| Summary: | 碩士 === 國立成功大學 === 機械工程學系碩博士班 === 90 === In this study, the deformation mechanism and stress analysis of the nanostructure have been simulated by molecular dynamics for various structures and sizes under tensile loading with displacement boundary condition. First, the FCC and HCP structures models are adojted. The many body potential functions for intermolecular are described by the tight-binding potential. Following the second law of Newton, the Gear fifth order predictor-corrector method is adopted to calculate atom’s physical properties, such as position and velocity, etc. To reduce the computer simulation time, the algorithms of Verlet neighbor list and cut-off potential are applied to calculate the interactive force between atoms.
Three parts are discussed, respective, (1) the nanostructure in the perfect of single crystal copper structure and perfect titanium structure. (2) the tensile deformation mechanism and stress analysis of the point defects effects. (3)the significance of effect as size reduced.
The results of loading : (1) the results of molecular dynamics simulation find the stress curve weren’t smooth. Those phenomenon can’t find in macroscopic. (2) defects will effect the limit stress and young’s modulus. (3) surface effect heavy in the nano-structure. On the one hand it use the Young’s modulus become variable and on the other the limit stress of titanium will decrease with the size increase. But copper will not clear in limited stress. Radius will not effect the young’s modulus.
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