Molecular Study on the Mechanical Properties of Nanosprings with Elliptic Cross Section

• Main Authors: Tsung-Yu Chuang, 莊宗諭
• Other Authors: I-Ling Chang
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/39946749458739745220

碩士 === 國立中正大學 === 機械工程所 === 97 === The development of one-dimensional nanostructures such as nanotubes, nanowires, nanorods and nanosprings has attracted a lot of attention from different scientific communities due to their possible applications and unique physical phenomena. Helical nanowires, or called nanosprings have special periodic and elastic properties, which are of particular interest to the semiconductor industry. Nanosprings could be employed to measure extremely small force of several nano-Newton and could be provided as an excellent energy dissipation mechanism. With the recent advance of nanotechnology, there is a growing interest in studying how the mechanical properties of the nanosprings 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 elliptical cross section. Various geometric sizes (wire diameter, radius, pitch), elliptic cross-sectional shapes (normal and binormal) 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 decrease, the nanospring stiffness would increase. The relationships between spring constant and pitch have different trends along different crystal orientations. The spring constant of normal nanospring is larger than the binormal one under the same crystal orientations and the same cross-sectional area. Also the simulation results were compared with the predictions based on continuum theory in order to clarify whether the classical theory could apply to nanosprings with elliptical cross section. Besides, the spectrum analysis on one-dimensional atomic system is attempted, and the resonance frequency is analyzed from both velocity and velocity-velocity autocorrelation function.