压电条SH声辐射场研究

具有一定宽度和厚度的无穷长压电条置于均匀各向同性半空间上, 压电条在电激励下产生机械振动从而在整个空间产生声场. 将压电条取为6mm晶系, 其对称主轴沿长度方向. 针对这 种压电换能器结构, 深入研究了SH波的激发和辐射特性. 首先将压电条中的声场展开为傅里 叶级数, 而将压电条下的无界半空间中的声场展开为傅里叶积分, 然后根据边界条件得到了 整个空间中声场的求解方案, 通过数值模拟计算了声场的分布特性, 并和传统方法进行了定 量的对比和分析. 最后采用最陡下降法(鞍点法)研究并得到了压电条声辐射场的远场近似表 达式, 分析了声场的指向性规律. 结果表明只有当频率f和压电条宽度a的乘积 fa<1 kHz·m 时, 传统方法得到的结果是可靠的，当频率升高时，压电条内应力和位移呈振荡式分布，频率愈高振荡愈激烈，且与传统方法的差异愈大.本文对声学微系统与声传感器件的研究具有 重要意义. 关键词： 压电条 6mm晶系 表面位移 指向性因子

Study of SH acoustic radiation field excited by a piezoelectric strip

A piezoelectric strip of infinite length but with finite width and thickness is placed on top of an isotropic elastic half space. The piezoelectric strip is excited by an electrical signal and the acoustic field is generated. The piezoelectric strip is of type 6mm crystal system oriented along its length direction. The SH wave is studied for the structure of this piezoelectric transducer. At first, the field is expanded as a Fourier series in the piezoelectric strip and as a Fourier integral in the half space. Then, the response of the solution inside the piezoelectric strip and in the half space is obtained by the boundary conditions. The acoustic field distribution is analyzed and compared to that obtained by the traditional method. Finally, the acoustic radiation field at the far field is investigated by the saddle point method and the directional factor is analyzed. It is found that the traditional method is valid only in the case where the product of the frequency with the width of the piezoelectric strip is less than1kHz·m. The stress and displacement in the piezoelectric strip are oscillatory distributions when the frequency increases. The greater the frequency, the greater the difference between the traditional method and the present method.