超声多波聚焦及声偏振方向控制方法

Ultrasonic multi-wave focusing and acoustical polarization direction control method

在超声多波聚焦思想的基础上,通过数值模拟计算,分析了时间反转法的多波聚焦特性以及对声场偏振方向进行控制的可行性。结果表明,在待测目标的不同位置处,时间反转法都能够实现多波聚焦的效果,使具有不同传播速度、不同偏振特性的多种声波自适应聚焦。但是,在介质的近表面处,由于受到表面波的影响,多波聚焦声场仍然具有椭圆偏振特性,无法实现声场偏振方向精确控制的目的;而位于介质内部的多波聚焦点受到表面波影响很小,数值计算结果表明此时多波聚焦声场具有线偏振特性,通过改变声源前后两个脉冲的激发幅度和相位,可以控制声场的偏振方向,达到偏振方向扫描的目的。该文的研究为精确检测裂纹方向或界面性质提供一种可能的途径。

On the basis of the idea of multi-wave focusing, the multi-wave focusing characteristic of time reversal method and the feasibility of controlling the polarization direction of the wave field are analyzed by numerical simulation. The results show that the time reversal method can realize the effect of multi-wave focusing at different positions of the target, which makes the different waveforms focused. However, at the near surface of the medium, the multi-wave focused field still has the elliptical polarization characteristic due to the influence of the surface wave, and can not achieve the precise control of the polarization direction of the wave field. The multi-wave focusing point inside the medium is rarely influenced by the surface wave, the numerical results show that the multi-wave focused field has the linear polarization characteristic. Through changing the excitation amplitude and phase of the front and rear pulses of the source, the polarization direction of the wave field can be controlled, and the purpose of polarization direction scanning is achieved. The study of this paper provides a probably new method to precisely detect crack direction and interface characteristic.