation of temperature. Total potential energy of different representative volume elements (RVEs) under biaxial and shear loadings have been provided by fitting a fourth-order polynomial in atomistic level. Linear elastic constants are obtained by computing the second derivative of potential energy per unit volume with respect to strain. To calculate the bulk modulus, a linear combination of elastic constants has been carried out. Then, the variation of yield stress, elastic constants, and bulk modulus for nano-crystalline RVE’s at different number of primary edge dislocations and temperature levels have been obtained. In order to provide a relation between various quantities in nano-scale to their counterparts in macro-scale, computed material properties from molecular dynamics simulation have been transferred to each gauss points of finite element mesh using appropriate hyperelasticity functions. The numerical results clearly show the behavior of material in the presence of primary dislocations and variation of temperature
  9. Keywords:
  10. Molecular Dynamics ; Mechanical Behavior ; Representative Volume Element ; Dislocation ; Temperature Related Hierarchial Multiscale Model ; Temperature Dependent Thermophysical Properties

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