Static and dynamic buckling behavior of CNTS with S-W defects

The excellent performance of carbon nanotubes (CNTs) allows them to be widely employed in various micro- and nano-electromechanical devices. However, different imperfections such as Stone–Wales (S-W) defects often arise in these structures during the preparation process. In this paper, special attention is paid to the effects of the number and location of defects as well as the diameter and chiral angle of CNTs on the static and dynamic buckling of CNTs with S-W defects. First, LAMMPS software is used to simulate the molecular dynamics (MDs) of CNTs with S-W defects, and their static buckling performances are discussed. Then based on the static buckling data, the dynamic buckling vibration performance of CNTs with S-W defects is analyzed in the context of the nonlocal elastic theory. Finally, the effective range of nonlocal parameters is established via the MD modeling. The results show that the existence of S-W defects will reduce the buckling performance and vibration characteristics of CNTs, and an increase in the number of defects will aggravate the influence of diameter and chiral angle on the buckling performance as well as the natural frequency and amplitude of the nanotube’s axial vibration.

Comparison between using generalized differential quadrature method and analytical solution in analyzing vibration behavior of nonuniform nanobeam systems

In this article, generalized differential quadrature method (GDQM) is used to study the free vibrational behavior of variable cross section nano beams. Eringen's nonlocal elastic theory is taken into account to model the small scale effects and nonuniformity is assumed by exponentially varying the width of nano beam. Governing equation of motion is solved using generalized differential quadrature method with different numbers of sampling points. Effects of increasing the sampling points in reaching more accurate results for first three frequency parameters are presented and it is shown that after a specific number of sampling points, results merge to a certain accurate number. It is concluded that generalized differential quadrature method is able to reach the correct answers comparing to analytical results. Moreover, due to the stiffness softening behavior of small-scale structures, necessity of using Eringen's nonlocal elastic theory to model the small scale effects due to the frequency variation is observed.

Analysis of Band Structures of Nanosized Phononic Crystals by Nonlocal Elastic Theory

Based on the nonlocal elastic continuum theory, the band structures of the nano-sized layered phononic crystals are analyzed by computing the localization factors and dispersion curves. Detailed calculations are performed for a nanosized HfO2–ZrO2 periodic layer stack. The size-effect on the band structures is examined. It is found that the nonlocal elastic continuum solution deviates from the classical elastic continuum theory and finally approaches the first-principle result as the thickness of each individual layer decreases. Due to the size-effect, there exists a cut-off frequency beyond which the waves cannot propagate through the system.