磁流变液调控的声子晶体结构中波传播研究

发布时间：2018-03-21 02:28

本文选题：声子晶体　切入点：磁流变液　出处：《宁波大学》2017年硕士论文　论文类型：学位论文

【摘要】：声子晶体是一种周期性排列结构的复合材料。当弹性波在声子晶体中传播时,由于其结构上周期性的排列,存在一定频率范围的弹性波将会被阻碍而不能在其中传播,这个不能传播的弹性波的频率范围就叫做声子晶体的带隙。一般来说,当构成声子晶体的材料和声子晶体的拓扑结构确定了之后,声子晶体的带隙也就随之确定了。面对目前复杂的工程应用环境,声子晶体带隙的确定性已不能满足工程实际需求,所以探究带隙可调控的声子晶体便成了我们需要完成的任务。磁流变液是一类性质可控的智能材料,被认为是最具发展潜力的智能材料之一。当没有外加磁场时,磁流变液以液态存在,而施加磁场以后,磁流变液迅速变成类固态,且这个转变是可逆的。这种现象反映在材料参数上则是磁流变液模量和粘度的改变。基于以上论述,本文提出了一类将磁流变液作为组成材料的声子晶体。由于磁流变液的模量可以由磁场来调控,这样利用磁流变液作为媒介就可以通过磁场来调节声子晶体的带隙。为了获得声子晶体在不同磁场下的带隙,我们首先用实验的方法测得了磁流变液随磁场变化的剪切储能模量和耗能模量图。其次,使用磁流变液构造了完美周期声子晶体模型和带有缺陷的声子晶体模型,实验中使用LMS仪器测得了其在不同磁通密度下的振动传输图谱,同时运用COMSOL仿真软件对实验的声子晶体加以建模并计算了带隙。最后,将实验得到的带隙范围和理论结果进行了对比,分析了产生误差的原因,并总结了磁场改变对带隙范围的影响规律。主要结论有:磁流变液的剪切储能模量和耗能模量随着磁通密度的增加而逐渐变大,直至磁流变液达到磁饱和状态;随着磁通密度的增大,磁流变液调控的一维声子晶体,二维声子晶体板的带隙出现了带隙所在频率变大,带隙宽度变宽的现象;以完美周期结构的铝/水声子晶体为比较对象,随着含有周期缺陷的数目的增加,以磁流变液作为缺陷的一维声子晶体梁出现了阻碍声子晶体中波的传播的现象;对于含有三个周期缺陷的声子晶体梁,随着磁通密度的增大,带隙所在频率变大,带隙宽度变宽,这和磁流变液调控完美周期声子晶体的带隙的规律有较好的一致性。
[Abstract]:The phonon crystal is a kind of composite material with periodic arrangement structure. When elastic wave propagates in phonon crystal, because of its periodic arrangement on the structure, there is an elastic wave in a certain frequency range which will be blocked and can not propagate in it. The frequency range of this nonpropagating elastic wave is called the band gap of the phonon crystal. In general, when the material that constitutes the phonon crystal and the topological structure of the phonon crystal are determined, The band gap of phonon crystal has been determined. Facing the complicated engineering application environment, the certainty of band gap of phonon crystal can no longer meet the practical requirement of engineering. So exploring band-gap, controllable phononic crystals is the task that we need to do. MRF is a kind of smart material with controllable properties, which is considered to be one of the most promising smart materials. When there is no external magnetic field, The magnetorheological fluid exists as a liquid, and after the application of the magnetic field, the magnetorheological fluid becomes a kind of solid state rapidly, and this transition is reversible. This phenomenon is reflected in the change of the modulus and viscosity of the magnetorheological fluid in the material parameters. In this paper, we propose a kind of phononic crystals which use magnetorheological fluid as the composition material. Because the modulus of MRF can be controlled by magnetic field, In this way, the band gap of phonon crystal can be adjusted by magnetic field by using the magnetorheological fluid as the medium. In order to obtain the band gap of phonon crystal under different magnetic fields, The shear energy storage modulus and energy dissipation modulus of the magnetorheological fluid varying with the magnetic field are measured by the experimental method. Secondly, the perfectly periodic phonon crystal model and the phononic crystal model with defects are constructed by using the magnetorheological fluid. In the experiment, LMS instrument was used to measure the vibration transmission atlas at different flux density, and the experimental phonon crystal was modeled and the band gap was calculated by COMSOL simulation software. The band gap range obtained from the experiment is compared with the theoretical results, and the causes of the errors are analyzed. The main conclusions are as follows: the shear energy storage modulus and the energy dissipation modulus of the magnetorheological fluid increase with the increase of magnetic flux density until the magnetorheological fluid reaches the state of magnetic saturation. With the increase of magnetic flux density, the band gap of two-dimensional phonon crystal plate increases with the increase of magnetic flux density. With the increase of the number of periodic defects, the one-dimensional phononic crystal beams with magnetorheological fluid as defects appear to hinder the propagation of waves in phononic crystals, and for the beams with three periodic defects, with the increase of magnetic flux density, The frequency of band gap becomes larger and the width of band gap becomes wider, which is in good agreement with the regulation of band gap of perfect periodic phonon crystal by magnetorheological fluid.
【学位授予单位】：宁波大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB33;O735

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