球形复合柱表面波声子晶体的带隙特性仿真

Numerical simulation study on band gap characteristics of surface phononic crystal with spherical composite column

设计了一种由镍球与环氧树脂垫层组成的复合柱沉积在铌酸锂基体上构成的表面波声子晶体结构,采用有限元法计算了其能带结构和位移矢量场.结果表明:与具有相同晶格常数的倒圆锥形表面波声子晶体结构相比,研究结构可以在更低的频率范围打开更宽的声表面波完全带隙,且随着复合柱半径增大,镍球体与压电基体的硬边界之间形成限制腔模,相邻高阶带隙间存在能量的耦合以及振动模式的继承;此外,温度场的引入可以实现带隙的主动调控,带隙频率范围随着温度升高向低频移动;通过增加复合柱体的层数,多振子结构与行波发生多极共振耦合,可在高阶能带间打开完全带隙.本文的研究结果为微米级表面波声子晶体结构在100 MHz以下频率范围的带隙特性优化提供了理论支持.

In the study of acoustic characteristics of micro-scale surface phononic crystal,the band gap characteristics below 100 MHz need to be further optimized.In this work,a piezoelectric surface phononic crystal with a composite column composed of nickel balls and epoxy backing is proposed.The finite element method is used to calculate the band gap characteristics and displacement vector field of the model.The influence of column radius on the band structure is studied,and meanwhile,the effect of the multi-layer composite column structure on the band gap is discussed via increasing the number of elements in the composite column,while the reason for the opening of the high-order band gap is analyzed in detail by combining the vibration mode.Furthermore,the temperature adjustability of the band gap is further studied.The results show that the spherical composite column deposition structure can open a wider complete band gap of surface acoustic wave in a lower frequency range than the existing inverse conical surface phononic crystal structure with the same lattice constant(Hsu J C,Lin F S 2018 Jpn.J.Appl.Phys.5707LB01).The restricted cavity mode is easily formed between the hard boundaries with the increase of column radius,which provides a possible way for low-order vibration modes to open high-order band gaps.There exist mode inheritance and energy coupling between adjacent modes,which leads the band gap to flatten and anti-flatten.Moreover,the real-time adjustment of band gap frequency by external temperature field can be realized via introducing the temperature-sensitive material epoxy resin into the structure.The band gap frequency range can be effectively reduced by increasing the number of composite cylinder layers,while the multi-vibrator structure can generate multipole resonance coupling with traveling wave and finally open a complete band gap between high-order frequency bands.This work provides a theoretical reference for analyzing the low-frequency band gap mechanism of micron-scale surface phononic crystal.