基于有限元的空耦超声相控阵Lamb波激发与检测

The numerical simulation of the excitation and detection of Lamb waves using air-coupled ultrasonic phased array with finite element method

近些年来,基于非接触式空气耦合超声换能器的无损检测技术在常规板材、纤维复合材料、层状结构材料、粘接界面等的检测中已经有了长足的发展。但是由于空气耦合超声自身特性的限制,如何提高空气声换能器的发射效率和接收灵敏度、提高接收信号的信噪比已成为这一领域的重要课题。本文提出了电容式空气超声换能器阵列的构建和制作方法,能够有效提高空气耦合超声换能器的发射效率和接收灵敏度,并应用有限元方法对一维空气声线阵的声束动态偏转特性进行了模拟,构建流固耦合模型对空气声场及各向同性板材中的位移场进行了计算。计算发现,相控阵声束动态偏转在板中能够激励出Lamb波A0和S0模式,并对其频域特性进行了分析。此模型可以用于模拟空气耦合超声相控阵对板材的Lamb波无损检测。

The non-contact air-coupled ultrasonic transducer and its use in non-destructive testing methods have been greatly advanced recent years. It has been used in the testing of thin plate, fiber-reinforced composite plate, laminated structure and bonding strength testing. However, due to the limitation nature of the air-coupled ultrasonic detection, the problem remaining is how to improve the transmitting and receiving efficiency and sensitivity. In this paper, an air-coupled capacitive ultrasonic phased array has been proposed for the enhancement of the efficiency. The finite element method is used to explore the dynamic transmitting characterization of a 1D linear phased array. The acoustic fields in air transmitted by the ultrasonic array are calculated and analyzed. The displacement fields in plate excited by the ultrasound are calculated and monitored. Lamb waves in plate are excited and then received in this model. Several Lamb wave modes, i.e. A0 and So are excited based on the dynamic scanning along the plate surface. This model could be used in the simulation of the air-coupled ultrasonic Lamb wave testing of a plate.