| Summary: | 碩士 === 國立中正大學 === 機械工程所 === 97 === Nanotechnology is now considered one of the most prominent areas to be explored in 21st century. The development of one-dimensional nanostructures such as nanotubes and nanowires has attracted a lot of attention from different scientific communities due to the possible applications and unique physical phenomena. Among them, helical nanowires and coiled nanotubes (referred hereafter generally as nanosprings) are innovative forms of one-dimensional nanostructures that have promising applications in nanoelectromechanical systems. Nanosprings could be employed to measure extremely small force of several nano-Newton and provided as an excellent energy dissipation mechanism. With the recent advance of nanotechnology, there is a growing interest in studying how mechanical properties of the nanostructured materials differ from their bulk counterparts.
In this study, molecular statics method incorporating minimum energy concept was employed to study the one-dimensional copper nanospring with faced-center-cubic crystal structure. Various geometric sizes (wire diameter, radius, pitch), number of turns, cross-sectional shapes (circular and elliptic) and crystal orientations of nanosprings were systematically modeled to investigate the size dependence of elastic properties. It was observed that as the wire diameter increases, and the radius and number of turns decrease, the nanospring stiffness would increase irrespective to the crystal orientations and cross-sectional shapes. Moreover, the elastic constants of nanosprings would become larger while the pitches become smaller for almost all the crystal orientations. Also the simulation results of nanosprings with circular cross sections were compared with the predictions based on continuum theory in order to clarify whether the classical theory could apply to nanosprings.
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