磁电弹固体周期结构覆层表面波的传播特性研究

A magneto-electro-elastic (MEE) solid with the coating structures such as strips, ridges, grooves, and steps arranged periodically on the surface is the basic configuration of the MEE acoustic surface wave devices. When a surface wave propagating along the surface and meeting such coating structures on its propagation path, the scattering phenomenon of the surface wave will occur. And the degree of the scatter is dependent on the ration of the wave length to the period of the coatings. For different ratioes, surface waves will bring lots of rich propagation behavior, such as, the new surface wave appears, the Bragg reflection of the surface waves and the surface waves transform into the bulk waves, etc, which can not exist under the condition of the smooth surface. These new wave phenomena can be applied for the design of all kinds of the MEE surface wave devices such as transducers, resonators, reflectors, filters and delay lines, etc, the high frequency devices. In this project, based on the investigations of the surface waves on the smooth surface of a MEE solid, we will investigate the diverse behaviors of the SH and the Rayleigh surface waves propagating along the mentioned above coating structures on the surface of a MEE solid, and the cases of the three kinds of ratioes will be considered by the theoretical, numerical, and the experimental methods. The investigations of this project will be guided theoretically for the design, application and the performance evaluation of the MEE acoustic surface wave devices. Further, it will enrich the mechanical results of the wave propagation of the MEE composites.

磁电弹固体表面具有条带、脊背、沟槽和台阶等周期性排列的结构覆层是磁电弹声表面波器件的基本构型。当表面波沿着固体表面传播，在其传播路径上遇到这样的结构覆层，表面波会发生散射，其散射的程度取决于表面波的波长与覆层结构周期的比值。对于不同的波厚比，表面波会发生丰富的传播行为，产生光滑表面条件下不可能发生的波动现象：如生成新的表面波，发生布拉格散射，表面波转换为体波等。这些新的波动行为可应用于设计高频换能器、谐振器、滤波器、反射器、延迟线等各种磁电弹声表面波器件。本项目在磁电弹固体光滑表面波传播特性研究的基础上，用理论、数值和实验相结合的方法，研究表面波在半无限大磁电弹固体表面周期结构覆层的传播特性；考虑三种不同波厚比条件下，SH和Rayleigh表面波多样的散射行为，为各种新型磁电弹声表面波器件的设计、应用和性能评价提供必要的理论指导，进一步丰富磁电弹复合材料波动问题的研究成果。

半无限大磁电弹固体表面具有周期性排列的条带、电极和沟槽等结构覆层是磁电弹声表面波器件的基本构型。该申请项目采用解析方法和有限元方法研究了BG和Rayleigh表面波在半无限大磁电弹固体表面周期排列的金属条带和沟槽结构覆层中的传播特性。主要研究内容有(1) 表面波波长在远大于结构覆层周期的条件下，BG波在周期排列的金属条带和沟槽中传播的频散特性、带隙特性、波速减慢效应、波幅衰减以及表面波的约束效应。(2)表面波波长等于二倍金属电极结构覆层周期的条件下，BG和Rayleigh表面波在布拉格谐振频率附近的传播特性。获得了BG波在布拉格谐振频率附近传播时显式的频散方程以及反射和透射系数。分别采用变分原理和微绕理论获得了Rayleigh波在金属电极的力学扰动下，在布拉格频率附近传播的一阶速度漂移和一阶反射系数的计算公式；数值结果表明，两种方法所得到的计算结果基本吻合。该项目的研究将为磁电弹谐振器、反射器、延迟线、滤波器等磁电弹声表面波器件的设计和应用奠定理论基础。