In this paper, a special beat phenomenon of metal nanowires is investigated by using the large scale molecular dynamics simulations. It is observed that the beat phenomenon exists not only in the vibration of <110> orientated Face Center Cubic (FCC) nanowires of different materials, but also in the vibration of <100> orientated Body Center Cubic (BCC) nanowires.Based on the atomic arrangement, a discrete spring-mass model is developed to explain the displacement characteristics of nanowire's vibration. It is found that the vibration frequency of nanowires rises slightly with the increase of initial actuation amplitude. The displacements of a typical atom in the nanowire are used to show the dynamical characteristics of beat phenomenon in vibration experiments. In addition, the beat phenomenon driven by a single actuation along one of the elementary directions has also been observed and shown in this work. Furthermore, a theoretical analysis is given for the excitation mechanism of beat phenomenon by analyzing the relation of excitation frequency between the two elementary directions.
In this paper, vibration behaviors of Fe nanowires are investigated by using the large-scale molecular dynamics (MD) simulations. It is observed that the vibration frequency of nanowires rises slightly and nonlinearly with the increase of initial actuation amplitude. Based on the atomic arrangement, a discrete spring-mass model is developed. Its nonlinear elastic relation is used to explain this phenomenon. In addition, Fe nanowires with different lengths and heights show different vibration properties in this work. The ratio between the length ([Formula: see text]) and the height ([Formula: see text]) of nanowires has a significant influence on vibration behaviors. The vibration properties of nanowires can be explained by the Euler–Bernoulli model when the ratio is relatively large, while they can be illustrated by the Timoshenko model when the ratio is relatively small.
Damping in double chains suspension bridge is non-uniform, which leads to coupled motion equations in main coordinate system. Based on the complex damping theory to solve equivalent viscous damping ratio used to describe energy dissipation characteristics of non-classical damping system approximately, a method is proposed to analyze seismic response of double chains suspension bridge considering non-classical damping modified by measured value. Influence of different damping forms on seismic response of double chains suspension bridge is analyzed, considering classical damping and non-classical damping respectively, through an example of double chains suspension bridge. The analysis shows that non-classical damping has significant effect on seismic response, and response based on the classical damping model is not reliable to double chains suspension bridge. Non-classical damping model should be used in seismic analysis of double chains suspension bridge, however, the seismic response of non-classical damping system under the longitudinal or vertical seismic wave can be substituted approximately by the seismic response calculated according to damping ratio of concrete tower and steel stiffening girder respectively, which can simplify the calculation during preliminary analysis.
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