变厚度板中水平剪切波的传播特性分析

为研究超声导波在储罐壁板等变壁厚结构中的传播特性,建立了SH波在空间自由边界中的传播模型,基于各向同性弹性介质Navier-Stokes方程,推导了变厚度板中SH波的频散方程,分析了变厚度板中水平剪切波走时t与倾斜角θ间的相互作用关系;通过简谐点源的远场响应并引入板厚与传播位移的非线性关系,得出了变厚度板中SH波的远场响应方程。在此基础上,仿真分析和实验验证了水平剪切波在不同倾斜角变厚度板中的传播特性,结果表明:在变厚度板的薄端激励水平剪切波并沿结构表面传播时,无频散现象,且无波包分离现象;但随着变厚度板倾斜角θ增大,水平剪切波的走时和接收信号幅值均逐渐递减,且呈非线性关系。

Propagation Characteristics of SH Wave in Plates with Variable Thickness

In order to study the propagation characteristics of ultrasonic guided waves in variable thickness plates such as tank wall, the propagation models of SH wave were established in free boundary space. The dispersion equation of SH wave in variable thickness plates was derived based on the Navier-Stokes equation of isotropic elastic medium, and the effects of the inclination angle θ on the travel time t of SH wave were analyzed. According to the far-field response of simple harmonic point source, the far-field response equation of SH wave in variable thickness plates was derived by introducing the non-linear relationship of the plate thickness and propagation displacement. Then, the propagation characteristics of SH wave in plates with different inclined angles were verified by finite element simulation and physical experiments. The results show that when SH wave is excited at the thin end of variable thickness plate and propagates along the structure surface, there is no dispersion phenomenon and no wave packet separation phenomenon. However, with the increase of the inclination angles θ of the variable thickness plates, the travel time and the received signal amplitudes of the SH wave decrease non-linearly.