中文摘要：

采用有限元／边界元法（FEM／BEM），分析了有限长叉指换能器在半无限大压电晶体128°YX—LiNb03中激发的表面波和体波在晶体表面上的分布情况。通过对频域内表面声场的分析，得到了表面上三个位移场分量含有的声波模式，对相应时域内各场分量的体波脉冲振幅进行处理，详细分析了各个模式的体波脉冲振幅随时间的分布关系。结果表明，除Rayleigh型表面波外，各场分量中还包含不同成分和比例的体波模式；在场分量1和场分量3中占主要成分的准纵波，以及在场分量2中占主要成分的准慢切变波，在表面上其传播损耗以指数衰减。

英文摘要：

Using the tool of Finite Element Method/ Boundary Element Method （FEM/BEM）, the distribution of the acoustic wave field which excited by finite-length IDT including the SAW and the bulk wave on the surface of the semi-infinite piezoelectric crystal can be analyzed. Through analyzing the acoustic wave field on the surface in frequency region, acoustic wave modes in three displacements on the surface can be received. The amplitude of the bulk wave pulses in different field components in corresponding time region can be deal with. The relationship between the pulse amplitudes of several bulk wave modes and the time can be analyzed in detail. The results show that there are different kinds and different scales of bulk wave modes except Rayleigh-type wave mode in the field. Quasi-longitudinal wave is the main part in the first field component and in the third field component; meanwhile quasi-slow shear wave in the second field component follows some exponential transmission rules separately on the surface.