On the snap-through time of a nanoscale elastic strip

关于纳米弹性窄带的回弹时间研究

We have examined the elastic snap-through behaviors of single crystal copper strips numerically and theoretically to investigate factors that influence the characteristic snap-through time scale.The strip is simply supported on both ends,and the snap-through is launched by suddenly removing the concentrated forces that have already been statically applied to produce an initial bending configuration.On the one hand,the process is implemented in the molecular dynamics(MD)simulator LAMMPS.On the other hand,a theoretical formulation is provided with the consideration of surface tension.Increasing surface tension is found to increase the snap-through time.The results show that the snap-through behavior is further closely related to the magnitude of the initially stored deformation and the strip thickness.Finally,snap-through times provided by the above numerical and theoretical analyses are on the same order of magnitude.This is an interesting agreement,especially considering that the huge gap of time scales between MD simulations and experiments has been a well-known fundamental issue.We believe that the present study about spontaneous processes such as snap-through has cast some light on the fbndamental issue that deformation in MD simulations generally happens much faster than in physical experiments.

我们通过数值模拟和理论建模两种方法研究了纳米尺寸单晶铜窄带的回弹行为,分析了回弹时间的各种影响因素.通过固定窄带两端并于其中点施加静荷载,使窄带产生初始弯曲.随后通过移除中点静何载促使回弹行为发生.本研究分别使用分子动力学模拟软件LAMMPS和考虑表面张力的连续力学模型对纳米弹性窄带回弹进行了研究.研究发现表面张力的增加会导致回单时间的增加.研究结果还表明回弹行为与窄带初始弯曲程度和窄带厚度均具有密切联系.此外,对比分子动力学模拟和连续模型所得结果,我们还发现两种方法获得的回弹时间处于同一量级.这一结论十分独特且有意义,因为目前分子动力学模拟结果在时间尺度上往往与实验结果存在巨大差异、我们相信,本研究关于回弹这一自发运动的研究有助于在一定程度上阐述分子动力学模拟所得的变形行为时间尺度远小于实验结果的原因.