磁流变弹性体基声子晶体的弹性波可调拓扑传输研究

Adjustable topological transmission of elastic waves in MR elastic matrix-based phonon crystals

将规则的铁质三脚杆以六角晶格形式嵌入磁流变弹性基体中设计了一种二维声学超材料,通过计算分析结构元胞的色散关系,找出k点必然简并狄拉克点,并通过旋转单个三脚杆打破晶格结构的空间对称性使狄拉克点完成了打开—简并—打开的变化过程。模拟量子谷霍尔效应,在k点必然简并狄拉克点的变化过程中导致了不同的谷赝自旋之间能带发生反转,实现了拓扑相变。通过对声学超材料超元胞色散关系的计算,发现了结构中存在的拓扑边界态,利用拓扑边界态设计弹性波拓扑传输通道,实现了对弹性波的精确引导,并可以通过外加磁场改变磁流变基体材料的剪切模量来改变拓扑传输通道的频率范围,实现了对拓扑传输通道传输频率的非接触式主动调控。研究结果可以为噪声及振动等的智能控制提供相应的参考。

Here,a 2-D acoustic metamaterial was designed by embedding regular iron tripod into magnetorheological elastic matrix in the form of hexagonal lattice.By calculating and analyzing the dispersion relationship of structural cells,the k-point was found to inevitably degenerate Dirac point.By rotating a single tripod to break the spatial symmetry of lattice structure,Dirac point completed the change process of opening-degenerating-opening.Simulated quantum valley Hall effect caused energy band inversion between different valley pseudospins in change process of k-point to inevitably degenerate Dirac point to realize topological phase transition.Through calculating dispersion relationship of super-cells of acoustic metamaterial,the topological boundary state existing in structure was found.The topological boundary state was used to design elastic wave topological transmission channel to realize accurate guidance of elastic wave,and external magnetic field was used to change shear modulus of MR matrix material,and further change the frequency range of topological transmission channel.Thus,the non-contact active control of transmission frequency for topological transmission channel was realized.It was shown that the study results can provide a reference for intelligent control of noise and vibration.